Estimation of the dietary requirement for vitamin D in adolescents aged 14-18 y: a dose-response, double-blind, randomized placebo-controlled trial

Vitamin D Status During Adolescence and the Impact of Lifestyle Changes: 2 Years' Follow-up From the Fit Futures Study

CONTEXT

Longitudinal data regarding vitamin D status in adolescence is scarce. This study presents population-based data from an Arctic adolescent population (n = 589) at 16 and 18 years.

OBJECTIVE

The aims of this study were to investigate changes in vitamin D status during 2 years in adolescence, and whether lifestyle changes were associated with serum 25-hydroxyvitamin D (s-25(OH)D) at follow-up.

METHODS

Fit Futures is a longitudinal study at 69°N in Norway. Participants had their s-25(OH)D levels analyzed in their first and third year of upper secondary school (median age 16 and 18 years), in Fit Futures 1 (FF1) and Fit Futures 2 (FF2), respectively. Self-reported lifestyle habits were registered through questionnaires. The association between lifestyle changes and s-25(OH)D levels at follow-up were calculated by regression analyses, controlling for baseline s-25(OH)D levels.

RESULTS

Longitudinal data were available for 309 girls and 280 boys. The proportion of adolescents with s-25(OH)D <50 nmol/L were 73.7% in FF1 and 77.1% in FF2, while the proportion <30 nmol/L constituted 35.7% in FF1 and 40.9% in FF2. Of those with s-25(OH)D <30 nmol/L (severe vitamin D deficiency) in FF1, 73.3% remained severely deficient in FF2. Among boys, an increase in UV exposure was significantly associated with higher s-25(OH)D levels in FF2 (beta; CI [nmol/L] 12.9; 9.1, 16.7). In girls, decreased vitamin/mineral supplement intake was significantly associated with lower s-25(OH)D at FF2 (-6.7; -10.2, -3.1), while increased UV (10.8; 7.0, 14.7) and combined hormonal contraceptive exposure (12.1; 6.0, 18.1) in FF2 was significantly associated with higher s-25(OH)D levels in FF2.

CONCLUSION

Severe vitamin D deficiency was prevalent throughout adolescence. Lifestyle changes may alter s-25(OH)D levels in this age group.

An Update on the Effects of Vitamin D on the Immune System and Autoimmune Diseases

Vitamin D intervenes in calcium and phosphate metabolism and bone homeostasis. Experimental studies have shown that 1,25-dihydroxyvitamin D (calcitriol) generates immunologic activities on the innate and adaptive immune system and endothelial membrane stability. Low levels of serum 25-hydroxyvitamin D (25(OH)D) are associated with an increased risk of developing immune-related diseases such as psoriasis, type 1 diabetes, multiple sclerosis, and autoimmune diseases. Various clinical trials describe the efficacy of supplementation of vitamin D and its metabolites for treating these diseases that result in variable outcomes. Different disease outcomes are observed in treatment with vitamin D as high inter-individual difference is present with complex gene expression in human peripheral blood mononuclear cells. However, it is still not fully known what level of serum 25(OH)D is needed. The current recommendation is to increase vitamin D intake and have enough sunlight exposure to have serum 25(OH)D at a level of 30 ng/mL (75 nmol/L) and better at 40–60 ng/mL (100–150 nmol/L) to obtain the optimal health benefits of vitamin D.

Adequacy of calcium and vitamin D nutritional status in a nationally representative sample of Irish teenagers aged 13-18 years

CONTEXT AND PURPOSE

In light of the key roles of vitamin D and calcium in adolescent bone health, there is a critical need for representative data on nutritional status for both micronutrients in teenagers. The present work used data from the recent representative National Teens' Food Survey II (2019-2020) to assess calcium and vitamin D intakes of teenagers in Ireland, including adequacy of such intakes, as well as, for the first time, to characterise serum 25-hydroxyvitamin D (25(OH)D) concentrations and their determinants.

METHODS

Usual calcium and vitamin D intake estimates were generated using food intake data (via 4-day weighed food records) from a nationally representative sample of teenagers aged 13-18 years in Ireland (n 428). Serum 25(OH)D was measured (via LC-MS/MS) in the 57.5% (n 246) who provided a blood sample.

RESULTS

Sixty-seven and 94% of Irish teenagers had intakes of calcium and vitamin D below the respective Estimated Average Requirements values, reflecting a high degree of inadequacy of intake for both micronutrients (and higher in girls than boys; P < 0.001). In addition, 21.7% and 33.1% of teenagers had serum 25(OH)D < 30 nmol/L (risk of vitamin D deficiency) and 30-49.9 nmol/L (inadequacy), respectively. Extended winter sampling, being aged 16-18 years, low total vitamin D intake, being overweight/obese or being of non-white skin type were significant (P < 0.05) predictors of serum 25(OH)D < 30 nmol/L.

CONCLUSIONS

There was a high prevalence of inadequacy of intake of calcium and vitamin D in Irish teenagers, and a fifth were at increased risk of vitamin D deficiency.

Implementation strategies for improving vitamin D status and increasing vitamin D intake in the UK: current controversies and future perspectives: proceedings of the 2nd Rank Prize Funds Forum on vitamin D

A multi-disciplinary expert group met to discuss vitamin D deficiency in the UK and strategies for improving population intakes and status. Changes to UK Government advice since the 1st Rank Forum on Vitamin D (2009) were discussed, including rationale for setting a reference nutrient intake (10 µg/d; 400 IU/d) for adults and children (4+ years). Current UK data show inadequate intakes among all age groups and high prevalence of low vitamin D status among specific groups (e.g. pregnant women and adolescent males/females). Evidence of widespread deficiency within some minority ethnic groups, resulting in nutritional rickets (particularly among Black and South Asian infants), raised particular concern. Latest data indicate that UK population vitamin D intakes and status reamain relatively unchanged since Government recommendations changed in 2016. Vitamin D food fortification was discussed as a potential strategy to increase population intakes. Data from dose-response and dietary modelling studies indicate dairy products, bread, hens' eggs and some meats as potential fortification vehicles. Vitamin D3 appears more effective than vitamin D2 for raising serum 25-hydroxyvitamin D concentration, which has implications for choice of fortificant. Other considerations for successful fortification strategies include: (i) need for 'real-world' cost information for use in modelling work; (ii) supportive food legislation; (iii) improved consumer and health professional understanding of vitamin D's importance; (iv) clinical consequences of inadequate vitamin D status and (v) consistent communication of Government advice across health/social care professions, and via the food industry. These areas urgently require further research to enable universal improvement in vitamin D intakes and status in the UK population.

How Much Does Serum 25(OH)D Improve by Vitamin D Supplement and Fortified Food in Children? A Systematic Review and Meta-Analysis

OBJECTIVES

This study was conducted to respond certain important questions regarding the efficacy of vitamin D fortification and supplementation in children using a meta-analytical approach.

METHODS

MEDLINE, PubMed, Embase, Cochrane Library, and Google Scholar were searched, and 2341 studies were found in a preliminary search. After screening of titles and abstracts, 31 studies were selected.

RESULTS

Significant raises in circulating 25-hydroxy vitamin D (25(OH)D) concentrations were observed in both groups that took vitamin D supplement (mean difference [MD] 28.7, 95% confidence interval [CI] 22.5-34.9) and vitamin D-fortified foods (MD 20.29, 95% CI 13.3-27.2). The meta-regression revealed a significant association between age of participants (B -1.4, 95% CI -2.8, -0.02, P = 0.047) and dose of vitamin D (B 0.007, 95% CI 0.003, 0.01, P < 0.001), with the effect on serum 25(OH)D concentrations. The analysis showed that serum 25(OH)D concentration increases by 0.7 nmol/L for every 100 IU of vitamin D intake after adjustment for age, baseline serum 25(OH)D and latitude which is far less than the reported amount in adults.

CONCLUSIONS

Altogether, these findings indicate that in a mass vitamin D fortification program, circulating 25(OH)D concentration response in children may be lower in children than in adults and vitamin D supplementation may still be needed in this subpopulation.

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.

Vitamin D: Dosing, levels, form, and route of administration: Does one approach fit all?

The 4^th International Conference on Controversies in Vitamin D was held as a virtual meeting in September, 2020, gathering together leading international scientific and medical experts in vitamin D. Since vitamin D has a crucial role in skeletal and extra-skeletal systems, the aim of the Conference was to discuss improved management of vitamin D dosing, therapeutic levels and form or route of administration in the general population and in different clinical conditions. A tailored approach, based on the specific mechanisms underlying vitamin D deficiency in different diseases that were discussed, was recommended. Specifically, in comparison to healthy populations, higher levels of vitamin D and greater amounts of vitamin D were deemed necessary in osteoporosis, diabetes mellitus, obesity (particularly after bariatric surgery), and in those treated with glucocorticoids. Emerging and still open issues were related to target vitamin D levels and the role of vitamin D supplementation in COVID-19 since low vitamin D may predispose to SARS-CoV-2 infection and to worse COVID-19 outcomes. Finally, whereas oral daily cholecalciferol appears to be the preferred choice for vitamin D supplementation in the general population, and in most clinical conditions, active vitamin D analogs may be indicated in patients with hypoparathyroidism and severe kidney and liver insufficiency. Parenteral vitamin D administration could be helpful in malabsorption syndromes or in states of vitamin D resistance.Specific guidelines for desired levels of vitamin D should be tailored to the different conditions affecting vitamin D metabolism with the goal to define disease-specific normative values.

Basal Vitamin D Status and Supplement Dose Are Primary Contributors to Maternal 25-Hydroxyvitamin D Response to Prenatal and Postpartum Cholecalciferol Supplementation

BACKGROUND

Variability in the 25-hydroxyvitamin D [25(OH)D] response to prenatal and postpartum vitamin D supplementation is an important consideration for establishing vitamin D deficiency prevention regimens.

OBJECTIVES

We aimed to examine interindividual variation in maternal and infant 25(OH)D following maternal vitamin D supplementation.

METHODS

In a randomized trial of maternal vitamin D supplementation (Maternal Vitamin D for Infant Growth Trial), healthy pregnant women (n = 1300) received a prenatal cholecalciferol (vitamin D-3) dose of 0, 4200, 16,800, or 28,000 IU/wk from 17 to 24 wk of gestation followed by placebo to 6 mo postpartum. A fifth group received 28,000 IU cholecalciferol/wk both prenatally and postpartum. In a subset of participants, associations of 25(OH)D with hypothesized explanatory factors were estimated in women at delivery (n = 655) and 6 mo postpartum (n = 566), and in their infants at birth (n = 502) and 6 mo of age (n = 215). Base models included initial 25(OH)D and supplemental vitamin D dose. Multivariable models were extended to include other individual characteristics and specimen-related factors. The model coefficient of determination (R2) was used to express the percentage of total variance explained.

RESULTS

Supplemental vitamin D intake and initial 25(OH)D accounted for the majority of variance in maternal 25(OH)D at delivery and postpartum (R2 = 70% and 79%, respectively). Additional characteristics, including BMI, contributed negligibly to remaining variance (<5% increase in R2). Variance in neonatal 25(OH)D was explained mostly by maternal delivery 25(OH)D and prenatal vitamin D intake (R2 = 82%). Variance in 25(OH)D in later infancy could only partly be explained by numerous biological, sociodemographic, and laboratory-related characteristics, including feeding practices (R2 = 43%).

CONCLUSIONS

Presupplementation 25(OH)D and vitamin D supplemental dose are the major determinants of the response to maternal prenatal vitamin D intake. Vitamin D dosing regimens to prevent maternal and infant vitamin D deficiency should take into consideration the mean 25(OH)D concentration of the target population.

Daily vitamin D3 in overweight and obese children and adolescents: a randomized controlled trial

PURPOSE

To assess the efficacy of different doses of vitamin D₃ on serum 25-hydroxyvitamin D (25(OH)D), intact parathyroid hormone(iPTH), calcium, phosphorus, and alkaline phosphatase concentrations in overweight and obese school-children.

METHODS

A total of 378 children and adolescents, 6-13 years of age, with age- and sex-specific body mass index(BMI) Z-score ≥ 1(according to the World Health Organization criteria) were allocated to receive 600, 1000, and 2000 IU vitamin D₃/days. 25(OH)D, iPTH, calcium, phosphorus, and alkaline phosphatase concentrations were measured at baseline, 6, and 12 months. In this intention-to-treat analysis, we fitted a linear mixed effect model involving a random effect of participants within treatment groups and fixed effects of dose, time, and their interactions.

RESULTS

Mean(SD) of age and BMI Z-score were 9.3 (1.7) years and 2.55 (0.73), respectively. The median (IQR) for 25(OH)D was 11.5 (8.9), 11.7 (10.5), 12.2 (10.2) ng/mL (28.75, 29.25, and 30.50 nmol/L) at baseline and 23.1 (8.0), 25.6 (8.3), 28.6 (10.4) ng/mL (57.75, 64.00, and 71.50 nmol/L) at the end of 12 months in 600, 1000, and 2000 IU, respectively (p values for dose, time, and the interaction being < 0.0001, < 0.0001,and 0.082, respectively). Prevalence of vitamin D deficiency (< 20 ng/mL) was 80.2, 77.5, and 75.5% in 600, 1000, and 2000 IU groups at baseline, respectively, which decreased to 34, 18.4, and 7.5%, respectively, at 12 months. Patterns of iPTH, calcium, phosphorus, and alkaline phosphatase response over time did not differ significantly among groups (p values = 0.452, 0.670, 0.377, 0.895, respectively).

CONCLUSIONS

Increases in 25(OH)D concentration were found with supplementation of 1000 and 2000 IU, compared with 600 IU/days, whereas there was no evidence of iPTH suppression or change in serum calcium, phosphorus, and alkaline phosphatase among children with excess weight.

Blueberries improve biomarkers of cardiometabolic function in participants with metabolic syndrome-results from a 6-month, double-blind, randomized controlled trial

BACKGROUND

Anthocyanin-rich blueberry intake is associated with reduced type 2 diabetes and cardiovascular disease (CVD) risk in prospective studies, although long-term randomized controlled trials (RCTs) have not been conducted in at-risk populations.

OBJECTIVE

In the longest-duration RCT to date, we examined the effect of 6-mo blueberry intake on insulin resistance and cardiometabolic function in metabolic syndrome.

METHODS

A double-blind, parallel RCT (n = 115; age 63 ± 7 y; 68% male; body mass index 31.2 ± 3.0 kg/m2) was conducted, which fed 2 dietarily achievable blueberry intakes [equivalent to 1/2 and 1 cup/d (75/150 g)] compared with matched placebo. Insulin resistance was assessed via the homeostasis model assessment of insulin resistance (primary endpoint) and confirmed by [6-6-2H2]-glucose-labeled, 2-step hyperinsulinemic clamp (n = 20). Clinically relevant cardiometabolic endpoints [including flow-mediated dilatation, augmentation index, lipoprotein status (by nuclear magnetic resonance spectroscopy), and nitric oxide (NO)-related metabolite assay] and anthocyanin metabolism were assessed.

RESULTS

A daily intake of 1 cup of blueberries improved endothelial function (flow-mediated dilatation: +1.45%; 95% CI: 0.83%, 2.1%; P = 0.003), systemic arterial stiffness (augmentation index: -2.24%; 95% CI: -3.97%, -0.61%; P = 0.04) and attenuated cyclic guanosine monophosphate concentrations. In statin nonusers (n = 71), elevated high-density lipoprotein cholesterol (+0.08 mmol/L; P = 0.03), high-density lipoprotein particle density (+0.48n, ×10-6; P = 0.002) and apolipoprotein A-I (+0.05 g/L; P = 0.01) concentrations were observed following the 1-cup/d intervention. Treatment compliance was 94.1% (wrapper returns) and total concentrations of anthocyanin-derived phenolic acid metabolites significantly increased, dose-dependently, in serum and 24-h urine (P < 0.01 and P < 0.001, respectively). Insulin resistance, pulse wave velocity, blood pressure, NO, and overall plasma thiol status were unaffected. Likewise, a half cup per day had no effect on any biomarkers.

CONCLUSIONS

Despite insulin resistance remaining unchanged we show, to our knowledge, the first sustained improvements in vascular function, lipid status, and underlying NO bioactivity following 1 cup blueberries/d. With effect sizes predictive of 12-15% reductions in CVD risk, blueberries should be included in dietary strategies to reduce individual and population CVD risk. This study was registered at clinicaltrials.gov as NCT02035592.

Current vitamin D status in European and Middle East countries and strategies to prevent vitamin D deficiency: a position statement of the European Calcified Tissue Society

Vitamin D deficiency (serum 25-hydroxyvitamin D (25(OH)D) <50 nmol/L or 20 ng/mL) is common in Europe and the Middle East. It occurs in <20% of the population in Northern Europe, in 30-60% in Western, Southern and Eastern Europe and up to 80% in Middle East countries. Severe deficiency (serum 25(OH)D <30 nmol/L or 12 ng/mL) is found in >10% of Europeans. The European Calcified Tissue Society (ECTS) advises that the measurement of serum 25(OH)D be standardized, for example, by the Vitamin D Standardization Program. Risk groups include young children, adolescents, pregnant women, older people (especially the institutionalized) and non-Western immigrants. Consequences of vitamin D deficiency include mineralization defects and lower bone mineral density causing fractures. Extra-skeletal consequences may be muscle weakness, falls and acute respiratory infection, and are the subject of large ongoing clinical trials. The ECTS advises to improve vitamin D status by food fortification and the use of vitamin D supplements in risk groups. Fortification of foods by adding vitamin D to dairy products, bread and cereals can improve the vitamin D status of the whole population, but quality assurance monitoring is needed to prevent intoxication. Specific risk groups such as infants and children up to 3 years, pregnant women, older persons and non-Western immigrants should routinely receive vitamin D supplements. Future research should include genetic studies to better define individual vulnerability for vitamin D deficiency, and Mendelian randomization studies to address the effect of vitamin D deficiency on long-term non-skeletal outcomes such as cancer.

A systematic review and meta-analysis of the response of serum 25-hydroxyvitamin D concentration to vitamin D supplementation from RCTs from around the globe

BACKGROUND/OBJECTIVES

Optimal doses of vitamin D (VitD) supplement in different populations are unclear. We aim to evaluate the relationship between VitD supplementation and post-intervention serum 25-hydroxyvitamin D [25(OH)D] concentration, to provide a recommended dosage of VitD for achieving an optimal 25(OH)D concentration for different populations.

SUBJECTS/METHODS

Literature search was conducted in Embase, etc. Randomized controlled trials about VitD supplemental intakes and their effect on 25(OH)D concentration were enrolled. The effect on 25(OH)D concentration between different supplementation doses in each population group was compared by meta-analysis. Multivariate meta-regression model is utilized to establish reference intake dosage of VitD.

RESULTS

A total of 136 articles were included about children (3-17 years), adults (18-64 years), postmenopausal women, the elderly ( >64 years), pregnant, or lactating women. Overall, intervention groups obtained higher 25(OH)D concentration than controls and there was obvious dose-response effect between intake dose and 25(OH)D concentration. Baseline 25(OH)D concentration and age were significant indicators for 25(OH)D concentration. To reach sufficient 25(OH)D concentration (75 nmol/L), the recommended VitD supplemental intakes was 1340 and 2250 IU/day for children and pregnant women, 2519 and 797 IU/day for European adults aged 18-64 and 65-85 years, 729, 2026, and 1229 IU/day for adults in North America, Asia and Middle East and Africa, respectively.

CONCLUSIONS

Regional- and age-specific recommended dosages of VitD supplements for population to achieve optimal 25(OH)D concentrations have been suggested.

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.

Assessing the effect of omega-3 fatty acid combined with vitamin D3 versus vitamin D3 alone on estradiol levels: a randomized, placebo-controlled trial in females with vitamin D deficiency

Purpose

Outcomes investigating the effect of vitamin D3 (VD3) and omega-3 fatty acids (Omega-3FA) on serum estradiol (E2) are scarce and conflicting. No previous study has investigated the effect of VD3 combination with Omega-3FA on E2 levels. This study was designed to investigate the effect of VD3, Omega-3FA and VD3 plus Omega-3FA on serum E2 levels in premenopausal females diagnosed with vitamin D deficiency (VDD).

Subjects and methods

This randomized, placebo-controlled clinical trial was designed to evaluate the effects of 50,000 IU VD3 taken weekly, 300 mg Omega-3FA taken daily and their combination by the study participants for 8 weeks. The mid-follicular serum levels of E2 and 25-hydroxy vitamin D (25OHD) were assessed at 8 weeks. The study was conducted during winter on a convenience sample of healthy premenopausal Jordanian females with diagnosed VDD. Fasting serum levels for 25OHD and E2 were assessed at baseline and the end of the trial (after 8 weeks). Data were entered into SPSS and analyzed.

Results

Healthy premenopausal Jordanian females (N=86) with diagnosed VDD, mean age 32.8±8.9 years, were recruited into the study. Supplementation of VD3 alone resulted in a significant increase in serum 25OHD (13.4±7.9–28.2±7.1 ng/mL, P<0.001) and a significant decrease in E2 levels (85.7±16.5–60.3±20.6 pg/mL, P=0.001). Omega-3FA intake led to a significant decrease in serum 25OHD levels (21.2±12.8–13.6±9.2 ng/mL, P=0.001) and a significant increase in E2 levels (56.3±19.2–78.4±23.7 pg/mL, P=0.006). Combination therapy (VD3 plus Omega-3FA) resulted in a significant increase in both 25OHD (12.0±4.7–35.1±9.5 ng/mL, P<0.001) and E2 (43.0±23.4–57.3±31.5 pg/mL, P=0.028) levels.

Conclusion

Results of this study provide vital insight into the effects of D3, Omega-3FA and a combination of their supplementation on premenopausal Jordanian females with diagnosed VDD. Eight weeks of therapy led to decreased E2 level by VD3 and increased level by Omega-3FA supplementation. With regard to 25OHD, its level was increased by VD3 and decreased by Omega-3FA supplementation. Combination of VD3 plus Omega-3FA increased the levels of both E2 and 25OHD.

Trial registration

This trial was registered at clinicaltrials.gov as NCT03333564.

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.

A systematic review and meta-analysis of prevalence of vitamin D deficiency among adolescent girls in selected Indian states

BACKGROUND:

Vitamin D deficiency among adolescents is an emerging public health priority as adolescence marks a period of rapid growth and the onset of the reproductive phase. However, lack of national prevalence data and intervention strategies is of public health concern.

OBJECTIVE:

The objective of this study was to determine the pooled prevalence of vitamin D deficiency among adolescent girls in selected Indian states.

METHODS:

A systematic literature review was performed using three different search engines. The searches yielded nine eligible articles. Study quality was assessed for 10 different criteria. Meta-analysis was performed to estimate pooled prevalence of vitamin D deficiency among adolescent girls and to assess the heterogeneity among selected studies.

RESULTS:

A sample of n=1352 was used to study prevalence among adolescent girls. The random effects combined estimate for overall prevalence was 25.70% (95% CI 3.89-2137.9). High heterogeneity (tau²=1.71, I²=100%) was observed and seven out of nine studies showed low to moderate risk and two showed high risk of bias. The test for overall effect was observed to be Z=0.77 ( p=0.44).

CONCLUSIONS:

High prevalence of vitamin D deficiency among adolescent girls identifies the need to introduce screening of adolescents and introduce proven public-health interventions such as fortification of foods to address deficiency.

Effect of vitamin D supplementation on serum 25-hydroxyvitamin D concentration in children and adolescents: a systematic review and meta-analysis protocol

INTRODUCTION

The importance of vitamin D for bone health as well as its role in non-skeletal functions has long been documented. However, review investigations on the effect of vitamin D supplementation on serum 25-hydroxyvitamin D (25(OH)D) levels in children and adolescents are scarce. The aims of the current study were to assess the impact of various doses of vitamin D supplementation on serum 25(OH)D concentrations in children and adolescents, and to identify relevant determinants of variations in the effect of vitamin D supplementation.

METHODS

PubMed, Scopus, ISI Web of Science and Cochrane Central Register of Controlled Trials databases up to 27 September 2017 will systematically be searched for randomised controlled trials of vitamin D supplementation. We considered articles with the following control groups as eligible: placebo control, control group without any supplementation or a comparative arm investigation. Two reviewers will assess articles for eligibility according to prespecified selection criteria, after which data extraction and quality appraisal will be conducted by two independent reviewers. The quality assessment will be assessed using the Jadad scale. Meta-analyses will be conducted where appropriate. We will express continuous measures (ie, serum 25(OH)D concentration) as mean differences with 95% CIs. Heterogeneity of the data will be investigated via visual inspection of the forest plots and using χ² test on N-1 df, with a significance level of α=0.1. We will also assess individual study and subgroup characteristics and perform a sensitivity analysis. Publication bias will be assessed using funnel plot and statistical analysis of Egger's test.

ETHICS AND DISSEMINATION

Ethics approval is not required because the work will be carried out on published documents. The authors will publish findings from this review through peer-reviewed publication or conference presentations.

PROSPERO REGISTRATION NUMBER

CRD42017067179.

Global prevalence and disease burden of vitamin D deficiency: a roadmap for action in low- and middle-income countries

Vitamin D is an essential nutrient for bone health and may influence the risks of respiratory illness, adverse pregnancy outcomes, and chronic diseases of adulthood. Because many countries have a relatively low supply of foods rich in vitamin D and inadequate exposure to natural ultraviolet B (UVB) radiation from sunlight, an important proportion of the global population is at risk of vitamin D deficiency. There is general agreement that the minimum serum/plasma 25-hydroxyvitamin D concentration (25(OH)D) that protects against vitamin D deficiency-related bone disease is approximately 30 nmol/L; therefore, this threshold is suitable to define vitamin D deficiency in population surveys. However, efforts to assess the vitamin D status of populations in low- and middle-income countries have been hampered by limited availability of population-representative 25(OH)D data, particularly among population subgroups most vulnerable to the skeletal and potential extraskeletal consequences of low vitamin D status, namely exclusively breastfed infants, children, adolescents, pregnant and lactating women, and the elderly. In the absence of 25(OH)D data, identification of communities that would benefit from public health interventions to improve vitamin D status may require proxy indicators of the population risk of vitamin D deficiency, such as the prevalence of rickets or metrics of usual UVB exposure. If a high prevalence of vitamin D deficiency is identified (>20% prevalence of 25(OH)D < 30 nmol/L) or the risk for vitamin D deficiency is determined to be high based on proxy indicators (e.g., prevalence of rickets >1%), food fortification and/or targeted vitamin D supplementation policies can be implemented to reduce the burden of vitamin D deficiency-related conditions in vulnerable populations.

Winter Cholecalciferol Supplementation at 55°N Has No Effect on Markers of Cardiometabolic Risk in Healthy Children Aged 4-8 Years

Background

Low serum 25-hydroxyvitamin D [25(OH)D] has been associated with unfavorable cardiometabolic risk profiles in many observational studies in children, but very few randomized controlled trials have investigated this.

Objective

We explored the effect of winter-time cholecalciferol (vitamin D3) supplementation on cardiometabolic risk markers in young, white, 4- to 8-y-old healthy Danish children (55°N) as part of the pan-European ODIN project.

Methods

In the ODIN Junior double-blind, placebo-controlled, dose-response trial, 119 children (mean ± SD age: 6.7 ± 1.5 y; 36% male; 82% normal weight) were randomly allocated to 0, 10 or 20 µg/d of vitamin D3 for 20 wk (October-March). Cardiometabolic risk markers including BMI-for-age z score (BMIz), waist circumference, systolic and diastolic blood pressure, serum triglycerides and cholesterol (total, LDL, HDL, and total:HDL), plasma glucose and insulin, and whole-blood glycated hemoglobin were measured at baseline and endpoint as secondary outcomes together with serum 25(OH)D. Intervention effects were evaluated in linear regression models as between-group differences at endpoint adjusted for baseline value of the outcome, and additionally for age, sex, baseline serum 25(OH)D, BMIz, time since breakfast, and breakfast content.

Results

Mean ± SD serum 25(OH)D was 56.7 ± 12.3 nmol/L at baseline and differed between groups at endpoint with concentrations of 31.1 ± 7.5, 61.8 ± 10.6, and 75.8 ± 11.5 nmol/L in the 0-, 10-, and 20 µg/d groups, respectively (P < 0.0001). Vitamin D3 supplementation had no effect on any of the cardiometabolic risk markers in analyses adjusted for baseline value of the outcome (all P ≥ 0.05), and additional covariate adjustment did not change the results notably.

Conclusions

Preventing the winter decline in serum 25(OH)D with daily vitamin D3 supplementation of 10 or 20 µg had no cardiometabolic effects in healthy 4- to 8-y-old Danish children. This trial was registered at www.clinicaltrials.gov as NCT02145195.

Winter Cholecalciferol Supplementation at 51°N Has No Effect on Markers of Cardiometabolic Risk in Healthy Adolescents Aged 14-18 Years

Background

Epidemiologic studies have supported inverse associations between low serum 25-hydroxyvitamin D [25(OH)D] and cardiometabolic risk markers, but few randomized trials have investigated the effect of vitamin D supplementation on these markers in adolescents.

Objective

The objective of this study was to investigate the effect of winter-time cholecalciferol (vitamin D3) supplementation on cardiometabolic risk markers in white, healthy 14- to 18-y-old adolescents in the UK (51°N) as part of the ODIN Project.

Methods

In a dose-response trial, 110 adolescents (mean ± SD age: 15.9 ± 1.4 y; 43% male; 81% normal weight) were randomly assigned to receive 0, 10 or 20 μg/d vitamin D3 for 20 wk (October-March). Cardiometabolic risk markers including BMI-for-age z score (BMIz), waist circumference, systolic and diastolic blood pressure, fasting plasma triglycerides, cholesterol (total, HDL, LDL, and total:HDL), and glucose were measured at baseline and endpoint as secondary outcomes, together with serum 25(OH)D. Intervention effects were evaluated in linear regression models as between-group differences at endpoint, adjusted for the baseline value of the outcome variable and additionally for age, sex, Tanner stage, BMIz, and baseline serum 25(OH)D.

Results

Mean ± SD baseline serum 25(OH)D was 49.1 ± 12.3 nmol/L and differed between groups at endpoint with concentrations of 30.7 ± 8.6, 56.6 ± 12.4, and 63.9 ± 10.6 nmol/L in the 0, 10, and 20 μg/d groups, respectively (P ≤ 0.001). Vitamin D3 supplementation had no effect on any of the cardiometabolic risk markers (all P > 0.05), except for lower HDL (-0.12 mmol/L; 95% CI: -0.21, 0.04 mmol/L; P = 0.003) and total cholesterol (-0.21 mmol/L; 95% CI: -0.42, 0.00 mmol/L; P = 0.05) in the 20 μg/d than in the 10 μg/d group, which disappeared in the fully adjusted analysis (P = 0.27 and P = 0.30, respectively).

Conclusions

Supplementation with vitamin D3 at 10 and 20 μg/d, which increased serum 25(OH)D concentrations during the winter-time, had no effect on markers of cardiometabolic risk in healthy 14- to 18-y-old adolescents. This trial was registered at clinicaltrials.gov as NCT02150122.

Interactions between Vitamin D Status, Calcium Intake and Parathyroid Hormone Concentrations in Healthy White-Skinned Pregnant Women at Northern Latitude

Adverse effects of low vitamin D status and calcium intakes in pregnancy may be mediated through functional effects on the calcium metabolic system. Little explored in pregnancy, we aimed to examine the relative importance of serum 25-hydroxyvitamin D (25(OH)D) and calcium intake on parathyroid hormone (PTH) concentrations in healthy white-skinned pregnant women. This cross-sectional analysis included 142 participants (14 ± 2 weeks' gestation) at baseline of a vitamin D intervention trial at 51.9 °N. Serum 25(OH)D, PTH, and albumin-corrected calcium were quantified biochemically. Total vitamin D and calcium intakes (diet and supplements) were estimated using a validated food frequency questionnaire. The mean ± SD vitamin D intake was 10.7 ± 5.2 μg/day. With a mean ± SD serum 25(OH)D of 54.9 ± 22.6 nmol/L, 44% of women were <50 nmol/L and 13% <30 nmol/L. Calcium intakes (mean ± SD) were 1182 ± 488 mg/day and 23% of participants consumed <800 mg/day. The mean ± SD serum albumin-adjusted calcium was 2.2 ± 0.1 mmol/L and geometric mean (95% CI) PTH was 9.2 (8.4, 10.2) pg/mL. PTH was inversely correlated with serum 25(OH)D (r = -0.311, p < 0.001), but not with calcium intake or serum calcium (r = -0.087 and 0.057, respectively, both p > 0.05). Analysis of variance showed that while serum 25(OH)D (dichotomised at 50 nmol/L) had a significant effect on PTH (p = 0.025), calcium intake (<800, 800⁻1000, ≥1000 mg/day) had no effect (p = 0.822). There was no 25(OH)D-calcium intake interaction effect on PTH (p = 0.941). In this group of white-skinned women with largely sufficient calcium intakes, serum 25(OH)D was important for maintaining normal PTH concentration.

Effect of Vitamin D Supplementation, Food Fortification, or Bolus Injection on Vitamin D Status in Children Aged 2-18 Years: A Meta-Analysis

Meta-analyses on the effect of vitamin D intake on status in children are lacking, especially those focused on vitamin D-fortified foods. The objective of this meta-analysis was to investigate the effect of vitamin D interventions (fortified foods, supplements, bolus injections) on vitamin D status in children 2-18 y of age. Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, literature searches were conducted up to December 2016. Randomized placebo-controlled vitamin D interventions in healthy children aged 2-18 y were included. A random-effects model was used with I2 assessing heterogeneity. We included 26 trials (5403 children) with interventions (n = 9 fortified foods, n = 15 supplements, n = 2 bolus injections) from 100-4000 IU vitamin D/d over 4 wk to 2 y. The serum 25-hydroxyvitamin D [25(OH)D] weighted mean difference for all 26 trials (23.5 nmol/L; 95% CI: 20.7, 26.3 nmol/L; I2 = 99.9%) resulted in a mean increase of 1.0 nmol/L (95% CI: 0.3, 1.7 nmol/L) for each increase of 100 IU vitamin D/d (per 1 µg/d : 0.4 nmol/L; 95% CI: 0.1, 0.7 nmol/L). The response per 100 IU vitamin D/d was greater in trials with a mean baseline serum 25(OH)D <30 nmol/L, with the use of fortified foods and with baseline vitamin D intakes <100 IU/d. In conclusion, the serum 25(OH)D response to vitamin D intake differs on the basis of baseline status, intakes, and delivery mode, but not age, sex, or latitude.

Estimation of the maternal vitamin D intake that maintains circulating 25-hydroxyvitamin D in late gestation at a concentration sufficient to keep umbilical cord sera ≥25-30 nmol/L: a dose-response, double-blind, randomized placebo-controlled trial in pregnant women at northern latitude

Background

In the absence of dose-response data, Dietary Reference Values for vitamin D in nonpregnant adults are extended to pregnancy.

Objective

The aim was to estimate vitamin D intake needed to maintain maternal 25-hydroxyvitamin D [25(OH)D] in late gestation at a concentration sufficient to prevent newborn 25(OH)D <25-30 nmol/L, a threshold indicative of increased risk of nutritional rickets.

Design

We conducted a 3-arm, dose-response, double-blind, randomized placebo-controlled trial in Cork, Ireland (51.9oN). A total of 144 white-skinned pregnant women were assigned to receive 0, 10 (400 IU), or 20 (800 IU) µg vitamin D3/d from ≤18 wk of gestation. Vitamin D metabolites at 14, 24, and 36 wk of gestation and in cord sera, including 25(OH)D3, 3-epi-25(OH)D3, 24,25(OH)2D3, and 25(OH)D2 were quantified by liquid chromatography-tandem mass spectrometry. A curvilinear regression model predicted the total vitamin D intake (from diet and antenatal supplements plus treatment dose) that maintained maternal 25(OH)D in late gestation at a concentration sufficient to maintain cord 25(OH)D at ≥25-30 nmol/L.

Results

Mean ± SD baseline 25(OH)D was 54.9 ± 10.7 nmol/L. Total vitamin D intakes at the study endpoint (36 wk of gestation) were 12.1 ± 8.0, 21.9 ± 5.3, and 33.7 ± 5.1 µg/d in the placebo and 10-µg and 20-µg vitamin D3 groups, respectively; and 25(OH)D was 24.3 ± 5.8 and 29.2 ± 5.6 nmol/L higher in the 10- and 20-µg groups, respectively, compared with placebo (P < 0.001). For maternal 25(OH)D concentrations ≥50 nmol/L, 95% of cord sera were ≥30 nmol/L and 99% were >25 nmol/L. The estimated vitamin D intake required to maintain serum 25(OH)D at ≥50 nmol/L in 97.5% of women was 28.9 µg/d.

Conclusions

Thirty micrograms of vitamin D per day safely maintained serum 25(OH)D concentrations at ≥50 nmol/L in almost all white-skinned women during pregnancy at a northern latitude, which kept 25(OH)D at >25 nmol/L in 99% and ≥30 nmol/L in 95% of umbilical cord sera. This trial was registered at www.clinicaltrials.gov as NCT02506439.

No improvement in vitamin D status in German infants and adolescents between 2009 and 2014 despite public recommendations to increase vitamin D intake in 2012

Purpose

Vitamin D is a key component for the growth and development of children and adolescents, influencing a multitude of functions. Worldwide epidemiological studies have shown that minimum vitamin D blood levels of ≥ 20.0 ng/ml, often defined as vitamin D sufficiency by international and national nutrition and pediatric organizations, are often not met in practice. In 2012 the D–A–CH (Germany, Austria, Switzerland) nutrition societies increased their vitamin D intake recommendations fourfold from 200 IU (5 µg) to 800 IU (20 µg) per day. The outcome of this study will contribute to answering the question as to whether the new recommendations for increased vitamin D intake improve the highly prevalent vitamin D deficiency status in German children and adolescents.

Methods

For this 6-year study (January 2009–December 2014) carried out in Mülheim an der Ruhr, Germany, healthy children and adolescents (n = 1929, age range 1–17 years, median age 11.0 years, 46.9% female) consulting a pediatric group practice (KIDS4.0) were recruited. Serum 25(OH)D determinations were performed using a competitive chemoluminescence immunoassay (CLIA, DiaSorin).

Results

The median serum vitamin D values for each year from 2009 to 2014 were 18.4, 13.0, 20.8, 16.4, 19.4 and 14.9 ng/ml. The summarized median 25(OH)D serum concentrations between the two time periods 2009–2012 and 2013–2014 after increasing recommendations for vitamin D intake did not show a significant difference (17.0 versus 16.8 ng/ml).

Conclusions

The increased D–A–CH recommendations for vitamin D intake had no influence on vitamin D levels in children and adolescents. The prevalence of vitamin D deficiency has not changed compared to previous studies.

Electronic supplementary material

The online version of this article (10.1007/s00394-018-1717-y) contains supplementary material, which is available to authorized users.

Vitamin D in pediatric age: consensus of the Italian Pediatric Society and the Italian Society of Preventive and Social Pediatrics, jointly with the Italian Federation of Pediatricians

Vitamin D plays a pivotal role in the regulation of calcium-phosphorus metabolism, particularly during pediatric age when nutritional rickets and impaired bone mass acquisition may occur.Besides its historical skeletal functions, in the last years it has been demonstrated that vitamin D directly or indirectly regulates up to 1250 genes, playing so-called extraskeletal actions. Indeed, recent data suggest a possible role of vitamin D in the pathogenesis of several pathological conditions, including infectious, allergic and autoimmune diseases. Thus, vitamin D deficiency may affect not only musculoskeletal health but also a potentially wide range of acute and chronic conditions. At present, the prevalence of vitamin D deficiency is high in Italian children and adolescents, and national recommendations on vitamin D supplementation during pediatric age are lacking. An expert panel of the Italian Society of Preventive and Social Pediatrics reviewed available literature focusing on randomized controlled trials of vitamin D supplementation to provide a practical approach to vitamin D supplementation for infants, children and adolescents.

Vitamin D Supplementation Guidelines for General Population and Groups at Risk of Vitamin D Deficiency in Poland-Recommendations of the Polish Society of Pediatric Endocrinology and Diabetes and the Expert Panel With Participation of National Specialist Consultants and Representatives of Scientific Societies-2018 Update

INTRODUCTION

Vitamin D deficiency is an important public health problem worldwide. Vitamin D deficiency confers a significant risk for both skeletal and non-skeletal disorders and a number of lifelong negative health outcomes. The objectives of this evidence-based guidelines document are to provide health care professionals in Poland, an updated recommendation for the prevention, diagnosis and treatment of vitamin D deficiency.

METHODS

A systematic literature search examining the prevention and treatment strategies for vitamin D deficiency was conducted. Updated recommendations were developed using the Grading of Recommendations, Assessment, Development and Evaluation system describing the strength of the recommendation and the quality of supporting evidence. Twenty-seven contributors representing different areas of expertise and medical specialties, including pediatricians, geriatricians, endocrinologists, epidemiologists, nephrologists, gynecologists and obstetricians evaluated the available published evidence related to vitamin D, formulated the goals of this document and developed a common consolidated position. The consensus group, representing six national specialist consultants and eight Polish and international scientific organizations/societies, participated in the process of grading evidence and drawing up the general and specific recommendations.

RESULTS

The updated recommendations define the diagnostic criteria for the evaluation of vitamin D status and describe the prevention and treatment strategies of vitamin D deficiency in the general population and in groups at increased risk of the deficiency. Age- and weight-specific recommendations for prevention, supplementation and treatment of vitamin D deficiency are presented, and detailed practice guidance is discussed regarding the management in primary and specialized health care.

CONCLUSION

Vitamin D deficiency remains still highly prevalent in Poland, in all age groups. Currently, there is a great necessity to implement a regular supplementation with recommended doses and to develop an effective strategy to alleviate vitamin D deficiency in the population. These updated recommendations are addressed to health professionals and the authorities pursuing comprehensive health policies and should also be included in public health programs aimed at preventing a broad spectrum of chronic diseases.

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.

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.

Vitamin D in adolescents: Are current recommendations enough?

Vitamin D is essential for bone development during adolescence and low vitamin D status during this critical period of growth may impact bone mineralization, potentially reducing peak bone mass and consequently increasing the risk of osteoporosis in adulthood. Therefore, the high prevalence of vitamin D inadequacy and deficiency in adolescent populations is of great concern. However, there is currently a lack of consensus on the 25-hydroxyvitamin D [25(OH)D] concentration, the widely accepted biomarker of vitamin D status, that defines adequacy, and the vitamin D intake requirements to maintain various 25(OH)D thresholds are not well established. While the current intake recommendations of 10-15μg/day may be sufficient to prevent vitamin D deficiency (25(OH)D<25-30nmol/l), greater intakes may be needed to achieve the higher threshold levels proposed to represent adequacy (25(OH)D>50nmol/l). This review will address these concerns and consider if the current dietary recommendations for vitamin D in adolescents are sufficient.

A weekly 35,000 IU vitamin D supplementation improves bone turnover markers in vitamin D deficient Saudi adolescent females

This study examined the effects of weekly 35,000 IU vitamin D supplementation for 4 weeks on bone turnover markers (BTMs). There was improvement in the levels of parathyroid hormone (PTH), osteocalcin, and carboxy-terminal telopeptides of crosslinks of type 1 collagen (βCTX) which paralleled the increase in vitamin D levels.

PURPOSE

The effects of vitamin D supplementation on bone turnover markers (BTMs) have been inconsistent. This study examined the effects of weekly 35,000 IU vitamin D supplementation for 1 month on BTMs.

METHODS

Sixty-eight vitamin D deficient adolescent females were given 35,000 IU of vitamin D3 for 4 weeks. Pre and post intervention blood samples were taken for 25(OH) D, PTH, osteocalcin and βCTX.

RESULTS

There was a significant increase in serum 25 (OH) D in the post intervention period which was accompanied by a significant decrease in PTH, osteocalcin and βCTX (P < 0.001).

CONCLUSIONS

We concluded that weekly 35,000 IU vitamin D supplementation for 4 weeks results in significant improvement of BTMs.

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.