Beta-carotene May Help Prevent Prostate Cancer

High dietary consumption of beta-carotene may help prevent prostate cancer, according to research presented here last month at the annual meeting of the American Society of Clinical Oncology.

For men with the lowest dietary intake of beta-carotene, supplements show some promise in preventing prostate cancer--although it is too soon to recommend widespread supplementation, said lead investigator Meir Stampfer, M.D., of Brigham and Women's Hospital and Harvard Medical School, both in Boston. Dr. Stampfer reported the latest results from the ongoing Physicians' Health Study of more than 22,000 U.S. doctors that began in 1982.

Many studies have linked foods rich in beta-carotene with a lower risk of lung and various other cancers. Supplements of the antioxidant, however, have not lived up to early expectations. In fact, last year's results from the Physicians' Health Study showed no reduced risk of any type of cancer among men taking 50 mg of beta-carotene every other day, when compared with men taking placebo.

In the latest analysis of that population, Dr. Stampfer and colleagues compared plasma levels of beta-carotene that were measured at baseline and 12 years later in a subgroup of 1,318 men in whom prostate cancer had developed during the study and 2,038 men who served as controls.

Plasma levels of beta-carotene reflect dietary consumption of the antioxidant vitamin, Dr. Stampfer said. The researchers found that prostate cancer was 36% more likely to develop in men in the lowest quartile of beta-carotene at baseline than in men in the highest baseline quartile. Also, among study participants with the lowest baseline levels, those who supplemented appeared to have a 19% reduced risk of cancer, although the decrease was not statistically significant, Dr. Stampfer said.

Still, the researchers concluded that "these subgroup analyses are compatible with the possibility that beta-carotene supplementation reduces risk of prostate cancer among those with low baseline levels."

Eating a diet rich in fruits and vegetables, though, is well-known to contribute to better health, he said. Indeed, it may be some other component of foods rich in beta-carotene that protects against cancer, and not the beta-carotene itself, he added.

Derek Raghavan, M.D., chief of the division of solid tumor oncology at the Roswell Park Cancer Institute in Buffalo, N.Y., agreed, noting that men should not supplement their diets with beta-carotene in hopes of preventing prostate cancer.

An estimated 334,500 new cases of prostate cancer will be diagnosed in the United States this year, and about 41,800 men will die from the disease, according to the American Cancer Society, headquartered in Atlanta. The disease is the second leading cause of cancer death in American men.