High calcium intake linked to mortality risk in women

High intakes of dietary and supplemental calcium in women are associated with a higher risk of death from all causes, and from cardiovascular disease in particular, compared with women who have lower calcium intakes, according to a study.

Experts recommend a high intake of calcium, which plays a pivotal role in human physiology, and as such more than 60% of middle-aged and older women in the United States take supplements, according to background information in the study, which appeared Feb. 13 on the website of the British Medical Journal. However, recent trials have indicated a higher risk of ischemic heart disease and stroke with calcium supplements.

To investigate further, researchers from Uppsala University in Sweden studied 61,443 Swedish women (born between 1914 and 1948) for an average of 19 years.

Data were taken from the Swedish Cause of Death Registry, and data on diet were taken from the Swedish Mammography Cohort. Total calcium intake included supplemental calcium. The average intake was 572 milligrams a day — the equivalent of five slices of cheese, according to the researchers — in the lowest quartile and 2,137 milligrams a day in the highest. Information was obtained from the women on menopausal status, postmenopausal estrogen therapy, parity information, weight and height, smoking habits, leisure-time physical activity and educational level.

Results showed that during 19 years of follow-up, 11,944 women (17%) died; 3,862 (32%) of those women died from cardiovascular disease.

Highest rates of all-cause, cardiovascular and heart disease were observed among those with a dietary calcium intake higher than 1,400 milligrams a day. The researchers also observed higher death rates among women with an intake below 600 milligrams a day.

Women who had a dietary intake of calcium exceeding 1,400 milligrams a day and also used supplements had a higher death rate compared with those not taking supplements. Women with a dietary calcium intake of more than 1,400 milligrams a day who took calcium supplements were more than twice as likely to die compared with women with an intake of 600 to 999 milligrams a day.

The researchers explained their findings by suggesting that diets very low or very high in calcium can override normal homeostatic control, causing changes in blood levels of calcium.

The researchers concluded that high calcium is associated with “higher all-cause and cardiovascular mortality rates,” so emphasis should be placed on individuals with a low intake of calcium rather than on increasing the intake of those already consuming satisfactory amounts.

The study is available at www.bmj.com/content/346/bmj.f228.

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