While people think “bone health” when they hear “vitamin D,” the relationship between the two is not as clear as you might think. It’s been known for years that vitamin D prevents osteomalacia, but its effects on osteoporosis, fractures, and bone density are a bit murkier.
The current train of thought is that vitamin D can help prevent osteoporosis and fractures and improve bone density, but only when vitamin D is taken in adequate doses. Past trials have used doses as low as 400 IU and as high as 2000 IU, and its effects on bone health in these trials have ranged from no effect to modest beneficial effect. A meta-analysis by Professor Bischoff-Ferrari showed that vitamin D supplementation of greater than 800 IU/day has beneficial effects on fractures, while lower doses do not, perhaps explaining past mixed results.