By Suzanne Rostler

NEW YORK (Reuters Health) - Including flaxseed as part of a low-fat diet may slow the growth of tumors in men with prostate cancer, preliminary study findings suggest.

In the study, prostate cancer patients who added about 3 heaping tablespoons of ground flaxseed daily to their juice, yogurt and other low-fat foods had more slowly-dividing tumor cells and a greater rate of tumor cell death than men who did not follow this diet, after about 5 weeks.

Cholesterol and testosterone levels of men on the low-fat diet, in which about 20% of total calories came from fat, were also significantly lower, but there was no change in sexual drive or function, the researchers report in the July issue of Urology.

``Data from this exploratory study suggest that the flaxseed-supplemented, fat-restricted diet appeared to influence several (markers) associated with prostatic (cancer),'' according to Dr. Wendy Demark-Wahnefried of Duke University Medical Center in Durham, North Carolina, and colleagues.

However, while the findings are ``compelling...we cannot make solid recommendations until randomized controlled trials are done,'' Demark-Wahnefried told Reuters Health. Specifically, studies will need to determine the long-term effect of the diet and investigate whether lower amounts of fat, flaxseed, or a combination of these factors is responsible for the diet's effect on tumors, she said.

Further, the investigators found no significant difference in levels of prostate specific antigen (PSA), a protein in the blood that indicates prostate cancer progression, between the two groups--although men in the early stages of the disease experienced a trend toward lower levels.

Flaxseed was commonly used in cereals and breads in the Middle Ages, but has not been a staple in the modern diet since the industrial age. It is rich in fiber and omega-3 fatty acids, which may affect levels of hormones that are involved in the progression of cancer. Flaxseed also contains a fiber-like compound, lignan, which is thought to bind to testosterone and possibly help remove it from the body. This could, in turn, help suppress the growth of prostate cancer cells.

Demark-Wahnefried explained that testosterone may be important for prostate cancer growth. Several conventional therapies block androgens such as testosterone as a way to control the spread of cancer, she said.

The study included 25 men with prostate cancer who followed a low-fat diet supplemented by flaxseed for an average of 34 days. The diet included about 30 grams of flaxseed daily, which was sprinkled on cereal or mixed into juices, yogurt or applesauce. Side effects included increased bowel movements, constipation and flatulence.

Prostate cancer (news - web sites) is the most common cancer among American men, excluding skin cancers. The American Cancer Society (news - web sites) estimates that more than 198,000 new cases of prostate cancer will be diagnosed in the US in 2001. While the cancer will be diagnosed in about 1 in 6 men, about 1 in 30 will die of the disease.

SOURCE: Urology 2001;58.