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.
A new randomized controlled trial led by Dr Helen Macdonald of the University of Aberdeen and recently published in the Journal of Bone and Mineral Research may further clarify past research.
This trial enrolled healthy women aged 60-70 living in vitamin D deprived Northeast Scotland for one year. Two-hundred sixty-three participants were randomized to take either placebo, 400 IU or 1,000 IU of vitamin D daily. No calcium was administered, but they reported good dietary intakes.
They measured bone mineral density at baseline and after a year. Here is what they found:
- Bone loss at the hip was significantly greater in the placebo and 400 IU groups (each losing 0.6% bone mineral density after a year) compared to the 1,000 IU group, which essentially showed no change in bone density.
- Bone mineral density at the lumbar spine was not statistically different after a year treatment in the groups (-0.5%, -0.2% and +0.2% for placebo, 400 IU vitamin D and 1,000 IU, respectively).
- In the 400 IU group, vitamin D levels rose from 13.4 ng/ml to 26 ng/ml, while in the 1,000 IU group, levels rose from 13 ng/ml to 30.4 ng/ml.
The researchers concluded,
“Our findings are in agreement with the conclusions that more than 400 IU a day may be required to improve bone health and that the mean 25(OH)D concentration at which benefit occurs is greater than 30 ng/ml.”
This was some sorely needed research in the form of a randomized controlled trial showing that 400 IU/day of vitamin D is not enough for bone health and that 1,000 IU/day is likely the minimum you need for bone health. Furthermore, this study shows that a minimum level of 30 ng/ml is required for good bone health and that even a little bit lower at 26 ng/ml is not good enough to prevent bone loss.
This should offer good guidance to the public and health care professionals, looking for measures to help improve patient’s bone health.