Prostate cancer patients may be better off taking flaxseed supplements, suggests a study led by Duke University Medical Center researchers who discovered that a diet supplemented with grounded flaxseed significantly slowed growth of cancerous cells in prostate tumors.

Flaxseed is often touted for its rich amount of omega-3 fatty acids, which are believed to provide a range of health benefits including possible inhibition of cancer cell growth.

The researchers early found that flaxseed, which looks just like sesame seed, when used with a low fat diet, is effective in halting prostate cancer growth. They believe that this health food may be able to interrupt a series of events that otherwise lead cells to divide irregularly and become cancerous.

"Our previous studies in animals and in humans had shown a correlation between flaxseed supplementation and slowed tumor growth, but the participants in those studies had taken flaxseed in conjunction with a low-fat diet," said Wendy Demark-Wahnefried, Ph.D., an author of the study, from Duke's School of Nursing.   "For this study, we demonstrated that it is flaxseed that primarily offers the protective benefit."

In the current study, Dr. Demark-Wahnefried and team started assigning four types of diets to four groups of patients with prostate cancer at least 3 weeks prior to their receiving surgery to remove their prostate cancer.

One group of men were assigned 30 grams of flaxseed daily, one flaxseed plus a diet with less than 20 percent fat, one a low fat diet and one a control diet without any intervention.   Each group consisted of about 40 prostate cancer patients.

Men who were assigned flaxseed mixed the supplement in drinks or sprinkle it on food such as yogurt, depending upon how they like to use it.   Flaxseed is grounded as unprocessed flaxseed can not be digested because of an indigestible seed coat.

Prostate cancer once removed was subject to microscopic examination to determine how quickly the cancer cells had multiplied.   Then the growth rates were compared to that before supplementation when patients started the dietary regimen.

Both men in the flaxseed supplement group and in the group on the flaxseed plus low fat diet experienced a significant reduction in the rate of prostate cancer growth compared to the men on the control diet and the low fat alone diet.

Specifically, the median proliferation rate was 1.5 in patients on flaxseed plus low-fat diet, 1.66 in the flaxseed-alone group, 2.56 in men who were on the low fat-diet and 3.23 in the control men.

"The results showed that the men who took just flaxseed as well as those who took flaxseed combined with a low-fat diet did the best, indicating that it is the flaxseed which is making the difference," Demark-Wahnefried said.

Demark-Wahnefried and colleagues suggest that omega 3 fatty acids may play a role in halting cancer proliferation.   Because of omega-3 fatty acids, flaxseed can alter the way cancer cells lump together or cling to other body cells, both factors determining how fast cancer cells proliferate.

The role of omega 3 fatty acids in flaxseed known as alpha-linolenic acid has not been well understood.   A study of 47,000 men found higher quantities of ALA from non-animal as well as meat and dairy sources in men who were suffering from advanced prostate cancer. The results were published in American Journal of Clinical Nutrition July 2004 80(1); 204-216.

Other compounds in flaxseed may also play a role, according to Demark-Wahnefried and colleagues.   They suspect that lignans found in flaxseed may have antiangiogenic properties, meaning they are able to cut off a tumor's blood supply, stunting its growth.  In addition, lignans may also affect androgen metabolism and have antimitotic, antioxidant, and estrogenic effects, which altogether have an effect on prostate cancer.

The preventative effect of flaxseed on prostate cancer development was studied early in 2002 by the same group of researchers.   They found that flaxseed used at a 5 percent of total calories in mice can prevent some mice from developing prostate cancer.   In the mice with prostate cancer, the size of tumor was significantly smaller in the mice that ate flaxseed-supplemented diet.   Furthermore, tumors in those on a flaxseed diet were less aggressive and fewer tumors spread to lungs and other organs.

"We are excited that this study showed that flaxseed is safe and associated with a protective effect on prostate cancer," Demark-Wahnefried said.

The researchers are poised to test the effectiveness of flaxseed supplementation in patients with recurrent prostate cancer, and eventually to study its role as a preventative.

The results of the current study funded by the National Institutes of Health were presented on Saturday, June 2, during a news briefing at the annual meeting of the American Society of Clinical Oncology, in Chicago.

Prostate cancer is just as common as another reproductive cancer.   One in every six American men is expected to develop prostate cancer. More than 218,000 men are to be diagnosed with the disease in 2007 and 27,000 will die from the disease, according to the American Cancer Society.