In the flaxseed study, researchers at Duke University Medical Center in North Carolina and colleagues evaluated the seed's role as a food supplement in 161 men who were scheduled to undergo surgery for prostate cancer.
"The growth rate was decreased in the men who got flaxseed," said Dr. Nancy Davidson, an oncologist at Johns Hopkins University in Baltimore who is president-elect of ASCO. "I think this is fascinating."
Flaxseed is rich in omega-3 fatty acids and lignans, a fiber found on the seed coat.
"We were looking at flaxseed because of its unique nutrient profile," said Wendy Demark-Wahnefried, a researcher in Duke's School of Nursing, who led the study.
Half of the men in the study added 30 grams of flaxseed daily to their diets for about 30 days. Half of the flaxseed group also went on a low-fat diet.
After the surgery, the researchers looked at the men's tumor cells to see how quickly the cancer had multiplied.
The cancer cells in both the flaxseed groups grew about 30 to 40 percent slower than the control group.