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Surprise surprise. Most anyone interested in nutrition has heard that omega-3 fats reduce the rate of cancer. Many early adopters of this information applied this to the plant-based sources of omega-3 (ALA). One of the highest sources of ALA is in flax seeds so flax seed oil in the '90s had gained widespread attention in the health community as an important source of nutrition. Ten years ago I was certainly caught up in that hype and had many of my patients take it. I rapidly found though that most people did not tolerate it well and I rapidly advised my patients to stop taking it.
Now it is very clear that only a very small percentage of the omega-3 in flax is converted to EPA and DHA. It is actually EPA and DHA that do the heavy lifting for cancer prevention, not ALA.
I am somewhat surprised at the results of this study. I never suspected that high amounts of ALA would actually increase prostate cancer but this appears to be the case. At worst I would have guessed that it had little influence on prostate cancer. I don't think this is support that flax seed oil should not be consumed at all as we certainly need sources of ALA in our diet. I think the problem results when, like many vegetarians, one seeks to use ALA as a replacement for fish oil. This study is a very powerful testimony that this is just not a wise strategy to follow.
It is also very important to realize that cod liver oil is the ideal source of EPA and DHA for prostate cancer prevention as it is loaded with vitamin D and vitamin D may be even more important than EPA and DHA in prevention of prostate cancer. Why make such a big deal out of this? Well prostate cancer is the number one cancer in men. So if you are a man or know or love someone who is, I strongly suggest you consider adding a source of high-quality cod liver oil in your diet. If you were ever curious as to exactly how EPA and DHA prevent prostate cancer the researchers offer the following possibilities:
- modification of membrane phospholipid composition
- alteration of cell signaling and receptor activity
- lipid peroxidation
- cyclooxygenase inhibition
- cytokine production
- interference with androgen activity
American Journal of Clinical Nutrition July 2004 80(1);204-216