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.

Effect of Ultraviolet Light-Exposed Mushrooms on Vitamin D Status: Liquid Chromatography-Tandem Mass Spectrometry Reanalysis of Biobanked Sera from a Randomized Controlled Trial and a Systematic Review plus Meta-Analysis.

BACKGROUND: Randomized controlled trial (RCT) data on the response of serum total 25-hydroxyvitamin D [25(OH)D] in healthy participants consuming UV light-exposed edible mushrooms are limited and mixed. OBJECTIVE: The objective was to undertake a systematic review and meta-analysis of responses of serum 25(OH)D [and serum 25-hydroxyergocalciferol, 25(OH)D2, and serum 25-hydroxycholecalciferol, 25(OH)D3, if available] to consumption of UV-exposed mushrooms by healthy participants. Biobanked sera from one RCT (originally analyzed by immunoassay) were reanalyzed by LC-MS/MS to generate serum 25(OH)D2 and serum 25(OH)D3 data. METHODS: Ovid MEDLINE, EMBASE, and Cochrane CENTRAL were searched for RCTs of UV-exposed mushrooms and data on serum 25(OH)D. Studies were screened for eligibility, and relevant data were extracted. Serum 25(OH)D data were re-analyzed by ANOVA and paired t tests. RESULTS: Our structured search yielded 6 RCTs meeting our inclusion criteria. Meta-analysis of all 6 RCTs showed serum 25(OH)D was not significantly increased (P = 0.12) by UV-exposed mushrooms, but there was high heterogeneity (I(2) = 87%). Including only the 3 European-based RCTs [mean baseline 25(OH)D, 38.6 nmol/L], serum 25(OH)D was increased significantly by UV-exposed mushrooms [weighted mean difference (WMD): 15.2 nmol/L; 95% CI: 1.5, 28.8 nmol/L, P = 0.03, I(2) = 88%], whereas there was no significant effect in the 3 US-based RCTs [P = 0.83; mean baseline 25(OH)D: 81.5 nmol/L]. Analysis of serum 25(OH)D2 and serum 25(OH)D3 (n = 5 RCTs) revealed a statistically significant increase (WMD: 20.6 nmol/L; 95% CI: 8.0, 33.3 nmol/L, P = 0.001, I(2 =) 99%) and decrease (WMD: -13.3 nmol/L; 95% CI: -15.8, -10.7 nmol/L, P < 0.00001, I(2) = 0%) after supplementation with UV-exposed mushrooms. CONCLUSIONS: Consumption of UV-exposed mushrooms may increase serum 25(OH)D when baseline vitamin D status is low via an increase in 25(OH)D2 (24.2 nmol/L) and despite a concomitant but relatively smaller reduction in 25(OH)D3 (-12.6 nmol/L). When baseline vitamin D status is high, the mean increase in 25(OH)D2 (18.3 nmol/L) and a relatively similar reduction in 25(OH)D3 (-13.6 nmol/L) may explain the lack of effect on serum 25(OH)D.

The 3 epimer of 25-hydroxycholecalciferol is present in the circulation of the majority of adults in a nationally representative sample and has endogenous origins.

Fundamental knowledge gaps in relation to the 3 epimer of 25-hydroxycholecalciferol [3-epi-25(OH)D3] limit our understanding of its relevance for vitamin D nutrition and health. The aims of this study were to characterize the 3-epi-25(OH)D3 concentrations in a nationally representative sample of adults and explore its determinants. We also used data from a recent randomized controlled trial (RCT) of supplemental cholecalciferol (vitamin D3) conducted in winter in older adults to directly test the impact of changes in vitamin D status on serum 3-epi-25(OH)D3 concentrations. Serum 25-hydroxycholecalciferol [25(OH)D3] and 3-epi-25(OH)D3 concentrations (via LC-tandem mass spectrometry) from our vitamin D3 RCT in adults (aged ≥50 y) and data on dietary, lifestyle, and biochemical characteristics of participants of the recent National Adult Nutrition Survey in Ireland (aged 18-84 y; n = 1122) were used in the present work. In the subsample of participants who had serum 3-epi-25(OH)D3 concentrations greater than the limit of quantification (n = 1082; 96.4%), the mean, 10th, 50th (median), and 90th percentile concentrations were 2.50, 1.05, 2.18, and 4.30 nmol/L, respectively, whereas the maximum 3-epi-25(OH)D3 concentration was 15.0 nmol/L. A regression model [explaining 29.9% of the variability in serum 3-epi-25(OH)D3] showed that age >50 y, vitamin D supplement use, dietary vitamin D, meat intake, season of blood sampling, and sun exposure habits were significant positive determinants, whereas increasing waist circumference and serum 25-hydroxyergocalciferol concentration were significant negative determinants. The RCT data showed that mean serum 25(OH)D3 and 3-epi-25(OH)D3 concentrations increased (49.3% and 42.1%, respectively) and decreased (-28.0% and -29.1%, respectively) significantly (P < 0.0001) with vitamin D3 (20 µg/d) and placebo supplementation, respectively, over 15 wk of winter. In conclusion, we provide data on serum 3-epi-25(OH)D3 in a nationally representative sample of adults. Our combined observational and RCT data might suggest that both dietary supply and dermal synthesis of vitamin D3 contribute to serum 3-epi-25(OH)D3 concentration.

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.

Incremental cholecalciferol supplementation up to 15 µg/d throughout winter at 51-55° N has no effect on biomarkers of cardiovascular risk in healthy young and older adults.

Two separate, identical, double-blind, randomized, placebo-controlled intervention studies were carried out in the south and north of Ireland (51-55°N). Men and women aged 20-40 y (n = 202) and ≥64 y (n = 192) received cholecalciferol at doses of 0 (P), 5 (D3-5), 10 (D3-10), or 15 (D3-15) µg/d (0-600 IU) during wintertime. Serum 25-hydroxyvitamin D [s25(OH)D], intact parathyroid hormone, systolic and diastolic blood pressure, fasting lipids, glucose and insulin, HOMA-IR, high-sensitivity CRP, matrix metalloproteinase-9, and its inhibitor (tissue inhibitor metalloproteinase-1) were measured at baseline (October) and 22 wk later at endpoint (March). Vitamin D receptor Fok I and Taq I genotypes were analyzed and dietary intakes of vitamin D and calcium were assessed. In young adults, s25(OH)D decreased from baseline to endpoint (P < 0.001), except in the D3-15 group, who maintained the baseline concentration of ~70 nmol/L. Older adults had lower s25(OH)D at baseline (median, 54.2 nmol/L) and concentrations increased in the D3-10 and D3-15 groups (P < 0.001). There were no significant effects of supplementation on cardiovascular disease (CVD) risk biomarkers in either age group. Fasting glucose and total and HDL cholesterol were lower (P < 0.05) in older adults with the Fok 1 ff genotype than in those with FF or Ff. Putative effects of vitamin D on cardio-metabolic health will only be evident at higher intakes than the current RDA and possibly in individuals at particular risk of low s25(OH)D and/or CVD risk.

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

BACKGROUND: The relative potency of 25-hydroxyvitamin D3 to vitamin D3 needs to be better defined so that food-composition tables can better reflect the true vitamin D nutritive value of certain foods. OBJECTIVE: We performed a randomized, controlled intervention study in apparently healthy, free-living adults to investigate whether the intake of 25-hydroxyvitamin D3 is 5 times more potent in raising serum 25-hydroxyvitamin D [25(OH)D] during winter compared with an equivalent amount of vitamin D3. DESIGN: A randomized, placebo-controlled, double-blind intervention study was conducted in adults aged ≥50 y (n = 56) who consumed a placebo, 20 µg vitamin D3, or 7 or 20 µg 25-hydroxyvitamin D3 daily throughout 10 wk of winter. Serum 25(OH)D was measured by using an enzyme-linked immunoassay, and serum albumin-corrected calcium (S-Ca) was assessed colorimetrically at the baseline, midpoint, and endpoint of the study. RESULTS: The mean (±SD) increases (per microgram of vitamin D compound) in serum 25(OH)D concentrations over baseline after 10 wk of supplementation were 0.96 ± 0.62, 4.02 ± 1.27, and 4.77 ± 1.04 nmol · L(-1) · µg intake(-1) for the 20-µg vitamin D3/d and 7- and 20-µg 25-hydroxyvitamin D3/d groups, respectively. A comparison of the 7- and 20-µg 25-hydroxyvitamin D3/d groups with the 20-µg vitamin D3/d group yielded conversion factors of 4.2 and 5, respectively. There was no effect of treatment on S-Ca concentrations and no incidence of hypercalcemia (S-Ca >2.6 nmol/L). CONCLUSIONS: Each microgram of orally consumed 25-hydroxyvitamin D3 was about 5 times more effective in raising serum 25(OH)D in older adults in winter than an equivalent amount of vitamin D3. This conversion factor could be used in food-compositional tables for relevant foods. This study was registered at clinicaltrials.gov as NCT01398202.

An updated systematic review and meta-analysis of the efficacy of vitamin D food fortification.

Food fortification is a potentially effective public health strategy to increase vitamin D intakes and circulating 25-hydroxyvitamin D [25(OH)D] concentrations. We updated a previous systematic review to evaluate current evidence from randomized controlled intervention studies in community-dwelling adults of the effect of fortified foods on 25(OH)D concentrations. Ovid MEDLINE, PubMed, CINAHL, Embase, and Cochrane Central Register of Controlled Trials were searched for randomized controlled intervention studies with vitamin D-fortified foods in free-living adults and data on circulating 25(OH)D. Two reviewers independently screened 441 papers for eligibility and extracted the relevant data. A meta-analysis of the absolute mean change in circulating 25(OH)D concentrations was conducted using a random effects model. Sixteen studies from 15 publications were included, of which 14 showed a significant effect of fortified foods on 25(OH)D concentrations. Heterogeneity was high (P = <0.0001, I(2) = 89%) and was partly explained by dose, latitude (range, 3-60°), and baseline 25(OH)D (range, 24.0-83.6 nmol/L). When combined in a random effects analysis (n = 1513; 767 treated, 746 controls), a mean individual intake of ~11 µg/d (440 IU/d) from fortified foods (range, 3-25 µg/d) increased 25(OH)D by 19.4 nmol/L (95% CI: 13.9, 24.9), corresponding to a 1.2 nmol/L (95% CI: 0.72, 1.68) increase in 25(OH)D for each 1 µg ingested. Vitamin D food fortification increases circulating 25(OH)D concentrations in community-dwelling adults. Safe and effective food-based strategies could increase 25(OH)D across the population distribution and prevent vitamin D deficiency with potential benefit for public health.

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 (n 12). 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.

Vitamin d status and indices of bone turnover in older European adults.

An increased rate of bone turnover increases risk of osteoporotic fracture later in life. The concentration of 25-hydroxyvitamin D that contributes to an elevated rate of bone turnover in older adults is unclear. The objective of this study was to investigate the associations between 25-hydroxyvitamin D and biochemical markers of bone turnover in an older, pan-European cohort. 25-hydroxyvitamin D and serum markers of bone-formation (osteocalcin and bone-specific alkaline phosphatase) were assessed by ELISA, while urinary markers of bone-resorption (pyridinoline and deoxypyridinoline) were assessed by HPLC. Six percent, 36 %, and 64 % of subjects had 25-hydroxyvitamin D concentrations < 25, < 50, and < 80 nmol/L throughout the year, respectively. 25-hydroxyvitamin D was significantly and inversely correlated with serum bone-specific alkaline phosphatase (r = 0.119; p = 0.022) and urinary pyridinoline (r = 0.207; p < 0.0001) and deoxypyridinoline (r = 0.230; p < 0.0001). Stratification on the basis of tertiles [T] of 25-hydroxyvitamin D (< 47.6 [T(1)]; 47.6 - 85.8 [T2]; > 85.8 [T3] nmol/L), showed that urinary pyridinoline and deoxypyridinoline were significantly lower in subjects in the 2(nd) and 3(rd) compared to the 1(st) tertile (p < 0.015). Low vitamin D status (< 50 nmol/L) was associated with an increased rate of bone turnover in this older pan-European cohort.

Cholecalciferol supplementation throughout winter does not affect markers of bone turnover in healthy young and elderly adults.

Although there have been several studies of the effect of vitamin D status on bone turnover in the elderly, the findings are unclear, and, furthermore, to date very few have investigated this in young adults. The objective of these randomized, placebo-controlled, double-blind, 2-center intervention studies was to investigate the effect of cholecalciferol supplementation (0, 5, 10, and 15 microg cholecalciferol/d) throughout winter time on indices of vitamin D status and bone turnover in young (aged 20-40 y; n = 215) and elderly (aged > or = 64 y; n = 204) adults, with relatively high mean calcium intakes of 976 and 874 mg/d, respectively. Fasting serum concentrations of 25-hydroxyvitamin D [25(OH)D], parathyroid hormone (PTH), osteocalcin, bone-specific alkaline phosphatase, and carboxyterminal collagen crosslinks were measured by enzyme immunoassays at baseline and endpoint. Fok I and Taq I vitamin D receptor (VDR) genotypes were determined by real-time PCR. Endpoint serum 25(OH)D increased (P < 0.0001) in a dose-related manner with increasing supplemental cholecalciferol (up to 15 microg/d) in 20-40-y olds and up to 10 microg/d in > or = 64-y olds. Endpoint serum PTH was lower (P < 0.05) in the 3 cholecalciferol-supplemented groups compared with that in the placebo group in > or = 64-y olds, but cholecalciferol supplementation did not affect other markers in either cohort and there was no significant interaction with VDR genotype. In conclusion, cholecalciferol supplementation alone throughout winter did not affect bone turnover markers in apparently healthy young and elderly adults, even when stratified by VDR genotype.

Existing and potentially novel functional markers of vitamin D status: a systematic review.

BACKGROUND: Although serum 25-hydroxyvitamin D [25(OH)D] is the currently accepted vitamin D status marker of choice, use of other biomarkers or functional endpoints have been suggested. OBJECTIVE: The objective was to systematically review the effectiveness of 25(OH)D, parathyroid hormone (PTH), bone turnover markers, bone mineral density (BMD), and calcium absorption as biomarkers of vitamin D status. DESIGN: Methods included a structured search on Ovid MEDLINE, EMBASE (Ovid), and Cochrane CENTRAL; rigorous inclusion/exclusion criteria; data extraction; quality assessment; meta-analysis; and meta-regression. RESULTS: Thirty-six vitamin D supplementation randomized controlled trials (RCTs) and 4 before-after studies were included. Vitamin D supplementation significantly raised circulating 25(OH)D in all but one RCT, but the response was highly heterogeneous [weighted mean difference (WMD): 34.1 nmol/L; 95% CI: 28.9, 39.2; 32 RCTs; I2 = 97%). Vitamin D supplementation (without calcium) significantly lowered circulating PTH (WMD: -0.29 pmol/L; 95% CI: -0.56, -0.02; 11 RCTs; I2 = 29%), but this was not apparent in the presence of calcium supplementation. There was a suggestion that whole-body or lumbar spine BMD may be a useful biomarker in older people but not in adolescents. Bone turnover markers were not useful biomarkers of vitamin D status, but 4 before-after studies suggested that intestinal calcium absorption may respond to vitamin D status. CONCLUSIONS: This systematic review confirmed that circulating 25(OH)D is a robust and reliable marker of vitamin D status. Further research is needed to clarify which population subgroups show responses of PTH, BMD, and/or calcium absorption in response to changes in vitamin D status.

Estimation of the dietary requirement for vitamin D in healthy adults.

BACKGROUND: Knowledge gaps have contributed to considerable variation among international dietary recommendations for vitamin D. OBJECTIVE: We aimed to establish the distribution of dietary vitamin D required to maintain serum 25-hydroxyvitamin D [25(OH)D] concentrations above several proposed cutoffs (ie, 25, 37.5, 50, and 80 nmol/L) during wintertime after adjustment for the effect of summer sunshine exposure and diet. DESIGN: A randomized, placebo-controlled, double-blind 22-wk intervention study was conducted in men and women aged 20-40 y (n = 238) by using different supplemental doses (0, 5, 10, and 15 microg/d) of vitamin D(3) throughout the winter. Serum 25(OH)D concentrations were measured by using enzyme-linked immunoassay at baseline (October 2006) and endpoint (March 2007). RESULTS: There were clear dose-related increments (P < 0.0001) in serum 25(OH)D with increasing supplemental vitamin D(3). The slope of the relation between vitamin D intake and serum 25(OH)D was 1.96 nmol x L(-1) x microg(-1) intake. The vitamin D intake that maintained serum 25(OH)D concentrations of >25 nmol/L in 97.5% of the sample was 8.7 microg/d. This intake ranged from 7.2 microg/d in those who enjoyed sunshine exposure, 8.8 microg/d in those who sometimes had sun exposure, and 12.3 microg/d in those who avoided sunshine. Vitamin D intakes required to maintain serum 25(OH)D concentrations of >37.5, >50, and >80 nmol/L in 97.5% of the sample were 19.9, 28.0, and 41.1 microg/d, respectively. CONCLUSION: The range of vitamin D intakes required to ensure maintenance of wintertime vitamin D status [as defined by incremental cutoffs of serum 25(OH)D] in the vast majority (>97.5%) of 20-40-y-old adults, considering a variety of sun exposure preferences, is between 7.2 and 41.1 microg/d.