Recently, data from a study of 10,000 Americans supported once again our contention that vitamin D is more important to bone health than is calcium. Even more, this new research suggests that high calcium intakes only aid bone density in those with very low vitamin D status.
Data from the U.S. National Health and Nutrition Examination Survey (NHANES III) published in early 2009, found that calcium intakes of 566 mg per day among women and 626 mg per day among men are likely adequate for those not burdened with low vitamin D levels. Among women only in those very low vitamin D levels (20 ng/mL or less) was there a positive association between calcium intake and bone density. Among women with a greater than 20 ng/mL vitamin D level, a calcium intake of over 566 mg per day was not associated with better bone density than that of women on just 566 mg calcium. Among men, calcium intake was not associated with bone density at any level of vitamin D studied.
So, if we need less calcium than previously thought, a good next question is, “Does higher calcium intake really prevent fractures, anyway?” The authors of this study answer that very question — and their answer is no. Summarizing the findings of more than a dozen large studies, they note the clear lack of association between calcium intake and osteoporosis fracture risk. In fact, a recent, large meta-analysis found higher calcium intakes to actually increase hip fracture risk. For further discussion of these recent findings on calcium intake and fracture see my blog post, “Higher calcium intake does not prevent fractures.”
Bischoff-Ferrari, HA, et al. 2009. Dietary calcium and serum 25-hydroxyvitamin D status in relation to BMD among U.S. adults. J of Bone Miner Res, 24(5):935-942.