Two fundamental "truths" of health advice are 1) calcium builds strong bones and 2) saturated fat clogs coronary arteries. Both may turn out to be wrong.

The calcium story has been building for decades. Because everyone knows that bones contain calcium, it seemed logical to assume that taking more of this mineral would make bones stronger. As a result, millions of women have been told to swallow a couple of calcium pills daily to ward off osteoporosis.

Had people bothered to look carefully at the research, however, their enthusiasm might have dimmed. More than 140 studies have been published on the role of dairy, milk and calcium supplements in reducing fractures. Two-thirds of them show no benefit from calcium consumption.

Adding vitamin D to calcium has produced mixed results. Only about half these trials have shown some benefit.

Epidemiological studies from around the world also suggest that calcium might not be the key to preventing osteoporosis. People in places where milk and dairy products are very popular (Scandinavia, U.S., U.K., New Zealand and Germany) have markedly higher rates of hip fractures than places like Africa, China, New Guinea, Iran and Brazil, where milk and dairy consumption is low.

A recent review in the British journal BMJ (Aug. 7, 2010) has challenged the general assumption that calcium supplements are safe. The investigators analyzed 11 well-controlled studies involving more than 12,000 subjects. They found that people assigned to take calcium were nearly 30 percent more likely to have a heart attack than those taking placebo pills. Although the absolute increase is not great, so many people take calcium tablets that the overall number of excess heart attacks could be quite high.

Contradicting conventional wisdom creates confusion and conflict. This appears especially evident when it comes to dietary advice.

Another recent study casts doubt on the superiority of the "prudent diet" for preventing heart disease (Annals of Internal Medicine, Aug 3, 2010). For decades, Americans have been urged to eat less fat, especially saturated fat, in an effort to control weight and reduce the risk of heart disease. But a new study compared the effects of an Atkins-style low-carb diet with a low-calorie, low-fat diet in 300 volunteers for two years.

Both groups lost about the same amount of weight, about 15 pounds at the end of the study. The real surprise was that the low-carb (higher fat) diet produced greater improvement in key cardiovascular risk factors, particularly good HDL cholesterol and blood pressure.

To better understand these complicated health issues, readers of this column may wish to consult our Guides to Osteoporosis and Heart Health for more detail about other strategies. Anyone who would like copies, please send $5 in check or money order with a long (No. 10), stamped (61 cents), self-addressed envelope to: Graedons' People's Pharmacy, No. CU-82, P.O. Box 52027, Durham, NC 27717-2027. Each can be downloaded for $2 from our website: www.PeoplesPharmacy.com.