Flaxseed May Curb Prostate Tumor Growth

Study: Popular Plant Product Slows Out-Of-Control Cancer Cell Division

(WebMD)  A diet rich in flaxseed may help curb the growth of prostate tumors, preliminary research suggests.

Reducing fat in the diet, however, does not appear to have any effect on prostate cancer growth, says researcher Wendy Demark-Wahnefried, Ph.D., a professor in the school of nursing and the department of surgery at Duke University Medical Center in Durham, N.C.

The researchers studied 161 men with prostate cancer scheduled to have their tumors surgically removed.

In the month prior to surgery, they were divided into four groups: one followed their regular diets, one took 30 grams of flaxseed a day, one restricted their dietary intake of fat to less than 20 percent of total calories, and one took flaxseed and restricted their dietary fat.

As measured by how fast their cancer cells were dividing, tumors grew about 30 percent to 40 percent slower in the men taking flaxseed whether or not they followed a low-fat diet.

"It's reasonable to suspect that reducing cell proliferation — the rate at which cancer cells divide — is a good thing and likely to be associated with relief of symptoms and better survival," Ted Gansler, M.D., director of medical content at the American Cancer Society in Atlanta, tells WebMD. Gansler was not involved with the research.

Demark-Wahnefried notes that flaxseed didn't cause side effects such as nausea or vomiting.

The research was presented at the annual meeting of the American Society of Clinical Oncology.

An edible seed, flaxseed has been used in breads and cereals since the Middle Ages, says Demark-Wahnefried. Sold in health food stores as well as many grocery stores, it's available in whole seed, ground meal, and seed oil forms.

In the study, the men took powdered flaxseed, which was ground and mixed into food or drink.

Demark-Wahnefried says her team decided to study flaxseed because it is rich in disease-fighting omega-3 fatty acids. Whole and powdered flaxseed are also chock full of lignans, a type of plant estrogen that is thought to curb the out-of-control cell growth that fuels cancer. Flaxseed oil does not contain lignans.

In previous studies, lignans slowed the growth of prostate cancer cells that were grown in laboratories, and flaxseed shrunk prostate tumors in mice, she says.

Based on animal and smaller studies, the researchers thought a low-fat diet, too, would have cancer-fighting effects. But in this study, the low-fat diet did not curb tumor growth.

Both Gansler and Demark-Wahnefried stressed that while promising, the results are preliminary. But unlike many other alternative products, there doesn't seem to be any downside to taking flaxseed, they say.

"At this point, we can't yet say flaxseed protects against prostate cancer," Demark-Wahnefried tells WebMD. "But it's a healthy, nutritious food, rich in fiber and omega-3 fatty acids, that is likely to offer health benefits."

Based on these and other promising findings, researchers plan further study of flaxseed in men with prostate cancer as well as in women with breast cancer, she says.