Omega-3s and Prostate Cancer

Alpha-linolenic acid (ALA) is the main omega-3 fatty acid found in plant foods, and it is found in large amounts in flax seeds. A number of studies have found a link between ALA and prostate cancer, but others have not. Until recently, the best review of the literature claimed that ALA does not cause prostate cancer. I thought its logic was sound, but it came from the Flax Council of Canada.

Now a new meta-analysis says that ALA does not cause prostate cancer. The abstract states:

When examined by study type (ie, retrospective compared with prospective or dietary ALA compared with tissue concentration) or by decade of publication, only the 6 studies examining blood or tissue ALA concentrations revealed a statistically significant association. With the exception of these studies, there was significant heterogeneity and evidence of publication bias. After adjustment for publication bias, there was no association between ALA and prostate cancer (RR: 0.96; 95% CI: 0.79, 1.17).

I’ve updated the article Omega-3 Fatty Acid Recommendations for Vegetarians with this information.

5 Responses to “Omega-3s and Prostate Cancer”

  1. rick Says:

    One thing that I have never understood is if the recommended ratio of omega-6:3 is 4:1, then why at the same time recommend not using any vegetable oils high in omega-6? I realize that most people’s diets are too high in omega-6 and too low in omega-3, but would not omitting all the high omega-6 oils combined with supplementing flaxseed, in the long-term tend to cause other health problems resulting from a ratio too low in omega-6 and too high in omega-3? After all, omega-6 is an essential fatty acid and I have seen nothing to indicate that we should not be ingesting fourfold the amount of omega-6 than omega-3.

  2. Jack Norris RD Says:


    The normal ratio of omega-6 to omega-3s for vegans is about 15 to 1. It would be very difficult for a vegan to get their ratio down below 4 to 1. Suggesting that vegans eliminate cooking oils that are high in omega-6s will help bring the ratio down, but since omega-6s are very prevalent in vegan foods, it is unlikely to reach such a low level as to be unhealthy.

  3. xzebrasx Says:

    Personally, I don’t find it difficult to balance my n-3:n-6 ratio at all. I eat about 30-60g of ground flax seeds every day, which seems to do the trick for me (I achieve a ratio of 1:1-1:3 on most days). From what I’ve read about this whole topic, a ratio of about 1:1 would probably be ideal, with 1:2 and 1:3 being acceptable as well. What are your thoughts on this?

  4. Jack Norris RD Says:

    I think 1:3 is pretty good. 1:1 is probably not necessary, but so few people achieve that ratio that I’m not aware of any research on such people over the long term.

  5. Flo Says:

    Not really related to Prostate Cancer, but I just wanted to make you aware of a short review (on DHA and veg*ans) recently published:

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