© 2005-2012 American Society of Clinical Oncology (ASCO). All rights reserved worldwide.
June 2, 2007
Adding flaxseed to the diet of men with prostate cancer may slow the growth of the cancer, but lowering dietary fat has no effect on prostate cancer growth, a new study suggests.
Flaxseed is a dietary supplement that has large amounts of omega-3 fatty acids and lignan, a chemical found in plants. Omega-3 fatty acids are believed to be important for slowing cell growth and play a role in other cellular functions. Lignan binds to hormones, such as testosterone, and blocks their cancer-promoting effects. In this study, researchers also looked at dietary fat restriction because previous studies suggested that low-fat diets may slow prostate cancer growth. The researchers also speculated that reducing the amount of fat in the men's diets might boost the activity of the omega-3 fatty acids within the flaxseed.
This phase II clinical trial followed 161 men diagnosed with prostate cancer who were scheduled to have their prostates removed at least three weeks later. The men were assigned to one of four groups: a control group of men who continued their regular diets, men who took 30 grams of flaxseed a day (ground and mixed with food or drink), men who restricted their dietary fat to less than 20% of their total calories, and men who took flaxseed and limited the amount of dietary fat. The men followed these diets until their surgery date, an average of 30 days.
After surgery, the tissues from the removed prostates were studied, and the researchers measured how fast the prostate cancer cells were growing. Results showed that the cancer cells grew significantly slower (about 30% to 40%) in the prostates of men who added flaxseed to their diet compared with men who did not take flaxseed and the men who followed a low-fat diet.
In the future, researchers are considering testing the effects of flaxseed for men with early prostate cancer who are under active surveillance (watchful waiting) and men at risk for the prostate cancer returning.
What This Means for Patients
"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, PhD, Professor in the School of Nursing and the Department of Surgery at Duke University Medical Center in Durham, North Carolina, and the study's senior author. "However, this is just the first study. We will need to repeat these results before we can make dietary recommendations."