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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) &mgr;g/d (0-600 lu) 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 ffgenotype than in those with FFor Ff. Putative effects of vitamin D on cardio-metabolic health will only be evident at higher intakes than the current PDA and possibly in individuals at particular risk of low s25(OH)D and/or CVD risk. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Epidemiological studies have shown that low vitamin D status results in impaired immune function and is associated with the prevalence of autoimmune and inflammatory conditions. Vitamin D supplementation has been shown to reduce circulating concentrations of inflammatory markers in such conditions. However, the possible beneficial effect of vitamin D supplementation in the general population, particularly for those individuals living at high latitudes where hypovitaminosis D is common during wintertime, remains unclear. The aim of this study was to assess the effect of vitamin D supplementation using doses of 5, 10, and 15 μg/d cholecalciferol (D3) compared with placebo on cytokine concentrations throughout winter in apparently healthy younger (aged 20-40 y) and older (aged ≥64 y) adults. A total of 211 younger and 202 older adults completed the 22-wk intervention (from October to March) with >85% compliance. Serum concentrations of 25-hydroxycholecalciferol [25)OH)D3], high sensitivity C-reactive protein, IL-6, IL-10, soluble CD40 ligand, TGFβ, TNFα, and fibrinogen were measured using ELISA. 25(OH)D3 concentrations significantly decreased in the placebo and 5 and 10/d μg D3 groups in the younger cohort and in the placebo group in the older cohort. Whereas 15 μg/d D3 supplementation maintained 25(OH(D3 concentrations in the younger cohort (baseline, 75.9 nmol/L; postintervention, 69.0 nmol/L) and significantly increased concentrations in the older cohort (baseline, 55.1 nmol/L; postintervention, 73.9 nmol/L), it had no significant effect on cytokine concentrations (ANCOVA, P> 0.05). The long-term effects of low vitamin D status remain to be elucidated and optimization of vitamin D status in otherwise healthy individuals may potentially have lasting beneficial effects on the immune system. [ABSTRACT FROM AUTHOR]

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 μg cholecalciferol/d) throughout wintertime on indices of vitamin D status and bone turnover in young (aged 20-40 y; n = 215( and elderly (aged ⩾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 μg/d( in 20-40-y olds and up to 10 μg/d in ⩾64-y olds. Endpoint serum PTH was lower (P < 0.051 in the 3 cholecalciferol-supplemented groups compared with that in the placebo group in ⩾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. [ABSTRACT FROM AUTHOR]