Feb. 15 (Bloomberg) -- Calcium and vitamin D supplements failed to prevent fractures in older women in a large U.S.- funded study that casts doubt on a bedrock therapy for women whose bones weaken after menopause.

The results from the $725 million Women's Health Initiative, published in the New England Journal of Medicine, show supplements boost bone density and kidney stone risk without substantially cutting fracture rates. A related study found the supplements didn't prevent colorectal cancer, another unexpected finding, researchers said.

Americans spend almost $1 billion a year on calcium supplements to ensure their bones stay strong. Doctors say that getting too little calcium may play a role in osteoporosis, the brittle-bone disease that affects 10 million people yearly in the U.S. and leads to 1.5 million fractures.

``With the widespread marketing of calcium and vitamin D, many women believe that they are completely protected against the development of osteoporosis if they are taking these supplements,'' wrote Joel Finkelstein, a Massachusetts General Hospital endocrinologist in Boston, in an editorial. ``This study should help correct this important misconception.''

Calcium, the most abundant mineral in the human body, can also be supplied by drinking milk and eating cheese and yogurt. Vitamin D, produced by the skin in response to sunlight, helps the body use calcium more efficiently.

The two studies are based on the same work involving 36,282 women aged 50 through 79. Roughly half the women took 1000 milligrams of calcium and 400 IU of vitamin D daily, the researchers said. The remainder took placebo pills.

Seven Years

After seven years, 14 of 10,000 women on supplements had hip fractures annually, compared with 16 per 10,000 on a placebo. Another 13 per 10,000 women on vitamins were diagnosed with colorectal cancer, compared with 12 of 10,000 on placebo.

The unexpected findings prompted questions about the design of a study in which the women were healthy and getting plenty of calcium in their diets, the dose of vitamins was lower than recommendations and the seven-year duration may have been shorter than necessary to determine an absolute benefit.

``The time course for this trial really is probably not sufficient to give us a clear answer for calcium or vitamin D,'' said Meir Stampfer, chairman of epidemiology and professor of nutrition at the Harvard School of Public Health. ``Basically, you have to make a judgment on incomplete data.''

Stampfer, who wasn't involved in the research, said in a phone interview he personally takes vitamin D for cancer prevention and would recommend both supplements for women.

`Just Take a Pill'

``This is very easy, just take a pill, as opposed to changing diet or physical activity,'' he said. ``I don't think it should be a U.S. policy that everyone should take supplements until we have evidence that it helps, but while we're waiting, I chose to go ahead and hedge my bets because it's safe and I believe it might be helpful.''

The study is continuing for another five years to see if differences develop, researchers said.

The bone study found a benefit for some women, those past age 60 who weren't already taking calcium. When they took their supplements faithfully, there was a small reduction in fractures, said lead researcher Rebecca D. Jackson, a professor of at Ohio State University in Columbus.

Older women ``should consider taking calcium and vitamin D supplements as the basis of what they do for bone health,'' Jackson said in a telephone interview.

Second Study

The second study failed to confirm the benefit seen in early research on calcium and vitamin D's ability to cut the risk of colorectal cancer, the No. 2 cause of death from cancer in the U.S. Lung cancer is the leading killer.

``Our results raise questions regarding the widely held concept that calcium and vitamin D supplementation will prevent colorectal cancer,'' said the researchers, led by Jean Wactawski-Wende, professor of preventive medicine at the University a Buffalo in New York. ``These results do not provide support for general use of calcium plus vitamin D supplementation to prevent colorectal cancer.''

Government surveys show more than half of adult men in the U.S. and 78 percent of women fail to get the standard recommended amount of calcium. While it's best to get calcium from the foods we eat, Americans who don't get enough should consider supplements, said Elizabeth G. Nabel, director of the National Heart, Lung, and Blood Institute.

``Hip fractures are the most debilitating fracture and certainly that fracture which has the greatest impact on loss of independence and potentially loss of life,'' Jackson said.

Four in Ten

Four in 10 women aged 50 and older will experience a broken bone at the hip, spine or wrist during their lifetimes, said Janet McGowan, from the National Institute of Arthritis and Musculoskeletal and Skin Diseases.

``Food provides you with so much more in terms of other nutrients that may help balance and even mitigate what might be the adverse event, kidney stones, that we saw in this study,'' McGowen said. ``So it seems like a good policy to try to achieve the guideline amounts with food and if you can't, a small amount of a supplement, as really supplementing, to bring you up to the level of 1200 mg a day.''

To contact the reporter on this story: Michelle Fay Cortez in Minneapolis at mcortez@bloomberg.net

Last Updated: February 15, 2006 17:00 EST