Question: I'm still not clear on the use of flaxseed oil and it's link to prostate cancer. When you say that evidence indicates that flaxseed oil may promote the growth of prostate tumors, do you mean flaxseed oil causes prostate cancer or that it stimulates the growth of existing prostate cancer cells? Also, does this warning apply to ground flaxseed meal?
Answer: The omega-3 fatty acids can be highly protective against heart disease. Flaxseed oil and fish oil are two concentrated sources of omega-3 fatty acids. However, some scientific evidence has caused me concern about recommending flaxseed oil because it may accelerate the progression of prostate cancer. Fish oil, in contrast, does not seem to have this harmful effect on prostate cancer.
Flaxseed oil is a rich source of alpha-linolenic acid, which has been shown to be beneficial in both heart disease and breast cancer. However, according to Charles E. Myers Jr., MD, a well-respected researcher at the University of Virginia Medical School in Charlottesville, "Clinical studies that are available suggest that alpha-linolenic acid may actually be dangerous for prostate cancer patients."
As he goes on to say, "There are now six epidemiology studies that have examined the association between dietary alpha-linolenic acid and risk of prostate cancer. Five out of six of these studies found an increase in the risk of prostate cancer associated with alpha-linolenic acid. I should also note that our laboratory, as well as others, found that alpha-linolenic acid is one of the most powerful growth stimuli for human prostate cancer cells."
Thus, I now recommend fish oil rather than flaxseed oil for men and either for women. The same applies to flaxseed meal as well as the oil, although flaxseed contains a number of phytochemicals, such as lignans, that are of potential value. One of the major lignans in flaxseed is secoisolariciresinol, a phytoestrogen and antioxidant. However, you can get these phytoestrogens in other foods, such as soy, without the potential problems of flaxseed and flaxseed oil.
Has anyone heard anything else about this? I'm trying to find more information on it. It seems like every other day they come out with studies saying everything causes cancer, but I'd like to look into this more.