vitamin D, calcium and fractures

The role of vitamin D, either alone or in combination with calcium, in reducing fractures in reducing fractures is a contentious issue.. Some studies have shown a reduction in the risk of fractures, others have shown no effect, and one recent study found an increased risk of hip fracture.
In the linked study, the DIPART (vitamin D Individual Patient Analysis of Randomized Trials) group reports an individual patient data analysis aimed at identifying factors that influence the efficacy of vitamin D or vitamin D plus calcium in reducing fractures. The study also assessed the influence of dosing regimens and the co-administration of calcium.
Trials using vita¬min D (low or high dose) combined with calcium reduced the overall risk of fracture (hazard ratio 0.92, 9S% confi¬dence interval 0.86 to 0.99), but that only low dose (10 ug) vitamin D combined with calcium reduced the risk of hip fracture (0.74, 0.60 to 0.91). They found no association between fracture history and treatment response, or any association with age, sex, or hormone replacement therapy. Vitamin D alone, irrespective of dose, had no effect on fracture risk.
Whether vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) are equi-potent is not yet established. Recent consensus has suggested that serum concentrations of 70•80 nmol/l are needed for normal health.
Vitamin D has direct effects on muscle strength modulated by specific vitamin D receptors in human muscle tissue. Supplementation may increase muscle strength, thereby reducing the risk of falls and subsequent non-verte¬bral fractures. In combination with calcium, vitamin D reduced first falls by 27% at 12 months and 39% at 20 months, with a decrease in body sway.
So vitamin D ( 10-20 µg / day ) and calcium ( 1000 mg calcium / day ) supplementation appears to have merit.

Sahota 2009 Reducing the risk of fractures with calcium and vitamin D BMJ vol 340 p 109-110

The DIPART group 2009 Patient level pooled analyses of 68500 patients from seven major vitamin D fracture trials in US and Europe. BMJ vol 340, pp 139-140

Martin Eastwood
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