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Role of Vitamin D in Bone Health

In a meta-analysis published in 2009, the impact of vitamin D supplements in preventing nonvertebral and hip fractures among older individuals (65 years and older) was evaluated:¹

• The studies included 12 double-blind randomized controlled trials for nonvertebral fractures (n= 42,279) and 8 randomized controlled trials for hip fractures (n = 40,886) comparing oral vitamin D with or without calcium;
• The pooled relative risk (RR) was 0.86 (95% CI, 0.77-0.96) for the prevention of nonvertebral fractures and 0.91 (95% CI, 0.78-1.05) for the prevention of hip fractures;
• For higher doses of vitamin D (> 400 IU), the pooled RR was 0.80 (95% CI, 0.72-0.89; n = 33,265 from 9 trials) for nonvertebral fractures and 0.82 (95% CI, 0.69-0.97; n = 31,872 from 5 trials) for hip fractures;
• Nonvertebral fracture prevention with vitamin D is dose dependent, and a higher dose should reduce fractures by at least 20% for individuals aged 65 years and older.

In another meta-analysis of randomized controlled trials, the impact of oral vitamin D with or without calcium in postmenopausal women and/or older men (50 years and older) specifically reporting a risk of hip fracture was reviewed:²

• Based on 4 studies (n = 9,083), the pooled RR of hip fracture for vitamin D alone was 1.10 (95% CI, 0.89-1.36);
• For the 6 studies of vitamin D with calcium supplementation (n = 45,509), the pooled RR for hip fracture was 0.82 (95% CI, 0.71-0.94);
• Total vitamin D appears to reduce the risk of hip fractures only when calcium supplementation is added.

In an evidence-based review published in 2008, the efficacy and safety of vitamin D in relation to bone health was evaluated:³

• There was inconclusive evidence of an association between 25 hydroxyvitamin D [25(OH) vitamin D] concentration and bone mineral content in infants;
• Fair evidence was found between 25(OH) vitamin D and bone mineral content or density in older children and older adults;
• There is inconsistent evidence of an association between 25(OH) vitamin D and some clinical outcomes (fractures, performance measures) in postmenopausal women and older men;
• There is fair evidence of an association between 25(OH) vitamin D and prevention of falls;
• There is good evidence that consuming vitamin D-fortified foods has a positive effect on 25(OH) vitamin D concentrations; milk products were the vitamin D-fortified foods used in most studies (dose: 137-1,000 IU/day);
• The evidence for a benefit of vitamin D intake on falls and fractures varied.

A cross-sectional study published in 2009 examined vitamin D status and bone mass, bone turnover and muscle strength in 350 Chinese adolescent girls aged 15 years:⁴

• 57.8% of subjects were vitamin-D deficient [25(OH) vitamin D levels ≤ 50 nmol/l] and 31.2% were severely deficient (< 25 nmol/L);
• Girls with adequate vitamin D status had a higher size-adjusted bone mineral content for the whole body (p < 0.001), distal forearm (p < 0.001), and proximal forearm (p < 0.01) than those with poorer vitamin D status after adjusting for potential confounders;
• Similar results were also found for handgrip muscle strength;
• Adequate vitamin D status during adolescence is important for optimizing bone mass, which may lead to higher peak bone mass at maturity.

Keywords: health studies, bone health, vitamin D

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