Prenatal vitamin d supplementation and child respiratory health: a randomised controlled trial

Vitamin D supplementation for women during pregnancy

BACKGROUND

Vitamin D supplementation during pregnancy may help improve maternal and neonatal health outcomes (such as fewer preterm birth and low birthweight babies) and reduce the risk of adverse pregnancy outcomes (such as severe postpartum haemorrhage).

OBJECTIVES

To examine whether vitamin D supplementation alone or in combination with calcium or other vitamins and minerals given to women during pregnancy can safely improve certain maternal and neonatal outcomes.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Trials Register (which includes results of comprehensive searches of CENTRAL, MEDLINE, Embase, CINAHL, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform, and relevant conference proceedings) (3 December 2022). We also searched the reference lists of retrieved studies.

SELECTION CRITERIA

Randomised and quasi-randomised trials evaluating the effect of supplementation with vitamin D alone or in combination with other micronutrients for women during pregnancy in comparison to placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Two review authors independently i) assessed the eligibility of studies against the inclusion criteria, ii) assessed trustworthiness based on pre-defined criteria of scientific integrity, iii) extracted data from included studies, and iv) assessed the risk of bias of the included studies. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

The previous version of this review included 30 studies; in this update, we have removed 20 of these studies to 'awaiting classification' following assessments of trustworthiness, one study has been excluded, and one new study included. This current review has a total of 10 included studies, 117 excluded studies, 34 studies in awaiting assessment, and seven ongoing studies. We used the GRADE approach to assess the certainty of the evidence. This removal of the studies resulted in evidence that was downgraded to low-certainty or very low-certainty due to study design limitations, inconsistency between studies, and imprecision. Supplementation with vitamin D compared to no intervention or a placebo A total of eight studies involving 2313 pregnant women were included in this comparison. We assessed four studies as having a low risk of bias for most domains and four studies as having high risk or unclear risk of bias for most domains. The evidence is very uncertain about the effect of supplementation with vitamin D during pregnancy compared to placebo or no intervention on pre-eclampsia (risk ratio (RR) 0.53, 95% confidence interval (CI) 0.21 to 1.33; 1 study, 165 women), gestational diabetes (RR 0.53, 95% CI 0.03 to 8.28; 1 study, 165 women), preterm birth (< 37 weeks) (RR 0.76, 95% CI 0.25 to 2.33; 3 studies, 1368 women), nephritic syndrome (RR 0.17, 95% CI 0.01 to 4.06; 1 study, 135 women), or hypercalcaemia (1 study; no cases reported). Supplementation with vitamin D during pregnancy may reduce the risk of severe postpartum haemorrhage; however, only one study reported this outcome (RR 0.68, 95% CI 0.51 to 0.91; 1 study, 1134 women; low-certainty evidence) and may reduce the risk of low birthweight; however, the upper CI suggests that an increase in risk cannot be ruled out (RR 0.69, 95% CI 0.44 to 1.08; 3 studies, 371 infants; low-certainty evidence). Supplementation with vitamin D + calcium compared to no intervention or a placebo One study involving 84 pregnant women was included in this comparison. Overall, this study was at moderate to high risk of bias. Pre-eclampsia, gestational diabetes, and maternal adverse events were not reported. The evidence is very uncertain about the effect of supplementation with vitamin D and calcium on preterm birth (RR not estimable; very low-certainty evidence) or for low birthweight (RR 1.45, 95% CI 0.14 to 14.94; very low-certainty evidence) compared to women who received placebo or no intervention. Supplementation with vitamin D + calcium + other vitamins and minerals versus calcium + other vitamins and minerals (but no vitamin D) One study involving 1298 pregnant women was included in this comparison. We assessed this study as having a low risk of bias in all domains. Pre-eclampsia was not reported. The evidence is very uncertain about the effect of supplementation with vitamin D, calcium, and other vitamins and minerals during pregnancy compared to no vitamin D on gestational diabetes (RR 0.42, 95% CI 0.10 to 1.73; very low-certainty evidence), maternal adverse events (hypercalcaemia no events and hypercalciuria RR 0.25, 95% CI 0.02 to 3.97; very low-certainty evidence), preterm birth (RR 1.04, 95% CI 0.68 to 1.59; low-certainty evidence), or low birthweight (RR 1.12, 95% CI 0.82 to 1.51; low-certainty evidence).

AUTHORS' CONCLUSIONS

This updated review using the trustworthy assessment tool removed 21 studies from the previous update and added one new study for a total of 10 included studies. In this setting, supplementation with vitamin D alone compared to no intervention or a placebo resulted in very uncertain evidence on pre-eclampsia, gestational diabetes, preterm birth, or nephritic syndrome. It may reduce the risk of severe postpartum haemorrhage; however, only one study reported this outcome. It may also reduce the risk of low birthweight; however, the upper CI suggests that an increase in risk cannot be ruled out. Supplementation with vitamin D and calcium versus placebo or no intervention resulted in very uncertain evidence on preterm birth and low birthweight. Pre-eclampsia, gestational diabetes, and maternal adverse events were not reported in the only study included in this comparison. Supplementation with vitamin D + calcium + other vitamins and minerals versus calcium + other vitamins and minerals (but no vitamin D) resulted in very uncertain evidence on gestational diabetes and maternal adverse events (hypercalciuria) and uncertain evidence on preterm birth and low birthweight. Pre-eclampsia was not reported in the only study included in this comparison. All findings warrant further research. Additional rigorous, high-quality, and larger randomised trials are required to evaluate the effects of vitamin D supplementation in pregnancy, particularly in relation to the risk of maternal adverse events.

Vitamin D Primary Prevention of Respiratory Infections and Asthma in Early Childhood: Evidence and Mechanisms

Respiratory infections are a leading cause of child morbidity worldwide, and asthma is the most common chronic disorder in childhood. Both conditions associate with high socioeconomic costs and are major reasons for medication prescriptions and hospitalizations in children. Vitamin D deficiency has concomitantly increased with asthma prevalence and is hypothesized to play a key role in the development. Current evidence suggests that high prenatal and early childhood vitamin D could be protective against respiratory infections and asthma in some studies where several mechanisms are proposed. However, other studies have reported no effects on these outcomes. Therefore, future large intervention studies on this topic are warranted. Mechanistic studies have shown that vitamin D holds antimicrobial properties by inducing production of several peptides through altered gene expression. Others have shown a complex interplay between asthma risk genotypes, the sphingolipid pathway, and prenatal vitamin D in early childhood asthma. Vitamin D has also been suggested to change both airway immune and microbiota profiles, which are directly related to asthma risk. Finally, systemic low-grade inflammation seems to be regulated by vitamin D exposure. This review presents the current literature of the primary preventive effect of vitamin D on early childhood asthma and respiratory infections. Mechanisms of actions are discussed, and gaps in knowledge are highlighted to facilitate planning of future intervention trials.

Environmental Interventions for Preventing Atopic Diseases

PURPOSE OF REVIEW

In this review, we detail the exposome (consisting of environmental factors such as diet, microbial colonization, allergens, pollutants, and stressors), mechanistic and clinical research supporting its influence on atopic disease, and potentiation from climate change. We highlight contemporary environmental interventions and available evidence substantiating their roles in atopic disease prevention, from observational cohorts to randomized controlled trials, when available.

RECENT FINDINGS

Early introduction to allergenic foods is an effective primary prevention strategy to reduce food allergy. Diverse dietary intake also appears to be a promising strategy for allergic disease prevention, but additional study is necessary. Air pollution and tobacco smoke are highly associated with allergic disease, among other medical comorbidities, paving the way for campaigns and legislation to reduce these exposures. There is no clear evidence that oral vitamin D supplementation, prebiotic or probiotic supplementation, daily emollient application, and antiviral prophylaxis are effective in preventing atopic disease, but these interventions require further study. While some environmental interventions have a well-defined role in the prevention of atopic disease, additional study of many remaining interventions is necessary to enhance our understanding of their role in disease prevention. Alignment of research findings from randomized controlled trials with public policy is essential to develop meaningful public health outcomes and prevent allergic disease on the population level.

Neonatal Vitamin D and Associations with Longitudinal Changes of Eczema up to 25 Years of Age

BACKGROUND

Early-life vitamin D is a potentially modifiable risk factor for the development of eczema, but there is a lack of data on longitudinal associations.

METHOD

We measured 25(OH)D3 levels from neonatal dried blood spots in 223 high-allergy-risk children. Latent class analysis was used to define longitudinal eczema phenotype up to 25 years (4 subclasses). Skin prick tests (SPTs) to 6 allergens and eczema outcomes at 6 time points were used to define eczema/sensitization phenotypes. Associations between 25(OH)D3 and prevalent eczema and eczema phenotypes were assessed using logistic regression models.

RESULTS

Median 25(OH)D3 level was 32.5 nmol/L (P25-P75 = 23.1 nmol/L). Each 10 nmol/L increase in neonatal 25(OH)D3 was associated with a 26% reduced odds of early-onset persistent eczema (adjusted multinomial odds ratio (aMOR) = 0.74, 95% CI = 0.56-0.98) and 30% increased odds of early-onset-resolving eczema (aMOR = 1.30, 95% CI = 1.05-1.62) when compared to minimal/no eczema up to 12 years. Similar associations were seen for eczema phenotype up to 25 years. We did not see any strong evidence for the association between neonatal 25(OH)D3 and prevalent eczema or eczema/sensitization phenotype.

CONCLUSIONS

Higher neonatal 25(OH)D3 levels, a reflection of maternal vitamin D levels in pregnancy, may reduce the risk of early-onset persistent eczema.

Immunonutrition: Diet Diversity, Gut Microbiome and Prevention of Allergic Diseases

Allergic diseases are increasing both in morbidity and mortality. Genetic, environmental, and dietary factors may all be involved in this increase. Nutrition during pregnancy, breastfeeding, and early life may play a particularly important role in preventing allergic diseases. Based on current systematic reviews, the intake of specific nutrients has failed to prevent allergic disease. Prevention strategies have shifted their focus to the overall diet which can be described using diet diversity. Infant and maternal diet diversity in pregnancy has been associated with reduced allergy outcomes in childhood. Overall, diet also seems to have a marked effect on the microbiome compared to single foods. Factors that may negate the allergy-preventative effect of overall diet diversity include the addition of emulsifiers, advanced glycation end-product content, and overuse of commercial baby foods. There is a need to perform randomized controlled trials using overall dietary intake to support international food allergy guidelines. These studies should ideally be conducted by multi-professional teams.

Maternal Dietary Vitamin D Intake during Pregnancy Is Associated with Allergic Disease Symptoms in Children at 3 Years Old: The Japan Environment and Children's Study

INTRODUCTION

Vitamin D plays an important role in the immune system, and postnatal vitamin D insufficiency is one of the risk factors for the development of allergic disease. However, the effects of women's vitamin D intake during pregnancy on the prevalence of allergic disease in their children remain controversial.

METHODS

From the Japan Environment and Children's Study, an ongoing nationwide birth cohort study, we obtained information on maternal dietary vitamin D intake determined using a food frequency questionnaire and parent-reported allergic disease symptoms based on the ISAAC questionnaire in children at 3 years of age.

RESULTS

From the full dataset of 103,060 pregnancies, we analyzed complete data for 73,309 mother-child pairs. The prevalence of current wheeze, current rhinitis, current rhino-conjunctivitis, current eczema, ever asthma, ever pollinosis, and ever atopic dermatitis in the children was 17.2%, 29.7%, 3.8%, 15.2%, 9.6%, 3.7%, and 11.0%, respectively. The ORs for current rhinitis were significantly lower in the 3rd, 4th, and 5th quintiles than in the 1st quintile after adjustment for various covariates and showed a linear association. The ORs for ever pollinosis were significantly lower in the 2nd, 3rd, and 4th quintiles than in the 1st quintile, showing a U-shaped curve. There was no clear association between mothers' dietary vitamin D intake and symptoms of asthma or atopic dermatitis in their 3-year-old children.

CONCLUSION

Maternal dietary vitamin D intake during pregnancy is associated with the ORs for nasal allergies in children at the age of 3 years. Further studies are warranted to evaluate the appropriate intake dose of vitamin D for pregnant women to prevent the development of nasal allergies in their children.

The Impact of Baseline 25-Hydroxyvitamin D Level and Gestational Age on Prenatal Vitamin D Supplementation to Prevent Offspring Asthma or Recurrent Wheezing

BACKGROUND

Prenatal vitamin D deficiency is associated with asthma or recurrent wheezing in offspring. However, evidence from randomized trials on the efficacy of vitamin D supplementation is inconclusive.

OBJECTIVES

We aimed to examine the differential efficacy of prenatal vitamin D supplementation based on the maternal baseline vitamin D status and the starting time of supplementation to prevent early life asthma or recurrent wheezing.

METHODS

We conducted a secondary analysis of the Vitamin D Antenatal Asthma Reduction Trial (VDAART), a randomized double-blind trial of prenatal vitamin D supplementation initiated at 10-18 weeks (wks) of gestation (4400 IU of intervention/day compared with 400 IU of placebo/day) to prevent offspring asthma or recurrent wheezing by the age of 6 years. We assessed the effect of modification of supplementation by maternal baseline vitamin D status at enrollment and the timing of initiation of supplementation.

RESULTS

An inverse relationship was observed between maternal 25-hydroxyvitamin D (25(OH)D) levels at trial entry and 25(OH)D levels during late pregnancy (32-38 wks of gestation) in both supplementation arms (P < 0.001). Overall, supplementation efficacy was not dependent on the maternal baseline 25(OH)D status. However, a trend toward the reduction of asthma or recurrent wheezing was observed across the baseline groups in the intervention arm (P = 0.01), with the greatest reduction observed in the most severely vitamin D-deficient women (25(OH)D < 12 ng/mL; adjusted odds ratio [aOR] = 0.48; confidence interval [CI]: 0.17, 1.34). Gestational age at trial enrollment modified supplementation efficacy, showing a greater reduction of offspring asthma or recurrent wheezing with earlier intervention during pregnancy (aOR = 0.85; CI = 0.76, 0.95), particularly in women who were 9-12 wk pregnant (aOR = 0.45; CI = 0.24, 0.82).

CONCLUSIONS

Pregnant women with severe vitamin D deficiency show the greatest 25(OH)D improvement because of supplementation. In these women, a vitamin D dose of 4400 IU might have a preventive role in the development of early life offspring asthma or recurrent wheezing. Gestational age is suggested to modify the efficacy of prenatal vitamin D supplementation, showing the highest beneficial effect if supplementation is started during the first trimester of pregnancy. This study is an ancillary analysis from the VDAART, which is registered in ClinicalTrials.gov as NCT00902621.

Association of Maternal Gestational Vitamin D Supplementation with Respiratory Health of Young Children

This study aimed to evaluate the association between maternal gestational Vitamin D3 supplementation and early respiratory health in offspring. This was a population-based record-linkage study which used data from the French National Health Database System. Maternal Vitamin D3 supplementation consisted of a single high oral dose of cholecalciferol, (100,000 IU) from the seventh month of pregnancy, according to national guidelines. In total, 125,756 term-born singleton children were included, of which 37% had respiratory illness defined as hospital admission due to respiratory causes or inhalation treatment up to 24 months of age. Infants prenatally exposed to maternal Vitamin D3 supplementation (n = 54,596) were more likely to have a longer gestational age (GA) at birth (GA 36-38 weeks, 22% vs. 20%, p < 0.001 in exposed vs. non-exposed infants, respectively). After adjusting for the main risk factors (maternal age, socioeconomic level, mode of delivery, obstetrical and neonatal pathology, birth weight appropriateness, sex, and birth season), the risk of RD was found to be 3% lower than their counterparts (aOR [IC 95%], 0.97 [0.95-0.99], p = 0.01). In conclusion, this study provides evidence for the association between maternal gestational Vitamin D3 supplementation and improved early respiratory outcomes in young children.

The Effects of Latitude and Temperate Weather on Vitamin D Deficiency and Women's Reproductive Health: A Scoping Review

INTRODUCTION

We conducted a scoping review to analyze the effects and implications of vitamin D deficiency on female reproductive health during the last decade, considering temperate planetary zones and climate change impacts.

METHODS

We used a qualitative methodology for a panoramic database review of PubMed, Web of Science, and Scopus covering articles from the last decade focused on populations living at latitudes higher than 40° N and 40° S. As descriptors, we used the phrases climate change, cholecalciferol or vitamin d3, pregnancy, and woman health and the Boolean operators AND and OR. We excluded letters to the editor, reviews, protocols, and clinical trials without human participants, as well as duplicate articles.

RESULTS

We included 35 studies in English, the majority of which were from North America or Europe. No studies were found from the Southern Hemisphere or having any direct relation with climate change, although studies demonstrated that latitude and environmental factors affected vitamin D deficiency, which had an impact on pregnant women and their children. Supplementation guidelines were not well developed, and there was a lack of studies among at-risk groups of women (eg, darker skin, higher latitudes, immigrants) across the life span.

DISCUSSION

Vitamin D deficiency is a global environmental problem that affects female reproductive health and depends on multiple environmental factors and human behavior. Therefore, we recommend consideration of environmental and sociocultural factors in public policy and clinical research and more research on the effectiveness of supplementation and fortification strategies. Health care professionals working in reproductive health need to generate actions for detection of, education on, and prevention of vitamin D deficiency among women across their life spans, considering the multicausality of the phenomenon, which includes environmental and climate factors in population health.

Is antenatal or early-life vitamin D associated with eczema or food allergy in childhood? A systematic review

OBJECTIVE

To summarise the associations between antenatal or early-life blood vitamin D and the development of eczema/food allergy in childhood.

DESIGN

A systematic review and meta-analyses were conducted to synthesize the published literature. Two reviewers independently performed the study selection and data extraction on Covidence. We assessed the risk of bias for observational studies by using the Newcastle-Ottawa Scale and the Cochrane Risk of Bias tool for clinical trials. The certainty of the evidence was assessed using Grading of Recommendations, Assessment, Development and Evaluations (GRADE).

DATA SOURCES

We systematically searched PubMed and Embase from inception and April 2022.

ELIGIBILITY CRITERIA

Human studies that investigated prospective associations between antenatal or early-life blood vitamin D levels, dietary intake or supplementation and childhood eczema/food allergy.

RESULTS

Forty-three articles including six randomised controlled trials (RCTs) were included. Four RCTs of vitamin D supplementation during pregnancy showed no evidence of an effect on the incidence of eczema (pooled odds ratio [OR] = 0.85; 0.67-1.08, I2  = 6.7%, n = 2074). Three RCTs reported null associations between supplementation in pregnancy/infancy and food allergy. From six cohort studies, increasing cord blood vitamin D levels were associated with reduced prevalence of eczema at/close to age one (OR per 10 nmol/L increase = 0.89; 0.84-0.94, I2  = 0%, 2025 participants). We found no evidence of an association between maternal antenatal or infant vitamin D level or dietary intake and the development of food allergy or eczema in offspring.

CONCLUSIONS

We found an association between higher vitamin D levels in cord blood and reduced risk of eczema in cohort studies. Further trials with maternal and infant supplementation are needed to confirm if vitamin D supplementation can effectively prevent eczema or food allergy in childhood.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, No. CRD42013005559.

Vitamin D Supplementation and Vitamin D Status during Pregnancy and the Risk of Congenital Anomalies-A Systematic Review and Meta-Analysis

Maternal dietary factors have been suggested as possible contributing influences for congenital anomalies (CAs). We aimed to assess the association between vitamin D supplementation or vitamin D status (s-25OHD) during pregnancy and CAs in the offspring. A comprehensive literature search was conducted in the three electronic databases: PubMed, Embase, and Cochrane Library. Included studies were critically appraised using appropriate tools (risk of bias 2, ROBINS-I). A protocol was registered in the International Prospective Register of Systematic Reviews (CRD42019127131). A meta-analysis of four randomised controlled trials (RCTs) including 3931 participants showed no effect of vitamin D supplementation on CAs, a relative risk of 0.76 (95% CI 0.45; 1.30), with moderate certainty in the effect estimates by GRADE assessment. Of the nine identified observational studies, six were excluded due to a critical risk of bias in accordance with ROBINS-I. Among the included observational studies, two studies found no association, whereas one case-control study identified an association between s-25OHD < 20 nmol/L and neural tube defects, with an adjusted odds ratio of 2.34 (95% CI: 1.07; 5.07). Interpretation of the results should be cautious given the low prevalence of CAs, RCTs with onset of supplementation after organogenesis, and low-quality observational studies.

Prevention of food allergy in infancy: the role of maternal interventions and exposures during pregnancy and lactation

There is increased focus on the role of maternal interventions in the prevention of food allergy in infancy. There is no role for maternal dietary modifications during pregnancy or lactation, such as allergen avoidance, as a means of infant allergy prevention. Although exclusive breastfeeding is the recommended infant nutrition source globally, the effect of breastfeeding on infant allergy prevention remains unclear. There is emerging evidence that irregular cow's milk exposure (ie, infrequent formula supplementation) might increase the risk of cow's milk allergy. Although further studies are required, there is also emerging evidence that maternal peanut ingestion during breastfeeding along with early peanut introduction in infancy might have a preventive role. The effect of maternal dietary supplementation with vitamin D, omega-3, and prebiotics or probiotics remains unclear.

25 Years of translational research in the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC)

The Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) mother-child cohorts have provided a foundation of 25 years of research on the origins, prevention, and natural history of childhood asthma and related disorders. COPSAC's approach is characterized by clinical translational research with longitudinal deep phenotyping and exposure assessments from pregnancy, in combination with multi-omic data layers and embedded randomized controlled trials. One trial showed that fish oil supplementation during pregnancy prevented childhood asthma and identified pregnant women with the highest benefits from supplementation, thereby creating the potential for personalized prevention. COPSAC revealed that airway colonization with pathogenic bacteria in early life is associated with an increased risk of asthma. Further, airway bacteria were shown to be a trigger of acute asthma-like symptoms, with benefit from antibiotic treatment. COPSAC identified an immature gut microbiome in early life as a risk factor for asthma and allergy and further demonstrated that asthma can be predicted by infant lung function. At a molecular level, COPSAC has identified novel susceptibility genes, early immune deviations, and metabolomic alterations associated with childhood asthma. Thus, the COPSAC research program has enhanced our understanding of the processes causing childhood asthma and has suggested means of personalized prevention and treatment.

Vitamin D and Omega-3 (Fatty Acid) Supplementation in Pregnancy for the Primary Prevention of Food Allergy in Children-Literature Review

During the last decades the prevalence of food allergy (FA), an adverse immune response to a specific food antigen, has risen, with negative effects on the quality of life (QoL) of many children and their families. The pathogenesis of FA is complex, involving both genetic and environmental factors. SPINK5, STAT6, HLA and FOXP3 are some of the genes that are reported to be implicated in FA development. Regarding environmental factors, particular interest has been focused on modification of the dietary habits of pregnant women for the primary prevention of FA. Specifically, Vitamin D and omega-3 (Ω-3) fatty acid supplementation during pregnancy may influence the development of FA in the offspring. Vitamin D is a hormone with various actions, including mediation of the immune system, reducing the production of inflammatory cytokines and promoting tolerance. Vitamin D deficiency in pregnancy suppresses T-regulatory cells in the fetus, and Vitamin D supplementation might protect against FA development. Dietary Ω-3 fatty acids are found mainly in fish and vegetable oils. They are beneficial for human health, playing a role in the immune system as anti-inflammatory agents, and providing cell membrane stabilization with inhibition of antigen presentation. It is documented that maternal supplementation with Ω-3 during pregnancy may protect from allergic sensitization in the children. The aim of this literature review was to explore the potential preventive role of maternal supplementation during pregnancy with Vitamin D and Ω-3 in the development of FA in the offspring. With the prevalence of FA rising, all the possible protective mechanisms and measures for FA prevention need to be explored, starting with those that can be modified.

Vitamin D for the management of asthma

BACKGROUND

Since the previous Cochrane Review on this topic in 2016, debate has continued surrounding a potential role for vitamin D in reducing risk of asthma exacerbation and improving asthma control. We therefore conducted an updated meta-analysis to include data from new trials completed since this date.

OBJECTIVES

To evaluate the effectiveness and safety of administration of vitamin D or its hydroxylated metabolites in reducing the risk of severe asthma exacerbations (defined as those requiring treatment with systemic corticosteroids) and improving asthma symptom control.

SEARCH METHODS

We searched the Cochrane Airways Group Trial Register and reference lists of articles. We contacted the authors of studies in order to identify additional trials. Date of last search: 8 September 2022.

SELECTION CRITERIA

We included double-blind, randomised, placebo-controlled trials of vitamin D in children and adults with asthma evaluating exacerbation risk or asthma symptom control, or both.

DATA COLLECTION AND ANALYSIS

Four review authors independently applied study inclusion criteria, extracted the data, and assessed risk of bias. We obtained missing data from the authors where possible. We reported results with 95% confidence intervals (CIs). The primary outcome was the incidence of severe asthma exacerbations requiring treatment with systemic corticosteroids. Secondary outcomes included the incidence of asthma exacerbations precipitating an emergency department visit or requiring hospital admission, or both, end-study childhood Asthma Control Test (cACT) or Asthma Control Test (ACT) scores, and end-study % predicted forced expiratory volume in one second (FEV1). We performed subgroup analyses to determine whether the effect of vitamin D on risk of asthma exacerbation was modified by baseline vitamin D status, vitamin D dose, frequency of dosing regimen, form of vitamin D given, and age of participants.

MAIN RESULTS

We included 20 studies in this review; 15 trials involving a total of 1155 children and five trials involving a total of 1070 adults contributed data to analyses. Participant ages ranged from 1 to 84 years, with two trials providing data specific to participants under five years (n = 69) and eight trials providing data specific to participants aged 5 to 16 (n = 766). Across the trials, 1245 participants were male and 1229 were female, with two studies not reporting sex distribution. Fifteen trials contributed to the primary outcome analysis of exacerbations requiring systemic corticosteroids. The duration of trials ranged from three to 40 months; all but two investigated effects of administering cholecalciferol (vitamin D3). As in the previous Cochrane Review, the majority of participants had mild to moderate asthma, and profound vitamin D deficiency (25-hydroxyvitamin D (25(OH)D) < 25 nmol/L) at baseline was rare. Administration of vitamin D or its hydroxylated metabolites did not reduce or increase the proportion of participants experiencing one or more asthma exacerbations treated with systemic corticosteroids (odds ratio (OR) 1.04, 95% CI 0.81 to 1.34; I2 = 0%; 14 studies, 1778 participants; high-quality evidence). This equates to an absolute risk of 226 per 1000 (95% CI 185 to 273) in the pooled vitamin D group, compared to a baseline risk of 219 participants per 1000 in the pooled placebo group. We also found no effect of vitamin D supplementation on the rate of exacerbations requiring systemic corticosteroids (rate ratio 0.86, 95% CI 0.62 to 1.19; I2 = 60%; 10 studies, 1599 participants; high-quality evidence), or the time to first exacerbation (hazard ratio 0.82, 95% CI 0.59 to 1.15; I2 = 22%; 3 studies, 850 participants; high-quality evidence). Subgroup analysis did not reveal any evidence of effect modification by baseline vitamin D status, vitamin D dose, frequency of dosing regimen, or age. A single trial investigating administration of calcidiol reported a benefit of the intervention for the primary outcome of asthma control. Vitamin D supplementation did not influence any secondary efficacy outcome meta-analysed, which were all based on moderate- or high-quality evidence. We observed no effect on the incidence of serious adverse events (OR 0.89, 95% CI 0.56 to 1.41; I2 = 0%; 12 studies, 1556 participants; high-quality evidence). The effect of vitamin D on fatal asthma exacerbations was not estimable, as no such events occurred in any trial. Six studies reported adverse reactions potentially attributable to vitamin D. These occurred across treatment and control arms and included hypercalciuria, hypervitaminosis D, kidney stones, gastrointestinal symptoms and mild itch. In one trial, we could not ascertain the total number of participants with hypercalciuria from the trial report. We assessed three trials as being at high risk of bias in at least one domain; none of these contributed data to the analysis of the outcomes reported above. Sensitivity analyses that excluded these trials from each outcome to which they contributed did not change the null findings.

AUTHORS' CONCLUSIONS

In contrast to findings of our previous Cochrane Review on this topic, this updated review does not find evidence to support a role for vitamin D supplementation or its hydroxylated metabolites to reduce risk of asthma exacerbations or improve asthma control. Participants with severe asthma and those with baseline 25(OH)D concentrations < 25 nmol/L were poorly represented, so further research is warranted here. A single study investigating effects of calcidiol yielded positive results, so further studies investigating effects of this metabolite are needed.

Maternal Vitamin D Supplementation for the Prevention of Respiratory Tract Infections in Offspring: A Meta-Analysis

BACKGROUND

Vitamin D may enhance immune system function and provide a protective effect against infections. Feto-maternal circulation plays an important role in supplying the developing fetus with nutrients and antibodies for its development and health during pregnancy and for its early years of life after birth. This meta-analysis aimed to determine the effectiveness of maternal vitamin D supplementation in preventing respiratory tract infections (RTIs) in children.

METHODS

We searched the Central and MEDLINE databases and went through all the reference lists in the related articles. We also searched for ongoing trials at http://www.who.int/ictrp/en/ and www.clinicaltrials.gov. Randomized controlled trials comparing vitamin D supplementation with a placebo or no treatment in pregnant women published in the English language up to March 2019 were included. Two reviewers extracted data independently using a predefined protocol and assessed the risk of bias using the Cochrane risk of bias tool, with differences agreed upon by consensus. The predefined primary outcome was the number of offspring who had RTIs. The secondary outcome was the presence of measurable serum immunoglobulin E levels.

RESULTS

Three trials involving 3,224 participants (mother-child pairs) met the inclusion criteria and were included in this review. The present analysis reported that maternal supplementation with vitamin D had no effect on RTIs among children (n=1,486 offspring; risk ratio, 0.95; 95% confidence interval, 0.82-1.11; random effects; I2 statistics, 0%).

CONCLUSION

Maternal vitamin D supplementation had no effect on RTIs in children. Therefore, consideration of other prevention methods in this regard is recommended.

Pre- and Postnatal Vitamin D Status and Allergy Outcomes in Early Childhood

The dramatic increase in the prevalence of allergic disease in recent decades reflects environmental and behavioural changes that have altered patterns of early immune development. The very early onset of allergic diseases points to the specific vulnerability of the developing immune system to environmental changes and the development of primary intervention strategies is crucial to address this unparalleled burden. Vitamin D is known to have immunomodulatory functions. While allergic disease is multifactorial, associations with reduced sunlight exposure have led to the hypothesis that suboptimal vitamin D levels during critical early periods may be one possible explanation. Interventions to improve vitamin D status, especially in early life, may be the key to allergic disease prevention.

Primary Prevention of Pediatric Asthma through Nutritional Interventions

Asthma is the most common chronic non-communicable disease in children, the pathogenesis of which involves several factors. The increasing burden of asthma worldwide has emphasized the need to identify the modifiable factors associated with the development of the disease. Recent research has focused on the relationship between dietary factors during the first 1000 days of life (including pregnancy)—when the immune system is particularly vulnerable to exogenous interferences—and allergic outcomes in children. Specific nutrients have been analyzed as potential targets for the prevention of childhood wheeze and asthma. Recent randomized controlled trials show that vitamin D supplementation during pregnancy, using higher doses than currently recommended, may be protective against early childhood wheezing but not school-age asthma. Omega-3 fatty acid supplementation during pregnancy and infancy may be associated with a reduced risk of childhood wheeze, although the evidence is conflicting. Data from observational studies suggest that some dietary patterns during pregnancy and infancy might also influence the risk of childhood asthma. However, the quality of the available evidence is insufficient to allow recommendations regarding dietary changes for the prevention of pediatric asthma. This review outlines the available high-quality evidence on the role of prenatal and perinatal nutritional interventions for the primary prevention of asthma in children and attempts to address unmet areas for future research in pediatric asthma prevention.

GRADE guidance 24 optimizing the integration of randomized and non-randomized studies of interventions in evidence syntheses and health guidelines

BACKGROUND AND OBJECTIVE

This is the 24th in the ongoing series of articles describing the GRADE approach for assessing the certainty of a body of evidence in systematic reviews and health technology assessments and how to move from evidence to recommendations in guidelines.

METHODS

Guideline developers and authors of systematic reviews and other evidence syntheses use randomized controlled studies (RCTs) and non-randomized studies of interventions (NRSI) as sources of evidence for questions about health interventions. RCTs with low risk of bias are the most trustworthy source of evidence for estimating relative effects of interventions because of protection against confounding and other biases. However, in several instances, NRSI can still provide valuable information as complementary, sequential, or replacement evidence for RCTs.

RESULTS

In this article we offer guidance on the decision regarding when to search for and include either or both types of studies in systematic reviews to inform health recommendations.

CONCLUSION

This work aims to help methodologists in review teams, technology assessors, guideline panelists, and anyone conducting evidence syntheses using GRADE.

Vitamin D supplementation in pregnant women or infants for preventing allergic diseases

Background:

It is still unclear if and to what extent antenatal or infant or childhood vitamin D supplementation would affect the development of allergy diseases later in life. This study aimed to review the efficacy of vitamin D supplementation in pregnant women, infants, or children for the prevention of allergies.

Methods:

MEDLINE (PubMed), EMBASE (OVID), and the Cochrane Central Register of Controlled Trials were searched up to March 1, 2020. We included only randomized controlled trials (RCTs). We performed a systematic review and meta-analysis for vitamin D supplementation in primary allergy prevention. These trials were assessed for risk of bias using the Cochrane Collaboration domains and the consensus was reached via discussion with the full study group. We descriptively summarized and quantitatively synthesized original data to evaluate vitamin D supplementation in primary allergy prevention by using Review Manager software for meta-analysis.

Results:

The search yielded 1251 studies. Seven RCTs were included in this analysis. A meta-analysis revealed that vitamin D supplementation for pregnant women or infants may not decrease the risk of developing allergic diseases, such as asthma or wheezing (supplementation for pregnant women, risk ratio [RR]: 1.01, 95% confidence interval [CI]: 0.81–1.26, P = 0.90, I² = 47%; supplementation for infants, RR: 1.00, 95% CI: 0.70–1.43, P = 0.99, I² = 0%; supplementation for pregnant women and infants, RR: 0.35, 95% CI: 0.10–1.25, P = 0.11), eczema (supplementation for pregnant women, RR: 0.95, 95% CI: 0.80–1.13, P = 0.77, I² = 0%; supplementation for infants, RR: 0.84, 95% CI: 0.64–1.11, P = 0.19, I² = 42%), allergic rhinitis (supplementation for pregnant women, RR: 0.93, 95% CI: 0.78–1.11, P = 0.15, I² = 47%), lower respiratory tract infection (LRTI) (supplementation for pregnant women, RR: 0.97, 95% CI: 0.85–1.11, P = 0.59, I² = 0%), or food allergy.

Conclusions:

Supplementation of vitamin D in pregnant women or infants does not have an effect on the primary prevention of allergic diseases.

Systematic Review Registration:

PROSPERO (CRD42020167747)

The maternal diet index in pregnancy is associated with offspring allergic diseases: the Healthy Start study

BACKGROUND

A systematic review showed limited associations between pregnancy diet and offspring allergy. We developed a maternal diet index during pregnancy that was associated with offspring allergy outcomes.

METHODS

Data came from Healthy Start, a Colorado pre-birth cohort of mother/offspring dyads. Food propensity questionnaires were completed during pregnancy. Offspring allergic rhinitis, atopic dermatitis, asthma, wheeze, and food allergy diagnosis up to age four were verified from electronic medical records. Data were randomized into test and replication sets. The index included the weighted combination of variables that best predicted a combined outcome of any allergy in the test set. Index utility was verified in the replication set. Separate adjusted and unadjusted logistic models estimated associations between the index and each offspring allergy diagnosis in the full sample.

RESULTS

The index included weighted measures of intake of vegetables, yogurt, fried potatoes, rice/grains, red meats, pure fruit juice, and cold cereals. Vegetables and yogurt were associated with the prevention of any allergy, while other components were associated with increased disease. In adjusted models, a one-unit increase in the index was significantly associated with reduced odds of offspring allergic rhinitis (odds ratio (CI) 0.82 [0.72-0.94]), atopic dermatitis (0.77 [0.69-0.86]), asthma (0.84 [0.74-0.96]), and wheeze (0.80 [0.71-0.90]), but not food allergy (0.84 [0.66-1.08]).

CONCLUSIONS

This is the first study that has shown associations between an index of maternal dietary intake during pregnancy and multiple offspring allergic diseases. The results give hope for prevention of allergic diseases in utero.

Vitamin D supplementation higher than 2000 IU/day compared to lower dose on maternal–fetal outcome: Systematic review and meta-analysis

Introduction:

Although vitamin D is widely known as an essential micronutrient during pregnancy, the exact supplementation dose to prevent maternal–fetal outcomes remains a question. This study aims to provide a systematic review and a meta-analysis of data from randomized controlled trial on > 2000 IU/day vitamin D supplementation compared to ⩽ 2000 IU/day; and ⩽ 2000 IU/day compared to placebo, on their effects on the incidence of preeclampsia, gestational diabetes mellitus, preterm birth, and differences on birth weight.

Methods:

A systematic literature search on PubMed, EBSCO-MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials databases was carried out to evaluate randomized controlled trial studies on the effects of oral vitamin D > 2000 IU/day versus ⩽ 2000 IU/day; and ⩽ 2000 IU/day versus placebo, on preeclampsia, gestational diabetes mellitus, preterm birth and birth weight. Risk ratio, mean difference, and 95% confidence interval were calculated.

Results:

There were a total of 27 randomized controlled trials selected. Maternal vitamin D supplementation > 2000 IU/day had a positive effect only on gestational diabetes mellitus (seven randomized controlled trials; risk ratio = 0.70, 95% confidence interval: 0.51–0.95, I2 = 0). Vitamin D supplementation ⩽ 2000 IU/day has reduced the risk of preeclampsia (three randomized controlled trials; risk ratio = 0.29, 95% confidence interval: 0.09–0.95, I2 = 0), with no significant difference when compared to > 2000 IU/day (eight randomized controlled trials; risk ratio = 0.80, 95% confidence interval: 0.51–1.24, I2 = 31). No difference in preterm birth risk and birth weight after vitamin D supplementation. The quality of evidence varies from moderate to very low certainty. The risk of preeclampsia and gestational diabetes mellitus after high-dose versus low-dose vitamin D supplementation was the ones with moderate certainty.

Conclusion:

Vitamin D supplementation > 2000 IU/day might be important to reduce the risk of gestational diabetes mellitus. Lower dose vitamin D supplementation (⩽ 2000 IU/day) seemed adequate to reduce the risk of preeclampsia, with no significant difference compared to the higher dose.

Potential Biomarkers, Risk Factors and their Associations with IgE-mediated Food Allergy in Early Life: A Narrative Review

Food allergy affects the quality of life of millions of people worldwide and presents a significant psychological and financial burden for both national and international public health. In the past few decades, the prevalence of allergic disease has been on the rise worldwide. Identified risk factors for food allergy include family history, mode of delivery, variations in infant feeding practices, prior diagnosis of other atopic diseases such as eczema, and social economic status. Identifying reliable biomarkers which predict the risk of developing food allergy in early life would be valuable in both preventing morbidity and mortality and by making current interventions available at the earliest opportunity. There is also the potential to identify new therapeutic targets. This narrative review provides details on the genetic, epigenetic, dietary and microbiome influences upon the development of food allergy and synthesizes the currently available data indicating potential biomarkers. While there is a large body of research evidence available within each field of potential risk factors, there are very limited number of studies which span multiple methodological fields, for example including immunology, microbiome, genetic/epigenetic factors and dietary assessment. We recommend that further collaborative research with detailed cohort phenotyping is required to identify biomarkers, and whether these vary between at-risk populations and the wider population. The low incidence of oral food challenge confirmed food allergy in the general population, and the complexities of designing nutritional intervention studies will provide challenges for researchers to address in generating high quality, reliable and reproducible research findings.

STATEMENT OF SIGNIFICANCE

Food allergy affects the quality of life of millions of people worldwide and presents a significant psychological and financial burden for both national and international public health. Identifying reliable biomarkers which predict the risk of developing food allergy would be valuable in both preventing morbidity and mortality and by making current interventions available at the earliest opportunity. This review provides details on the genetic, epigenetic, dietary and microbiome influences upon the development of food allergy. This helps in identifying reliable biomarkers to predict the risk of developing food allergy, which could be valuable in both preventing morbidity and mortality and by making interventions available at the earliest opportunity.

Maternal Nutritional Status and Development of Atopic Dermatitis in Their Offspring

Atopic dermatitis (AD) is the leading chronic skin inflammatory disease and the initial manifestation of atopic march. Available evidence supports the notion that primary prevention early in life leads to a decreased incidence of AD, thus possibly decreasing the subsequent occurrence of atopic march. Nutritional status is essential to a proper functioning immune system and is valued for its important role in AD. Essential nutrients, which include carbohydrates, proteins, lipids, vitamins, and minerals, are transferred from the mother to the fetus through the placenta during gestation. Various nutrients, such as polyunsaturated fatty acids (PUFAs) and vitamin D, were studied in relation to maternal status and offspring allergy. However, no strong evidence indicates that a single nutrient or food in mothers' diet significantly affects the risk of childhood AD. In the light of current evidence, mothers should not either increase nor avoid consuming these nutrients to prevent or ameliorate allergic diseases in their offspring. Each essential nutrient has an important role in fetal development, and current government recommendations suggest specific intake amounts for pregnant women. This review discusses evidence on how various nutrients, including lipids (monounsaturated fatty acids, PUFAs, saturated fatty acids, and short-chain fatty acids), carbohydrates (oligosaccharides and polysaccharides), proteins, vitamins (A, B, C, D, and E), and trace minerals (magnesium, iron, zinc, copper, selenium, and strontium) in maternal status are associated with the development of AD and their possible mechanisms.

EAACI guideline: Preventing the development of food allergy in infants and young children (2020 update)

BACKGROUND

This guideline from the European Academy of Allergy and Clinical Immunology (EAACI) recommends approaches to prevent the development of immediate-onset / IgE-mediated food allergy in infants and young children. It is an update of a 2014 EAACI guideline.

METHODS

The guideline was developed using the AGREE II framework and the GRADE approach. An international Task Force with representatives from 11 countries and different disciplinary and clinical backgrounds systematically reviewed research and considered expert opinion. Recommendations were created by weighing up benefits and harms, considering the certainty of evidence and examining values, preferences and resource implications. The guideline was peer-reviewed by external experts, and feedback was incorporated from public consultation.

RESULTS

All of the recommendations about preventing food allergy relate to infants (up to 1 year) and young children (up to 5 years), regardless of risk of allergy. There was insufficient evidence about preventing food allergy in other age groups. The EAACI Task Force suggests avoiding the use of regular cow's milk formula as supplementary feed for breastfed infants in the first week of life. The EAACI Task Force suggests introducing well-cooked, but not raw egg or uncooked pasteurized, egg into the infant diet as part of complementary feeding. In populations where there is a high prevalence of peanut allergy, the EAACI Task Force suggests introducing peanuts in an age-appropriate form as part of complementary feeding. According to the studies, it appears that the most effective age to introduce egg and peanut is from four to 6 months of life. The EAACI Task Force suggests against the following for preventing food allergy: (i) avoiding dietary food allergens during pregnancy or breastfeeding; and (ii) using soy protein formula in the first 6 months of life as a means of preventing food allergy. There is no recommendation for or against the following: use of vitamin supplements, fish oil, prebiotics, probiotics or synbiotics in pregnancy, when breastfeeding or in infancy; altering the duration of exclusive breastfeeding; and hydrolysed infant formulas, regular cow's milk-based infant formula after a week of age or use of emollients.

CONCLUSIONS

Key changes from the 2014 guideline include suggesting (i) the introduction of peanut and well-cooked egg as part of complementary feeding (moderate certainty of evidence) and (ii) avoiding supplementation with regular cow's milk formula in the first week of life (low certainty of evidence). There remains uncertainty in how to prevent food allergy, and further well-powered, multinational research using robust diagnostic criteria is needed.

Halting the March: Primary Prevention of Atopic Dermatitis and Food Allergies

Atopic dermatitis (AD) is one of the most common inflammatory skin conditions, affecting 15% to 30% of children and 2% to 10% of adults. Population-based studies suggest that having AD is associated with subsequent development of other atopic diseases, in what is known as the "atopic march." We will provide an overview of studies that investigate primary prevention strategies for the first 2 diseases in the march, namely, AD and food allergies (FA). These strategies include emollients, breastfeeding, microbial exposures, probiotics, vitamin D and UV light, water hardness, and immunotherapy. Some studies, including randomized controlled trials on emollients and microbial supplementation, have found encouraging results; however, the evidence remains limited and contradictory. With regard to breastfeeding, microbial and lifestyle exposures, vitamin D and UV light, water hardness, and immunotherapy, the lack of randomized controlled trials makes it difficult to draw definitive conclusions. Current American Academy of Pediatrics guidelines support the idea that breastfeeding for 3 to 4 months can decrease AD incidence in children less than 2 years old. Recommendations regarding a direct relationship between breastfeeding on FA, however, cannot be made because of insufficient data. Regarding microbial supplementation, most guidelines do not recommend probiotics or prebiotics for the purpose of preventing allergic diseases because of limited evidence. Before definitive conclusions can be made regarding these interventions, more well-designed, longitudinal, and randomized controlled trials, particularly in at-risk populations, are required.

Effect of Vitamin D Supplementation in Early Life on Children's Growth and Body Composition: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background: Vitamin D deficiency during pregnancy or infancy is associated with adverse growth in children. No systematic review has been conducted to summarize available evidence on the effect of vitamin D supplementation in pregnancy and infancy on growth and body composition in children. Objective: We aim to summarize the available evidence on the effect of vitamin D supplementation in pregnancy and infancy on child growth and body composition. Method: A systematic review and meta-analysis were performed on the effects of vitamin D supplementation during early life on children’s growth and body composition (bone, lean and fat). A literature search of randomized controlled trials (RCTs) was conducted to identify relevant studies on the effects of vitamin D supplementation during pregnancy and infancy on children’s body composition (bone, lean and fat) in PubMed, EMBASE and Cochrane Library from inception to 31 December 2020. A Cochrane Risk Assessment Tool was used for quality assessment. The comparison was vitamin D supplementation vs. placebo or standard care. Random-effects and fixed-effect meta-analyses were conducted. The effects are presented as mean differences (MDs) or risk ratios (RRs) with 95% confidence intervals (CIs). Results: A total of 3960 participants from eleven randomized controlled trials were eligible for inclusion. Vitamin D supplementation during pregnancy was associated with higher triceps skinfold thickness (mm) (MD 0.33, 95% CI, 0.12, 0.54; I² = 34%) in neonates. Vitamin D supplementation during pregnancy or infancy was associated with significantly increased length for age z-score in infants at 1 year of age (MD 0.29, 95% CI, 0.03, 0.54; I² = 0%), and was associated with lower body mass index (BMI) (kg/m²) (MD −0.19, 95% CI −0.34, −0.04; I² = 0%) and body mass index z-score (BMIZ) (MD −0.12, 95% CI −0.21, −0.04; I² = 0%) in offspring at 3–6 years of age. Vitamin D supplementation during early life was not observed to be associated with children’s bone, lean or fat mass. Conclusion: Vitamin D supplementation during pregnancy or infancy may be associated with reduced adiposity in childhood. Further large clinical trials of the effects of vitamin D supplementation on childhood body composition are warranted.

Association Between Vitamin D and Novel SARS-CoV-2 Respiratory Dysfunction - A Scoping Review of Current Evidence and Its Implication for COVID-19 Pandemic

OBJECTIVES

To assess the association between vitamin D deficiency and increased morbidity/mortality with COVID-19 respiratory dysfunction.

DESIGN

Scoping review.

DATA SOURCES

Ovid MEDLINE (1946 to 24 of April 2020) and PubMed (2020 to 17 of September 2020).

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

A search using the search terms: [(cholecalciferol or ergocalciferol or vitamin D2 or vitamin D3 or vitamin D or 25OHD) and (SARS-CoV-2 or coronavirus or COVID or betacoronavirus or MERS-CoV or SARS-CoV or respiratory infection or acute respiratory distress syndrome or ARDS)]m.p. was conducted on the 24/04/2020 (Search A) and 17/09/2020 (Search B).

RESULTS

91 studies were identified as being concerned with Acute Respiratory Infection (ARI)/Acute Respiratory Distress Syndrome (ARDS) and vitamin D, and 25 publications specifically explored the role of vitamin D deficiency in the development and progression of SARS-CoV-2/COVID-19 related ARDS. Search "A" identified three main themes of indirect evidence supporting such an association. Consistent epidemiological evidence exists linking low vitamin D levels to increased risk and severity of respiratory tract infections. We also report on plausible biological processes supporting such an association; and present weaker evidence supporting the benefit of vitamin D supplementation in reducing the risk and severity of ARIs. Uncertainty remains about what constitutes an appropriate dosing regimen in relation to reducing risk/severity of ARI/ARDS. More recent evidence (Search B) provided new insights into some direct links between vitamin D and COVID-19; with a number of cohort and ecological studies supporting an association with PCR-positivity for SARS-CoV-2 and vitamin D deficiency. The exact efficacy of the vitamin D supplementation for prevention of, or as an adjunct treatment for COVID-19 remains to be determined; but a number of randomized control trials (RCTs) currently underway are actively investigating these potential benefits.

CONCLUSION

Our rapid review of literature supports the need for observational studies with COVID-19 infected populations to measure and assess vitamin D levels in relation to risk/severity and outcomes; alongside RCTs designed to evaluate the efficacy of supplementation both in preventive and therapeutic contexts. The overlap in the vitamin D associated biological pathways with the dysregulation reported to drive COVID-19 outcomes warrants further investigation.

Prenatal vitamin D supplementation and child respiratory health: A systematic review and meta-analysis of randomized controlled trials

Background

Systematic review and meta-analyses of observational studies on maternal vitamin D status and risk of respiratory allergic conditions indicated that mothers who had supplementation during pregnancy could decrease the risk of recurrent wheeze or asthma in their offspring.

Objectives

We conducted this meta-analysis of Randomized Controlled Trials with the primary intention of detecting the effect of prenatal vitamin D supplementation on the offspring's asthma. Secondary outcomes under respiratory health include eczema, lower respiratory tract infections, Immunoglobulin E positive test, upper respiratory tract infections, and allergic rhinitis.

Methods

A comprehensive search of PubMed, ScienceDirect, Google Scholar, and Cochrane Library databases was performed to retrieve randomized controlled trials. Risk Ratio with 95% confidence intervals was computed from dichotomous data using a random-effects model, with I² >50% representing notable heterogeneity.

Results

Six clinical trials met the inclusion criteria, involving a total of 2898 subjects (1461 experimental group and 1437 control group). There was non-significant inverse relationship between vitamin D intake during pregnancy and the occurrence of asthma in offspring (pooled RR = 0.89, 95% CI = 0.69-1.15, I ²  = 46% and Z-static = 0.90, P-value = 0.37). There is no significant difference in the risk of assessed childhood respiratory problems due to maternal supplementation of vitamin D during pregnancy.

Conclusion and implications

Currently, there is no fertile evidence to promote vitamin D supplementation in pregnancy for childhood respiratory health. Future clinical trials should emphasize early initiation of vitamin D supplementation, consider 6 weeks to 6 months postnatal critical window for vitamin D deficiency for offspring, lower risk dose of vitamin D, and identify different phenotypes of asthma and response to vitamin D supplementation.

Dietary factors during pregnancy and atopic outcomes in childhood: A systematic review from the European Academy of Allergy and Clinical Immunology

RATIONALE

Allergic diseases are an increasing public health concern, and early life environment is critical to immune development. Maternal diet during pregnancy has been linked to offspring allergy risk. In turn, maternal diet is a potentially modifiable factor, which could be targeted as an allergy prevention strategy. In this systematic review, we focused on non-allergen-specific modifying factors of the maternal diet in pregnancy on allergy outcomes in their offspring.

METHODS

We undertook a systematic review of studies investigating the association between maternal diet during pregnancy and allergic outcomes (asthma/wheeze, hay fever/allergic rhinitis/seasonal allergies, eczema/atopic dermatitis (AD), food allergies, and allergic sensitization) in offspring. Studies evaluating the effect of food allergen intake were excluded. We searched three bibliographic databases (MEDLINE, EMBASE, and Web of Science) through February 26, 2019. Evidence was critically appraised using modified versions of the Cochrane Collaboration Risk of Bias tool for intervention trials and the National Institute for Clinical Excellence methodological checklist for cohort and case-control studies and meta-analysis performed from RCTs.

RESULTS

We identified 95 papers: 17 RCTs and 78 observational (case-control, cross-sectional, and cohort) studies. Observational studies varied in design and dietary intakes and often had contradictory findings. Based on our meta-analysis, RCTs showed that vitamin D supplementation (OR: 0.72; 95% CI: 0.56-0.92) is associated with a reduced risk of wheeze/asthma. A positive trend for omega-3 fatty acids was observed for asthma/wheeze, but this did not reach statistical significance (OR: 0.70; 95% CI: 0.45-1.08). Omega-3 supplementation was also associated with a non-significant decreased risk of allergic rhinitis (OR: 0.76; 95% CI: 0.56-1.04). Neither vitamin D nor omega-3 fatty acids were associated with an altered risk of AD or food allergy.

CONCLUSIONS

Prenatal supplementation with vitamin D may have beneficial effects for prevention of asthma. Additional nutritional factors seem to be required for modulating the risk of skin and gastrointestinal outcomes. We found no consistent evidence regarding other dietary factors, perhaps due to differences in study design and host features that were not considered. While confirmatory studies are required, there is also a need for performing RCTs beyond single nutrients/foods.

Preventing food allergy in infancy and childhood: Systematic review of randomised controlled trials

BACKGROUND

This systematic review of ways to prevent immediate-onset/IgE-mediated food allergy will inform guidelines by the European Academy of Allergy and Immunology (EAACI).

METHODS

The GRADE approach was used. Eleven databases were searched from 1946 to October 2019 for randomized controlled trials (and large prospective cohort studies in the case of breastfeeding). The studies included heterogeneous interventions, populations, and outcomes and so were summarized narratively.

RESULTS

Forty-six studies examined interventions to reduce the risk of food allergy in infancy (up to 1 year) or early childhood. The following interventions for pregnant or breastfeeding women and/or infants may have little to no effect on preventing food allergy, but the evidence is very uncertain: dietary avoidance of food allergens, vitamin supplements, fish oil, probiotics, prebiotics, synbiotics, and emollients. Breastfeeding, hydrolyzed formulas, and avoiding cow's milk formula may not reduce the risk of cow's milk protein allergy; however, temporary supplementation with cow's milk formula in the first week of life may increase the risk of cow's milk allergy. Introducing well-cooked egg, but not pasteurized raw egg, from 4 to 6 months probably reduces the risk of hen's egg allergy. Introducing regular peanut consumption into the diet of an infant at increased risk beginning from 4 to 11 months probably results in a large reduction in peanut allergy in countries with a high prevalence. These conclusions about introducing peanut are based on moderate certainty evidence, from single trials in high-income countries.

CONCLUSIONS

Sixty percent of the included studies were published in the last 10 years, but much still remains to be understood about preventing food allergy. In particular, there is a need to validate the potential benefits of early introduction of food allergens in a wider range of populations.

Null association between serum 25-hydroxyvitamin D levels with allergic rhinitis, allergic sensitization and non-allergic rhinitis: A Mendelian randomization study

BACKGROUND

Previous observational studies have not found a conclusive association between serum 25-hydroxyvitamin D (25(OH)D) levels and allergic rhinitis (AR) or allergic sensitization (AS).

OBJECTIVE

To investigate a causal association between 25(OH)D levels with risk of AR and AS, using a two-sample Mendelian randomization (MR) approach.

METHODS

Seven single nucleotide polymorphisms (SNPs), previously shown to be associated with serum 25(OH)D levels, were identified as instrumental variables. The primary outcome was AR, and the secondary outcomes were AS and non-allergic rhinitis (NAR). The genome-wide association (GWA) summary statistics of the outcomes were obtained from two cohort studies (EAGLE Consortium and UK Biobank). An MR analysis with random-effects inverse-variance weighted method was performed as the primary analysis to estimate overall effect size (odds ratio [OR] and 95% confidence interval [CI]). Sensitivity analysis using weighted median method and MR-Egger regression method was conducted. A subgroup analysis based on 25(OH)D synthesis-related SNPs was further applied.

RESULTS

Serum 25(OH)D levels were not causally associated with risk of AR (OR: 0.960; 95% CI: 0.779-1.184), AS (OR: 1.059; 95% CI: 0.686 to 1.634) or NAR (OR: 0.937; 95% CI: 0.588-1.491). Subgroup analysis also showed null association between 25(OH)D synthesis-related SNPs and the outcomes. Sensitivity analyses yielded similar results.

CONCLUSIONS AND CLINICAL RELEVANCE

This MR study found no evidence supporting a causal association between serum 25(OH)D levels and risk of AR, AS and NAR in European-ancestry population. This argues against the previous postulation that vitamin D supplementation is effective in prevention of allergic diseases.

Maternal Vitamin D Levels during Late Pregnancy and Risk of Allergic Diseases and Sensitization during the First Year of Life-A Birth Cohort Study

Allergic diseases are the most common chronic illness in childhood. Findings from developed countries have reported associations between Vitamin D levels during pregnancy and offspring allergy risk. This prospective cohort study aimed to determine the associations between maternal Vitamin D levels during late pregnancy and allergic diseases in Malaysian infants during the first year of life. Serum 25(OH)D concentrations of 380 pregnant women in the third trimester were measured using a chemiluminescent immunoassay. Children's allergic outcomes were assessed at 3, 6, and 12 months based on parental reports. Specific IgE antibodies against food and inhalant allergens were measured in infants at 12 months of age. A total of 43.2% pregnant women were Vitamin D deficient (<30 nmol/L) and 56.8% were nondeficient (≥30 nmol/L). A total of 27.6% of the infants had eczema, 6.1% had wheeze, 27.4% had food sensitization, 10.8% had inhalant allergen sensitization, and 3.8% had IgE-mediated food allergy during the first year of life. Compared with the nondeficient group, maternal Vitamin D deficiency in late pregnancy was not associated with any allergic outcomes after adjustment for potential confounding factors. In conclusion, the present study does not support an association between maternal Vitamin D levels in late pregnancy and allergic outcomes during the first year of life.

In "High-Risk" Infants with Sufficient Vitamin D Status at Birth, Infant Vitamin D Supplementation Had No Effect on Allergy Outcomes: A Randomized Controlled Trial

Lower vitamin D status at birth and during infancy has been associated with increased incidence of eczema and food allergies. The aim of this study was to investigate the effect of early infancy vitamin D supplementation on allergic disease outcomes in infants at “hereditary risk” of allergic disease, but who had sufficient vitamin D levels at birth. Here, we report the early childhood follow-up to 2.5 years of age of “high-risk” infants who participated in a double-blinded, randomized controlled trial. For inclusion in this trial, late gestation (36–40 weeks) maternal 25-hydroxyvitamin D levels needed to be ≥50 nmol/L. Infants were randomized to either oral vitamin D supplementation of 400 IU/day (n = 97) or a placebo (n = 98) for the first six months of life. Vitamin D levels and allergic disease outcomes were followed up. There were no statistically significant differences in incidence of any medically diagnosed allergic disease outcomes or allergen sensitization rates between the vitamin D-supplemented and placebo groups at either 1 year or at 2.5 years of age. In conclusion, for “allergy high-risk” infants who had sufficient vitamin D status at birth, early infancy oral vitamin D supplementation does not appear to reduce the development of early childhood allergic disease.

Dietary Interventions and Nutritional Factors in the Prevention of Pediatric Asthma

Asthma is the most frequent chronic disease in children, and its pathogenesis involves genetic, epigenetic, and environmental factors. The rapid rise in the prevalence of asthma registered over the last few decades has stressed the need to identify the environmental and modifiable factors associated with the development of the disease. In particular, there is increasing interest in the role of modifiable nutritional factors specific to both the prenatal and post-natal early life as, during this time, the immune system is particularly vulnerable to exogenous interferences. Several dietary factors, including maternal diet during pregnancy, the duration of breastfeeding, the use of special milk formulas, the timing of the introduction of complementary foods, and prenatal and early life supplementation with vitamins and probiotics/prebiotics, have been addressed as potential targets for the prevention of asthma. In this review, we outline recent findings on the potential role of prenatal and perinatal dietary and nutritional interventions for the primary prevention of pediatric asthma. Moreover, we addressed unmet needs and areas for future research in the prevention of childhood-onset asthma.

The effect of an educational program for pregnant women to prevent allergic diseases in infants: study protocol for a randomized controlled trial

BACKGROUND

Allergic diseases in infants have dramatically increased in developed countries during the past few decades. To date, extensive research has been done on risk factors for allergies in infancy, and preventive measures against them. However, the effect of the primary approach to preventing infantile allergy is still limited. The aim of this trial is to evaluate whether prenatal education interventions, including the latest public research results on allergic diseases, prevent the onset of infant allergies.

METHODS/DESIGN

We designed a randomized controlled, two-arm (standard prenatal education vs our education), parallel-group, assessor-blind trial. A sample of 120 pregnant women will be recruited at Chiba Aiyu-kai Kinen Hospital and allocation is by computer-generated randomization. Pregnant women in the intervention arm participate in the childbirth education program established by the specialist and a pediatric allergy educator. The program was developed based on evidences supporting interventions on primary prevention, which are suggested to be beneficial to infantile allergies in recent studies. The primary objective of the study is to determine whether it is possible to establish effective behaviors for allergy prevention in early infancy in the children of pregnant women who participate in an educational program developed by pediatric allergy specialists. Four months after birth, their behaviors will be compared against those of pregnant women who did not participate in the program.

DISCUSSION

Allergies are common in many individuals worldwide, and can be present from babyhood through the person's lifetime. One of the strong points of this study is that it should provide pregnant women with accumulated information on preventive knowledge against allergy, that can be effective in some cases, and that women can apply a combination of these behaviors before and after pregnancy. The results of our program will be publicized to help change the behaviors of mothers, and, if the program is effective, for preventing allergies in infants, it will be disclosed worldwide as a new preventive strategy for allergy in infants.

TRIAL REGISTRATION

UMIN-CTR, ID: UMIN000034730 Retrospectively registered on 1 December 2018.

Regimens of vitamin D supplementation for women during pregnancy

BACKGROUND

Vitamin D deficiency during pregnancy increases the risk of pre-eclampsia, gestational diabetes, preterm birth, and low birthweight. In a previous Cochrane Review we found that supplementing pregnant women with vitamin D alone compared to no vitamin D supplementation may reduce the risk of pre-eclampsia, gestational diabetes, and low birthweight and may increase the risk of preterm births if it is combined with calcium. However the effects of different vitamin D regimens are not yet clear.

OBJECTIVES

To assess the effects and safety of different regimens of vitamin D supplementation alone or in combination with calcium or other vitamins, minerals or nutrients during pregnancy, specifically doses of 601 international units per day (IU/d) or more versus 600 IU/d or less; and 4000 IU/d or more versus 3999 IU/d or less.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (12 July 2018), and the reference lists of retrieved studies.

SELECTION CRITERIA

Randomised trials evaluating the effect of different vitamin D regimens (dose, frequency, duration, and time of commencement of supplementation during pregnancy), alone or in combination with other nutrients on pregnancy and neonatal health outcomes. We only included trials that compared 601 IU/d or more versus 600 IU/d or less and 4000 IU/d or more versus 3999 IU/d or less. We did not include in the analysis groups that received no vitamin D, as that comparison is assessed in another Cochrane Review.

DATA COLLECTION AND ANALYSIS

Two review authors independently: i) assessed the eligibility of studies against the inclusion criteria; ii) extracted data from included studies, and iii) assessed the risk of bias of the included studies. Our primary maternal outcomes were: pre-eclampsia, gestational diabetes, and any adverse effects; our primary infant outcomes were preterm birth and low birthweight. Data were checked for accuracy. The certainty of the evidence was assessed using the GRADE approach.

MAIN RESULTS

In this review, we included data from 30 trials involving 7289 women. We excluded 11 trials, identified 16 ongoing/unpublished trials and two trials are awaiting classification. Overall risk of bias for the trials was mixed.Comparison 1. 601 IU/d or more versus 600 IU/d or less of vitamin D alone or with any other nutrient (19 trials; 5214 participants)Supplementation with 601 IU/d or more of vitamin D during pregnancy may make little or no difference to the risk of pre-eclampsia (risk ratio (RR) 0.96, 95% confidence interval (CI) 0.65 to 1.42); 5 trials; 1553 participants,low-certainty evidence), may reduce the risk of gestational diabetes (RR 0.54, 95% CI 0.34 to 0.86; 5 trials; 1846 participants; moderate-certainty evidence), may make little or no difference to the risk of preterm birth (RR 1.25, 95% CI 0.92 to 1.69; 4 trials; 2294 participants; low-certainty evidence); and may make little or no difference to the risk of low birthweight (RR 0.90, 95% CI 0.66 to 1.24; 4 trials; 1550 participants; very low-certainty evidence) compared to women receiving 600 IU/d or less.Comparison 2. 4000 IU or more versus 3999 IU or less of vitamin D alone (15 trials; 4763 participants)Supplementation with 4000 IU/d or more of vitamin D during pregnancy may make little or no difference to the risk of: pre-eclampsia (RR 0.87, 95% CI 0.62 to 1.22; 4 trials, 1903 participants, low-certainty evidence); gestational diabetes (RR 0.89, 95% CI 0.56 to 1.42; 5 trials, 2276 participants; low-certainty evidence); preterm birth (RR 0.85, 95% CI 0.64 to 1.12; 6 trials, 2948 participants, low-certainty evidence); and low birthweight (RR 0.92, 95% CI 0.49 to 1.70; 2 trials; 1099 participants; low-certainty evidence) compared to women receiving 3999 IU/d or less.Adverse events (such as hypercalcaemia, hypocalcaemia, hypercalciuria, and hypovitaminosis D) were reported differently in most trials; however, in general, there was little to no side effects reported or similar cases between groups.

AUTHORS' CONCLUSIONS

Supplementing pregnant women with more than the current vitamin D recommendation may reduce the risk of gestational diabetes; however, it may make little or no difference to the risk of pre-eclampsia, preterm birth and low birthweight. Supplementing pregnant women with more than the current upper limit for vitamin D seems not to increase the risk of the outcomes evaluated. In general, the GRADE was considered low certainty for most of the primary outcomes due to serious risk of bias and imprecision of results. With respect to safety, it appears that vitamin D supplementation is a safe intervention during pregnancy, although the parameters used to determine this were either not reported or not consistent between trials. Future trials should be consistent in their reports of adverse events. There are 16 ongoing trials that when published, will increase the body of knowledge.

Vitamin D supplementation for women during pregnancy

BACKGROUND

Vitamin D supplementation during pregnancy may be needed to protect against adverse pregnancy outcomes. This is an update of a review that was first published in 2012 and then in 2016.

OBJECTIVES

To examine whether vitamin D supplementation alone or in combination with calcium or other vitamins and minerals given to women during pregnancy can safely improve maternal and neonatal outcomes.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register (12 July 2018), contacted relevant organisations (15 May 2018), reference lists of retrieved trials and registries at clinicaltrials.gov and WHO International Clinical Trials Registry Platform (12 July 2018). Abstracts were included if they had enough information to extract the data.

SELECTION CRITERIA

Randomised and quasi-randomised trials evaluating the effect of supplementation with vitamin D alone or in combination with other micronutrients for women during pregnancy in comparison to placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Two review authors independently i) assessed the eligibility of trials against the inclusion criteria, ii) extracted data from included trials, and iii) assessed the risk of bias of the included trials. The certainty of the evidence was assessed using the GRADE approach.

MAIN RESULTS

We included 30 trials (7033 women), excluded 60 trials, identified six as ongoing/unpublished trials and two trials are awaiting assessments.Supplementation with vitamin D alone versus placebo/no interventionA total of 22 trials involving 3725 pregnant women were included in this comparison; 19 trials were assessed as having low-to-moderate risk of bias for most domains and three trials were assessed as having high risk of bias for most domains. Supplementation with vitamin D alone during pregnancy probably reduces the risk of pre-eclampsia (risk ratio (RR) 0.48, 95% confidence interval (CI) 0.30 to 0.79; 4 trials, 499 women, moderate-certainty evidence) and gestational diabetes (RR 0.51, 95% CI 0.27 to 0.97; 4 trials, 446 women, moderate-certainty evidence); and probably reduces the risk of having a baby with low birthweight (less than 2500 g) (RR 0.55, 95% CI 0.35 to 0.87; 5 trials, 697 women, moderate-certainty evidence) compared to women who received placebo or no intervention. Vitamin D supplementation may make little or no difference in the risk of having a preterm birth < 37 weeks compared to no intervention or placebo (RR 0.66, 95% CI 0.34 to 1.30; 7 trials, 1640 women, low-certainty evidence). In terms of maternal adverse events, vitamin D supplementation may reduce the risk of severe postpartum haemorrhage (RR 0.68, 95% CI 0.51 to 0.91; 1 trial, 1134 women, low-certainty evidence). There were no cases of hypercalcaemia (1 trial, 1134 women, low-certainty evidence), and we are very uncertain as to whether vitamin D increases or decreases the risk of nephritic syndrome (RR 0.17, 95% CI 0.01 to 4.06; 1 trial, 135 women, very low-certainty evidence). However, given the scarcity of data in general for maternal adverse events, no firm conclusions can be drawn.Supplementation with vitamin D and calcium versus placebo/no interventionNine trials involving 1916 pregnant women were included in this comparison; three trials were assessed as having low risk of bias for allocation and blinding, four trials were assessed as having high risk of bias and two had some components having a low risk, high risk, or unclear risk. Supplementation with vitamin D and calcium during pregnancy probably reduces the risk of pre-eclampsia (RR 0.50, 95% CI 0.32 to 0.78; 4 trials, 1174 women, moderate-certainty evidence). The effect of the intervention is uncertain on gestational diabetes (RR 0.33,% CI 0.01 to 7.84; 1 trial, 54 women, very low-certainty evidence); and low birthweight (less than 2500 g) (RR 0.68, 95% CI 0.10 to 4.55; 2 trials, 110 women, very low-certainty evidence) compared to women who received placebo or no intervention. Supplementation with vitamin D and calcium during pregnancy may increase the risk of preterm birth < 37 weeks in comparison to women who received placebo or no intervention (RR 1.52, 95% CI 1.01 to 2.28; 5 trials, 942 women, low-certainty evidence). No trial in this comparison reported on maternal adverse events.Supplementation with vitamin D + calcium + other vitamins and minerals versus calcium + other vitamins and minerals (but no vitamin D)One trial in 1300 participants was included in this comparison; it was assessed as having low risk of bias. Pre-eclampsia was not assessed. Supplementation with vitamin D + other nutrients may make little or no difference in the risk of preterm birth < 37 weeks (RR 1.04, 95% CI 0.68 to 1.59; 1 trial, 1298 women, low-certainty evidence); or low birthweight (less than 2500 g) (RR 1.12, 95% CI 0.82 to 1.51; 1 trial, 1298 women, low-certainty evidence). It is unclear whether it makes any difference to the risk of gestational diabetes (RR 0.42, 95% CI 0.10 to 1.73) or maternal adverse events (hypercalcaemia no events; hypercalciuria RR 0.25, 95% CI 0.02 to 3.97; 1 trial, 1298 women,) because the certainty of the evidence for both outcomes was found to be very low.

AUTHORS' CONCLUSIONS

We included 30 trials (7033 women) across three separate comparisons. Our GRADE assessments ranged from moderate to very low, with downgrading decisions based on limitations in study design, imprecision and indirectness.Supplementing pregnant women with vitamin D alone probably reduces the risk of pre-eclampsia, gestational diabetes, low birthweight and may reduce the risk of severe postpartum haemorrhage. It may make little or no difference in the risk of having a preterm birth < 37 weeks' gestation. Supplementing pregnant women with vitamin D and calcium probably reduces the risk of pre-eclampsia but may increase the risk of preterm births < 37 weeks (these findings warrant further research). Supplementing pregnant women with vitamin D and other nutrients may make little or no difference in the risk of preterm birth < 37 weeks' gestation or low birthweight (less than 2500 g). Additional rigorous high quality and larger randomised trials are required to evaluate the effects of vitamin D supplementation in pregnancy, particularly in relation to the risk of maternal adverse events.

High-Dose Vitamin D Supplementation Does Not Prevent Allergic Sensitization of Infants

OBJECTIVE

To investigate the effect of vitamin D supplementation dose on allergic sensitization and allergic diseases in infants, and to evaluate whether vitamin D status in pregnancy and at birth are associated with infant allergy outcomes.

STUDY DESIGN

Altogether, 975 infants participated in a randomized, controlled trial of daily vitamin D supplementation of 10 μg (400 IU) or 30 μg (1200 IU) from the age of 2 weeks. At 12 months of age, food and aeroallergen IgE antibodies were measured, and the occurrence of allergic diseases and wheezing were evaluated.

RESULTS

We found no differences between the vitamin D supplementation groups in food (OR, 0.98; 95% CI, 0.66-1.46) or aeroallergen sensitization at 12 months (OR, 0.76; 95% CI,0.34-1.71). Allergic diseases or wheezing did not differ between groups, except for milk allergy which occurred more often in infants administered 30 μg vitamin D compared with the 10 μg dose (OR, 2.23; 95% CI, 1.00-4.96). Infants with high cord blood 25-hydroxyvitamin D (≥100 nmol/L) had a higher risk of food allergen sensitization compared with those with lower 25(OH)D concentration (75-99.9 nmol/L; OR, 2.00; 95% CI, 1.19-3.39).

CONCLUSIONS

High-dose vitamin D supplementation did not prevent allergic sensitization, allergic diseases, or wheezing during the first year of life. In contrast, we observed an increased risk of milk allergy in infants randomized to higher vitamin D supplementation, and an increased risk of allergic sensitization in infants with high cord blood vitamin D status, indicating a possible adverse effect of high concentrations of vitamin D.

Effects of Vitamin D Supplementation During Pregnancy on Birth Size: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

During pregnancy, vitamin D supplementation may be a feasible strategy to help prevent low birthweight (LBW) and small for gestational age (SGA) births. However, evidence from randomized controlled trials (RCTs) is inconclusive, probably due to heterogeneity in study design and type of intervention. A systematic literature search in the PubMed-Medline, EMBASE, and Cochrane Central Register of Controlled Trials databases was carried out to evaluate the effects of oral vitamin D supplementation during pregnancy on birthweight, birth length, head circumference, LBW, and SGA. The fixed-effects or random-effects models were used to calculate mean difference (MD), risk ratio (RR), and 95% Confidence Interval (CI). On a total of 13 RCTs, maternal vitamin D supplementation had a positive effect on birthweight (12 RCTs; MD = 103.17 g, 95% CI 62.29⁻144.04 g), length (6 RCTs; MD = 0.22 cm, 95% CI 0.11⁻0.33 cm), and head circumference (6 RCTs; MD:0.19 cm, 95% CI 0.13⁻0.24 cm). In line with these findings, we also demonstrated that maternal vitamin D supplementation reduced the risk of LBW (3 RCTs; RR = 0.40, 95% CI 0.22⁻0.74) and SGA (5 RCTS; RR = 0.69, 95% CI 0.51⁻0.92). The present systematic review and meta-analysis confirmed the well-established effect of maternal vitamin D supplementation on birth size. However, further research is required to better define risks and benefits associated with such interventions and the potential implications for public health.

Primary Prevention of Food Allergy

PURPOSE OF REVIEW

The goal of this review is to present an updated summary of the various approaches to prevent childhood food allergies and report recent advances in potential prevention trials for food allergy.

RECENT FINDINGS

Several approaches related to maternal dietary supplementation as well as infant GI-based supplementation have been tried and are the subject of ongoing clinical investigation. The prevalence of food allergy appears to be increasing but several, varied approaches to prevention are being actively pursued such that an effective strategy may not be too far in the future.

Vitamin D supplementation during pregnancy and the risk of wheezing in offspring: a systematic review and dose-response meta-analysis

Background: In the past few years, growing evidence supports a preventive role of vitamin D supplementation during pregnancy for wheezing or asthma in offspring. However, the optimal dose of vitamin D intake is unclear. We conducted a meta-analysis to examine the linear and nonlinear dose-response pattern of vitamin D intake during pregnancy and asthma or wheezing in offspring. Questions/purposes: The purpose of this study was to answer the following question: Which dose of vitamin D is more effective in preventing wheezing in offspring? Method: We identified relevant studies by searching PubMed, EMBASE and CENTRAL up to December 2017 and by hand-searching reference lists. Meta-analysis and subgroup analysis were performed. Fixed or random effects model linear trends analyses were conducted based on the heterogeneity test. Then, if the data did not show linear trends, we considered a nonlinear trend analysis instead. Results: A total of 6068 participants were included in the study. Our analysis showed an inverse relationship between the intake of vitamin D during pregnancy and the occurrence of wheezing in offspring (pooled OR = 0.68, 95% CI = 0.55-0.83, I² =  24%, Z statistic = 3.64, p < 0.01). We found a nonlinear U-shaped association between vitamin D supplementation during pregnancy and asthma or wheezing in offspring, with the lowest risk at approximately 800 IU/d. Publication bias was shown in a funnel plot without Egger's test. Conclusions: Vitamin D intake during pregnancy is inversely related to wheezing or asthma in offspring. Furthermore, the trend analysis indicates that offspring may benefit from approximately 800 IU/d vitamin D intake during pregnancy.

Direct infant UV light exposure is associated with eczema and immune development

BACKGROUND

Suboptimal vitamin D levels during critical periods of immune development have emerged as an explanation for higher rates of allergic diseases associated with industrialization and residing at higher latitudes.

OBJECTIVE

We sought to determine the effects of early postnatal vitamin D supplementation on infant eczema and immune development.

METHODS

By using a double-blind randomized controlled trial, newborn infants were randomized to receive vitamin D supplementation (400 IU/d) or a placebo until 6 months of age. Some infants also wore personal UV dosimeters to measure direct UV light (290-380 nm) exposure. Infant vitamin D levels were measured at 3 and 6 months of age. Eczema, wheeze, and immune function outcomes were assessed at 6 months of age.

RESULTS

At 3 (P < .01) and 6 (P = .02) months of age, vitamin D levels were greater for the vitamin D-supplemented group than the placebo group, but there was no difference in eczema incidence between groups. Infants with eczema were found to have had less UV light exposure (median, 555 Joules per square meter [J/m²; interquartile range, 322-1210 J/m²]) compared with those without eczema (median, 998 J/m² [interquartile range, 676-1577 J/m²]; P = .02). UV light exposure was also inversely correlated with IL-2, GM-CSF, and eotaxin production to Toll-like receptor ligands.

CONCLUSION

This study is the first to demonstrate an association between greater direct UV light exposures in early infancy with lower incidence of eczema and proinflammatory immune markers by 6 months of age. Our findings indicate that UV light exposure appears more beneficial than vitamin D supplementation as an allergy prevention strategy in early life.

Prenatal Diet and the Development of Childhood Allergic Diseases: Food for Thought

PURPOSE OF REVIEW

The development of allergic disease is shaped by genetics and the environment, including diet. Many studies suggest a role for maternal diet during pregnancy. In this article, we discuss potential mechanisms by which specific nutrients, particular foods, and dietary patterns may influence allergic disease development and review studies examining the relationship between prenatal diet and the risk of childhood allergy.

RECENT FINDINGS

The combination of in utero exposures and genetic predisposition may contribute to the development of allergic disease by altering immune and organ development. Inflammation predominates in the first and third trimesters whereas the second trimester is characterized by anti-inflammatory and Th2 immune responses. Maternal dietary exposures during pregnancy may interact with inherited genetic risk factors influence immune system development. There are varied results regarding the impact of maternal prenatal diet on the development of childhood allergies. Well-designed randomized controlled studies are needed to clarify this area.

The Implications of Vitamin D Status During Pregnancy on Mother and her Developing Child

Pregnancy is a time of tremendous growth and physiological changes for mother and her developing fetus with lifelong implications for the child. The concert of actions that must occur so mother does not reject the foreign tissue of the fetus is substantial. There must be exquisite balance between maternal tolerance to these foreign proteins of paternal origin but also immune surveillance and function such that the mother is not immunocompromised. When this process goes awry, the mother may experience such pregnancy complications as preeclampsia and infections. Vitamin D deficiency affects these processes. Controversy continues with regard to the optimal daily intake of vitamin D, when sunlight exposure should be taken into account, and how to define sufficiency during such vulnerable and critical periods of development. The importance of vitamin D supplementation during pregnancy in preventing some of the health risks to the mother and fetus appears linked to achieving 25(OH)D concentrations >40 ng/mL, the beginning point of the plateau where conversion of the vitamin D metabolite 25(OH)D, the pre-hormone, to 1,25(OH)2D, the active hormone, is optimized. Throughout pregnancy, the delivery of adequate vitamin D substrate-through sunlight or supplement-is required to protect both mother and fetus, and when in sufficient supply, favorably impacts the epigenome of the fetus, and in turn, long term health. There is a growing need for future research endeavors to focus not only on critical period(s) from pre-conception through pregnancy, but throughout life to prevent certain epigenetic changes that adversely affect health. There is urgency based on emerging research to correct deficiency and maintain optimal vitamin D status. The impact of vitamin D and its metabolites on genetic signaling during pregnancy in both mother and fetus is an area of great activity and still in its early stages. While vitamin D repletion during pregnancy minimizes the risk of certain adverse outcomes (e.g., preterm birth, asthma, preeclampsia, and gestational diabetes), the mechanisms of how these processes occur are not fully understood. As we intensify our research efforts in these areas. it is only a matter of time that such mechanisms will be defined.

Early life vitamin D status and asthma and wheeze: a systematic review and meta-analysis

BACKGROUND

Vitamin D deficiency has been linked to an increased risk of asthma. This study aimed to quantify the effect of early life vitamin D status on asthma and wheeze later in life.

METHODS

PubMed, Embase, CINAHL, and CNKI databases, the Cochrane Central Register of Controlled Trials, and Google Scholar were searched up to July 2017. We included randomized controlled trials (RCTs) and cohort studies with vitamin D level in blood (maternal or cord or infant) or intake (maternal intake during pregnancy or infant intake) and asthma and/or wheeze. Two reviewers independently extracted data. Fixed- and random-effects models were used to summarize the risk estimates of comparisons between highest vs. lowest vitamin D categories.

RESULTS

Of the 1485 studies identified, three RCTs and 33 cohort studies were included. We did not include the RCTs (1619 participants) in the meta-analysis as the comparators and outcome definitions were heterogenous. Three RCTs reported a non-statistically significant effect of vitamin D supplementation during pregnancy on offspring wheeze/asthma at 3 years of age. Pooled estimates of cohort studies suggest no association between antenatal blood vitamin D levels or vitamin D intake and offspring asthma assessed either > 5 years or ≤ 5 years. The estimate for blood vitamin D remained unchanged when two studies assessing asthma in adulthood were excluded, but a significant inverse association emerged between vitamin D intake and childhood asthma. We found no association between antenatal vitamin D level and wheeze. On the other hand, vitamin D intake during pregnancy may have a protective effect against wheeze.

CONCLUSIONS

The pooled estimates from cohort studies show no association between antenatal blood vitamin D level and asthma/wheeze in later life. Whereas, the pooled estimates from cohort studies suggest that antenatal vitamin D intake may have an effect on childhood asthma > 5 years or childhood wheeze. The inconsistent results from studies assessing vitamin D either in blood or intake may be explained by previously reported non-linear association between blood vitamin D3 and childhood asthma. Further trials with enough power and longer follow-up time should be conducted to confirm the results.

Relation of Prenatal Air Pollutant and Nutritional Exposures with Biomarkers of Allergic Disease in Adolescence

Prenatal exposures may be critical for immune system development, with consequences for allergic disease susceptibility. We examined associations of prenatal exposures (nutrient intakes and air pollutants) with allergic disease biomarkers in adolescence. We used data from 857 mother-child pairs in Project Viva, a Massachusetts-based pre-birth cohort. Outcomes of interest at follow-up (median age 12.9 years) were fractional exhaled nitric oxide (FeNO) and total serum IgE. We applied Bayesian Kernel Machine Regression analyses to estimate multivariate exposure-response functions, allowing for exposure interactions. Exposures were expressed as z-scores of log-transformed data and we report effects in % change in FeNO or IgE z-score per increase in exposure from the 25th to 75th percentile. FeNO levels were lower with higher intakes of prenatal vitamin D (-16.15%, 95% CI: -20.38 to -2.88%), folate from foods (-3.86%, 95% CI: -8.33 to 0.83%) and n-3 PUFAs (-9.21%, 95% CI -16.81 to -0.92%). Prenatal air pollutants were associated with higher FeNO and IgE, with the strongest associations detected for PM2.5 with IgE (25.6% increase, 95% CI 9.34% to 44.29%). We identified a potential synergistic interaction (p = 0.02) between vitamin E (food + supplements) and PM2.5; this exposure combination was associated with further increases in FeNO levels.