High intakes of calcium in women are associated with higher death rates from all causes and from cardiovascular disease, but not from stroke. This is the conclusion of a prospective longitudinal cohort study by researchers in Sweden.
The researchers studied 61,433 women born between 1914 and 1948. The women were part of a Swedish mammography cohort and were followed for a median of 19 years.
The highest rates of death from all causes, cardiovascular disease, and ischemic heart disease (but not stroke) were observed among those women with a dietary calcium intake higher than 1400 mg/day. Women whose dietary intake of calcium exceeded 1400 mg/day who also used calcium supplements had a higher mortality rate than women who had a similarly high intake of calcium but did not take supplements.
The researchers note that diets that are low or very high in calcium can “override normal homeostatic control, causing changes in blood levels of calcium or calciotropic hormones.” They also point out that “calcium-enriched meals can reduce calcitriol, the active vitamin D metabolite, by inhibition of 1α hydroxylase and also increase serum levels of fibroblast growth factor 23. Higher levels of circulating fibroblast growth factor 23 are associated with an increased risk of cardiovascular events and all cause mortality.”
The researchers caution “for the prevention of fractures in elderly people and simultaneous avoidance of possible serious adverse events … emphasis should be placed on [maintaining sufficient calcium intake] rather than increasing the intake of those already consuming satisfactory amounts.”