Relative effectiveness of oral 25-hydroxyvitamin D3 and vitamin D3 in raising wintertime serum 25-hydroxyvitamin D in older adults

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

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

Vitamin D-enhanced eggs are protective of wintertime serum 25-hydroxyvitamin D in a randomized controlled trial of adults

BACKGROUND

Despite numerous animal studies that have illustrated the impact of additional vitamin D in the diet of hens on the resulting egg vitamin D content, the effect of the consumption of such eggs on vitamin D status of healthy individuals has not, to our knowledge, been tested.

OBJECTIVE

We performed a randomized controlled trial (RCT) to investigate the effect of the consumption of vitamin D-enhanced eggs (produced by feeding hens at the maximum concentration of vitamin D3 or serum 25-hydroxyvitamin D [25(OH)D3] lawfully allowed in feed) on winter serum 25(OH)D in healthy adults.

DESIGN

We conducted an 8-wk winter RCT in adults aged 45-70 y (n = 55) who were stratified into 3 groups and were requested to consume ≤2 eggs/wk (control group, in which status was expected to decline), 7 vitamin D3-enhanced eggs/wk, or seven 25(OH)D3-enhanced eggs/wk. Serum 25(OH)D was the primary outcome.

RESULTS

Although there was no significant difference (P > 0.1; ANOVA) in the mean preintervention serum 25(OH)D in the 3 groups, it was ∼7-8 nmol/L lower in the control group than in the 2 groups who consumed vitamin D-enhanced eggs. With the use of an ANCOVA, in which baseline 25(OH)D was accounted for, vitamin D3-egg and 25(OH)D3-egg groups were shown to have had significantly higher (P ≤ 0.005) postintervention serum 25(OH)D than in the control group. With the use of a within-group analysis, it was shown that, although serum 25(OH)D in the control group significantly decreased over winter (mean ± SD: -6.4 ± 6.7 nmol/L; P = 0.001), there was no change in the 2 groups who consumed vitamin D-enhanced eggs (P > 0.1 for both).

CONCLUSION

Weekly consumption of 7 vitamin D-enhanced eggs has an important impact on winter vitamin D status in adults. This trial was registered at clinicaltrials.gov as NCT02678364.

Interlaboratory Trial for Measurement of Vitamin D and 25-Hydroxyvitamin D [25(OH)D] in Foods and a Dietary Supplement Using Liquid Chromatography-Mass Spectrometry

Assessment of total vitamin D intake from foods and dietary supplements (DSs) may be incomplete if 25-hydroxyvitamin D [25(OH)D] intake is not included. However, 25(OH)D data for such intake assessments are lacking, no food or DS reference materials (RMs) are available, and comparison of laboratory performance has been needed. The primary goal of this study was to evaluate whether vitamin D3 and 25(OH)D3 concentrations in food and DS materials could be measured with acceptable reproducibility. Five experienced laboratories from the United States and other countries participated, all using liquid chromatography tandem-mass spectrometry but no common analytical protocol; however, various methods were used for determining vitamin D3 in the DS. Five animal-based materials (including three commercially available RMs) and one DS were analyzed. Reproducibility results for the materials were acceptable. Thus, it is possible to obtain consistent results among experienced laboratories for vitamin D3 and 25(OH)D3 in foods and a DS.

Vitamin D3 and 25-hydroxyvitamin D3 in pork and their relationship to vitamin D status in pigs

The content of vitamin D in pork produced in conventional systems depends on the vitamin D concentration in the pig feed. Both vitamin D₃ and 25-hydroxyvitamin D₃ (25(OH)D₃) are essential sources of dietary vitamin D; however, bioavailability assessed by serum 25(OH)D₃ concentration is reported to be different between the two sources. Furthermore, the relationship between serum 25(OH)D₃ level and the tissue content of vitamin D₃ and 25(OH)D₃ is unknown. The objective of this study was to investigate the potential of increasing the content of vitamin D in different pig tissues by increasing the levels of vitamin D₃ and 25(OH)D₃ in the pig feed for 49 d before slaughter. Concurrently, the 25(OH)D₃ level in serum was investigated as a biomarker to assess the content of vitamin D₃ and 25(OH)D₃ in pig tissues. Adipose tissue, white and red muscle, the liver and serum were sampled from pigs fed feed containing either vitamin D₃ or 25(OH)D₃ at 5, 20, 35 or 50 µg/kg feed for 7 weeks before slaughter. The tissue 25(OH)D₃ level was significantly higher in the pigs fed 25(OH)D₃ compared with those fed vitamin D₃, while the tissue vitamin D₃ level was higher in the pigs fed vitamin D₃ compared with those fed 25(OH)D₃. The content of 25(OH)D₃ in the different tissues fully correlated with the serum 25(OH)D₃ level, whereas the correlation between the tissue content of vitamin D₃ and serum 25(OH)D₃ was dependent on the source of the ingested vitamin D₃.

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

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

Supplementation of Merino ewes with cholecalciferol in late pregnancy improves the vitamin D status of ewes and lambs at birth but is not correlated with an improvement in immune function in lambs

Functional deficiencies of the immune system are known to predispose human and animal neonates to death. Thus, immune competency may be a significant factor influencing the mortality of lambs. Vitamin D has been recognised to improve immune function and is transferred across the placenta. This study tested the hypotheses that (1) supplementation of Merino ewes with cholecalciferol during late pregnancy will increase the concentrations of vitamin D in the ewe and lamb at birth and (2) supplementation of Merino ewes with cholecalciferol during late pregnancy is correlated with an increase in innate phagocytic and adaptive antibody immune responses in the lamb. Merino ewes (n = 53) were injected intramuscularly with 1 × 106 IU cholecalciferol at Days 113 and 141 of pregnancy. A control group (n = 58) consisted of ewes receiving no additional nutritional treatments. The vitamin D status of ewes and lambs was assessed up until 1 month post-lambing. Lamb immune function was assessed by analysing the functional capacity of phagocytes, and the plasma IgG and anti-tetanus-toxoid antibody concentrations between birth and weaning. Maternal supplementation with cholecalciferol increased the plasma 25(OH)D concentrations of both ewes (137 vs 79 nmol/L; P < 0.001) and lambs (49 vs 24 nmol/L; P < 0.001) at birth compared with the controls. Supplementation with cholecalciferol had no significant effect on the phagocytic capacity of monocytes or polymorphonuclear leukocytes, the concentration of IgG in the colostrum or plasma of lambs, or the vaccine-specific antibody response against tetanus toxoid. Overall, the results support our first hypothesis, but suggest that maternal supplementation with 1 × 106 IU cholecalciferol does not improve innate, passive or adaptive immune function in lambs.

Dietary vitamin D dose-response in healthy children 2 to 8 y of age: a 12-wk randomized controlled trial using fortified foods

BACKGROUND

Vitamin D is fundamental for bone health. A high proportion of Canadian 2- to 8-y-olds do not meet the Estimated Average Requirement (EAR) of 400 IU/d.

OBJECTIVE

The objective was to determine whether vitamin D intakes consistent with the EAR or Recommended Dietary Allowance (RDA), through fortification of additional dairy products, would result in higher vitamin D status in young children.

DESIGN

Participants aged 2-8 y (n = 77; Montreal, Canada) were randomly assigned to 1 of 3 dietary vitamin D targets (control; EAR: 400 IU/d; or RDA: 600 IU/d) for 12 wk (January to April 2014). Anthropometric measurements, demographic characteristics, dietary intakes, fasting serum parathyroid hormone, 25-hydroxyvitamin D [25(OH)D], and ionized calcium were compared by using mixed-model ANOVA.

RESULTS

Participants' mean ± SD age was 5.1 ± 1.9 y; 54.5% were boys with body mass index z scores of 0.50 ± 0.85. Compliance was 85% overall. No differences were observed in baseline dietary vitamin D intakes or serum 25(OH)D. At 12 wk, the EAR and RDA groups had significantly higher vitamin D intakes [median (IQR): control, 227 (184-305) IU/d; EAR, 410 (363-516) IU/d; and RDA, 554 (493-653) IU/d; P < 0.05] and serum 25(OH)D concentrations (control: 55.8 ± 12.3 nmol/L; EAR: 64.1 ± 10.0 nmol/L; and RDA: 63.7 ± 12.4 nmol/L; P < 0.05) than the control group. Ninety-six percent of children in the EAR and RDA groups and 67% of the control group had 25(OH)D concentrations ≥50 nmol/L.

CONCLUSION

Increasing the vitamin D intakes of young children through fortification of alternative dairy products results in significantly higher serum concentrations of 25(OH)D and a significantly greater proportion of children with serum 25(OH)D ≥50 nmol/L during periods of minimal ultraviolet B radiation exposure. This trial was registered at clinicaltrials.gov as NCT02097160 and had Health Canada Temporary Marketing Authorization Letters for both products (TM-13-0432 and TM-13-0433).

Vitamin D content in human breast milk: a 9-mo follow-up study

BACKGROUND

Parents are advised to avoid the direct sun exposure of their newborns. Therefore, the vitamin D status of exclusively breastfed newborns is entirely dependent on the supply of vitamin D from breast milk.

OBJECTIVES

We explored concentrations of ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3) (vitamin D) and 25-hydroxivitamin D2 plus D3 (25-hydroxyvitamin D [25(OH)D]) in foremilk and hindmilk during the first 9 mo of lactation and identified indexes of importance to the concentrations.

DESIGN

We collected blood and breast-milk samples from mothers at 2 wk (n = 107), 4 mo, (n = 90), and 9 mo (n = 48) postpartum. Blood samples from infants were collected 4 and 9 mo after birth. We measured concentrations of vitamin D metabolites in blood and milk samples with the use of liquid chromatography-tandem mass spectrometry.

RESULTS

Concentrations of vitamin D and 25(OH)D correlated significantly and were higher in hindmilk than in foremilk. Milk concentrations were also correlated with maternal plasma 25(OH)D concentrations. In foremilk and hindmilk, concentrations were a median (IQR) of 1.35% (1.04-1.84%) and 2.10% (1.63-2.65%), respectively, of maternal plasma 25(OH)D concentrations (P < 0.01). Milk concentrations showed a significant seasonal variation. Mothers who were taking vitamin D supplements had higher concentrations than did nonusers. Medians (IQRs) of infant daily intake through breast milk of vitamin D and 25(OH)D were 0.10 μg (0.02-0.40 μg) and 0.34 μg (0.24-0.47 μg), respectively, which were equal to a median (IQR) antirachitic activity of 77 IU/d (52-110 IU/d).

CONCLUSIONS

The supply of vitamin D from breast milk is limited. Exclusively breastfed infants received <20% of the daily dose recommended by the Institute of Medicine for infants during the first year of life. This trial was registered at clinicaltrials.gov as NCT02548520.

A 24-month prospective study on the efficacy and safety of two different monthly regimens of vitamin D supplementation in pre-menopausal women with systemic lupus erythematosus

BACKGROUND

Low vitamin D (vit.D) serum levels are common in patients with systemic lupus erythematosus (SLE) and seem to correlate with higher disease activity. We investigated the effects of different regimens of vit.D supplementation in SLE patients with inactive disease.

METHODS

This 24-month prospective study included 34 SLE women who were randomized to receive, together with their ongoing treatment, a standard regimen (SR) of cholecalcipherol (25,000 UI monthly) or an intensive regimen (IR) (300,000 UI initial bolus followed by 50,000 UI monthly) for one year and then were switched to the other regimen in the second year. Patients were seen quarterly for assessment of 25-OH vit.D levels, disease activity, SLE serology and bone metabolism markers.

RESULTS

By intra-patient comparison, only the IR was found able to significantly raise vit.D serum levels. After 12 months, values above 30 ng/ml were found in 75% of patients in IR while in only 28% in SR. No significant differences in disease activity and SLE serology were found at any time point between SR and IR. No changes in the mineral metabolism were observed.

CONCLUSIONS

The IR was safe and effective in obtaining sufficient levels of vit.D in most SLE patients. However, both regimens of supplementation did not differently affect disease activity nor SLE serology.

The role of red meat in the diet: nutrition and health benefits

Red meat has been an important part of the human diet throughout human evolution. When included as part of a healthy, varied diet, red meat provides a rich source of high biological value protein and essential nutrients, some of which are more bioavailable than in alternative food sources. Particular nutrients in red meat have been identified as being in short supply in the diets of some groups of the population. The present paper discusses the role of red meat in the diets of young infants, adolescents, women of childbearing age and older adults and highlights key nutrients red meat can provide for these groups. The role of red meat in relation to satiety and weight control is discussed as the inclusion of lean red meat in a healthy, varied diet may help weight loss as part of an energy-reduced diet. A summary of the UK advice on the amount of red meat that can be consumed as part of a healthy, varied diet is also provided.

Optimal Vitamin D Supplementation Doses that Minimize the Risk for Both Low and High Serum 25-Hydroxyvitamin D Concentrations in the General Population

The Recommended Dietary Allowance (RDA) is the nutrient intake considered to be sufficient to meet the requirements of 97.5% of the population. Recent reports revealed a statistical error in the calculation of the RDA for vitamin D opening the question of what the recommendation should be. We took a dual approach to answer this question: (1) we aggregated 108 published estimates on vitamin D supplementation and vitamin D status; and (2) we analyzed 13,987 observations of program participants. The aggregation of published data revealed that 2909 IU of vitamin D per day is needed to achieve serum 25-hydroxyvitamin D (25(OH)D) concentrations of 50 nmol/L or more in 97.5% of healthy individuals. For normal weight, overweight and obese program participants this was 3094, 4450 and 7248 IU respectively. These supplementation doses would also result in 2.5% of normal weight, overweight and obese participants having 25(OH)D concentrations above 210, 200 and 214 nmol/L respectively. As these concentrations are high, an approach that minimizes the risk for both low and high concentrations seems desirable. With this approach we estimated, for example, that doses of 1885, 2802 and 6235 IU per day are required for normal weight, overweight and obese individuals respectively to achieve natural 25(OH)D concentrations (defined as 58 to 171 nmol/L). In conclusion, the large extent of variability in 25(OH)D concentrations makes a RDA for vitamin D neither desirable nor feasible. We therefore propose recommendations be articulated in the form of an optimal intake that minimizes the risk for both low and high serum 25(OH)D concentrations. This contribution includes body weight specific recommendations for optimal intakes for various combinations of lower and upper 25(OH)D concentration targets.

Quantifying the vitamin D economy

Vitamin D enters the body through multiple routes and in a variety of chemical forms. Utilization varies with input, demand, and genetics. Vitamin D and its metabolites are carried in the blood on a Gc protein that has three principal alleles with differing binding affinities and ethnic prevalences. Three major metabolites are produced, which act via two routes, endocrine and autocrine/paracrine, and in two compartments, extracellular and intracellular. Metabolic consumption is influenced by physiological controls, noxious stimuli, and tissue demand. When administered as a supplement, varying dosing schedules produce major differences in serum metabolite profiles. To understand vitamin D's role in human physiology, it is necessary both to identify the foregoing entities, mechanisms, and pathways and, specifically, to quantify them. This review was performed to delineate the principal entities and transitions involved in the vitamin D economy, summarize the status of present knowledge of the applicable rates and masses, draw inferences about functions that are implicit in these quantifications, and point out implications for the determination of adequacy.

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.

Determinants of 25-hydroxyvitamin D in older Irish adults

BACKGROUND

vitamin D deficiency is prevalent in older adults living in Northern Europe and is influenced by several factors which may vary significantly with age.

OBJECTIVE

we aimed to investigate the determinants of 25-hydroxyvitamin D [25(OH)D] in older Irish adults and in particular to examine the effect of supplement use and surrogate markers of sun exposure.

METHODS

subjects were non-institutionalised community dwelling Irish adults aged over 60 years who were participants of a large cross-sectional study comprising three disease defined cohorts. Serum 25(OH)D was measured by liquid chromatography mass spectroscopy. Associations between 25(OH)D and potential confounders were explored in forward regression models in each cohort.

RESULTS

the three cohorts comprised 1895, 1233 and 1316 participants (respective mean ages 70.1, 71.0 and 80.4 years). Statistical models explained between a fifth to a third of the variation in 25(OH)D. Supplement use and global solar radiation were positive predictors of 25(OH)D in all cohorts whereas the only universal negative predictor was body mass index. Supplement use was associated with a mean increase in 25(OH)D of between 21.4 and 35.4 nmol/l. The other main predictors varied by cohort but included sun holiday travel, enjoyment of sunshine when outside, use of vitamin D fortified milk, smoking, oily fish and egg consumption and physical frailty.

CONCLUSION

supplement use was the most important determinant of vitamin D status. Vitamin D fortified milk and spending time in the sun, even in the oldest old may also be useful strategies to improve 25(OH)D.

The clinical use of vitamin D metabolites and their potential developments: a position statement from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO) and the International Osteoporosis Foundation (IOF)

Several compounds are produced along the complex pathways of vitamin D3 metabolism, and synthetic analogs have been generated to improve kinetics and/or vitamin D receptor activation. These metabolites display different chemical properties with respect to the parental or native vitamin D3, i.e., cholecalciferol, which has been, so far, the supplement most employed in the treatment of vitamin D inadequacy. Hydrophilic properties of vitamin D3 derivatives facilitate their intestinal absorption and their manageability in the case of intoxication because of the shorter half-life. Calcidiol is a more hydrophilic compound than parental vitamin D3. Active vitamin D analogs, capable of binding the vitamin D receptor evoking vitamin D-related biological effects, are mandatorily employed in hypoparathyroidism and kidney failure with impaired 1α-hydroxylation. They have been shown to increase BMD, supposedly ameliorating calcium absorption and/or directly affecting bone cells, although their use in these conditions is jeopardized by the development of hypercalciuria and mild hypercalcemia. Further studies are needed to assess their overall safety and effectiveness in the long-term and new intermittent regimens, especially when combined with the most effective antifracture agents.

Effect of a monthly dose of calcidiol in improving vitamin D deficiency and secondary hyperparathyroidism in HIV-infected patients

There are no data about the optimal supplementation therapy in HIV-infected patients with vitamin D (25OHD) deficiency. The aim of this study was to assess the effect of an oral monthly dose of 16,000 IU calcidiol. We performed a longitudinal cohort study of 365 HIV-infected patients (24 % females) was with sequential determinations of 25OHD, serum parathyroid hormone (PTH), calcium, and alkaline phosphatase. The efficacy and safety of supplementation in 123 patients were compared against dietary and sun exposure advice. Overall, mean baseline 25OHD levels were 19.1 ng/ml (IQR 12-23.6), 63 % of patients had 25OHD deficiency and 27 % secondary hyperparathyroidism. After a median time of 9.3 months (95.61 patients-year on-treatment), 25OHD levels increased in comparison with non-supplemented patients (+16.4 vs. +3.2 ng/ml; p < 0.01), decreasing the rate of 25OHD deficiency (from 84 to 24 %), and decreasing serum PTH (-4.9 pg/ml) and the rate of secondary hyperparathyroidism (from 43 to 31 %; p < 0.001). This improvement was observed irrespective of HIV/HCV coinfection or the use of efavirenz. In a regression analysis, adjusting by seasonality, a lower baseline 25OHD was associated with persistence of deficiency (relative risk, RR 1.07; 95 % CI 1.03-1.1; p < 0.001), whereas calcidiol supplementation was the only factor associated with significant improvement (RR 0.38; 95 % CI 0.12-0.46; p < 0.001). This monthly dose showed no clinical toxicity, and no patient had 25OHD levels above 100 ng/ml, nor hypercalcemia. The use of monthly calcidiol is safe, easy to take, and largely effective to improve vitamin D deficiency and secondary hyperparathyroidism in HIV-infected patients.

Small Increments in Vitamin D Intake by Irish Adults over a Decade Show That Strategic Initiatives to Fortify the Food Supply Are Needed

BACKGROUND

Food fortification could be an effective method of increasing vitamin D intakes and preventing deficiency with minimal risk of excessive dosing.

OBJECTIVE

Secular trends in vitamin D intakes were examined over a 10-y period.

METHODS

We compared vitamin D intakes among 18- to 64-y-old adults from the base diet, fortified foods, and supplements in 2 nationally representative dietary surveys in 1999 and 2009 implemented using the same methodology.

RESULTS

There was a slight increase in the median (IQR) intake of vitamin D from 2.9 (3.2) to 3.5 (3.7) μg/d (mean ± SD, 4.3 ± 4.0 to 5.0 ± 6.4 μg). The median (IQR) intake from the base diet was 2.3 (1.6) μg/d in 1999 and 2.1 (1.8) μg/d in 2009. In vitamin D supplement users, median (IQR) intakes were 7.6 (6.7) and 8.7 (7.2) μg/d and the prevalence of inadequacy decreased from 67% to 57% in 2009. Although the consumption of vitamin D-containing supplements was similar in the 2 surveys (17% and 16%), the use of calcium-vitamin D supplements increased from 3% to 10% among women aged 50-64 y. The prevalence of fortified food consumption was also similar at 60%, and median (IQR) vitamin D intakes in consumers were 2.9 (2.2) and 3.7 (2.9) μg/d in 1999 and 2009, respectively. Mathematical modeling of food fortification using modified vitamin D composition data showed that there is potential to increase vitamin D intakes at the lower end of the distribution, without increasing the risk of exceeding the Tolerable Upper Intake Level.

CONCLUSIONS

We report small increases in vitamin D intakes among Irish adults over a decade of focus on vitamin D and in the context of a voluntary fortification policy. Strategic management of vitamin D in the food supply is required to yield measurable benefits.

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'.

Calcifediol versus vitamin D3 effects on gait speed and trunk sway in young postmenopausal women: a double-blind randomized controlled trial

In this double-blind RCT, 4-month treatment with calcifediol compared with vitamin D3 improved gait speed by 18% among young postmenopausal women. Consistently, change in 25(OH)D blood levels over time were significantly correlated with improvement in gait speed in these women. No effect could be demonstrated for trunk sway.

INTRODUCTION

The aim of this study is to test the effect of calcifediol compared with vitamin D3 on gait speed and trunk sway.

METHODS

Twenty healthy postmenopausal women with an average 25(OH)D level of 13.2 ng/ml (SD = ±3.9) and a mean age of 61.5 years (SD = ±7.2) were randomized to either 20 μg of calcifediol or 20 μg (800 IU) of vitamin D3 per day in a double-blind manner. At baseline and at 4 months of follow-up, the same physiotherapist blinded to treatment allocation tested 8-m gait speed and a body sway test battery (Sway star pitch and roll angle plus velocity while walking 8 m, and standing on both legs on a hard and soft surface). All analyses adjusted for baseline measurement, age, and body mass index.

RESULTS

Mean 25(OH)D levels increased to 69.3 ng/ml (SD = ±9.5) in the calcifediol group and to 30.5 ng/ml (SD = ±5.0) in the vitamin D3 group (p < 0.0001). Women receiving calcifediol compared with vitamin D3 had an 18% greater improvement in gait speed at 4-month follow-up (p = 0.046) adjusting for baseline gait speed, age, and body mass index. Also, change in gait speed was significantly correlated with change in serum 25(OH)D concentrations (r = 0.5; p = 0.04). Across three tests of trunk sway, there were no consistent differences between groups and no significant correlation between change in 25(OH)D serum concentrations and change in trunk sway.

CONCLUSIONS

Calcifediol improved gait speed in early postmenopausal women compared with vitamin D3 and change in 25(OH)D level was moderately correlated with improvement in gait speed. A benefit on trunk sway could not be demonstrated.

Oral Calcidiol Is More Effective Than Cholecalciferol Supplementation to Reach Adequate 25(OH)D Levels in Patients with Autoimmune Diseases Chronically Treated with Low Doses of Glucocorticoids: A "Real-Life" Study

Glucocorticoids (GCs) are the cornerstone of the therapy in many autoimmune and inflammatory diseases. However, it is well known that their use is a double edged sword, as their beneficial effects are associated almost universally with unwanted effects, as, for example glucocorticoid-induced osteoporosis (GIO). Over the last years, several clinical practice guidelines emphasize the need of preventing bone mass loss and reduce the incidence of fractures associated with GC use. Calcium and vitamin D supplementation, as adjunctive therapy, are included in all the practice guidelines. However, no standard vitamin D dose has been established. Several studies with postmenopausal women show that maintaining the levels above 30-33 ng/mL help improve the response to bisphosphonates. It is unknown if the response is the same in GIO, but in the clinical practice the levels are maintained at around the same values. In this study we demonstrate that patients with autoimmune diseases, undergoing glucocorticoid therapy, often present suboptimal 25(OH)D levels. Patients with higher body mass index and those receiving higher doses of glucocorticoids are at increased risk of having lower levels of 25(OH)D. In these patients, calcidiol supplementations are more effective than cholecalciferol to reach adequate 25(OH)D levels.

Dietary calcium does not interact with vitamin D₃ in terms of determining the response and catabolism of serum 25-hydroxyvitamin D during winter in older adults

BACKGROUND

Interactions between calcium and vitamin D may have implications for the regulation of serum 25-hydroxyvitamin D [25(OH)D] and its catabolism and, consequently, the vitamin D dietary requirement.

OBJECTIVE

We investigated whether different calcium intakes influenced serum 25(OH)D and indexes of vitamin D activation and catabolism during winter and in the context of both adequate and inadequate vitamin D intakes.

DESIGN

A 15-wk winter-based, randomized, placebo-controlled, double-blind vitamin D₃ intervention (20 μg/d) study was carried out in free-living men and women aged ≥50 y (n = 125) who were stratified according to calcium intakes [moderate-low (<700 mg/d) or high (>1000 mg/d) intake]. The serum 25(OH)D concentration was the primary outcome, and serum calcium, parathyroid hormone (PTH), 1,25-dihydroxyvitamin D [1,25(OH)₂D], 24,25-dihydroxyvitamin D [24,25(OH)₂D], the ratio of 24,25(OH)₂D to 25(OH)D, vitamin D-binding protein, and free 25(OH)D were exploratory outcomes.

RESULTS

A repeated-measures ANOVA showed there was no significant (P = 0.2) time × vitamin D treatment × calcium intake grouping interaction effect on the mean serum 25(OH)D concentration over the 15-wk intervention period. Serum 25(OH)D concentrations increased (P ≤ 0.005) and decreased (P ≤ 0.002) in vitamin D₃ and placebo groups, respectively, and were of similar magnitudes in subjects with calcium intakes <700 mg/d (and even <550 mg/d) compared with >1000 mg/d. The response of serum PTH, 1,25(OH)₂D, 24,25(OH)₂D, the ratio of 24,25(OH)₂D to 25(OH)D, and free 25(OH)D significantly differed in vitamin D₃ and placebo groups but not by calcium intake grouping.

CONCLUSIONS

We found no evidence of a vitamin D sparing effect of high calcium intake, which has been referred to by some authors as "vitamin D economy." Thus, recent dietary vitamin D requirement estimates will cover the vitamin D needs of even those individuals who have inadequate calcium intakes.

Vitamin D as an anti-microbial and anti-inflammatory therapy for Cystic Fibrosis

Cystic fibrosis (CF) is characterized by chronic infection and inflammation in the airways that lead to progressive lung damage and early death. Current anti-inflammatory therapies are limited by extensive adverse effects or insufficient efficacy. There is a large body of studies indicating beneficial anti-microbial and anti-inflammatory properties of vitamin D. Since most patients with CF present with vitamin D deficiency, and serum vitamin D levels demonstrate a positive correlation with lung function and negative correlation with airway inflammation and infection, correcting vitamin D deficiency may be an attractive therapeutic strategy in CF. The function of vitamin D is intricately tied to its metabolism, which may be impaired at multiple steps in patients with CF, with a potential to limit the efficacy of vitamin D supplementation. It is likely that the aforementioned beneficial properties of vitamin D require supplementation with doses of vitamin D markedly higher than those recommended to maintain proper bone function. This review will illustrate the potential for supplementation with vitamin D or its metabolites to modulate inflammation and improve defence against chronic infection in CF lung, as well as appropriate vitamin D supplementation strategies for improving lung function in CF.

Including food 25-hydroxyvitamin D in intake estimates may reduce the discrepancy between dietary and serum measures of vitamin D status

The discrepancy between the commonly used vitamin D status measures-intake and serum 25-hydroxyvitamin D [25(OH)D] concentrations--has been perplexing. Sun exposure increases serum 25(OH)D concentrations and is often used as an explanation for the higher population-based serum concentrations in the face of apparently low vitamin D intake. However, sun exposure may not be the total explanation. 25(OH)D, a metabolite of vitamin D, is known to be present in animal-based foods. It has been measured and reported only sporadically and is not currently factored into U.S. estimates of vitamin D intake. Previously unavailable preliminary USDA data specifying the 25(OH)D content of a subset of foods allowed exploration of the potential change in the reported overall vitamin D content of foods when the presence of 25(OH)D was included. The issue of 25(OH)D potency was addressed, and available commodity intake estimates were used to outline trends in projected vitamin D intake when 25(OH)D in foods was taken into account. Given the data available, there were notable increases in the total vitamin D content of a number of animal-based foods when potency-adjusted 25(OH)D was included, and in turn there was a potentially meaningful increase (1.7-2.9 μg or 15-30% of average requirement) in vitamin D intake estimates. The apparent increase could reduce discrepancies between intake estimates and serum 25(OH)D concentrations. The relevance to dietary interventions is discussed, and the need for continued exploration regarding 25(OH)D measurement is highlighted.

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

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

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.

Vitamin D supplementation increases calcium absorption without a threshold effect

BACKGROUND

The maximal calcium absorption in response to vitamin D has been proposed as a biomarker for vitamin D sufficiency.

OBJECTIVE

The objective was to determine whether there is a threshold beyond which increasing doses of vitamin D, or concentrations of serum 25-hydroxyvitamin D [25(OH)D], no longer increase calcium absorption.

DESIGN

This was a placebo-controlled, dose-response, randomized, double-blind study of the effect of vitamin D on calcium absorption in healthy postmenopausal women. Seventy-six healthy postmenopausal women were randomly assigned to placebo or 800 IU (20 μg), 2000 IU (50 μg), or 4000 IU (100 μg) vitamin D₃ for 8 wk. The technique of dual isotopes of stable calcium was used with a calcium carrier to measure calcium absorption at baseline and after 8 wk.

RESULTS

Seventy-one women with a mean ± SD age of 58.8 ± 4.9 y completed the study. The mean calcium intake was 1142 ± 509 mg/d and serum 25(OH)D was 63 ± 14 nmol/L at baseline. A statistically significant linear trend of an increase in calcium absorption adjusted for age and body mass index with increasing vitamin D₃ dose or serum 25(OH)D concentration was observed. A 6.7% absolute increase in calcium absorption was found in the highest vitamin D₃ group (100 μg). No evidence of nonlinearity was observed in the dose-response curve.

CONCLUSIONS

No evidence of a threshold of calcium absorption was found with a serum 25(OH)D range from 40 to 130 nmol/L. Calcium absorption in this range is not a useful biomarker to determine nutritional recommendations for vitamin D.

Serum 25(OH)D response to vitamin D3 supplementation: a meta-regression analysis

OBJECTIVE

The aim of this study was to review factors that influence serum 25(OH)D when patients are given vitamin D supplements.

METHODS

From a comprehensive search of all randomized controlled clinical trials with vitamin D3 supplementation available on PubMed up to November 2011, we selected 33 with 43 treatment arms that included at least 30 adult participants. The achieved pooled mean difference (PMD) and 95% confidence intervals (CIs) were calculated using the random-effects models. Meta-regression and subgroup analyses were performed for prespecified factors, including dose, duration, baseline serum 25(OH)D, and age.

RESULTS

With a mean baseline serum 25(OH)D of 50.4 nmol/L, PMD was 37 nmol/L (95% CI, 33-41) with significant heterogeneity among studies. Dose (slope: 0.006; P < 0.001), trial duration (slope: 0.21; P < 0.001), baseline serum 25(OH)D (slope: -0.19; P < 0.001), and age (slope: 0.42; P < 0.001) independently influenced vitamin D response. Similar results were found in studies with a mean baseline serum 25(OH)D <50 nmol/L. In subgroup analyses, the PMD was higher with doses ≥800 IU/d (39.3 nmol/L) after 6 to 12 mo (41.7 nmol/L), with baseline 25(OH)D <50 nmol/L (39.6 nmol/L), and in adults aged >80 y (40.5 nmol/L).

CONCLUSION

This meta regression indicates that a higher increase in serum levels of 25(OH)D in adults is found with a dose of ≥800 IU/d, after at least 6 to 12 mo, and even when baseline 25(OH)D is low and in adults >80 y.

Low vitamin D status is associated with reduced muscle mass and impaired physical performance in frail elderly people

BACKGROUND/OBJECTIVES

Serum 25-hydroxyvitamin D (25(OH)D) status has been associated with muscle mass, strength and physical performance in healthy elderly people. Yet, in pre-frail and frail elderly people this association has not been studied. The objective of this study was to explore the association between vitamin D intake and serum 25(OH)D status with muscle mass, strength and physical performance in a pre-frail and frail elderly population.

SUBJECTS/METHODS

This cross-sectional study included 127 pre-frail and frail elderly people in The Netherlands. Whole body and appendicular lean mass (ALM) (dual energy X-ray absorptiometry), leg strength (one repetition maximum), handgrip strength and physical performance (short physical performance battery) were measured, and blood samples were collected for the assessment of serum 25(OH)D status (liquid chromatography-tandem mass spectrometry). In addition, habitual dietary intake (3-day food records) and physical activity data (accelerometers) were collected.

RESULTS

In total, 53% of the participants had a serum 25(OH)D level below 50  nmol/l. After adjustment for confounding factors, 25(OH)D status was associated with ALM (β=0.012, P=0.05) and with physical performance (β=0.020, P<0.05). Vitamin D intake was associated with physical performance (β=0.18, P<0.05) but not with ALM (P>0.05).

CONCLUSION

In this frail elderly population, 25(OH)D status is low and suggests a modest association with reduced ALM and impaired physical performance. In addition, vitamin D intake tended to be associated with impaired physical performance. Our findings highlight the need for well-designed intervention trials to assess the impact of vitamin D supplementation on 25(OH)D status, muscle mass and physical performance in pre-frail and frail elderly people.

Natural vitamin D content in animal products

Humans derive most vitamin D from the action of sunlight in their skin. However, in view of the current Western lifestyle with most daily activities taking place indoors, sun exposure is often not sufficient for adequate vitamin D production. For this reason, dietary intake is also of great importance. Animal foodstuffs (e.g., fish, meat, offal, egg, dairy) are the main sources for naturally occurring cholecalciferol (vitamin D-3). This paper therefore aims to provide an up-to-date overview of vitamin D-3 content in various animal foods. The focus lies on the natural vitamin D-3 content because there are many countries in which foods are not regularly fortified with vitamin D. The published data show that the highest values of vitamin D are found in fish and especially in fish liver, but offal also provides considerable amounts of vitamin D. The content in muscle meat is generally much lower. Vitamin D concentrations in egg yolks range between the values for meat and offal. If milk and dairy products are not fortified, they are normally low in vitamin D, with the exception of butter because of its high fat content. However, as recommendations for vitamin D intake have recently been increased considerably, it is difficult to cover the requirements solely by foodstuffs.

Vitamin D in plants: a review of occurrence, analysis, and biosynthesis

The major function of vitamin D in vertebrates is maintenance of calcium homeostasis, but vitamin D insufficiency has also been linked to an increased risk of hypertension, autoimmune diseases, diabetes, and cancer. Therefore, there is a growing awareness about vitamin D as a requirement for optimal health. Vitamin D3 is synthesized in the skin by a photochemical conversion of provitamin D3, but the necessary rays are only emitted all year round in places that lie below a 35° latitude. Unfortunately, very few food sources naturally contain vitamin D and the general population as a results fail to meet the requirements. Fish have the highest natural content of vitamin D expected to derive from an accumulation in the food chain originating from microalgae. Microalgae contain both vitamin D3 and provitamin D3, which suggests that vitamin D3 exist in the plant kingdom and vitamin D3 has also been identified in several plant species as a surprise to many. The term vitamin D also includes vitamin D2 that is produced in fungi and yeasts by UVB-exposure of provitamin D2. Small amounts can be found in plants contaminated with fungi and traditionally only vitamin D2 has been considered present in plants. This review summarizes the current knowledge on sterol biosynthesis leading to provitamin D. It also addresses the occurrence of vitamin D and its hydroxylated metabolites in higher plants and in algae and discusses limitations and advantages of analytical methods used in studies of vitamin D and related compounds including recent advances in analytical technologies. Finally, perspectives for a future production of vitamin D biofortified fruits, vegetables, and fish will be presented.

All-source basal vitamin D inputs are greater than previously thought and cutaneous inputs are smaller

The magnitude of vitamin D inputs in individuals not taking supplements is unknown; however, there is a great deal of information on quantitative response to varying supplement doses. We reanalyzed individual 25-hydroxyvitamin D [25(OH)D] concentration data from 8 studies involving cholecalciferol supplementation (total sample size = 3000). We extrapolated individual study dose-response curves to zero concentration values for serum 25(OH)D by using both linear and curvilinear approaches and measured seasonal oscillation in the serum 25(OH)D concentration. The total basal input (food plus solar) was calculated to range from a low of 778 iu/d in patients with end-stage renal disease to a high of 2667 iu/d in healthy Caucasian adults. Consistent with expectations, obese individuals had lower baseline, unsupplemented 25(OH)D concentrations and a smaller response to supplements. Similarly, African Americans had both lower baseline concentrations and lower calculated basal, all-source inputs. Seasonal oscillation in 4 studies ranged from 5.20 to 11.4 nmol/L, reflecting a mean cutaneous synthesis of cholecalciferol ranging from 209 to 651 iu/d at the summer peak. We conclude that: 1) all-source, basal vitamin D inputs are approximately an order of magnitude higher than can be explained by traditional food sources; 2) cutaneous, solar input in these cohorts accounts for only 10-25% of unsupplemented input at the summer peak; and 3) the remainder must come from undocumented food sources, possibly in part as preformed 25(OH)D.

Vitamin D content of food and its contribution to vitamin D status: a brief overview and Australian focus

There are only a few natural foods that contain nutritionally significant quantities of vitamin D. These include egg yolk, some fatty fish, and in much lower concentrations, meat. The published values of the vitamin D content of food are summarised here and their contribution to dietary vitamin D intake is discussed, with particular reference to Australia. Dietary vitamin D is unlikely to reach the level recommended by the US Institute of Medicine. It is therefore concluded that dietary vitamin D will only be a component of vitamin D supply, with UV exposure and/or oral supplements continuing to be the main sources of vitamin D to maintain adequate status.