Supplements of calcium and vitamin D may have too much for some older women, says new research. Calcium and vitamin D are commonly recommended for older women, but the usual supplements may send calcium excretion and blood levels too high for some women, shows a new study published online June 18, 2014 in Menopause, the journal of The North American Menopause Society (NAMS). The study, "Incidence of hypercalciuria and hypercalcemia during vitamin D and calcium supplementation in older womenand The study also will be published in print in the November 2014 paper edition of Menopause.
For the past several decades women may have been advised by their doctors to take too high a dose of calcium supplements. Or they may have been told to take too high a dose of vitamin D. Hypercalciuria and hypercalcemia commonly occur with vitamin D and calcium supplements.
Why is there an increase in kidney stones among women?
Whether hypercalciuria and hypercalcemia are caused by calcium, vitamin D, or both is unclear. These findings may have relevance to the reported increase in kidney stones in the Women's Health Initiative trial. Because calcium 1,200 mg and vitamin D 800 IU/day are widely recommended in postmenopausal women, systematic evaluation of the safety of supplements is warranted in clinical management and in future studies.
This randomized, placebo-controlled trial included 163 older (ages 57 to 90) white women whose vitamin D levels were too low. The women took calcium citrate tablets to meet their recommended intake of 1,200 mg/day, and they took various doses of vitamin D, ranging from 400 to 4,800 IU/day. (The trial was limited by ethnicity because different ethnic groups metabolize calcium and vitamin D differently.)
Are women showing excess calcium in their blood and/or urine?
About 9% of the women developed excess levels of calcium in their blood (hypercalcemia), and 31% developed excess levels in their urine (hypercalciuria), even though they were taking normal doses of the supplements and did not have hyperparathyroidism, a condition in which the body makes too much calcium-regulating hormone. These excess blood and urine calcium levels may lead to kidney stones or other problems.
The good news in this study is that the investigators found a way to predict which women were likely to develop these excess levels. The risk of developing excess urine calcium was 15 times higher for women who started out with a 24-hour urine calcium level above 132 mg than for women with lower levels. And the risk was 20 times higher for women who started with levels above 180 mg than for women with lower levels. But every one-year increase in age reduced the risk by 10%.
"Even a modest calcium supplementation of 500 mg/day may be too high for some women," note the authors, according to the June 18, 2014 news release, "Supplements of calcium and vitamin D may have too much for some older women." The authors recommend measuring blood and urine calcium levels before women start using the supplements and again within three months
"I would recommend that women determine how much calcium they typically get through their food sources before taking a hefty calcium supplement. They may not need as much as they think," says NAMS Executive Director Margery Gass, MD. The National Institute on Aging and the Office of Dietary Supplements supported the study with a grant. You also may wish to check out the website of the NIH/National Institute on Aging, Office of Dietary Supplements. Or see, "Administrative Supplements for Research on Dietary Supplements."