Taking calcium supplements to treat or reduce the risk of osteoporosis has been
linked to a “significantly increased risk of heart attacks,” according to
research by scientists at the University of Zurich, published Thursday in the
prestigious journal Heart.
Prof. Sabine Rohrmann, of the cancer
epidemiology and prevention division at the Swiss university’s Institute of
Social and Preventive Medicine, and her team also found that “boosting overall
dietary calcium confers no significant heart health benefit.”
Calcium
supplements are commonly recommended to the elderly and to women who have gone
through menopause, to prevent bone thinning.
The Swiss authors based
their findings on almost 24,000 participants in one of the German arms of the
European Prospective Investigation into Cancer and Nutrition (EPIC) study in
Heidelberg. All the participants were between 35 and 64 years old when they
joined the study, which lasted from 1994 to 1998.
In an editorial in the
same journal, Prof. Ian Reid and Prof. Mark Bolland of the University of
Auckland in New Zealand wrote that the safety of calcium supplements “is now
coming under increasing scrutiny.” They pointed to previous research, showing a
link between these supplements and kidney stones, as well as stomach and
abdominal symptoms, and noted that while trial evidence suggested that calcium
supplements cut levels of cardiovascular risk factors, this didn’t actually
translate into fewer heart attacks and strokes.
The editorial writers
also suggested that many women taking calcium supplements to ward off brittle
bones were already healthier than those who didn’t, and that the overall
protective effect was modest – in the order of just 10 percent.
They
noted that eating food high in calcium, including milk products, green leafy
vegetables and bony fish like sardines were greatly preferable to taking
supplements. Calcium consumed in food, the New Zealand researchers wrote, is
taken in small amounts spread throughout the day, so it is absorbed slowly. But
bottled supplements cause calcium levels in the blood to soar above the normal
range, and it is this flooding effect that might ultimately be harmful, they
suggest.
“It is now becoming clear that taking this micronutrient in one
or two daily doses is not natural, in that it does not reproduce the same
metabolic effects as calcium in food,” they said. “Given that it is neither safe
nor effective, boosting calcium intake from supplements should be
discouraged.”
After receiving a copy of the article, the Health Ministry
told The Jerusalem Post that calcium was a valuable nutrient and that health
authorities around the world recommended it to strengthen and preserve the
health of bones.
“There have been some epidemiological studies that
analyzed data on the use of calcium in certain populations and found that there
may be a statistical connection between the use of calcium supplements and the
rise in prevalence of heart attacks,” the ministry statement
said.
However, it added, “not enough scientific data has been accumulated
to bring about a change in the positions of leading health organizations in the
world, including Israel.”
The ministry, the US Food and Drug
Administration and their European counterparts have not changed their
recommendations on calcium consumption, but “they continue to follow the subject
and will work to limit calcium supplements if adequate scientific data
accumulate.”
The ministry statement concluded that it was “looking into
the possibility of limiting the maximum permitted level of vitamins and minerals
in general and other nutritional supplements to prevent
overconsumption.”
Prof. Sofia Ish-Shalom, a veteran endocrinologist and
head of Rambam Medical Center’s unit for bone and mineral metabolism, told the
Post regarding the new research that it was “best to get calcium intake from
food, but there are people – including many Jews and Arabs, apparently due to
genetics – [who] develop lactose intolerance. They have difficulty digesting
milk products.
If people do not get enough calcium from food, they can
take supplements making a total – including food – of 1,000 to 1,200 milligrams
of calcium per day if they are post-menopausal women or men over
60.
Teenagers should also get 1,200 mg., but other age groups should take
less.”
There is not enough evidence, continued Ish-Shalom, that calcium
supplements are dangerous to the heart, as not enough epidemiological evidence
exists.
“There are self-reported events, but that is different from
actual data on heart attacks,” she said. But she urged additional studies on the
alleged connection.
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