Towards prevention of vitamin D deficiency and beyond: knowledge gaps and research needs in vitamin D nutrition and public health

Seasonal variation of total and bioavailable 25-hydroxyvitamin D [25(OH)D] in the healthy adult Slovenian population

Objective: The aim of our study was to compare the total 25(OH)D fraction, the bioavailable vitamin fraction, and the free vitamin D fraction in spring and fall in a group of healthy individuals. Methods: In our study, we collected blood samples from healthy participants at the end of both summer and winter, and measured serum levels of albumin, DBP, and 25(OH)D. Utilizing these data, we calculated the percentage of free and bioavailable vitamin D. Our cohort comprised 87 participants, with a male-to-female ratio of 14:73, aged 35.95 ± 12.55 years, ranging from 19 to 70 years. We employed the chemiluminescence method to determine the vitamin 25(OH)D levels, the ELISA method was utilized to determine DBP levels, the albumin BCP Assay was performed using the ADVIA biochemical analyzer (Siemens) and an online calculator was used to determine the free and bioavailable 25(OH)D levels. Results: Our findings indicate significantly lower 25(OH)D levels in winter (44.13 ± 17.82 nmol/L) compared to summer (74.97 ± 22.75 nmol/L; p < 0.001). For vitamin D binding protein there was no significant difference from summer (236.2 ± 164.39 mg/L) to winter (239.86 ± 141.9 mg/L; p = 0.77), albumin levels were significantly higher in summer (49.37 ± 4.15 g/L vs. 47.97 ± 3.91 g/L, p = 0.01), but the magnitude of the change may not be large enough to be solely responsible for the stability of vitamin D levels throughout the year. In the winter season a significantly lower calculated bioavailable 25(OH)D vitamin (7.45 ± 5.66 nmol/L against 13.11 ± 8.27 nmol/L; p < 0.001) was observed, and the free fraction also showed a significant decrease (17.3 ± 12.9 pmol/L versus 29.7 ± 19.1 pmol/L; p < 0.0001). We observed a moderately positive correlation between 25(OH)D and bioavailable percentage in winter (r = 0.680; p < 0.001), in contrast with a lower positive association in summer (r = 0.343; p < 0.001). Conclusion: Our data suggest a positive correlation between total and bioavailable 25(OH)D levels. In addition to the statistically significant variation in 25(OH)D between the two observation periods, there was an additional variation in the free vitamin D percentage. The summertime synthesis of vitamin D in the skin could contribute directly to the free fraction of vitamin D. Standardizing the measurement of free 25(OH)D and clinical studies is necessary to establish reference values before these methods can be implemented in clinical practice.

Vitamin D supplementation and calcium: Many-faced gods or nobody in fighting against Corona Virus Disease 2019

In December 2019, Corona Virus Disease 2019 (COVID-19) was first identified and designated as a pandemic in March 2020 due to rapid spread of the virus globally. At the beginning of the pandemic, only a few treatment options, mainly focused on supportive care and repurposing medications, were available. Due to its effects on immune system, vitamin D was a topic of interest during the pandemic, and researchers investigated its potential impact on COVID-19 outcomes. However, the results of studies about the impact of vitamin D on the disease are inconclusive. In the present narrative review, different roles of vitamin D regarding the COVID-19 have been discussed to show that vitamin D supplementation should be recommended carefully.

Serum 25-hydroxyvitamin D threshold and risk of rickets in young children: a systematic review and individual participant data meta-analysis to inform the development of dietary requirements for vitamin D

PURPOSE

The objective of this systematic review was to determine a minimum serum 25-hydroxyvitamin D (25OHD) threshold based on the risk of having rickets in young children. This work was commissioned by the WHO and FAO within the framework of the update of the vitamin D requirements for children 0-3 years old.

METHODS

A systematic search of Embase was conducted to identify studies involving children below  4 years of age with serum 25OHD levels and radiologically confirmed rickets, without any restriction related to the geographical location or language. Study-level and individual participant data (IPD)-level random effects multi-level meta-analyses were conducted. The odds, sensitivity and specificity for rickets at different serum 25OHD thresholds were calculated for all children as well as for children with adequate calcium intakes only.

RESULTS

A total of 120 studies with 5412 participants were included. At the study-level, children with rickets had a mean serum 25OHD of 23 nmol/L (95% CI 19-27). At the IPD level, children with rickets had a median and mean serum 25OHD of 23 and 29 nmol/L, respectively. More than half (55%) of the children with rickets had serum 25OHD below 25 nmol/L, 62% below 30 nmol/L, and 79% below 40 nmol/L. Analysis of odds, sensitivities and specificities for nutritional rickets at different serum 25OHD thresholds suggested a minimal risk threshold of around 28 nmol/L for children with adequate calcium intakes and 40 nmol/L for children with low calcium intakes.

CONCLUSION

This systematic review and IPD meta-analysis suggests that from a public health perspective and to inform the development of dietary requirements for vitamin D, a minimum serum 25OHD threshold of around 28 nmol/L and above would represent a low risk of nutritional rickets for the majority of children with an adequate calcium intake.

How effective is public health policy in Scotland on vitamin D deficiency during pregnancy?

OBJECTIVE

To evaluate the uptake of universal vitamin D supplementation during pregnancy, its effectiveness in preventing vitamin D deficiency and the factors associated with these.

DESIGN

The regional public health organisation in Ayrshire, Scotland has a policy of universal provision of vitamin D supplements (10 µg/d) to all pregnant women for the duration of their pregnancy. Pregnant women in this area were recruited at their 12-week antenatal appointment. Blood samples were collected at the 12-week and 34-week appointments. To account for the seasonal variation, women were recruited in two cohorts: summer and winter. Telephone interviews were conducted at 34 weeks to assess the uptake of vitamin D supplements during pregnancy. Other variables were obtained from medical records.

SETTING

The study was conducted in the NHS Ayrshire and Arran Health Board in Scotland.

PARTICIPANTS

612 pregnant women (aged 15-44 years) living in Ayrshire (latitude 55°), Scotland.

RESULTS

Sixty-six percentage took supplementation as recommended. Consumption of supplementation was significantly associated with a higher median serum 25-hydroxyvitamin D concentrations at 34 weeks. Despite this at 34 weeks, 33 % of the summer cohort had insufficient or deficient vitamin D status, while 15 % of the winter cohort had insufficient or deficient status. In multivariable analysis, only adherence and season were independent predictors of vitamin D status.

CONCLUSIONS

While supplementation improved and maintained vitamin D status during pregnancy, it was not adequate to ensure all those insufficient at 12 weeks achieved sufficient status at the end of pregnancy.

Influence of food matrix delivery system on the bioavailability of vitamin D3: A randomized crossover trial in postmenopausal women

OBJECTIVES

Vitamin D insufficiency (blood 25-hydroxyvitamin D <50 nmol/L) is a global health problem. Vitamin D food fortification might be a solution, but knowledge is sparse on which food matrices yield the highest bioavailability. The aim of this study was to investigate the influence of different food matrices including complex formations with whey proteins on the human bioavailability of vitamin D.

METHODS

In this randomized, multiple crossover trial, we enrolled 30 postmenopausal women 60 to 80 y of age with vitamin D insufficiency. We measured changes in serum concentrations of vitamin D₃ (D₃) postprandially for 24 h in response to the intake of 500 mL of different food matrices with 200 µg D₃ added compared with a control (500 mL of water). Foods included apple juice with whey protein isolate (WPI), apple juice, semi-skim milk, and water (with D₃). The food matrices were provided in a randomized order with ≥10-d washout period between them. On each intervention day, blood samples were collected at 0, 2, 4, 6, 8, 10, 12 and 24 h.

RESULTS

D₃ with WPI in juice did not enhance area under the curve (AUC) of serum D₃ compared with juice without WPI (370 nmol ×  24 h/L; 95% confidence interval [CI], 321-419 versus 357 nmol ×  24 h/L; 95% CI, 308-406 nmol ×  24 h/L; P = 0.65). However, compared with juice, the AUC was significantly higher in response to the intake of D₃ in milk (452 nmol ×  24 h/L; 95% CI, 402-502 nmol ×  24 h/L) and water with D₃ (479 nmol ×  24 h/L; 95% CI, 430-527 nmol ×  24 h/L; P < 0.05). No difference was observed between milk and water (P = 0.34).

CONCLUSIONS

The bioavailability of D₃ was superior in milk and water compared with juice, regardless of whether WPI was added.

Vitamin D binding protein gene polymorphisms are associated with lower plasma 25-hydroxy-cholecalciferol concentrations in Ethiopian lactating women

Ethiopian women have been reported to have low plasma 25-hydroxy-cholecalciferol (25(OH)D) concentrations despite an abundance of sunshine. Low dietary vitamin D intake, limited skin exposure to sun, and genetics are among factors suggested to affect vitamin D status in this population. In this study (Clinical Trial NCT02210884), we hypothesized that polymorphisms in the vitamin D binding protein (VDBP) gene (rs7041, rs4588) are associated with reduced plasma 25(OH)D concentrations in Ethiopian women. Lactating Ethiopian women (n = 110) were randomly assigned to weekly administration of vitamin D3 (15,000 IU) or a placebo. Plasma 25(OH)D was measured at baseline (within 2 weeks of delivery, before supplementation) and at 3, 6, and 12 months after delivery. Associations between VDBP polymorphism status for rs7041 and rs4588 and plasma 25(OH)D were determined by analysis of variance and multiple linear and logistic regressions. Multiple linear regression with maternal age as a covariate revealed that rs7041 is associated with reduced plasma 25(OH)D (P = .021) and more risk alleles at rs7041 and rs4588 are associated with reduced plasma 25(OH)D (P = .017). Logistic regression models for vitamin D insufficiency showed that additional risk alleles for rs7041 and rs4588 are associated with increased odds ratios (OR = 1.66; 95% CI, 1.10-2.62; P = .019) for plasma 25(OH)D below 40 nmol/L. Supplementation increased plasma 25(OH)D at 3 months in women with fewer risk alleles and across all genotypes at 6 and 12 months. VDBP polymorphisms may contribute to vitamin D insufficiency in Ethiopian lactating women. Furthermore, VDBP polymorphisms may blunt short-term responses to vitamin D supplementation and require longer periods of intervention.

Vitamin D status of the Russian adult population from 2013 to 2018

Vitamin D deficiency is widespread globally, however available data for the Russian adult population is fragmented. This cross-sectional study used secondary data for individuals undergoing testing for vitamin D concentrations from 2013 to 2018 by InVitro laboratory. 25(OH)D serum concentration was determined using chemiluminescent microparticle immunoassay. The mean, median, and proportion with severe, deficient, insufficient and sufficient 25-hydroxyvitamin D (25(OH)D) concentrations were estimated. Splines examined the effect of latitude on 25(OH)D concentrations. Data were available for 30,040 subjects age ≥ 18 years. 24.2% of the sampled population had sufficient (30-< 150 25(OH)D ng/mL), 34% deficient (10-19.9 ng/mL) and 5.6% severely deficient (< 10 ng/mL) status. Average 25(OH)D concentrations were highest among 30-44 years and lowest amongst older adults; females had modestly higher values. Concentrations were 15% higher in fall/summer vs. winter/spring. A non-linear relationship was observed by latitude; the highest 25(OH)D concentrations were observed near 54°N, decreasing at more southern latitudes for women and more northern latitudes for both sexes. These results are comparable to other Northern European publications and limited Russian samples demonstrating low concentrations. Acknowledging that nationally-representative and randomly sampled data are needed, the present data suggest the burden may be high and identifies some population sub-groups and geographic areas with a higher potential deficiency of vitamin D.

Prevalence of vitamin D deficiency and association with parathyroid hormone

Objectives

We evaluated the prevalence of 25-hydroxyvitamin D (25-(OH)D) deficiency in our setting according to season, sex, and age. We also studied the association with parathyroid hormone (PTH) levels.

Methods

The study population comprised all patients with requests for assessment of 25-(OH)D between January 1 and December 31, 2018, as registered in the database of the laboratory information system. Major exclusion criteria were pediatric samples (<18 years) and factors affecting 25-(OH)D and/or PTH levels (i.e., kidney injury, liver disease, PTH disorders).

Results

Among 33,601 patients (24,028 women, 9,573 men), the prevalence of 25-(OH)D deficiency was 48%. Prevalence was greater in males than in females (53% vs. 46%). By age group, deficiency was more prevalent in quartile 1 (Q1, 74-87 years) and less prevalent in quartile 2 (Q2, 60-73 years). By season, deficiency was greater in spring (nonsignificant differences with respect to winter) and lower in summer. The association between 25-(OH)D and PTH was assessed in 9,368 persons. Linear regression analysis showed a weak association (coefficient - 0.303). Multiple logistic regression analysis revealed a significant association between 25-(OH)D deficiency and increased PTH (Odds ratio (OR), 1.63). Other risk factors for increased PTH include female sex (OR, 1.27), season (winter, OR 1.63, spring OR 1.16), and age (quartile 1, OR, 3).

Conclusions

The prevalence of 25-(OH)D deficiency differed according to sex, age, and season of the year. Furthermore, elevation of PTH is mainly influenced by low 25-(OH)D, female sex, season, and age.

Individual participant data (IPD)-level meta-analysis of randomised controlled trials to estimate the vitamin D dietary requirements in dark-skinned individuals resident at high latitude

CONTEXT AND PURPOSE

There is an urgent need to develop vitamin D dietary recommendations for dark-skinned populations resident at high latitude. Using data from randomised controlled trials (RCTs) with vitamin D3-supplements/fortified foods, we undertook an individual participant data-level meta-regression (IPD) analysis of the response of wintertime serum 25-hydroxyvitamin (25(OH)D) to total vitamin D intake among dark-skinned children and adults residing at ≥ 40° N and derived dietary requirement values for vitamin D.

METHODS

IPD analysis using data from 677 dark-skinned participants (of Black or South Asian descent; ages 5-86 years) in 10 RCTs with vitamin D supplements/fortified foods identified via a systematic review and predefined eligibility criteria. Outcome measures were vitamin D intake estimates across a range of 25(OH)D thresholds.

RESULTS

To maintain serum 25(OH)D concentrations ≥ 25 and 30 nmol/L in 97.5% of individuals, 23.9 and 27.3 µg/day of vitamin D, respectively, were required among South Asian and 24.1 and 33.2 µg/day, respectively, among Black participants. Overall, our age-stratified intake estimates did not exceed age-specific Tolerable Upper Intake Levels for vitamin D. The vitamin D intake required by dark-skinned individuals to maintain 97.5% of winter 25(OH)D concentrations ≥ 50 nmol/L was 66.8 µg/day. This intake predicted that the upper 2.5% of individuals could potentially achieve serum 25(OH)D concentrations ≥ 158 nmol/L, which has been linked to potential adverse effects in older adults in supplementation studies.

CONCLUSIONS

Our IPD-derived vitamin D intakes required to maintain 97.5% of winter 25(OH)D concentrations ≥ 25, 30 and 50 nmol/L are substantially higher than the equivalent estimates for White individuals. These requirement estimates are also higher than those currently recommended internationally by several agencies, which are based predominantly on data from Whites and derived from standard meta-regression based on aggregate data. Much more work is needed in dark-skinned populations both in the dose-response relationship and risk characterisation for health outcomes.

TRAIL REGISTRATION

PROSPERO International Prospective Register of Systematic Reviews (Registration Number: CRD42018097260).

Vitamin D biomarkers for Dietary Reference Intake development in children: a systematic review and meta-analysis

BACKGROUND

Circulating 25-hydroxyvitamin D [25(OH)D] has been the accepted vitamin D exposure/intake biomarker of choice within recent DRI exercises, but use of other vitamin D-related biomarkers as well as functional markers has been suggested. These may be of value in future vitamin D DRI exercises, such as the FAO/WHO's one for young children.

OBJECTIVES

To systematically review the usefulness of circulating 25(OH)D, parathyroid hormone (PTH), free and bioavailable 25(OH)D, C3-epimer of 25(OH)D, vitamin D3, 24,25-dihydroxyvitamin D [24,25(OH)2D], and bone turnover markers and calcium absorption as vitamin D biomarkers for DRI development in children.

METHODS

Methods included structured searches of published articles, full-text reviews, data extraction, quality assessment, meta-analysis, and random-effects meta-regression.

RESULTS

Fifty-nine vitamin D supplementation randomized controlled trials (RCTs) were included (39 in infants/children as the priority group and the remainder in adults since pediatric studies were absent/limited). Vitamin D supplementation significantly raised circulating 25(OH)D in infants and children, but the response was highly heterogeneous [weighted mean difference (WMD): 27.7 nmol/L; 95% CI: 22.9, 32.5; 27 RCTs; I2 = 93%]. Meta-regression suggested an increase by 1.7 nmol/L (95% CI: 0.7, 2.6) in serum 25(OH)D per each 100-IU increment in vitamin D intake (P = 0.0005). Vitamin D supplementation had a significant effect on circulating 24,25(OH)2D (WMD: 3.4 nmol/L; 95% CI: 2.4, 4.5; 13 RCTs; I2 = 95%), with a dose-response relation (+0.15 nmol/L per 100 IU; 95% CI: -0.01, 0.29). With circulating PTH, although there was a significant effect of vitamin D on WMD (P = 0.05), there was no significant dose-response relation (P = 0.32). Pediatric data were too limited in relation to the usefulness of the other biomarkers.

CONCLUSIONS

Circulating 25(OH)D may be a useful biomarker of vitamin D exposure/intake for DRI development in infants and children. Circulating 24,25(OH)2D also showed some promise, but further data are needed, especially in infants and children.

Global differences in vitamin D status and dietary intake: a review of the data

BACKGROUND

Internationally, concern has been repeatedly raised about the little notable progress in the collection, analysis and use of population micronutrient status and deficiency data globally. The need for representative status and intake data for vitamin D has been highlighted as a research priority for well over a decade.

AIM AND METHODS

A narrative review which aims to provide a summary and assessment of vitamin D nutritional status data globally. This review divides the world into the Food and Agriculture Organisation's (FAO) major regions: the Americas, Europe, Oceania, Africa and Asia. Emphasis was placed on published data on the prevalence of serum 25-hydroxyvitamin D (25(OH)D) < 25/30 and <50 nmol/L (reflecting vitamin D deficiency and inadequacy, respectively) as well as vitamin D intake, where possible from nationally representative surveys.

RESULTS

Collating data from the limited number of available representative surveys from individual countries might suggest a relatively low overall prevalence of vitamin D deficiency in South America, Oceania and North America, whereas there is more moderate prevalence in Europe and Asia, and possibly Africa. Overall, the prevalence of serum 25(OH)D < 25/30 and <50 nmol/L ranges from ~5 to 18% and 24 to 49%, respectively, depending on FAO world region. Usual intakes of vitamin D can also vary by FAO world region, but in general, with a few exceptions, there are very high levels of inadequacy of vitamin D intake.

CONCLUSIONS

While the burden of vitamin D deficiency and inadequacy varies by world regions and not just by UVB availability, the global burden overall translates into enormous numbers of individuals at risk.

Safety of Vitamin D Food Fortification and Supplementation: Evidence from Randomized Controlled Trials and Observational Studies

The safety considerations of food-based solutions for vitamin D deficiency prevention, such as fortification and supplementation, are critical. On the basis of collective data from 20 randomized controlled trials (RCTs) and 20 national healthy surveys, as well as prospective cohort studies (PCSs) across the ODIN project (“Food-based solutions for optimal vitamin D nutrition and health through the life cycle”, FP7-613977), we analyzed the potential safety issues arising from vitamin D intakes and/or supplementation. These adverse consequences included high serum 25-hydroxyvitamin D (S-25(OH)D) concentrations (>125 nmol/L), high serum calcium concentrations, and vitamin D intakes in excess of the tolerable upper intake levels (ULs). In the RCTs (n = 3353, with vitamin D doses from 5–175 µg/day), there were no reported adverse effects. The prevalence of high S-25(OH)D was <10% when vitamin D supplements were administered, and <0.1% for fortified foods. Elevated serum calcium was observed among <0.5% in both administration types. No ODIN RCT participants exceeded the age-specific ULs. In observational studies (n = 61,082), the prevalence of high 25(OH)D among children/adolescents, adults, and older adults was <0.3%, with no evidence of adverse effects. In conclusion, high S-25(OH)D concentrations >125 nmol/L were rare in the RCTs and PCSs, and no associated adverse effects were observed.

Differences in the Concentration of Vitamin D Metabolites in Plasma Due to the Low-Carbohydrate-High-Fat Diet and the Eastern European Diet-A Pilot Study

Vitamin D deficiency is a global problem with many health consequences, and it is currently recommended to supplement vitamin D. Change of diet should also be considered to ensure adequate vitamin D in the human body. The aim of this study was to assess the concentration of vitamin D metabolites in two different groups: one group on the low-carbohydrate-high-fat (LCHF) diet and the other group on the Eastern European (EE) diet. In the first stage, 817 participants declaring traditional EE diet or LCHF diet were investigated. Nutrition (self-reported 3-day estimated food record) and basic anthropometric parameters were assessed. After extra screening, 67 participants on the EE diet and 41 on the LCHF diet were qualified for the second stage. Plasma 25-hydroxycholecalciferol (25(OH)D₃) and (25(OH)D₂) concentration was measured by the validated HPLC—MS/MS method. Plasma 25(OH)D₃ concentration was significantly higher in the group on the LCHF diet (34.9 ± 15.9 ng/mL) than in the group on the EE diet (22.6 ± 12.1 ng/mL). No statistical differences were observed in plasma 25(OH)D₂ concentration between the study groups (p > 0.05). Women had a higher plasma 25(OH)D₂ concentration than men regardless of diet type. The LCHF diet had a positive influence on plasma vitamin D concentration. However, long-term use of the LCHF diet remains contentious due to the high risk of cardiovascular disease. This study confirmed that the type of diet influences the concentration of vitamin D metabolites in the plasma.

Risk evaluation of vitamin D insufficiency or deficiency in children using simple scores: The Healthy Growth Study

Although identification of population groups at high risk for low vitamin D status is of public health importance,there are no risk prediction tools available for children in Southern Europe that can cover this need. The present study aimed to develop and validate 2 simple scores that evaluate the risk for vitamin D insufficiency or deficiency in children. A cross-sectional epidemiological study was conducted among 2280 schoolchildren (9--13-year-old) living in Greece. The total sample was randomly divided into 2 subsamples of 1524 and 756 children, used in the development and validation of the 2 scores, respectively. Multivariate logistic regression analyses were used to develop the 2 risk evaluation scores, while receiver operating characteristic curves were employed to identify the optimal "points of change" for each risk score, upon which vitamin D insufficiency and deficiency is diagnosed with the highest possible sensitivity and specificity. The components of the 2 risk evaluation scores included children's age, gender, region of residence, screen-time, body weight status, maternal education, and season. The increase in each score by 1 unit elevated the likelihood for vitamin D insufficiency and deficiency by 31% and 28%, respectively. The receiver operating characteristic curves showed that the optimal "points of change" for each risk score, upon which vitamin D insufficiency or deficiency is diagnosed with the highest possible sensitivity and specificity were 8.5 and 12.5, respectively. In conclusion, this study developed 2 simple scores that evaluate the risk for vitamin D insufficiency or deficiency in children living in Greece. However, more studies are required for these scores to be validated in other populations of children from different countries.

Effect of Vitamin D Deficiency on Contrast Sensitivity Function

PURPOSE

The purpose of this study is to investigate the effects of vitamin D (vit D) deficiency on contrast sensitivity (CS) function and retinal layers.

MATERIALS AND METHODS

Group 1 consisted of 42 patients aged between 18 and 50 years with vit D deficiency and Group 2 consisted of sex- and age-matched 34 healthy subjects with normal vit D levels. Functional acuity contrast testing (FACT) was performed using the Optec 6500 vision testing system. The average retinal nerve fiber layer (RNFL) thickness and macular thickness (MT) obtained from nine macular areas in the Early Treatment Diabetic Retinopathy Study were evaluated using SD-OCT (RS-3000; Nidek Inc., Fremont, CA, USA) following a detailed ophthalmologic examination. Measurements were performed on both eyes.

RESULTS

A lower CS was found in Group 1 compared to Group 2 in all spatial frequencies. A statistically significant difference was observed between the groups in 6, 12 and 18 cpd spatial frequencies, respectively. (p = .004, p = .001, p = .042, respectively). There was no statistically significant difference between groups in terms of RNFL thicknesses (p = .200). There was an increase in MT in Group 1. However, this increase was statistically significant in the inferior inner area in the right eye, and in the inferior inner, temporal inner and outer macular areas in the left eye (p = .018, p = .003, p = .033, p = .040, respectively).

CONCLUSION

It was observed that vit D deficiency had negative effects on CS function and also caused thickness difference in certain segments of retinal layers.

Food-based strategies for prevention of vitamin D deficiency as informed by vitamin D dietary guidelines, and consideration of minimal-risk UVB radiation exposure in future guidelines

There is widespread acknowledgement of the presence of vitamin D deficiency in the community and the pressing need to address this. From a public health perspective, emphasis has been placed on addressing vitamin D deficiency through dietary means. However, naturally rich food sources of vitamin D are few and infrequently consumed, and nutrition survey data from various countries have indicated that habitual vitamin D intakes in the community are much lower than the current vitamin D dietary guidelines. This review will briefly overview the extent of vitamin D deficiency within the community, its causes, and how our food chain, once its embraces the evidence-based practise of food fortification and potentially biofortification, can cater for meeting the dietary vitamin D needs of the community. Finally, international authorities, briefed with establishing vitamin D dietary guidelines over the past decade, have struggled with uncertainties and gaps in our understanding of the relative contribution of sunshine and diet to vitamin D status and vitamin D requirements for health maintenance. The review will also consider how emerging evidence of a possible minimal-risk UVB radiation exposure relative to skin cancer that also enables vitamin D production could greatly inform future vitamin D dietary guidelines.

Bone Health, Body Composition, and Vitamin D Status of Black Preadolescent Children in South Africa

Optimal bone health is important in children to reduce the risk of osteoporosis later in life. Both body composition and vitamin D play an important role in bone health. This study aimed to describe bone health, body composition, and vitamin D status, and the relationship between these among a group of conveniently sampled black preadolescent South African children (n = 84) using a cross-sectional study. Body composition, bone mineral density (BMD), and bone mineral content (BMC) were assessed using dual x-ray absorptiometry. Levels of 25-hydroxyvitamin D (25(OH)D) (n = 59) were assessed using dried blood spots. A quarter (25%) of children presented with low bone mass density for their chronological age (BMD Z-score < -2) and 7% with low BMC-for-age (BMC Z-score < -2), while only 34% of the children had sufficient vitamin D status (25(OH)D ≥ 30 ng/mL). Lean mass was the greatest body compositional determinant for variances observed in bone health measures. Body composition and bone health parameters were not significantly different across vitamin D status groups (p > 0.05), except for lumbar spine bone mineral apparent density (LS-BMAD) (p < 0.01). No association was found between bone parameters at all sites and levels of 25(OH)D (p > 0.05). Further research, using larger representative samples of South African children including all race groups is needed before any conclusions and subsequent recommendation among this population group can be made.

Contribution of nutrition science to the vitamin D field-Clarity or confusion?

Recent opinion pieces have questioned whether nutrition science is fit for purpose, suggesting that the evidence-base for dietary recommendations is populated with poor quality science and unresolved controversy. Nutrition science is accused of not keeping up with the times and making little real-world progress to stem the growing global malnutrition crisis, by failing to apply cutting-edge techniques to nutrition problems. Nutritional epidemiology has been blamed for harming public health nutrition and the public perception of science itself, by selectively reporting biased, confounded data. Focussed on obesity and associated disorders and hunger, these articles do not refer to micronutrient deficiencies or advances in micronutrient research. There is a serious public health problem of low vitamin D status. Given that the field of vitamin D has experienced an exponential increase in peer-reviewed publications over the last 50 years, it seems timely that we take these cues to reflect upon whether the expanded body of scientific literature has contributed to a deeper knowledge of vitamin D in health and disease, leading to improved nutrition policy and patient care, or whether it has led to so much confusion and controversy that progress has been impeded. We consider whether the accusations of poor science and biased reporting levelled at nutrition science are evident within the vitamin D nutrition research area and whether they have compromised dietary recommendations for vitamin D. In evaluating whether reformation is required, we discuss the confusion and controversy within the field and signpost common ground within the vitamin D community. We outline vitamin D nutrition research that has presented strategies for vitamin D deficiency prevention within the population, particularly using food first approaches that could extend beyond high income settings to low- and middle-income countries. Finally, we encourage government and industry to implement technical advances and drive real-world progress.

Antenatal vitamin D exposure and childhood eczema, food allergy, asthma and allergic rhinitis at 2 and 5 years of age in the atopic disease-specific Cork BASELINE Birth Cohort Study

BACKGROUND

Prospective studies of antenatal and infant vitamin D exposure and atopic disease from extensively characterised, disease-specific, maternal-infant cohorts with gold standard analysis of vitamin D status and clinically validated atopic outcomes are lacking. This study aimed to investigate associations between intrauterine vitamin D status and atopic outcomes in an extensively characterised, disease-specific, maternal-infant cohort.

METHODS

Circulating 25-hydroxyvitamin D (25(OH)D) was measured in maternal sera at 15 weeks of gestation (n = 1537) and umbilical cord blood (n = 1050) using a CDC-accredited LC-MS/MS platform, and the association with clinically validated atopic disease outcomes (eczema, food allergy, asthma, allergic rhinitis) at 2 and 5 years was explored using multivariable logistic regression.

RESULTS

Persistent eczema in the first 2 years of life was present in 5% of infants. Food allergy at 2 years was confirmed in 4%. The prevalence of aeroallergen sensitisation at 2 years was 8%. Asthma at 5 years was reported in 15% and allergic rhinitis in 5% of 5-year-olds. There were no significant differences in the distributions of maternal 25(OH)D at 15 weeks of gestation (mean [SD] 58.4 [26.2] and 58.5 [26.1] nmol/L) and cord 25(OH)D concentrations (mean [SD] 35.2 [17.8] and 35.4 [18.3] nmol/L) between children with and without atopic disease. Neither maternal (aOR [95% CI]: 1.02 [0.97, 1.08], P = 0.450) nor cord 25(OH)D (aOR [95% CI]: 1.00 [0.91, 1.09], P = 0.991) were significant predictors of atopic disease outcomes in fully adjusted models.

CONCLUSION

These data in a disease-specific cohort with prospectively collected, validated atopic outcomes do not support an association between antenatal exposure to vitamin D and atopic disease outcomes in childhood.

Summary Outcomes of the ODIN Project on Food Fortification for Vitamin D Deficiency Prevention

Food-based solutions for optimal vitamin D nutrition and health through the life cycle (ODIN) was a cross-disciplinary, collaborative project, including 30 partners from 19 countries, which aimed to develop evidence-based solutions to prevent low vitamin D status (25-hydroxyvitamin D (25(OH)D) < 30 nmol/L) using a food-first approach. This paper provides a summary overview of some of the important ODIN outcomes and outlines some outstanding data requirements. In a study of almost 56,000 individuals, the first internationally standardised dataset of vitamin D status showed that 13% of EU residents overall, across a latitude gradient of 35° N to 69° N, had serum 25(OH)D < 30 nmol/L and 40% were < 50 nmol/L. The risk of low vitamin D status was several-fold higher among persons of ethnic minority. However, additional data from quality bio-banked sera would be required to improve these estimates. To address the question of dietary requirements for vitamin D among under-researched life-stage and population groups, four dose-response RCTs conducted in Northern Europe showed that vitamin D₃ intakes of 8 and 13 μg/day prevented 25(OH)D decreasing below 30 nmol/L in white children and adolescents and 20 and 30 μg/day, respectively, achieved ≥50 nmol/L. Among white women during pregnancy, 30 μg/day is required to prevent umbilical cord 25(OH)D, representing new-born vitamin D status, below 25 nmol/L. While 8 μg/day protected white women in Finland at the 30 nmol/L cut-off, 18 μg/day was needed by women of East African descent to prevent 25(OH)D decreasing below 30 nmol/L during wintertime. Replicate RCTs are needed in young children <5 years and in school-age children, teens and pregnant women of ethnic minority. Using a series of food production studies, food-based RCTs and dietary modelling experiments, ODIN research shows that diverse fortification strategies could safely increase population intakes and prevent low vitamin D status. Building on this solid technological platform, implementation research is now warranted to scale up interventions in real-world settings to eradicate vitamin D deficiency.

Vitamin D Requirements for the Future-Lessons Learned and Charting a Path Forward

Estimates of dietary requirements for vitamin D or Dietary Reference Values (DRV) are crucial from a public health perspective in providing a framework for prevention of vitamin D deficiency and optimizing vitamin D status of individuals. While these important public health policy instruments were developed with the evidence-base and data available at the time, there are some issues that need to be clarified or considered in future iterations of DRV for vitamin D. This is important as it will allow for more fine-tuned and truer estimates of the dietary requirements for vitamin D and thus provide for more population protection. The present review will overview some of the confusion that has arisen in relation to the application and/or interpretation of the definitions of the Estimated Average Requirement (EAR) and Recommended Dietary Allowance (RDA). It will also highlight some of the clarifications needed and, in particular, how utilization of a new approach in terms of using individual participant-level data (IPD), over and beyond aggregated data, from randomised controlled trials with vitamin D may have a key role in generating these more fine-tuned and truer estimates, which is of importance as we move towards the next iteration of vitamin D DRVs.

Is vitamin D deficiency a public health concern for low middle income countries? A systematic literature review

PURPOSE

Vitamin D deficiency has been receiving increasing attention as a potential public health concern in low and lower-middle income countries (LMICs), of which there are currently 83. We aimed to conduct a comprehensive systematic literature review (SLR) of available data on vitamin D status and prevalence of vitamin D deficiency in all 83 LMICs.

METHODS

We followed the general methodology for SLRs in the area of serum 25-hydroxyvitamin D. Highest priority was placed on identifying relevant population-based studies, followed by cross-sectional studies, and to a lesser extent case-control studies. We adopted the public health convention that a prevalence of vitamin D deficiency (serum 25-hydroxyvitamin D < 25/30 nmol/L) at > 20% in the entire population and/or at-risk population subgroups (infants, children, women of child-bearing age, pregnancy) constitutes a public health issue that may warrant intervention.

RESULTS

Our SLR revealed that of the 83 LMICs, 65% (n = 54 countries) had no published studies with vitamin D data suitable for inclusion. Using data from the remaining third, a number of LMICs had evidence of excess burden of vitamin D deficiency in one or more population subgroup(s) using the above convention (Afghanistan, Pakistan, India, Tunisia and Mongolia) as well as possibly other LMICs, albeit with much more limited data. Several LMICs had no evidence of excess burden.

CONCLUSION

Vitamin D deficiency is a public health issue in some, but certainly not all, LMICs. There is a clear need for targeting public health strategies for prevention of vitamin D deficiency in those LMICs with excess burden.

Vitamin D in adolescence: evidence-based dietary requirements and implications for public health policy

Vitamin D is a unique nutrient. First, it acts as a pro-hormone and secondly, the requirement for vitamin D can be met by both endogenous synthesis from sunlight and by dietary sources. This complicates the determination of dietary requirements for vitamin D, which along with the definition of optimal vitamin D status, have been highly controversial and much debated over recent years. Adolescents are a population group at high risk of low vitamin D status, which is concerning given the important role of vitamin D, and calcium, in promoting normal bone mineralisation and attainment of peak bone mass during this rapid growth phase. Dietary vitamin D recommendations are important from a public health perspective in helping to avoid deficiency and optimise vitamin D status for health. However limited experimental data from winter-based dose-response randomised trials in adolescents has hindered the development of evidence-based dietary requirements for vitamin D in this population group. This review will highlight how specifically designed randomised trials and the approach adopted for estimating such requirements can lead to improved recommendations. Such data indicate that vitamin D intakes of between 10 and about 30 µg/d may be required to avoid deficiency and ensure adequacy in adolescents, considerably greater than the current recommendations of 10-15 µg/d. Finally this review will consider the implications of this on public health policy, in terms of future refinements of vitamin D requirement recommendations and prioritisation of public health strategies to help prevent vitamin D deficiency.

25-Hydroxyvitamin D as a Biomarker of Vitamin D Status and Its Modeling to Inform Strategies for Prevention of Vitamin D Deficiency within the Population

There is substantial evidence that the prevalence of vitamin D deficiency is unacceptably high in the population, and this requires action from a public health perspective. Circulating 25-hydroxyvitamin D [25(OH)D] is a robust and reliable marker of vitamin D status and has been used by numerous agencies in the establishment of vitamin D dietary requirements and for population surveillance of vitamin D deficiency or inadequacy. In a wider context, modeling of serum 25(OH)D data and its contributory sources, namely dietary vitamin D supply and UVB availability, can inform our understanding of population vitamin D status. The aim of this review is to provide the current status of knowledge in relation to modeling of such vitamin D-relevant data. We begin by highlighting the importance of the measurement of 25(OH)D and its standardization, both of which have led to new key data on the prevalence of vitamin D deficiency and inadequacy in North America and Europe. We then overview how state-of-the-art modeling can be used to inform our understanding of the potential effect of ergocalciferol and 25(OH)D on vitamin D intake estimates and how meteorological data on UVB availability, when coupled with other key data, can help predict population serum 25(OH)D concentration, even accounting for seasonal fluctuations, and lastly, how these in silico approaches can help inform policymakers on strategic options on addressing low vitamin D status through food-based approaches and supplementation. The potential of exemplar food-based solutions will be highlighted, as will the possibility of synergies between vitamin D and other dairy food-based micronutrients, in relation to vitamin D status and bone health. Lastly, we will briefly consider the interactions between season and vitamin D supplements on vitamin D status and health.

A systematic review of vitamin D status in southern European countries

PURPOSE

Despite an acknowledged dearth of data on serum 25-hydroxyvitamin D (25(OH)D) concentrations from Southern European countries, inter-country comparison is hampered by inconsistent data reporting. The purpose of the current study was to conduct a systematic literature review of available data on serum 25(OH)D concentrations and estimate vitamin D status in Southern European and Eastern Mediterranean countries, both at a population level and within key population subgroups, stratified by age, sex, season and country.

METHODS

A systematic review of the literature was conducted to identify and retrieve scientific articles reporting data on serum 25(OH)D concentration and/or vitamin D status following standard procedures.

RESULTS

Data were extracted from 107 studies, stratified by sex and age group, representing 630,093 individuals. More than one-third of the studies reported mean 25(OH)D concentrations below 50 nmol/L and ~ 10% reported mean serum 25(OH)D concentrations below 25 nmol/L. Overall, females, neonates/ infants and adolescents had the higher prevalence of poor vitamin D status. As expected, there was considerable variability between studies. Specifically, mean 25(OH)D ranged from 6.0 (in Italian centenarians) to 158 nmol/L (in elderly Turkish men); the prevalence of serum 25(OH)D < 50 nmol/L ranged from 6.8 to 97.9% (in Italian neonates).

CONCLUSIONS

Contrary to expectations, there was a high prevalence of low vitamin D status in the Southern Europe and the Eastern Mediterranean regions, despite abundant sunshine. These data further emphasize the need for strategies, such as fortification of foods with vitamin D and/or vitamin D supplementation, which will be tailored to the needs of specific population groups with higher risk of insufficiency or deficiency, to efficiently tackle the pandemic of hypovitaminosis D in Europe.

Improved Dietary Guidelines for Vitamin D: Application of Individual Participant Data (IPD)-Level Meta-Regression Analyses

Dietary Reference Values (DRVs) for vitamin D have a key role in the prevention of vitamin D deficiency. However, despite adopting similar risk assessment protocols, estimates from authoritative agencies over the last 6 years have been diverse. This may have arisen from diverse approaches to data analysis. Modelling strategies for pooling of individual subject data from cognate vitamin D randomized controlled trials (RCTs) are likely to provide the most appropriate DRV estimates. Thus, the objective of the present work was to undertake the first-ever individual participant data (IPD)-level meta-regression, which is increasingly recognized as best practice, from seven winter-based RCTs (with 882 participants ranging in age from 4 to 90 years) of the vitamin D intake-serum 25-hydroxyvitamin D (25(OH)D) dose-response. Our IPD-derived estimates of vitamin D intakes required to maintain 97.5% of 25(OH)D concentrations >25, 30, and 50 nmol/L across the population are 10, 13, and 26 µg/day, respectively. In contrast, standard meta-regression analyses with aggregate data (as used by several agencies in recent years) from the same RCTs estimated that a vitamin D intake requirement of 14 µg/day would maintain 97.5% of 25(OH)D >50 nmol/L. These first IPD-derived estimates offer improved dietary recommendations for vitamin D because the underpinning modeling captures the between-person variability in response of serum 25(OH)D to vitamin D intake.

Vitamin D metabolite concentrations in umbilical cord blood serum and associations with clinical characteristics in a large prospective mother-infant cohort in Ireland

Vitamin D deficiency is widespread among mothers and neonates and quality clinical and analytical data are lacking. We used a CDC-accredited LC-MS/MS method to analyze vitamin D metabolites in cord sera from 1050 maternal-infant dyads in the prospective SCOPE Ireland Pregnancy and BASELINE Birth cohort studies, based in Cork, Ireland. The mean±SD total 25(OH)D was 34.9±18.1nmol/L; 35% of cords (50% during winter) had 25(OH)D <25nmol/L, 46% were <30nmol/L and 80% were <50nmol/L. In this predominantly white cohort, the main predictor of cord 25(OH)D [adj. mean difference in nmol/L (95% CI)] was summer delivery [19.2 (17.4, 20.9), P<0.0001]. Maternal smoking during pregnancy (9% prevalence) was negatively associated (P<0.002) with cord 25(OH)D [-4.83 (-7.9, -1.5) nmol/L]. There were no associations between cord 25(OH)D and birth weight or any anthropometric measures at birth. Despite the high prevalence of vitamin D deficiency at birth, there were no documented musculoskeletal complications during infancy, which was likely due to widespread supplementation with vitamin D. The mean±SD concentration of 3-epi-25(OH)D₃, detectable in 99.4% of cord samples, was 3.3±1.9nmol/L. The proportion of 25(OH)D as 3-epi-25(OH)D₃ was 11.2%. Cord 3-epi-25(OH)D₃ concentrations were positively predicted by cord 25(OH)D₃ [0.101 (0.099, 0.103) nmol/L, P<0.0001] and negatively by gestational age [-0.104 (-0.131, -0.076) nmol/L, P<0.0001] and maternal age [-0.010 (-0.019, -0.001) nmol/L, P<0.05]. 25(OH)D₂ was detected in 98% of cord sera (mean±SD; 2.2±1.9nmol/L) despite low antenatal consumption of vitamin D₂ supplements. In conclusion, these first CDC-accredited data of vitamin D metabolites in umbilical cord blood emphasise the high risk of very low vitamin D status in infants born to un-supplemented mothers. Experimental data to define maternal vitamin D requirements for prevention of neonatal deficiency at high latitude are required.

Prevalence of vitamin D deficiency and insufficiency among schoolchildren in Greece: the role of sex, degree of urbanisation and seasonality

The current study was aiming to report the prevalence of suboptimal vitamin D status among schoolchildren in Greece and investigate the role of sex, urbanisation and seasonality on vitamin D status. A sample of 2386 schoolchildren (9–13 years old) from four distinct prefectures was examined. The prevalence of 25-hydroxyvitamin D (25(OH)D) concentration <30 and <50 nmol/l (vitamin D deficiency and insufficiency respectively) was 5·2 and 52·5 %, respectively. Girls had a higher prevalence of 25(OH)D<30 (7·2 v. 3·2 %) and 50 nmol/l (57·0 v. 48·0 %) than boys (P<0·001). The highest prevalence rates of 25(OH)D<30 and 50 nmol/l (9·1 and 73·1 %, respectively) were observed during spring (April to June), whereas the lowest (1·5 and 31·9 %, respectively) during autumn (October to December). The prevalence of 25(OH)D<50 nmol/l was higher in urban/semi-urban than rural regions, particularly during spring months (74·6 v. 47·2 %; P<0·001). Female sex, urban/semi-urban region of residence and spring months were found to increase the likelihood of vitamin D deficiency and insufficiency, with the highest OR observed for spring months (7·47; 95 % CI 3·23, 17·3 and 5·14; 95 % CI 3·84, 6·89 for 25(OH)D<30 and 50 nmol/l respectively). In conclusion, despite the southerly latitude, the prevalence of low vitamin D status among primary schoolchildren in Greece is comparable to or exceeds the prevalence reported among children and adolescents on a European level. Sub-populations at highest risk are girls in urban/semi-urban areas during spring months, thus indicating the need for effective initiatives to support adequate vitamin D status in these population groups.

Food-based solutions for vitamin D deficiency: putting policy into practice and the key role for research

Recent re-evaluations of dietary reference values (DRV) for vitamin D have established intake requirements between 10 and 20 µg/d. National nutrition surveys indicate that habitual mean intakes of vitamin D in the population are typically in the range 3-7 µg/d. As vitamin D supplementation will not be effective at a population level because the uptake is generally low, creative food-based solutions are needed to bridge the gap between current intakes and these new requirement values. The overarching aim of this review is to highlight how food-based solutions can have an important role in bridging this gap and counteracting vitamin D inadequacy in Europe and elsewhere. The present review initially briefly overviews very recent new European DRV for vitamin D and, while not in agreement on requirement estimates, how they point very clearly to the need for food-based solutions. The review discusses the need for traditional fortification of foods in the dairy and other sectors, and finally overviews recent advances in the area of biofortification of food with vitamin D. In conclusion, increasing vitamin D intakes across the population distribution is important from a public health perspective to reduce the high degree of inadequacy of vitamin D intake in Europe. Fortification, including biofortification, of a wider range of foods, which accommodate diversity, is likely to have the potential to increase vitamin D intakes across the population distribution. Research has had, and will continue to have, a key role in terms of developing food-based solutions and tackling vitamin D deficiency.

Vitamin D status is associated with uteroplacental dysfunction indicated by pre-eclampsia and small-for-gestational-age birth in a large prospective pregnancy cohort in Ireland with low vitamin D status

BACKGROUND

Associations between vitamin D and pregnancy outcomes have been inconsistent.

OBJECTIVES

We described the distribution of 25-hydroxyvitamin D3 [25(OH)D3], 3-epi-25(OH)D3, and 25(OH)D2 in early pregnancy and investigated associations with pre-eclampsia and small-for-gestational-age (SGA) birth, which are indicative of uteroplacental dysfunction.

DESIGN

The SCOPE (Screening for Pregnancy Endpoints) Ireland prospective pregnancy cohort study included 1768 well-characterized low-risk, nulliparous women resident at 52°N. Serum 25(OH)D3, 3-epi-25(OH)D3, and 25(OH)D2 were quantified at 15 wk of gestation with the use of a CDC-accredited liquid chromatography-tandem mass spectrometry method.

RESULTS

The mean ± SD total 25(OH)D concentration was 56.7 ± 25.9 nmol/L, and 17% and 44% of women had 25(OH)D concentrations <30 and <50 nmol/L, respectively. The prevalence of pre-eclampsia was 3.8%, and 10.7% of infants were SGA. There was a lower risk of pre-eclampsia plus SGA combined (13.6%) at 25(OH)D concentrations >75 nmol/L (adjusted OR: 0.64; 95% CI: 0.43, 0.96). The main predictors of 25(OH)D were the use of vitamin D-containing supplements (adjusted mean difference: 20.1 nmol/L; 95% CI: 18.5, 22.7 nmol/L) and summer sampling (adjusted mean difference: 15.5 nmol/L; 95% CI: 13.4, 17.6 nmol/L). Non-Caucasian ethnicity (adjusted mean difference: -19.3 nmol/L; 95% CI: -25.4, -13.2 nmol/L) and smoking (adjusted mean difference: -7.0 nmol/L; 95% CI: -10.5, -3.6 nmol/L) were negative predictors of 25(OH)D. The mean ± SD concentration of 3-epi-25(OH)D3, which was detectable in 99.9% of samples, was 2.6 ± 1.6 nmol/L. Determinants of 3-epi-25(OH)D3 were 25(OH)D3 (adjusted mean difference: 0.052 nmol/L; 95% CI: 0.050, 0.053 nmol/L) and maternal age (adjusted mean difference: -0.018 nmol/L; 95% CI: -0.026, -0.009 nmol/L). The mean ± SD concentration of 25(OH)D2 was 3.1 ± 2.7 nmol/L, which was present in all samples. No adverse effects of 25(OH)D concentrations >125 nmol/L were observed.

CONCLUSIONS

In the first report to our knowledge of CDC-accredited 25(OH)D data and pregnancy outcomes from a large, clinically validated, prospective cohort study, we observed a protective association of a 25(OH)D concentration >75 nmol/L and a reduced risk of uteroplacental dysfunction as indicated by a composite outcome of SGA and pre-eclampsia. Well-designed, adequately powered randomized controlled trials are required to verify this observation. The SCOPE pregnancy cohort was registered at www.anzctr.org.au as ACTRN12607000551493.

Standardizing serum 25-hydroxyvitamin D data from four Nordic population samples using the Vitamin D Standardization Program protocols: Shedding new light on vitamin D status in Nordic individuals

Knowledge about the distributions of serum 25-hydroxyvitamin D (25(OH)D) concentrations in representative population samples is critical for the quantification of vitamin D deficiency as well as for setting dietary reference values and food-based strategies for its prevention. Such data for the European Union are of variable quality making it difficult to estimate the prevalence of vitamin D deficiency across member states. As a consequence of the widespread, method-related differences in measurements of serum 25(OH)D concentrations, the Vitamin D Standardization Program (VDSP) developed protocols for standardizing existing serum 25(OH)D data from national surveys around the world. The objective of the present work was to apply the VDSP protocols to existing serum 25(OH)D data from a Danish, a Norwegian, and a Finnish population-based health survey and from a Danish randomized controlled trial. A specifically-selected subset (n 100-150) of bio-banked serum samples from each of the studies were reanalyzed for 25(OH)D by LC-MS/MS and a calibration equation developed between old and new 25(OH)D data, and this equation was applied to the entire data-sets from each study. Compared to estimates based on the original serum 25(OH)D data, the percentage vitamin D deficiency (< 30 nmol/L) decreased by 21.5% in the Danish health survey but by only 1.4% in the Norwegian health survey; but was relatively unchanged (0% and 0.2%) in the Finish survey or Danish RCT, respectively, following VDSP standardization. In conclusion, standardization of serum 25(OH)D concentrations is absolutely necessary in order to compare serum 25(OH)D concentrations across different study populations, which is needed to quantify and prevent vitamin D deficiency.

Vitamin D and oxidation-induced DNA damage: is there a connection?

Oxidation-induced damage to DNA can cause mutations, phenotypic changes and apoptosis. Agents that oppose such damage offer potential therapies for disease prevention. Vitamin D administration reportedly lowered DNA damage in type 2 diabetic mice, and higher DNA damage was reported in mononuclear cells of severely asthmatic patients who were vitamin D deficient. We hypothesised that lower vitamin D status associates with higher oxidation-induced DNA damage. Vitamin D deficiency (plasma 25(OH)D < 50 nmol/l) is highly prevalent worldwide, and association with DNA damage has high potential importance and impact in regard to the future health of vitamin D deficient young adults. In this study, oxidation-induced DNA damage in peripheral lymphocytes of 121 young (18-26 years) adults was measured using the formamidopyrimidine DNA glycosylase (FPG)-assisted comet assay. Plasma 25(OH)D was measured by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Correlational analysis was performed between 25(OH)D and DNA damage. Differences in DNA damage across tertiles of 25(OH)D were explored using analysis of variance. DNA damage in those with 25(OH)D <50 nmol and ≥50 nmol/l was compared using the unpaired t-test. Mean (SD) DNA damage (as %DNA in comet tail) and plasma 25(OH)D were, respectively, 18.58 (3.39)% and 44.7 (13.03) nmol/l. Most (82/121; 68%) of the subjects were deficient in vitamin D (25(OH)D <50nmol/l). No significant correlation was seen between 25(OH)D and DNA damage (r = -0.0824; P > 0.05). No significant difference was seen across 25(OH)D tertiles: mean (SD) %DNA in comet tail/25(OH)D nmol/l values in lowest, middle and highest tertiles were, respectively, 18.64 (3.30)/31.6 (4.4), 18.90 (3.98)/42.9 (3.5), 18.19 (2.84)/59.9 (8.5), nor across the binary divide: 18.73 (3.63)% in <50nmol/l group vs. 18.27 (2.84)% in the ≥50 nmol/l group. No association between vitamin D and oxidation-induced DNA damage was observed, but vitamin D deficiency was highly prevalent in the young adults studied, and we cannot rule out an ameliorative effect of correction of vitamin D deficiency on DNA damage.

Vitamin D-Fortified Bread Is as Effective as Supplement in Improving Vitamin D Status: A Randomized Clinical Trial

CONTEXT

Bread can potentially be a suitable vehicle for fortification with vitamin D.

OBJECTIVE

This study was undertaken to evaluate the following: 1) the bioavailability of vitamin D from the fortified Iranian bread and 2) the possible effects of daily consumption of the fortified bread on certain health aspects.

DESIGN, SETTING, AND PARTICIPANTS

This was a randomized, double-blind, placebo-controlled trial conducted over 8 weeks in 90 healthy subjects aged 20-60 years.

INTERVENTION

Subjects were randomly allocated to one of three groups: 1) fortified bread (FP; 50 g bread fortified with 25 μg vitamin D3 plus placebo daily; n = 30); 2) supplement (SP; 50 g plain bread plus 25 μg vitamin D supplement daily; n = 30); and 3) control (CP; 50 g plain bread plus placebo daily; n = 30).

OUTCOME MEASURES

Initial and final anthropometric and biochemical assessments were performed.

RESULTS

The within-group changes of serum 25-hydroxyvitamin D concentrations were 39.0 ± 22.6 (P < .001), 28.9 ± 31.2 (P < .001), and -9.2 ± 12.3 nmol/L in the FP, SP, and CP groups, respectively. Only in FP and SP groups, serum intact PTH concentrations decreased approximately 13.5% and 14.5%, respectively. Visceral fat also showed a significant decrement in FP (-1.05% ± 1.4%; P ≤ .001) and SP (-0.96% ± 1.7%; P = .006). Serum low-density lipoprotein cholesterol concentration showed a within-group reduction in FP (-10.4 ± 11.2 mg/dL; P < .001) and an insignificant decrement in SP (-6.6 ± 20.2 mg/dL; P = .083). Serum high-density lipoprotein increased in both vitamin D-supplemented groups (FP: 9.7 ± 7.6 vs SP: 5.7 ± 6.7 mg/dL; P < .001).

CONCLUSION

Vitamin D-fortified bread could be potentially effective in raising circulating 25-hydroxyvitamin D levels of the population to nearly adequate levels.

Vitamin D deficiency in Europe: pandemic?

BACKGROUND

Vitamin D deficiency has been described as being pandemic, but serum 25-hydroxyvitamin D [25(OH)D] distribution data for the European Union are of very variable quality. The NIH-led international Vitamin D Standardization Program (VDSP) has developed protocols for standardizing existing 25(OH)D values from national health/nutrition surveys.

OBJECTIVE

This study applied VDSP protocols to serum 25(OH)D data from representative childhood/teenage and adult/older adult European populations, representing a sizable geographical footprint, to better quantify the prevalence of vitamin D deficiency in Europe.

DESIGN

The VDSP protocols were applied in 14 population studies [reanalysis of subsets of serum 25(OH)D in 11 studies and complete analysis of all samples from 3 studies that had not previously measured it] by using certified liquid chromatography-tandem mass spectrometry on biobanked sera. These data were combined with standardized serum 25(OH)D data from 4 previously standardized studies (for a total n= 55,844). Prevalence estimates of vitamin D deficiency [using various serum 25(OH)D thresholds] were generated on the basis of standardized 25(OH)D data.

RESULTS

An overall pooled estimate, irrespective of age group, ethnic mix, and latitude of study populations, showed that 13.0% of the 55,844 European individuals had serum 25(OH)D concentrations <30 nmol/L on average in the year, with 17.7% and 8.3% in those sampled during the extended winter (October-March) and summer (April-November) periods, respectively. According to an alternate suggested definition of vitamin D deficiency (<50 nmol/L), the prevalence was 40.4%. Dark-skinned ethnic subgroups had much higher (3- to 71-fold) prevalence of serum 25(OH)D <30 nmol/L than did white populations.

CONCLUSIONS

Vitamin D deficiency is evident throughout the European population at prevalence rates that are concerning and that require action from a public health perspective. What direction these strategies take will depend on European policy but should aim to ensure vitamin D intakes that are protective against vitamin D deficiency in the majority of the European population.

Pre-diagnostic vitamin D concentrations and cancer risks in older individuals: an analysis of cohorts participating in the CHANCES consortium

The associations of circulating 25-hydroxyvitamin D [25(OH)D] concentrations with total and site-specific cancer incidence have been examined in several epidemiological studies with overall inconclusive findings. Very little is known about the association of vitamin D with cancer incidence in older populations. We assessed the association of pre-diagnostic serum 25(OH)D levels with incidence of all cancers combined and incidence of lung, colorectal, breast, prostate and lymphoid malignancies among older adults. Pre-diagnostic 25(OH)D concentrations and cancer incidence were available in total for 15,486 older adults (mean age 63, range 50-84 years) participating in two cohort studies: ESTHER (Germany) and TROMSØ (Norway); and a subset of previously published nested-case control data from a another cohort study: EPIC-Elderly (Greece, Denmark, Netherlands, Spain and Sweden) from the CHANCES consortium on health and aging. Cox proportional hazards or logistic regression were used to derive multivariable adjusted hazard and odds ratios, respectively, and their 95% confidence intervals across 25(OH)D categories. Meta-analyses with random effects models were used to pool study-specific risk estimates. Overall, lower 25(OH)D concentrations were not significantly associated with increased incidence of most of the cancers assessed. However, there was some evidence of increased breast cancer and decreased lymphoma risk with higher 25(OH)D concentrations. Our meta-analyses with individual participant data from three large European population-based cohort studies provide at best limited support for the hypothesis that vitamin D may have a major role in cancer development and prevention among European older adults.

Tackling inadequate vitamin D intakes within the population: fortification of dairy products with vitamin D may not be enough

Dietary recommendations for vitamin D are designed by authoritative agencies to prevent vitamin D deficiency in the population, and while individual target intakes around the globe vary, they are generally between 10 and 20 μg/day [400-800 IU/day], depending on age, assuming little or no sunshine exposure. National dietary surveys report usual intakes of vitamin D that are much lower than these targets, at about 3-7 μg/day [120-280 IU/day], depending on usual diet, age, sex, and mandatory or voluntary fortification practices, and there is widespread dietary inadequacy around the globe. While acknowledging the valuable contribution fortified milk makes to vitamin D intakes among consumers, particularly in children, and the continued need for fortification of milk and other dairy products, additional strategic approaches to fortification, including biofortification, of a wider range of foods, have the potential to increase vitamin D intakes in the population and minimize the prevalence of low serum 25(OH)D without increasing the risk of excessive dosing. Careful consideration must be given to the range of products used for fortification and the amount of vitamin D used in each; there is a need for well-designed and sustainable fortification, and biofortification strategies for vitamin D, which use a range of foods to accommodate dietary diversity. Clinical patients may require additional consideration in terms of addressing low vitamin D status.

An Integrated Predictive Model of Population Serum 25-Hydroxyvitamin D for Application in Strategy Development for Vitamin D Deficiency Prevention

BACKGROUND

To enable food-based strategies for the prevention of vitamin D deficiency to be evidence-based, there is a need to develop integrated predictive models of population serum 25-hydroxyvitamin D [25(OH)D] that are responsive to both solar and dietary inputs of vitamin D.

OBJECTIVES

The objectives of this work were to develop and validate an integrated mathematical model with the use of data on UVB availability, exposure, and dietary intake to predict serum 25(OH)D concentrations in a nationally representative sample of adults, and then test the model's performance with the use of 3 hypothetical fortification scenarios as exemplars.

METHODS

Data on UVB availability and hours of sunlight in Ireland were used in a mathematical model to predict serum 25(OH)D in Irish adults aged 18-64 y. An equation from our dose-related vitamin D supplementation trial in adults was developed and integrated into the model, which allowed us to predict the impact of changes in dietary vitamin D on the contribution to annual serum 25(OH)D concentrations, accounting for seasonality of UVB availability. Recently published estimates of the impact of 3 vitamin D food fortification scenarios on vitamin D intake in a representative sample of Irish adults were used in the model as a test.

RESULTS

The UVB- and vitamin D intake-serum 25(OH)D components of the integrated model were both validated with the use of independent data. The model predicted that the percentage of vitamin D deficiency [serum 25(OH)D <30 nmol/L] in the adult population during an extended winter period was 18.1% (vs. 18.6% measured), which could be reduced in a stepwise manner with the incorporation of an increased number of vitamin D-fortified foods, down to 6.6% with the inclusion of enhanced fortified dairy-related products, fat spreads, fruit juice and drinks, and cereal products.

CONCLUSION

Mathematical models have the ability to inform how vitamin D food fortification in various constructs may affect population serum 25(OH)D concentrations and the prevalence of vitamin D deficiency.

Vitamin D deficiency is common among adults in Wallonia (Belgium, 51°30' North): findings from the Nutrition, Environment and Cardio-Vascular Health study

Data on the vitamin D status of the population of Wallonia (Belgium, 51°30' North) are scarce. This study was carried out to estimate vitamin D deficiency, identify potential determinants, and analyze their relationship with vitamin D supplementation. We tested the hypothesis that vitamin D deficiency is common in the general population, particularly among subjects without supplementation. Vitamin D deficiency was defined as a serum level of 25-hydroxyvitamin D (25(OH)D) concentration less than 50nmol/L. Data were analyzed from 915 participants of the Nutrition, Environment and Cardio-Vascular Health cross-sectional survey. The median (interquartile range) 25(OH)D level was 53.1 (37.8-69.9) nmol/L, and 44.7% of the subjects were vitamin D deficient. Subjects without vitamin D supplementation were more concerned by vitamin D deficiency than those with supplementation (odds ratio [OR], 3.35; P < .0001). From a multivariate standpoint, the potential determinants of vitamin D deficiency among subjects without vitamin D supplementation were season, specifically spring and winter (OR, 7.36 and 6.44, respectively), obesity (OR, 2.19), low household income (OR, 1.73), and lack of solarium use (OR, 1.79). For subjects with supplementation, the only determinant observed for vitamin D deficiency was obesity (OR, 5.00). This work evidenced the high prevalence of 25(OH)D deficiency in the general population, especially among nonsupplemented subjects with obesity, low household income, and/or lack of light. Vitamin D supplementation looks effective in our population, especially via a stabilization of vitamin D coverage throughout the seasons. The best dietary strategy to achieve optimal 25(OH)D concentrations all year round in the general population requires more research.

Vitamin D: dietary requirements and food fortification as a means of helping achieve adequate vitamin D status

Vitamin D deficiency is evident in many parts of the globe, even in the sunnier regions, for a variety of reasons. Such deficiency contributes to risk of metabolic bone disease as well as potentially other non-skeletal chronic diseases in both early-life and later-life, and thus strategies for its prevention are of major public health importance. Dietary Reference Intervals (called Dietary Reference Intakes (DRI) and Dietary Reference Values (DRVs) in North America and Europe, respectively) for vitamin D have a key role in protecting against vitamin D deficiency in the population, and these have been re-evaluated in recent years on both sides of the Atlantic. The current DRI and DRVs for vitamin D and their basis will be overviewed in this review as well as some limitations that existed within the evidence-base and which contribute some degree of uncertainty to these new requirement estimates for vitamin D. The review will also compare current population intake estimates for children and adults in North America and Europe against the estimated average requirement (EAR) for vitamin D, as a benchmark of nutritional adequacy. While vitamin D supplementation has been suggested as a method of bridging the gap between current vitamin D intakes and new recommendations, the level of usage of vitamin D supplements in many countries as well as the vitamin D content of available supplements in these countries, appears to be low. The fortification of food with vitamin D has been suggested as a strategy for increasing intake with potentially the widest reach and impact in the population. The present review will highlight the need to re-evaluate current food fortification practices as well as consider new additional food-based approaches, such as biofortification of food with vitamin D, as a means of collectively tackling the low intakes of vitamin D within populations and the consequent high prevalence of low vitamin D status that are observed. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

Skin changes after bariatric surgery

Today, obesity is considered an epidemic all over the world and it is recognized as one of the major public health problems. Bariatric surgery is considered an appropriate therapeutic option for obesity with progressively increasing demands. The changes resulting from massive weight loss after bariatric surgery are related to numerous complications. This article will present the dermatological alterations that can be found after bariatric surgery. They will be subdivided into dermatoses that are secondary to metabolic and nutritional disorders, those derived from cutaneous structural modifications after major weight loss and the influence the latter may have in improving of certain dermatoses.

Ultraviolet radiation exposure and serum vitamin D levels in young children

AIM

Health benefits of adequate vitamin D levels in the blood include better bone health and a reduced incidence of a range of chronic diseases and infections. Ultraviolet (UV) radiation exposure from the sun is the main source of vitamin D; however, such exposure, especially from a young age, is also a potential risk factor for skin cancer. The current study examined the association of UV exposure with vitamin D production in young children to determine the period of weekly exposure prior to blood testing that affected serum 25-hydroxyvitamin D (25(OH)D) levels.

METHODS

Between 2009 and 2011, healthy children aged 3, 6 and 9 years were recruited from the community for a cross-sectional study of nutritional factors and DNA damage. Parents of 464 children provided information on the children's average weekly sun exposure and level of sun protection during each of the 16 weeks before blood sample collection by a domiciliary phlebotomist.

RESULTS

Serum 25(OH)D levels were best predicted from UV exposure during the week before blood collection for samples drawn in autumn, summer or spring. For samples drawn in winter, serum 25(OH)D levels were best predicted by UV exposure during the 2 weeks before blood collection.

CONCLUSIONS

Consistent weekly sun exposure may be beneficial for young children, especially in winter, to maintain healthy vitamin D levels in the blood. However, confirmation of these results is needed before their public health significance can be fully evaluated.

Dietary vitamin D₂--a potentially underestimated contributor to vitamin D nutritional status of adults?

It has been suggested that vitamin D₂ is not very prevalent in the human food chain. However, data from a number of recent intervention studies suggest that the majority of subjects had measurable serum 25-hydroxyvitamin D₂ (25(OH)D₂) concentrations. Serum 25(OH)D₂, unlike 25(OH)D₃, is not directly influenced by exposure of skin to sun and thus has dietary origins; however, quantifying dietary vitamin D₂ is difficult due to the limitations of food composition data. Therefore, the present study aimed to characterise serum 25(OH)D₂ concentrations in the participants of the National Adult Nutrition Survey (NANS) in Ireland, and to use these serum concentrations to estimate the intake of vitamin D₂ using a mathematical modelling approach. Serum 25(OH)D₂ concentration was measured by a liquid chromatography-tandem MS method, and information on diet as well as subject characteristics was obtained from the NANS. Of these participants, 78.7 % (n 884) had serum 25(OH)D₂ concentrations above the limit of quantification, and the mean, maximum, 10th, 50th (median) and 90th percentile values of serum 25(OH)D₂ concentrations were 3.69, 27.6, 1.71, 2.96 and 6.36 nmol/l, respectively. To approximate the intake of vitamin D₂ from these serum 25(OH)D₂ concentrations, we used recently published data on the relationship between vitamin D intake and the responses of serum 25(OH)D concentrations. The projected 5th to 95th percentile intakes of vitamin D₂ for adults were in the range of 0.9-1.2 and 5-6 μg/d, respectively, and the median intake ranged from 1.7 to 2.3 μg/d. In conclusion, the present data demonstrate that 25(OH)D₂ concentrations are present in the sera of adults from this nationally representative sample. Vitamin D₂ may have an impact on nutritional adequacy at a population level and thus warrants further investigation.