Background: Currently, there is a lack of clarity in the literature as to whether there is a definitive difference between the effects of vitamins D2 and D3 in the raising of serum 25-hydroxyvitamin D [25(OH)D].Objective: The objective of this article was to report a systematic review and meta-analysis of randomized controlled trials (RCTs) that have directly compared the effects of vitamin D2 and vitamin D3 on serum 25(OH)D concentrations in humans.Design: The ISI Web of Knowledge (January 1966 to July 2011) database was searched electronically for all relevant studies in adults that directly compared vitamin D3 with vitamin D2. The Cochrane Clinical Trials Registry, International Standard Randomized Controlled Trials Number register, and clinicaltrials.gov were also searched for any unpublished trials.Results: A meta-analysis of RCTs indicated that supplementation with vitamin D3 had a significant and positive effect in the raising of serum 25(OH)D concentrations compared with the effect of vitamin D2 (P = 0.001). When the frequency of dosage administration was compared, there was a significant response for vitamin D3 when given as a bolus dose (P = 0.0002) compared with administration of vitamin D2, but the effect was lost with daily supplementation.Conclusions: This meta-analysis indicates that vitamin D3 is more efficacious at raising serum 25(OH)D concentrations than is vitamin D2, and thus vitamin D3 could potentially become the preferred choice for supplementation. However, additional research is required to examine the metabolic pathways involved in oral and intramuscular administration of vitamin D and the effects across age, sex, and ethnicity, which this review was unable to verify.

Although menopausal status and hormone replacement therapy use dominate women's bone health, diet may influence early postmenopausal bone loss. Fruit and vegetable intake may protect against premenopausal bone loss.

A small positive effect of protein supplementation on lumbar spine BMD in randomized placebo-controlled trials supports the positive association between protein intake and bone health found in cross-sectional surveys. However, these results were not supported by cohort study findings for hip fracture risk. Any effects found were small and had 95% CIs that were close to zero. Therefore, there is a small benefit of protein on bone health, but the benefit may not necessarily translate into reduced fracture risk in the long term.

Background: Alkali provision may explain why fruit and vegetables benefit bone health. Objective: We aimed to determine the effects of alkali-providing potassium citrate (double-blind) and fruit and vegetable intake (single-blind) on bone turnover over 2 y. Design: We conducted a randomized placebo-controlled trial in 276 postmenopausal women (aged 55-65 y). Women were randomly assigned to 4 groups: high-dose potassium citrate (55.5 mEq/d), low-dose potassium citrate (18.5 mEq/d), placebo, and 300 g additional fruit and vegetables/d (equivalent of 18.5 mEq alkali). Serum and fasted urine for bone markers were collected at baseline and at 3, 6, 12, 18, and 24 mo. An additional urine sample was collected at 4 -6 wk. Bone mineral density (BMD) was measured at baseline and 2 y. Results: Repeated-measures ANOVA showed no difference between groups for urinary free deoxypyridinoline cross-links relative to creatinine (fDPD/Cr), serum N-terminal propeptide of type 1 collagen, or beta C-terminal telopeptide, although, at 4 -6 wk, fDPD/Cr was lower in the high-dose potassium citrate group (P ҃ 0.04). Mean Ȁ SD spine BMD loss in the placebo group (1.8 Ȁ 3.9%) did not differ significantly from that in the treatment groups (2.1 Ȁ 3.2%; P ҃ 0.88). Hip BMD loss in the placebo and low-dose potassium citrate groups was 1.3 Ȁ 2.3% and 2.2 Ȁ 2.3%, respectively (P ҃ 0.14). Conclusions: Two-year potassium citrate supplementation does not reduce bone turnover or increase BMD in healthy postmenopausal women, which suggests that alkali provision does not explain any long-term benefit of fruit and vegetable intake on bone.Am J Clin Nutr 2008;88:465-74.

These longitudinal data show significant regional and ethnic differences in UVB exposure and vitamin D status for postmenopausal women at northerly latitudes. The numbers of women who are vitamin D deficient is a major concern and public health problem.

There are conflicting views in the literature as to whether vitamin D and vitamin D are equally effective in increasing and maintaining serum concentrations of 25-hydroxyvitamin D [25(OH)D], particularly at lower doses of vitamin D. We aimed to investigate whether vitamin D or vitamin D fortified in juice or food, at a relatively low dose of 15 μg/d, was effective in increasing serum total 25(OH)D and to compare their respective efficacy in South Asian and white European women over the winter months within the setting of a large randomized controlled trial. A randomized, double-blind, placebo-controlled food-fortification trial was conducted in healthy South Asian and white European women aged 20-64 y ( = 335; Surrey, United Kingdom) who consumed placebo, juice supplemented with 15 μg vitamin D, biscuit supplemented with 15 μg vitamin D, juice supplemented with 15 μg vitamin D, or biscuit supplemented with 15 μg vitamin D daily for 12 wk. Serum 25(OH)D was measured by liquid chromatography-tandem mass spectrometry at baseline and at weeks 6 and 12 of the study. Postintervention in the 2 ethnic groups combined, both the vitamin D biscuit and the vitamin D juice groups showed a significantly greater absolute incremental change (Δ) in total 25(OH)D when compared with the vitamin D biscuit group [Δ (95% CI): 15.3 nmol/L (7.4, 23.3 nmol/L) ( < 0.0003) and 16.0 nmol/L (8.0, 23.9 nmol/L) ( < 0.0001)], the vitamin D juice group [Δ (95% CI): 16.3 nmol/L (8.4, 24.2 nmol/L) ( < 0.0001) and 16.9 nmol/L (9.0, 24.8 nmol/L) ( < 0.0001)], and the placebo group [Δ (95% CI): 42.3 nmol/L (34.4, 50.2 nmol/L) ( < 0.0001) and 42.9 nmol/L (35.0, 50.8 nmol/L) ( < 0.0002)]. With the use of a daily dose of vitamin D relevant to public health recommendations (15 μg) and in vehicles relevant to food-fortification strategies, vitamin D was more effective than vitamin D in increasing serum 25(OH)D in the wintertime. Vitamin D may therefore be a preferential form to optimize vitamin D status within the general population. This trial was registered at www.controlled-trials.com as ISRCTN23421591.

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