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 in Menopause,
the journal of The North American Menopause Society.
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.)
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, who recommend measuring blood and urine calcium levels before
women start using the supplements and again within three months.
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