Calcium and vitamin D may not cut cholesterol
NEW YORK (Reuters Health) - People looking to improve their heart health by lowering their cholesterol levels won't find help from calcium and vitamin D supplements, according to a new study.
While claims have been made for a beneficial effect of calcium and vitamin D on cholesterol levels, supporting evidence is thin, the study's lead author, Dr. Swapnil Rajpathak of the Albert Einstein College of Medicine in New York, noted in an email to Reuters Health.
High levels of cholesterol and other lipids (harmful blood fats such as triglycerides) are a well-established risk factor for
cardiovascular disease -- the number one killer of Americans. So anything that could lower levels might be a welcome addition to millions of medicine cabinets.
Calcium is a prime candidate. The mineral is thought to interfere with the body's absorption of lipids, and possibly even trigger their breakdown. However, only slight effects have been observed in just a few small and relatively short-run clinical trials. Vitamin D's link to lipids has been studied even less, Rajpathak and his colleagues explain in a report in the American Journal of Clinical Nutrition.
They sought more robust results within a large, long-term data set: the Women's Health Initiative. They identified 1,191 post-menopausal women, with about half randomly assigned a daily supplement of calcium (1000 milligrams) plus vitamin D (400 IU). The rest took identical-looking placebos.
After five years of supplementation, no differences were seen between the two groups in any of the lipids measured, including total cholesterol levels, "bad" LDL cholesterol and triglyceride levels, and "good" HDL cholesterol levels. Both arms of the trial experienced relatively small drops in each lipid measured, including levels of heart-healthy HDL cholesterol.
The study has its limitations, however, Rajpathak and his colleagues point out. The participants were all older women, making it difficult to say how men or younger women may respond to the same supplements. And the fact that the women were on calcium and vitamin D simultaneously meant that the supplements' independent effects couldn't be teased out.
And a canceling out of positive and negative effects of calcium and vitamin D on cholesterol can't be ruled out, Dr. Ian Reid, of the University of Auckland in New Zealand, who was not involved in the study, noted in an email to Reuters Health. However, "not knowing about the participants' use of lipid-lowering drugs (such as statins) worries me more," he said.
In a smaller study of postmenopausal women published in 2004, Reid and his colleagues found significant benefits for calcium supplementation alone: a potential reduction of up to 30 percent in the risk of experiencing a cardiovascular event.
Yet a recently published systematic review of several studies supports the conclusion of Rajpathak's study. The reviewers found no clear role for calcium and vitamin D in heart disease prevention. (See Reuters Health report, March 1, 2010.)
Of course, there's no need to toss out the vitamins just yet. "High intake of calcium and vitamin D may be useful for other health-related outcomes," said Rajpathak. Supporting bone health, for example, is one important use. As for lipid control, his recommendations will probably come as no surprise: eat a healthy diet and exercise.
SOURCE: American Journal of Clinical Nutrition, online February 24, 2010
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