The flaxseed study was aimed at fighting prostate cancer, not treating a side effect. The edible seed has been used for hundreds of years in cereals and breads and is high in beneficial omega-3 fatty acids and in lignan, a substance that can affect hormone levels and perhaps squelch their cancer-promoting effects.

Four groups of about 40 men who were scheduled to have their prostates removed three weeks later were assigned to get either 30 grams of powdered flaxseed, a low-fat diet, both or neither until their surgery.

After the men's prostates were removed, researchers found that tumors had been growing 30 to 40 percent slower in the two groups taking flaxseed, based on how quickly cells were multiplying. Low-fat diets had no effect on this, said Wendy Demark-Wahnefried of Duke University Medical Center, who led the study.

"Our findings are compelling but they're preliminary," she cautioned.

But several doctors said flaxseed is nutritious and seems to have little downside other than a sawdust-like consistency, since it must be used ground or powdered because it has an inedible hull or coating.

Scientists plan to study flaxseed on men with prostate cancer that comes back after initial treatment, and Canadian scientists also are testing it for breast cancer, she said.

The shark cartilage study was done because Congress ordered it. Some very small early studies suggested high doses of it might extend survival of people with advanced cases of non-small cell lung cancer.

Dr. Charles Lu of the University of Texas M.D. Anderson Cancer Center in Houston tested Neovastat, a shark cartilage liquid extract that the Canadian company Aeterna-Zentaris was trying to develop as a regular pharmaceutical product.

All 379 people in the study, which was done throughout Canada and the United States, were given standard chemotherapy and radiation. Half also were given shark cartilage twice a day.

After about four years there was no difference in survival, which averaged 15 months for both groups.

On the Net:

Cancer meeting: www.asco.org

Cancer society: www.cancer.org

National Center for Complementary and Alternative Medicine: www.nccam.nih.gov

Ginseng Board of Wisconsin: www.ginsengboard.com