Older women taking calcium supplements
to maintain bone strength may be putting themselves
at increased risk of heart attack, researchers in New
Zealand report.
The researchers cautioned that they
do not consider their findings the definitive word
on the subject, but said the higher heart attack risk
they saw merits further
study.
“This effect could outweigh any benefits on bone from calcium supplements,” researchers
led by Ian Reid of the University of Auckland wrote in the British Medical
Journal (BMJ).
Many women take calcium supplements to try to prevent osteoporosis, a condition
in which bones become weak and brittle, leading to fractures.
The study involved
1,471 healthy post-menopausal women, average age 74, who already had participated
in a study on the effects of calcium on bone density
and fracture
rates. Of them, 732 were given a daily calcium supplement and 739 were given
a placebo. They were followed for five years.
Heart attacks were more common
in the women taking the calcium supplements, with 31
women who took supplements experiencing a heart attack
compared to
21 women
who got a placebo, the researchers said.
The researchers noted that previous
research had suggested that taking calcium supplements
might protect against vascular disease by lowering
levels of
bad cholesterol in the blood. They said that because calcium supplements
raise
blood calcium levels, this possibly accelerates the formation of deposits
in the arteries
that could lead to heart attack.
The new results “are not conclusive
but suggest that high calcium intakes might have an adverse effect on vascular
health,” the researchers wrote. “In
the meantime this potentially detrimental effect should be balanced against
the likely benefits of calcium on bone, particularly in elderly women,” they
wrote.
Source: Vascular
Events in Healthy Older Women Receiving Calcium Supplementation:
Randomised
controlled trial BMJ, January 15, 2008).
