Flaxseed is rich in omega-3 fatty acids, which are believed to influence cell signaling and the production of cell membranes and to reduce cell proliferation.
Flaxseed also has high quantities of lignan, which binds to hormones like testosterone and estrogen, and may block their cancer-promoting effects.
In previous studies, lignan slowed the growth of prostate cancer cells that were grown in laboratories, and flaxseed reduced tumor size in mice with prostate cancer.
Various forms of flaxseed are widely used as dietary supplements for a range of purposes, but this is the first study to rigorously test its effects against prostate cancer.
"We know that many of our patients take a variety of dietary supplements. These results demonstrate that flaxseed may well protect against prostate cancer growth," said Wendy Demark-Wahnefried, a professor at Duke University Medical Center and the study's senior author. "But this is just the first study. We will need to replicate these results before we can make recommendations. "
This trial followed 161 men who had been diagnosed with prostate cancer and then scheduled surgery to have their prostates removed at least three weeks later.
The men were randomized into four arms: a control group that maintained their regular diets, men who took flaxseed (30g per day), men who restricted their dietary intakes of fat (to less than 20% of their total calories) and men who took flaxseed and also restricted their intake of dietary fat.
The flaxseed was ground and mixed with food or drink. After a median follow-up of 30 days, patients had surgery to remove their prostates, and the pathology of the tumors was studied. The primary endpoint of the study was prostate cancer cell proliferation rates, measured as a ratio of the number of cancer cells actively dividing versus those that were not dividing.
The scores were 2.38 for the control group, 1.71 for the flaxseed group, 2.93 for the low-fat group, and 1.58 for the combined flaxseed and low-fat group. These scores indicated that cancer cells in the two flaxseed groups grew at a significantly slower rate (roughly 30% to 40% slower) than the placebo or dietary fat groups.
In order to further assess flaxseed's anti-cancer effects, future studies will likely focus on men with prostate cancer who have selected watchful waiting (close monitoring of the cancer but no active treatment) and men who are at risk of prostate cancer recurrence after treatment. Investigators also plan to look at dose levels for flaxseed supplementation and the effects of taking it for longer periods of time.
From the June 4, 2007, Prepared Foods e-Flash