Men's Osteoporosis Support Group

Dietary calcium, vitamin D and BMD

J Bone Miner Res. 2009 May;24(5):935-42. Dietary calcium and serum 25-hydroxyvitamin D status in relation to BMD among U.S. adults. Bischoff-Ferrari HA and others. PMID: 19113911. This study's purpose was to study the relative importance of dietary calcium and 25-hydroxyvitamin D [25(OH)D] status in regard to hip bone mineral density (BMD) in men and women not taking calcium supplements nor having prior radius or hip fractures. Individuals were placed in sex-specific quartiles of calcium intake for 25(OH)D categories of 50, 50-74, and 75+ nM. The only individuals whose BMD appeared to benefit from higher calcium intake were women with 25(OH)D status < 50 nM. If 25(OH)D status was >50 nM and calcium intake was in the lowest quartile (>566 md/d for women and 626 mg/d for men) there was no association between higher calcium intake and BMD. There was a significant stepwise increase with higher 25(OH)D concentrations. The authors concluded, "Among men and women, 25(OH)D status seems to be the dominant predictor of BMD relative to calcium intake. Only women with 25(OH)D concentrations <50 nM seem to benefit from a higher calcium intake."

Editor's comments. These results are somewhat complex, but it appears that the bottom line is that serum vitamin D status is the important predictor of hip BMD. This suggests that knowing your serum vitamin D level is at least 50 nM or greater is significant and important, and a test result you should have done routinely. Far more so than it would be to just try to increase the intake of calcium. This is reasonable because vitamin D facilitates the absorption of calcium from the gut. So as long as your intake of calcium is at least 566 mg/d or higher (for men), and your serum vitamin D level is > 50 nM, the body appears to be able to maintain hip BMD. Note these results don't necessarily apply to individuals with untreated osteoporosis, that was not the study population in the research protocol. Logically they should for anyone whose osteoporosis is actively treated with an FDA-approved medication.

A recent Update also covers this topic, with greater detail regarding the intake of vitamin D3, a more potent form of the vitamin than vitamin D2. And remember that sunshine activates vitamin D pathways via skin exposure in humans. So this is a way to help maintain a normal serum vitamin D level. It appears that a fairly minimal skin exposure about 3 times weekly is adequate for vitamin D production, especially in fair-skinned individuals. For a discussion of the risks and benefits of getting sun skin exposure see this article from www.skincancer.org.

The bottom line is that maintaining a serum vitamin D level greater than 50 nM is beneficial to BMD. Be sure your serum vitamin D level is at least that high.

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