Prostate cancer is the leading cancer among American men. Now a pilot study suggests that flaxseed, in conjunction with a low-fat diet, may have a protective effect against the disease. The report, from researchers at Duke University Medical Center, appears in the July issue of the journal Urology.

Twenty-five men with prostate cancer who were awaiting surgery ate a low-fat diet and consumed three tablespoons (about 30 grams) of finely-ground flaxseed a day. The researchers took blood tests at the outset of the study to measure the subjects' prostate-specific antigen (PSA), testosterone and cholesterol levels. The men then followed the diet for an average of 34 days before undergoing surgery, at which point they were tested again and compared to an historic cancer case roughly matched in age, race and progression of the disease.

The scientists found that both the testosterone and cholesterol levels of the men decreased over the course of the study. And, although PSA levels in the general sample population did not decrease, when the men were classified according to the severity of their cancers, those with early-stage prostate cancer did show a decrease in PSA levels as well.

"It's not surprising that a diet therapy that was only taken for an average of 34 days had little effect on men with aggressive disease," lead author Wendy Demark-Wahnefried says. "But what we did see was that for the men on the diet, their tumor cells did not divide as quickly and there was a greater rate of apoptosis (tumor cell death) in this group."

The authors caution that the study's data "must be interpreted with caution" because it is impossible to determine if the benefits seen in this small, short trial were due to the flaxseed, the low-fat diet or a combination of the two. Randomized controlled trials are needed, they say, to reduce bias and error, as well as investigate the flaxseed and diet elements independently.