Some women may be more likely to develop too high calcium levels

According to a new US study older women who already have high calcium concentrations in their blood or urine may achieve potentially harmful levels when taking additionally calcium supplements.

In the randomized controlled trial, the blood and urine calcium concentrations of 163 white women (ages
57 to 90) whose vitamin D levels were too low were measured (1). 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 study results showed that about 9% of the women developed excess levels of calcium in their blood (hypercalcemia) and 31% developed excess levels in their urine (hypercalciuria). None of them had hyper- parathyroidism, a condition in which the body makes too much calcium-regulating hormone. The risk of developing excess urine calcium was 15 times higher for women who started out with a 24-hour urine cal- cium 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 re- duced the risk by 10%.

The researchers concluded that even a modest calcium supplementation of 500 mg/day may be too high for some women who already have higher calcium levels. Excess blood and urine calcium levels may lead to kidney stones or other problems. They recommended to measure blood and urine calcium levels before women start using the supplements and again within three months. In addition, women may determine how much calcium they typically get through their food sources.

1. Gallagher J. C. et al. Incidence of hypercalciuria and hypercalcemia during vitamin D and calcium supplementation in older women. Menopause. Published online June 2014.