Estimation of the dietary requirement for vitamin D in healthy adolescent white girls

Rapidly Increasing Serum 25(OH)D Boosts the Immune System, against Infections-Sepsis and COVID-19

Vitamin D deficiency is a global public health problem, a pandemic that commonly affects the elderly and those with comorbidities such as obesity, diabetes, hypertension, respiratory disorders, recurrent infections, immune deficiency, and malignancies, as well as ethnic minorities living in temperate countries. The same groups were worst affected by COVID-19. Since vitamin D deficiency weakens the immune system, it increases the risk of infections, complications, and deaths, such as from sepsis and COVID-19. Deficiency can be remedied cost-effectively through targeted food fortification, supplementation, and/or daily safe sun exposure. Its endocrine functions are limited to mineral metabolism, musculoskeletal systems, specific cell membrane interactions, and parathyroid gland functions. Except for the rapid, endocrine, and cell membrane-based non-genomic functions, all other biological and physiological activities of vitamin D depend on the adequate intracellular synthesis of 1,25(OH)2D (calcitriol) in peripheral target cells via the genome. Calcitriol mediates autocrine (intracrine) and paracrine signalling in immune cells, which provides broader, protective immune functions crucial to overcoming infections. The synthesis of 1,25(OH)2D (calcitriol) in peripheral target cells is dependent on diffusion and endocytosis of D3 and 25(OH)D from the circulation into them, which requires maintenance of serum 25(OH)D concentration above 50 ng/mL. Therefore, in acute infections such as sepsis and respiratory infections like COVID-19, it is necessary to rapidly provide its precursors, D3 and 25(OH)D, through the circulation to generate adequate intracellular calcitriol. Immune defence is one of the crucial non-hormonal functions of vitamin D. A single oral (bolus) dose or divided upfront loading doses between 100,000 and 500,000 IU, using 50,000 IU vitamin D3 increase the serum 25(OH)D concentrations to a therapeutic level of above 50 ng/mL that lasts between two to three months. This takes three to five days to raise serum 25(OH)D. In contrast, a single oral dose of calcifediol (0.014 mg/kg body weight) can generate the needed 25(OH)D concentration within four hours. Considering both D3 and 25(OH)D enter immune cells for generating calcitriol, using the combination of D3 (medium-term) and calcifediol (immediate) is cost-effective and leads to the best clinical outcome. To maximise protection against infections, particularly to reduce COVID-19-associated complications and deaths, healthcare workers should advise patients on safe sun exposure, adequate vitamin D supplementation and balanced diets containing zinc, magnesium, and other micronutrients to support the immune system. Meanwhile, governments, the World Health Organisation, the Centers for Disease Control, and governments should consider similar recommendations to physicians and the public, change the outdated vitamin D and other micronutrient recommendations directed to their population, and organise targetted food fortification programs for the vulnerable groups. This article discusses a rational approach to maintaining a sustained serum 25(OH)D concentration above 50 ng/mL, necessary to attain a robust immune system for overcoming infections. Such would cost-effectively improve the population’s health and reduce healthcare costs. It also describes three cost-effective, straightforward protocols for achieving and sustaining therapeutic serum 25(OH)D concentrations above 50 ng/mL (>125 nmol/L) to keep the population healthy, reduce absenteeism, improve productivity, and lower healthcare costs.

Approaches to setting dietary reference values for micronutrients, and translation into recommendations

Dietary reference values (DRV) are estimates of the daily amounts of nutrients or food energy that meet the needs of healthy people. In the UK, three terms are used to express these estimates, assuming a normal distribution of requirements in a population. These are the estimated average requirement, the lower reference nutrient intake and the reference nutrient intake. DRV are for use in a variety of settings, including the assessment of adequacy and safety of nutrient or energy intake in a population group, in the design of meal provision in care settings, in food labelling and in considering food fortification strategies. DRV, and other expressions of nutrient requirements, assume a relationship between the intake of a nutrient and some criterion of adequacy, the outcome. Estimates of requirements are based on a diverse range of measures of adequacy, according to available evidence. The Scientific Advisory Committee on Nutrition (SACN) is the body responsible for reviewing and setting DRV for the UK population. The work of SACN is guided by a framework of evidence that relates food and nutrients to health. There have been calls for the harmonisation of approaches used in the setting of nutrient requirements, globally, and an increased transparency in the decision-making process. Some progress has been made in this regard, but there is a great deal of work to be done.

Vitamin D Metabolism and Guidelines for Vitamin D Supplementation

Vitamin D is essential for bone health and is known to be involved in immunomodulation and cell proliferation. Vitamin D status remains a significant health issue worldwide. However, there has been no clear consensus on vitamin D deficiency and its measurement in serum, and clinical practice of vitamin D deficiency treatment remains inconsistent. The major circulating metabolite of vitamin D, 25-hydroxyvitamin D (25(OH)D), is widely used as a biomarker of vitamin D status. Other metabolic pathways are recognised as important to vitamin D function and measurement of other metabolites may become important in the future. The utility of free 25(OH)D rather than total 25(OH)D needs further assessment. Data used to estimate the vitamin D intake required to achieve a serum 25(OH)D concentration were drawn from individual studies which reported dose-response data. The studies differ in their choice of subjects, dose of vitamin D, frequency of dosing regimen and methods used for the measurement of 25(OH)D concentration. Baseline 25(OH)D, body mass index, ethnicity, type of vitamin D (D₂ or D₃) and genetics affect the response of serum 25(OH)D to vitamin D supplementation. The diversity of opinions that exist on this topic are reflected in the guidelines. Government and scientific societies have published their recommendations for vitamin D intake which vary from 400-1000 IU/d (10-25 μg/d) for an average adult. It was not possible to establish a range of serum 25(OH)D concentrations associated with selected non-musculoskeletal health outcomes. To recommend treatment targets, future studies need to be on infants, children, pregnant and lactating women.

Vitamin D status in children and adults in Sweden: dietary intake and 25-hydroxyvitamin D concentrations in children aged 10-12 years and adults aged 18-80 years

The study aimed to estimate vitamin D intake and plasma/serum 25-hydroxyvitamin D (25(OH)D) concentrations, investigate determinants of 25(OH)D concentrations and compare two 25(OH)D assays. We conducted two nationwide cross-sectional studies in Sweden with 206 school children aged 10-12 years and 1797 adults aged 18-80 years (n 268 provided blood samples). A web-based dietary record was used to assess dietary intake. Plasma/serum 25(OH)D was analysed by liquid chromatography-mass spectrometry (LC-MS) and immunoassay in adults and LC-MS/MS in children. Most participants reported a vitamin D intake below the average requirement (AR), 16 % of children and 33 % of adults met the AR (7⋅5 μg). In adults, plasma 25(OH)D below 30 and 50 nmol/l were found in 1 and 18 % of participants during the summer period and in 9 and 40 % of participants during the winter period, respectively. In children, serum 25(OH)D below 30 and 50 nmol/l were found in 5 and 42 % of participants (samples collected March-May), respectively. Higher 25(OH)D concentrations were associated with the summer season, vacations in sunny locations (adults), and dietary intake of vitamin D and use of vitamin D supplements, while lower concentrations were associated with a higher BMI and an origin outside of Europe. Concentrations of 25(OH)D were lower using the immunoassay than with the LC-MS assay, but associations with dietary factors and seasonal variability were similar. In conclusion, vitamin D intake was lower than the AR, especially in children. The 25(OH)D concentrations were low in many participants, but few participants had a concentration below 30 nmol/l.

Individual participant data (IPD)-level meta-analysis of randomised controlled trials among dark-skinned populations to estimate the dietary requirement for vitamin D

BACKGROUND

Estimation of the dietary requirements for vitamin D is crucial from a public health perspective in providing a framework for the prevention of vitamin D deficiency. It has been shown that pooling individual participant-level data (IPD) from selected randomised controlled trials (RCTs) of white children and adults facilitated the generation of more accurate estimates of the vitamin D requirement. Recent RCT data suggest the vitamin D requirement of dark-skinned, particularly black, individuals, an at-risk group of vitamin D deficiency, is greater than those of white counterparts. Thus, we wished to develop a study protocol for the conduct of an IPD-level meta-analysis of vitamin D requirements using data from appropriate vitamin D RCTs in dark-skinned population subgroups.

METHODS

The study protocol details the steps needed within such an IPD meta-analysis which will include its registration, constituent systematic review to identify all appropriate RCTs on the basis of pre-specified eligibility criteria, the associated data collection, handling, and synthesis, as well as checking the integrity of the IPD, followed by implementation of a one/two-stage IPD meta-analysis and derivation of vitamin D requirement estimates.

DISCUSSION

As dark-skinned population subgroups are at increased risk of vitamin D deficiency, further investigation of dietary recommendations for vitamin D in these subgroups is needed. We strongly believe that application of an IPD-based meta-analysis is a highly strategic approach by which to undertake some of this further investigation. Such IPD-based analysis, however, will need collaboration across the principal investigators of the identified RCTs meeting with the eligibility criteria, and the availability of this study protocol will be important to highlight the potential of IPD-based analysis for estimation of the dietary requirement for vitamin D for this particular population subgroup as well as for other at-risk target populations.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO International Prospective Register of Systematic Reviews (registration number: CRD42018092343).

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.

Update of the tolerable upper intake level for vitamin D for infants

Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to revise the tolerable upper intake level (UL) for vitamin D for infants (≤ 1 year) set in 2012. From its literature review, the Panel concluded that the available evidence on daily vitamin D intake and the risk of adverse health outcomes (hypercalciuria, hypercalcaemia, nephrocalcinosis and abnormal growth patterns) cannot be used alone for deriving the UL for infants. The Panel conducted a meta-regression analysis of collected data, to derive a dose-response relationship between daily supplemental intake of vitamin D and mean achieved serum 25(OH)D concentrations. Considering that a serum 25(OH)D concentration of 200 nmol/L or below is unlikely to pose a risk of adverse health outcomes in infants, the Panel estimated the percentage of infants reaching a concentration above this value at different intakes of vitamin D. Based on the overall evidence, the Panel kept the UL of 25 μg/day for infants aged up to 6 months and set a UL of 35 μg/day for infants 6-12 months. The Panel was also asked to advise on the safety of the consumption of infant formulae with an increased maximum vitamin D content of 3 μg/100 kcal (Commission Delegated Regulation (EU) 2016/127 repealing Directive 2006/141/EC in 2020). For infants aged up to 4 months, the intake assessment showed that the use of infant formulae containing vitamin D at 3 μg/100 kcal may lead some infants to receive an intake above the UL of 25 μg/day from formulae alone without considering vitamin D supplemental intake. For infants aged 4-12 months, the 95th percentile of vitamin D intake (high consumers) estimated from formulae and foods fortified or not with vitamin D does not exceed the ULs, without considering vitamin D supplemental intake.

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.

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.

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 replacement in children, adolescents and pregnant women in the Middle East and North Africa: A systematic review and meta-analysis of randomized controlled trials

INTRODUCTION

Hypovitaminosis D affects one-third to two-thirds of children and pregnant women from the Middle East and North Africa (MENA) region.

OBJECTIVE

To evaluate in infants, children, adolescents and pregnant women, from the MENA region, the effect of supplementation with different vitamin D doses on the change in 25-hydroxyvitamin D [25(OH)D] level reached, and other skeletal and non-skeletal outcomes.

METHODS

This is a systematic review of randomized controlled trials of vitamin D supplementation conducted in the MENA region. We conducted a comprehensive literature search in 7 databases, without language or time restriction, until November 2016. Two reviewers abstracted data from the included studies, independently and in duplicate. We calculated the mean difference (MD) and 95% CI of 25(OH)D level reached when at least 2 studies were eligible in each comparison (low (<800IU), intermediate (800-2000IU) or high (>2000IU) daily dose of vitamin D, or placebo). We pooled data using RevMan version 5.3.

RESULTS

We identified a total of 15 eligible trials: one in infants, 4 in children and adolescents and 10 in pregnant women. In children and adolescents, an intermediate vitamin D dose (1901IU/d), resulted in a mean difference in 25(OH)D level of 13.5 (95% confidence interval (CI) 8.1-18.8) ng/ml, compared to placebo, favoring the intermediate dose (p<0.001). The proportion of children and adolescents reaching a 25(OH)D level≥ 20ng/ml was 74% in the intermediate dose group. In pregnant women, four trials started supplementation at 12-16weeks of gestation and continued until delivery, and six trials started supplementation at 20-28weeks' gestation and stopped it at delivery. The MD in 25(OH)D level reached was 8.6 (95% CI 5.3-11.9) ng/ml (p<0.001) comparing the high dose (3662IU/d) to the intermediate dose (1836IU/d), and 12.3 (95% CI 6.4-18.2) ng/ml (p<0.001), comparing the high dose (3399IU/d) to the low dose (375IU/d). Comparing the intermediate (1832IU/d) to the low dose (301IU/d), the MD in 25(OH)D level achieved was 7.8 (95% CI 4.5-10.8) ng/ml (p<0.001). The proportion of pregnant women reaching a 25(OH)D level≥20ng/ml was 80%-90%, 73% and 27%-43% in the high, intermediate, and low dose groups, respectively. The risk of bias in the included studies, for children, adolescents and pregnant women, ranged from low to high across all doamins.

CONCLUSION

In children, adolescents and pregnant women from the MENA, an intermediate vitamin D dose of 1000-2000IU daily may be necessary to allow for the majority of the population to reach a desirable 25(OH)D level of 20ng/ml. Further high quality RCTs are required to confirm/refute the beneficial impact of vitamin D supplementation on various clinically important outcomes.

Estimation of the dietary requirement for vitamin D in white children aged 4-8 y: a randomized, controlled, dose-response trial

BACKGROUND

Children in northern latitudes are at high risk of vitamin D deficiency during winter because of negligible dermal vitamin D₃ production. However, to our knowledge, the dietary requirement for maintaining the nutritional adequacy of vitamin D in young children has not been investigated.

OBJECTIVE

We aimed to establish the distribution of vitamin D intakes required to maintain winter serum 25-hydroxyvitamin D [25(OH)D] concentrations above the proposed cutoffs (25, 30, 40, and 50 nmol/L) in white Danish children aged 4-8 y living at 55°N.

DESIGN

In a double-blind, randomized, controlled trial 119 children (mean age: 6.7 y) were assigned to 0 (placebo), 10, or 20 μg vitamin D₃/d supplementation for 20 wk. We measured anthropometry, dietary vitamin D, and serum 25(OH)D with liquid chromatography-tandem mass spectrometry at baseline and endpoint.

RESULTS

The mean ± SD baseline serum 25(OH)D was 56.7 ± 12.3 nmol/L (range: 28.7-101.4 nmol/L). Serum 25(OH)D increased by a mean ± SE of 4.9 ± 1.3 and 17.7 ± 1.8 nmol/L in the groups receiving 10 and 20 μg vitamin D₃/d, respectively, and decreased by 24.1 ± 1.2 nmol/L in the placebo group (P < 0.001). A nonlinear model of serum 25(OH)D as a function of total vitamin D intake (diet and supplements) was fit to the data. The estimated vitamin D intakes required to maintain winter serum 25(OH)D >30 (avoiding deficiency) and >50 nmol/L (ensuring adequacy) in 97.5% of participants were 8.3 and 19.5 μg/d, respectively, and 4.4 μg/d was required to maintain serum 25(OH)D >40 nmol/L in 50% of participants.

CONCLUSIONS

Vitamin D intakes between 8 and 20 μg/d are required by white 4- to 8-y-olds during winter in northern latitudes to maintain serum 25(OH)D >30-50 nmol/L depending on chosen serum 25(OH)D threshold. This trial was registered at clinicaltrials.gov as NCT02145195.

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

BACKGROUND

Adolescents are a population group at high risk of low vitamin D status, yet the evidence base for establishing dietary vitamin D requirements remains weak.

OBJECTIVE

The aim was to establish the distribution of vitamin D intakes required to maintain serum 25-hydroxyvitamin D [25(OH)D] concentrations above proposed cutoffs (25, 30, 40, and 50 nmol/L) during winter in white males and females (14-18 y of age) in the United Kingdom (51°N).

DESIGN

In a dose-response trial, 110 adolescents (aged 15.9 ± 1.4 y; 43% males) were randomly assigned to receive 0, 10, or 20 μg vitamin D₃ supplements/d for 20 wk during winter. A nonlinear regression model was fit to total vitamin D intake and postintervention serum 25(OH)D concentrations, and regression-predicted values estimated the vitamin D intakes required to maintain serum 25(OH)D concentrations above specific cutoffs.

RESULTS

Mean ± SD serum 25(OH)D concentrations increased from 49.2 ± 12.0 to 56.6 ± 12.4 nmol/L and from 51.7 ± 13.4 to 63.9 ± 10.6 nmol/L in the 10- and 20-μg/d groups, respectively, and decreased in the placebo group from 46.8 ± 11.4 to 30.7 ± 8.6 nmol/L (all P ≤ 0.001). Vitamin D intakes required to maintain 25(OH)D concentrations >25 and >30 nmol/L in 97.5% of adolescents were estimated to be 10.1 and 13.1 μg/d, respectively, and 6.6 μg/d to maintain 50% of adolescents at concentrations >40 nmol/L. Because the response of 25(OH)D reached a plateau at 46 nmol/L, there is uncertainty in estimating the vitamin D intake required to maintain 25(OH)D concentrations >50 nmol/L in 97.5% of adolescents, but it exceeded 30 μg/d.

CONCLUSION

Vitamin D intakes between 10 and ∼30 μg/d are required by white adolescents during winter to maintain serum 25(OH)D concentrations >25-50 nmol/L, depending on the serum 25(OH)D threshold chosen. This trial was registered at clinicaltrials.gov as NCT02150122 and as International Standard Randomized Controlled Trial Number ISRCTN40736890.

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.

Estimations of dietary vitamin D requirements in black and white children

BACKGROUND

The Institute of Medicine (IOM) dietary guidelines for vitamin D are based on limited pediatric data. Our objective was to estimate the dietary vitamin D requirements for maintaining serum 25-hydroxyvitamin D [25(OH)D] concentrations at the various IOM-considered thresholds of vitamin D status (12, 16, and 20 ng/ml) during fall and winter in children.

METHODS

Ninety-six healthy 8- to 14-y-old Pittsburgh-area black and white children enrolled in a randomized, placebo-controlled trial of vitamin D3 1,000 IU daily for 6 mo with baseline and 2-mo follow-up assessments completed during October through April were studied. Vitamin D intake from diet and study supplement adjusted for adherence and serum 25(OH)D were measured.

RESULTS

The vitamin D intakes needed to maintain serum 25(OH)D concentrations at 12, 16, and 20 ng/ml in 90% of the children were 581, 1,062, and 1543 IU/day, respectively. The estimated vitamin D intakes needed to maintain serum 25(OH)D concentrations at 20 ng/ml in 97.5% of the children was 2,098 IU/day.

CONCLUSION

Our data suggest that the current vitamin D recommended dietary allowance (RDA) (600 IU/day) is insufficient to cover the skeletal health needs of at least 50% of black and white children.

Correlation of objectively measured light exposure and serum vitamin D in men aged over 60 years

Diminished vitamin D is common among older individuals. Sunlight contributes more to vitamin D synthesis than diet or supplementation. This study examined associations between objectively measured light exposure, vitamin D serum levels, and bone biomarkers in 100 men aged over 60 years. Light exposure was measured in lux via Actigraph monitors for 1 week. Significantly, greater levels of vitamin D were observed in participants with higher light exposure. Seasonal differences in lux were also noted. Significant differences in bone markers were not found. Objective measurement of light exposure is an inexpensive, simple, and effective way to address vitamin D deficiency.

Effects of school meals with weekly fish servings on vitamin D status in Danish children: secondary outcomes from the OPUS (Optimal well-being, development and health for Danish children through a healthy New Nordic Diet) School Meal Study

Children's vitamin D intake and status can be optimised to meet recommendations. We investigated if nutritionally balanced school meals with weekly fish servings affected serum 25-hydroxyvitamin D (25(OH)D) and markers related to bone in 8- to 11-year-old Danish children. We conducted an explorative secondary outcome analysis on data from 784 children from the OPUS School Meal Study, a cluster-randomised cross-over trial where children received school meals for 3 months and habitual lunch for 3 months. At baseline, and at the end of each dietary period, 25(OH)D, parathyroid hormone (PTH), osteocalcin (OC), insulin-like growth factor-1 (IGF-1), bone mineral content (BMC), bone area (BA), bone mineral density (BMD), dietary intake and physical activity were assessed. School meals increased vitamin D intake by 0·9 (95 % CI 0·7, 1·1) μg/d. No consistent effects were found on 25(OH)D, BMC, BA, BMD, IGF-1 or OC. However, season-modified effects were observed with 25(OH)D, i.e. children completing the school meal period in January/February had higher 25(OH)D status (5·5 (95 % CI 1·8, 9·2) nmol/l; P = 0·004) than children completing the control period in these months. A similar tendency was indicated in November/December (4·1 (95 % CI –0·12, 8·3) nmol/l; P = 0·057). However, the effect was opposite in March/April (–4·0 (95 % CI –7·0, –0·9) nmol/l; P = 0·010), and no difference was found in May/June (P = 0·214). Unexpectedly, the school meals slightly increased PTH (0·18 (95 % CI 0·07, 0·29) pmol/l) compared with habitual lunch. Small increases in dietary vitamin D might hold potential to mitigate the winter nadir in Danish children's 25(OH)D status while higher increases appear necessary to affect status throughout the year. More trials on effects of vitamin D intake from natural foods are needed.

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: 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'.

Hypovitaminosis D in adolescent females--an analytical cohort study in the United Arab Emirates

BACKGROUND

Despite living in a sunny country, hypovitaminosis D is common in women of reproductive age in Al Ain, United Arab Emirates (UAE).

AIMS AND OBJECTIVES

To establish the prevalence of hypovitaminosis D in adolescent female Emirati nationals and its risk factors.

METHODS

This was an analytical prospective cohort study of 350 female Emirati nationals aged 11-18 years attending public schools in Al Ain. Socio-economic status, diet and amount of sun exposure were evaluated by face-to-face interviews. Serum total 25 (OH) vitamin D (D2 + D3) levels were measured by electrochemiluminescence assay. The prevalence of hypovitaminosis D was calculated and the association with risk factors analysed.

RESULTS

Data were complete for 293 girls. Only one girl [prevalence 0.3%, 95% confidence interval (CI) 0.01-1.9] had vitamin D sufficiency (serum vitamin D levels >75 nmol/L). Three girls (1.0%, 95% CI 0.2-2.9) had vitamin D insufficiency (50-75 nmol/L), 58 (19.8%, 95% CI 15.0-25.5) were deficient (27.5-50 nmol/L) and 231 (78.8%, 95% CI 68.9-89.6) had severe deficiency (<27.5 nmol/L). Serum vitamin D levels declined between the ages of 11 and 13 years before progressively rising until the age of 18 years but without regaining the levels they were at the age of 11. There was no statistically significant difference between the vitamin D status groups in age, body mass index, accommodation type, family income, percentage of surface area unexposed to the sun when outdoors, consumption of oily fish or total vitamin D intake.

CONCLUSION

The finding of a high prevalence of hypovitaminosis D in adolescent females in UAE is of serious concern for their health and that of their infants during their reproductive lives. Adolescent girls with a similar social and cultural background currently living in less sunny, industrialised countries might also be at risk.

Optimizing bone health in children and adolescents

The pediatrician plays a major role in helping optimize bone health in children and adolescents. This clinical report reviews normal bone acquisition in infants, children, and adolescents and discusses factors affecting bone health in this age group. Previous recommended daily allowances for calcium and vitamin D are updated, and clinical guidance is provided regarding weight-bearing activities and recommendations for calcium and vitamin D intake and supplementation. Routine calcium supplementation is not recommended for healthy children and adolescents, but increased dietary intake to meet daily requirements is encouraged. The American Academy of Pediatrics endorses the higher recommended dietary allowances for vitamin D advised by the Institute of Medicine and supports testing for vitamin D deficiency in children and adolescents with conditions associated with increased bone fragility. Universal screening for vitamin D deficiency is not routinely recommended in healthy children or in children with dark skin or obesity because there is insufficient evidence of the cost-benefit of such a practice in reducing fracture risk. The preferred test to assess bone health is dual-energy x-ray absorptiometry, but caution is advised when interpreting results in children and adolescents who may not yet have achieved peak bone mass. For analyses, z scores should be used instead of T scores, and corrections should be made for size. Office-based strategies for the pediatrician to optimize bone health are provided. This clinical report has been endorsed by American Bone Health.

Adequacy of vitamin D intakes in children and teenagers from the base diet, fortified foods and supplements

OBJECTIVE

To describe vitamin D intakes in children and teenagers and the contribution from supplements and fortified foods in addition to the base diet.

DESIGN

Analysis of 7 d weighed food records collected during the Children's and Teens' National Nutrition Surveys in Ireland. Food composition data for vitamin D were updated from international analytical sources.

SETTING

Nationally representative cross-sectional dietary surveys.

SUBJECTS

Children (n 594; 5-12 years) and teenagers (n 441; 13-17 years).

RESULTS

Median vitamin D intakes were 1.9, 2.1 and 2.4 μg/d in 5-8-, 9-12- and 13-17-year-olds, respectively. The prevalence of vitamin D-containing supplement use was 21, 16 and 15% in 5-8-, 9-12- and 13-17-year-olds and median intakes in users ranged from 6.0 to 6.7 μg/d. The prevalence of inadequate intakes, defined as the percentage with mean daily intakes below the Estimated Average Requirement of 10 μg/d, ranged from 88 to 96% in supplement users. Foods fortified with vitamin D, mainly breakfast cereals, fat spreads and milk, were consumed by 71, 70 and 63 % of 5-8-, 9-12- and 13-17-year-olds. Non-supplement users who consumed vitamin D-fortified foods had median intakes of 1.9-2.5 μg/d, compared with 1.2-1.4 μg/d in those who did not consume fortified foods.

CONCLUSIONS

It is currently not possible for children consuming the habitual diet to meet the US Institute of Medicine dietary reference intake for vitamin D. In the absence of nationally representative 25-hydroxyvitamin D data in children, the implications of this observation for prevalence of vitamin D deficiency and health consequences are speculative.

Recommended dietary intakes for vitamin D: Where do they come from, what do they achieve and how can we meet them?

There is substantial evidence that the prevalence of vitamin D deficiency is high across Europe, particularly, but not exclusively, among those resident at Northerly latitudes. This has significant implications for human health throughout the lifecycle and impacts upon healthy growth and development and successful ageing for current and possibly future generations. In recent years, there have been several important reports from North America and Europe in relation to dietary reference values (DRVs) for vitamin D. These may be of enormous value from a public health perspective in terms of preventing vitamin D deficiency and promoting adequate vitamin D status in the population. In this concise review, we provide a brief summary of current DRVs for vitamin D, their background and their application to vitamin D deficiency prevention. The review also provides some brief guidance with respect to applying the DRVs in a clinical nutrition setting. In addition, the review illustrates how current dietary intakes of most populations, young and adult, are well short of the newly established DRVs. Accordingly, the review highlights potential food-based or dietary strategies for increasing the distribution of vitamin D intake in the population with the aim of preventing vitamin D deficiency. Finally, despite the explosion in scientific research in vitamin D and health, there are many fundamental gaps in the field of vitamin D from the public health perspective. The impact of these knowledge gaps on current DRVs for vitamin D is highlighted, as are some future developments that may help address these gaps.

A randomized trial of vitamin D₃ supplementation in children: dose-response effects on vitamin D metabolites and calcium absorption

CONTEXT

Changes in serum vitamin D metabolites and calcium absorption with varying doses of oral vitamin D₃ in healthy children are unknown.

OBJECTIVE

Our objective was to examine the dose-response effects of supplemental vitamin D₃ on serum vitamin D metabolites and calcium absorption in children living at two U.S. latitudes.

DESIGN

Black and white children (n = 323) participated in a multisite (U.S. latitudes 34° N and 40° N), triple-masked trial. Children were randomized to receive oral vitamin D₃ (0, 400, 1000, 2000, and 4000 IU/d) and were sampled over 12 weeks in winter. Serum 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)₂D) were measured using RIA and intact PTH (iPTH) by immunoradiometric assay. Fractional calcium absorption was determined from an oral stable isotope ⁴⁴Ca (5 mg) in a 150-mg calcium meal. Nonlinear and linear regression models were fit for vitamin D metabolites, iPTH, and calcium absorption.

RESULTS

The mean baseline 25(OH)D value for the entire sample was 70.0 nmol/L. Increases in 25(OH)D depended on dose with 12-week changes ranging from -10 nmol/L for placebo to 76 nmol/L for 4000 IU. Larger 25(OH)D gains were observed for whites vs blacks at the highest dose (P < .01). Gains for 1,25(OH)₂D were not significant (P = .07), and decreases in iPTH were not dose-dependent. There was no dose effect of vitamin D on fractional calcium absorption when adjusted for pill compliance, race, sex, or baseline 25(OH)D.

CONCLUSION

Large increases in serum 25(OH)D with vitamin D₃ supplementation did not increase calcium absorption in healthy children living at 2 different latitudes. Supplementation with 400 IU/d was sufficient to maintain wintertime 25(OH)D concentrations in healthy black, but not white, children.

A review of vitamin D status and CVD

Beyond the well-accepted effects on the skeleton, low vitamin D status has been linked to increased risk of several non-skeletal disease, including CVD. If low serum 25-hydroxyvitamin D (25(OH)D) concentration is causally linked to risk of CVD then this is important not only because low vitamin D status is quite common particularly in winter in countries above 40°N, but also of key relevance is the fact that such low vitamin D status can be improved by food-based strategies. The overarching aim of the present paper is to review the current evidence-base to support a link between low vitamin D status and CVD risk. The review initially briefly overviews how mechanistically vitamin D may play a role in CVD and then reviews the current available evidence-base to support a link between low vitamin D status and CVD risk, with particular emphasis on data from the randomised control trials, cohort studies and recent meta-analysis data as well as to the conclusions of a number of authoritative agencies/bodies. Finally, the review summarises current serum 25(OH)D concentrations within a select number of adult populations in the context of different definitions of vitamin D status proposed recently, and then briefly highlights food-based strategies for increasing vitamin D intake and status. In conclusion, at present the data for a causal link between low vitamin D status and CVD are mixed and ambiguous; however, should causality be affirmed by ongoing and future studies, there are food-based strategies for enhanced vitamin D status in the population which could ultimately lower risk of CVD.

Vitamin D deficiency at the Arctic Circle - a study in food-allergic adolescents and controls

AIM

At the extremes of latitude, UVB intensity is insufficient for adequate vitamin D synthesis in winter. Fatty fish, vitamin D enriched milk, margarine and eggs are main dietary sources of vitamin D. Their elimination may increase the risk of vitamin D deficiency. The aim was to assess vitamin D status in food-allergic adolescents eliminating milk, egg and/or fish compared with adolescents on normal diets.

METHODS

In winter, vitamin D intake was assessed by a food frequency questionnaire in 20 food-allergic adolescents and 42 controls in the population-based Obstructive Lung Disease In Northern Sweden (OLIN) cohort studies. Vitamin D supplementation was queried. Serum 25-hydroxyvitamin D [S-25(OH)D] and S-parathormone (S-PTH) levels were determined.

RESULTS

Mean (SD) dietary vitamin D intake was 7.9 (3.6) μg/day in allergic adolescents and 7.8 (3.4) in controls (p > 0.05). Mean (SD) S-25(OH)D levels in supplement consumers were 44 (18) nmol/L compared with 35 (10) in non-consumers (p = 0.03). S-25(OH)D and S-PTH levels were similar in food-allergic adolescents and controls (p > 0.05). Eighty-two percentage had deficient S-25(OH)D levels <50 nmol/L, and none reached levels >75 nmol/L.

CONCLUSION

Vitamin D deficiency was as common in food-allergic adolescents as in controls although the vitamin D intake met national recommendations. Large-scale studies on the prevalence of vitamin D deficiency in this region are needed.

Serum 25-hydroxyvitamin D levels in preschool-age children in northern Sweden are inadequate after summer and diminish further during winter

BACKGROUND AND OBJECTIVE

Despite studies indicating that vitamin D intake among Swedish children does not meet the recommendation, little is known of their vitamin D status. The aim of the present study was to examine vitamin D status in preschool-age children in relation to vitamin D intake, season, body mass index, and skin color.

METHODS

Preschool-age children (n = 90; mean age 54 ± 7.1 months), all living in northern Sweden (latitude 63° north), half of them with fair skin, half with darker complexion, were recruited from well-baby clinics. The study group was examined first in August-September (late summer) and then the following January-February (winter). Skin type, vitamin D intake, anthropometrics, serum 25-hydroxyvitamin D (S-25[OH] D), and serum parathyroid hormone were assessed.

RESULTS

Mean ± SD S-25(OH) D in summer and winter were 60 ± 15 nmol/L and 55 ± 16 nmol/L, respectively (P < 0.001). Fifteen percent and 10% had S-25(OH) D ≥ 75 nmol/L, and 25% and 40% had S-25(OH) D <50 nmol/L, respectively. The mean vitamin D intake was higher in dark-skinned compared with fair-skinned children. In spite of this, S-25(OH) D in dark-skinned children was lower compared with fair-skinned children during both seasons. The dietary intake of vitamin D was positively associated with S-25(OH) D levels.

CONCLUSIONS

Vitamin D status is inadequate in preschool-age children living in northern Sweden, especially in dark-skinned children and during the winter despite vitamin D intakes meeting the recommendations, prompting strategies to improve intake of vitamin D in this population.

Vitamin D and calcium status in South African adolescents with alcohol use disorders

Adequate vitamin D and calcium are essential for optimal adolescent skeletal development. Adolescent vitamin D insufficiency/deficiency and poor calcium intake have been reported worldwide. Heavy alcohol use impacts negatively on skeletal health, which is concerning since heavy adolescent drinking is a rising public health problem. This study aimed to examine biochemical vitamin D status and dietary intakes of calcium and vitamin D in 12-16 year-old adolescents with alcohol use disorders (AUD), but without co-morbid substance use disorders, compared to adolescents without AUD. Substance use, serum 25-hydroxyvitamin D (s-25(OH)D) concentrations, energy, calcium and vitamin D intakes were assessed in heavy drinkers (meeting DSM-IV criteria for AUD) (n = 81) and in light/non-drinkers without AUD (non-AUD) (n = 81), matched for age, gender, language, socio-economic status and education. Lifetime alcohol dose was orders of magnitude higher in AUD adolescents compared to non-AUD adolescents. AUD adolescents had a binge drinking pattern and "weekends-only" style of alcohol consumption. Significantly lower (p = 0.038) s-25(OH)D (adjusted for gender, smoking, vitamin D intake) were evident in AUD adolescents compared to non-AUD adolescents. High levels of vitamin D insufficiency/deficiency (s-25(OH)D < 29.9 ng/mL) were prevalent in both groups, but was significantly higher (p = 0.013) in the AUD group (90%) compared to the non-AUD group (70%). All participants were at risk of inadequate calcium and vitamin D intakes (Estimated Average Requirement cut-point method). Both groups were at risk of inadequate calcium intake and had poor biochemical vitamin D status, with binge drinking potentially increasing the risk of the latter. This may have negative implications for peak bone mass accrual and future osteoporosis risk, particularly with protracted binge drinking.

Vitamin D: still a topical matter in children and adolescents. A position paper by the Committee on Nutrition of the French Society of Paediatrics

The aims of the present position paper by the Committee on Nutrition of the French Society of Paediatrics were to summarize the recently published data on vitamin D in infants, children and adolescents, i.e., on metabolism, physiological effects, and requirements and to make recommendations on supplementation after careful review of the evidence. Scientific evidence indicates that calcium and vitamin D play key roles in bone health. The current evidence, limited to observational studies, however, does not support other benefits for vitamin D. More targeted research should continue, especially interventional studies. In the absence of any underlying risk of vitamin D deficiency, the recommendations are as follows: pregnant women: a single dose of 80,000 to 100,000 IU at the beginning of the 7th month of pregnancy; breastfed infants: 1000 to 1200 IU/day; children less than 18 months of age, receiving milk supplemented with vitamin D: an additional daily dose of 600 to 800 IU; children less than 18 months of age receiving milk not supplemented with vitamin D: daily dose of 1000 to 1200 IU; children from 18 months to 5 years of age: 2 doses of 80,000 to 100,000 IU every winter (November and February). In the presence of an underlying risk of vitamin D deficiency (dark skin; lack of exposure of the skin to ultraviolet B [UVB] radiation from sunshine in summer; skin disease responsible for decreased exposure of the skin to UVB radiation from sunshine in summer; wearing skin-covering clothes in summer; intestinal malabsorption or maldigestion; cholestasis; renal insufficiency; nephrotic syndrome; drugs [rifampicin; antiepileptic treatment: phenobarbital, phenytoin]; obesity; vegan diet), it may be justified to start vitamin D supplementation in winter in children 5 to 10 years of age as well as to maintain supplementation of vitamin D every 3 months all year long in children 1 to 10 years of age and in adolescents. In some pathological conditions, doses of vitamin D can be increased. If necessary, the determination of 25(OH) vitamin D serum concentration will help determine the level of vitamin D supplementation.

Determinants of vitamin D status in young children: results from the Belgian arm of the IDEFICS (Identification and Prevention of Dietary- and Lifestyle-Induced Health Effects in Children and Infants) Study

Objective

To describe the vitamin D status of Belgian children and examine the influence of non-nutritional determinants, in particular of anthropometric variables.

Design

Cross-sectional data of Belgian participants of the EU 6th Framework Programme IDEFICS (Identification and Prevention of Dietary- and Lifestyle-Induced Health Effects in Children and Infants) Study.

Setting

25-Hydroxyvitamin D (25(OH)D) was measured using RIA. Vitamin D status was categorized as deficient (<25 nmol/l), insufficient (25–50 nmol/l), sufficient (50–75 nmol/l) and optimal (≥75 nmol/l). Anthropometric measurements included height, weight, waist and hip circumferences and triceps and subscapular skinfold thicknesses.

Subjects

Children (n 357) aged 4–11 years.

Results

Serum 25(OH)D ranged from 13·6 to 123·5 nmol/l (mean 47·2 (sd 14·6) nmol/l); with 5 % deficient, 53 % insufficient, 40 % sufficient and 2 % optimal. No significant differences were found by age and gender. Significant differences in 25(OH)D were observed for month of sampling (P < 0·001), number of hours playing outside per week (r = 0·140), weight (r = −0·121), triceps (r = −0·112) and subscapular (r = −0·119) skinfold thickness, sum of two skinfold thicknesses (r = −0·125) and waist circumference (r = −0·108). Linear regression analysis of 25(OH)D adjusted for age, month of sampling and hours playing outside per week suggested that (i) weight, (ii) BMI Z-score, (iii) waist circumference and (iv) triceps and subscapular skinfold thickness (as well as the sum of both) independently influenced 25(OH)D.

Conclusions

The majority of Belgian children had a suboptimal vitamin D status, with more than half having an insufficient status in winter and spring. Month of the year, weekly number of hours playing outside and body composition – both central and abdominal obesity – were identified as important determinants of vitamin D status in Belgian children.

Calcium and vitamin D requirements for optimal bone mass during adolescence

PURPOSE OF REVIEW

There remains very strong interest in the calcium and vitamin D requirements of adolescents related to bone health. The Institute of Medicine (IOM) released new dietary guidelines in late 2010 for these nutrients. These guidelines were primarily based on literature published in 2009 and earlier and emphasized the role of vitamin D combined with calcium in optimizing bone health. A series of research studies published in 2010 and 2011, mostly not included in the IOM report, have further addressed these issues.

RECENT FINDINGS

These most recently published data are generally consistent with the IOM report and earlier data in supporting calcium intakes of 1300 mg/day and vitamin D intakes of 600 IU/day for adolescents. However, there is some suggestion that a slightly higher Recommended Dietary Allowance for vitamin D might be considered at some future time.

SUMMARY

New dietary guidelines and recent research support increased vitamin D intakes compared with previous recommendations, but not very high doses. Further studies are needed related to high-dose vitamin D intake.

A systematic review and meta-regression analysis of the vitamin D intake–serum 25-hydroxyvitamin D relationship to inform European recommendations

The present study used a systematic review approach to identify relevant randomised control trials (RCT) with vitamin D and then apply meta-regression to explore the most appropriate model of the vitamin D intake–serum 25-hydroxyvitamin D (25(OH)D) relationship to underpin setting reference intake values. Methods included an updated structured search on Ovid MEDLINE; rigorous inclusion/exclusion criteria; data extraction; and meta-regression (using different model constructs). In particular, priority was given to data from winter-based RCT performed at latitudes >49·5°N (n12). A combined weighted linear model meta-regression analyses of natural log (Ln) total vitamin D intake (i.e. diet and supplemental vitamin D)v. achieved serum 25(OH)D in winter (that used by the North American Dietary Reference Intake Committee) produced a curvilinear relationship (mean (95 % lower CI) serum 25(OH)D (nmol/l) = 9·2 (8·5) Ln (total vitamin D)). Use of non-transformed total vitamin D intake data (maximum 1400 IU/d; 35 μg/d) provided for a more linear relationship (mean serum 25(OH)D (nmol/l) = 0·044 × (total vitamin D)+33·035). Although inputting an intake of 600 IU/d (i.e. the RDA) into the 95 % lower CI curvilinear and linear models predicted a serum 25(OH)D of 54·4 and 55·2 nmol/l, respectively, the total vitamin D intake that would achieve 50 (and 40) nmol/l serum 25(OH)D was 359 (111) and 480 (260) IU/d, respectively. Inclusion of 95 % range in the model to account for inter-individual variability increased the predicted intake of vitamin D needed to maintain serum 25(OH)D ≥ 50 nmol/l to 930 IU/d. The model used to describe the vitamin D intake–status relationship needs to be considered carefully when setting new reference intake values in the Europe.

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

The North American Institute of Medicine (IOM) recently published their report on dietary reference intakes (DRI) for Ca and vitamin D. The DRI committee's deliberations underpinning this most comprehensive report on vitamin D nutrition to date benefited hugely from a much expanded knowledge base in vitamin D over the last decade or more. However, since their release, the vitamin D DRI have been the subject of intense controversy, which is largely due to the persistence of fundamental knowledge gaps in vitamin D. These can be identified at the levels of exposure, metabolism, storage, status, dose-response, function and beneficial or adverse health effects, as well as safe and effective application of intake recommendations at the population level through sustainable food-based approaches. The present review provides a brief overview of the approach used by the IOM committee to revise the DRI for vitamin D and to collate from a number of authoritative sources key knowledge gaps in vitamin D nutrition from the public health perspective. A number of research topics are outlined and data requirements within these are identified and mapped to the risk assessment framework used by the DRI committee. While not intended as an exhaustive list, it provides a basis for organising and prioritising research efforts in the area of vitamin D, which may offer a perspective on the major areas in need of attention. It is intended to be of use to researchers, national policy makers, the public health community, industry groups and other relevant stakeholders including funding institutions.

Vitamin D deficiency and age at menarche: a prospective study

BACKGROUND

Early menarche is a risk factor for cardiometabolic disease and cancer. Latitude, which influences sun exposure, is inversely related to age at menarche. This association might be related to vitamin D, but to our knowledge it has not been investigated in prospective epidemiologic studies.

OBJECTIVE

We studied the association between vitamin D status and the occurrence of menarche in a prospective study in girls from Bogota, Colombia.

DESIGN

We measured plasma 25-hydroxyvitamin D [25(OH)D] concentrations in a random sample of 242 girls (mean ± SD age: 8.8 ± 1.6 y) and followed them for a median of 30 mo. Girls were asked periodically about the occurrence and date of menarche. Baseline 25(OH)D concentrations were categorized as <50 nmol/L (deficient), ≥50 and <75 nmol/L, or ≥75 nmol/L (sufficient). The incidence of menarche was compared between groups by using time-to-event analyses.

RESULTS

A total of 57% of girls in the vitamin D-deficient group reached menarche during follow-up compared with 23% of girls in the vitamin D-sufficient group (P-trend = 0.0004). The estimated mean (±SE) ages at menarche in the same groups were 11.8 ± 0.2 y and 12.6 ± 0.2 y, respectively (P = 0.0009). After adjustment for baseline age and BMI-for-age z score in a Cox proportional hazards model, the probability of menarche was twice as high in vitamin D-deficient girls than in girls who were vitamin D-sufficient (HR: 2.05; 95% CI: 1.03, 4.07; P = 0.04). Similar results were obtained in girls aged ≥9 y at baseline (HR: 2.39; 95% CI: 1.14, 5.00; P = 0.02).

CONCLUSION

Vitamin D deficiency is associated with earlier menarche.