Calcium-heart attack link found
Calcium supplements, taken by millions of elderly people and post-menopausal women to prevent bone thinning, may double the risk of having a heart attack, a study has found.
Researchers warned that the pills should be "taken with caution", and experts commenting on the findings in the online edition of the journal Heart questioned their safety.
Previous studies linked higher calcium intake with a reduction of heart disease risk factors such as high blood pressure, obesity and Type 2 diabetes. But the new research from Germany points to a vital difference between dietary calcium from sources such as milk, cheese, greens and kale, and supplements.
Taken in supplement form, the mineral floods the bloodstream, causing changes that may produce hard deposits on the walls of arteries, scientists believe.
Researchers analysed data on 23,980 German men and women aged 35 to 64 taking part in a study called the European Prospective Investigation into Cancer and Nutrition. Over a period of 11 years, a total of 354 heart attacks, 260 strokes and 267 associated deaths were recorded.
Participants whose diets included a moderate intake of calcium - around 820 milligrams (mg) daily - from all sources had a 31% lower heart attack risk than those with the lowest intake. But no significant benefit was seen when calcium intakes rose to more than 1,100 mg per day.
The picture changed for the worse when the scientists focused on supplements. People taking supplements that included calcium were 86% more likely to suffer a heart attack than those taking no supplements.
Dr Carrie Ruxton, from the Health Supplements Information Service, which is funded by an association representing supplement manufacturers, criticised the research. She pointed out that calcium intakes were only measured once, and no attempt was made to observe the effect of modifying them or make comparisons with a "dummy" placebo supplement.
She said: "Vitamin and mineral supplements were never intended to treat chronic health conditions. Instead, their role is to help people meet recommended nutrient intakes. According to the UK National Diet and Nutrition Survey, women consume only 740mg of calcium per day from food sources on average."
A Department of Health spokeswoman said it will consider the study carefully once the complete article has been published. She said: "The majority of people do not need to take a calcium supplement. A healthy balanced diet will provide all the nutrients, including calcium, that they need. Good sources of calcium include milk and dairy foods, fortified dairy food alternatives, eg soya drink, and green leafy vegetables."