While calcium supplements noticeably improved bone health in postmenopausal women, vitamin D supplements did not reduce bone turnover, according to a small study.
Bone turnover is the bodys natural process for breaking down old bone. In young people, the body forms enough new bone to replace what is lost. Bone mass in women begins to decline after age 30, and the process speeds up after menopause, according to background information in the study, which was published Sept. 24 on the website of the Journal of Clinical Endocrinology & Metabolism.
Vitamin D and calcium interact to suppress bone turnover by decreasing parathyroid hormone levels, the studys lead author, John Aloia, MD, of Winthrop University Hospital in Mineola, N.Y., said in a news release. This can be beneficial in women who are vitamin D deficient. In women who already are receiving the recommended daily allowance of vitamin D, however, the study found there was no advantage to adding a vitamin D supplement.
The study was double-blind (meaning neither patients nor clinicians knew who was receiving which medication) and placebo-controlled, with 159 postmenopausal women divided into four groups. One group received a combination of vitamin D and calcium, one was given 1,200 milligrams of calcium daily, one took 4,000 IU of vitamin D daily and the last group received placebos.
To measure the effect supplements had on bone health, the researchers measured bone turnover markers serum PTH, cross-linked C-telopeptide and procollagen type I N-terminal propeptide over the course of six months. In all, 120 women completed the study.
The researchers found a significant decline in bone turnover markers among women who were given daily calcium supplements. The vitamin D supplements did not have a significant effect on bone turnover markers; the supplements did decrease fasting parathyroid hormone levels, but not as significantly as when combined with calcium.
These findings suggest that vitamin D supplements over the recommended dietary allowance do not protect bone health, whereas calcium supplements do have an effect, Aloia said. Women do need to be cautious about the possibility of vascular side effects from too much calcium and should consult their physicians about whether their diet is adequate or whether they should take supplements at all.
The Journal of Clinical Endocrinology & Metabolism is the official publication of The Endocrine Society. Study abstract: http://jcem.endojournals.org/content/early/2013/09/23/jc.2013-2121.abstract