New Study: Will Omega-3s Boost Your Risk of Prostate Cancer?

Two yesterdays ago, I said I was going to “post this tomorrow.” On one hand, that didn’t happen. On the other hand, a one-day delay is still more timely than usual for me, so I’m counting this as a blogging victory. Whip out the kazoos!

As some of you’ve already seen, a major study came out this week with some unexpected findings about DHA, an omega-3 fat abundant in fish. The study linked high blood levels of DHA to aggressive prostate cancer (and trans fats to lower prostate cancer rates). To date, it’s the biggest fat-and-prostate-cancer study of its kind—which makes these findings all the more peculiar. Given the widespread use of fish oil supplements for quelling inflammation and boosting cardiovascular health, it’s a little spooky to think DHA is really a double-edged sword. But is this study really a slam against fish fat?

This analysis wound up as a guest post for Mark’s Daily Apple, so head over there to read the full thing:

Overall, the study itself isn’t too shabby—and the researchers readily admitted their findings surprised them. But this study is far from a harbinger of doom for seafood lovers. The take-home points, and some additional thoughts:

  • Serum fatty acids aren’t a perfect mirror of diet—and the men with higher levels of DHA weren’t necessarily eating more fish. In fact, it seems low-fat diets can actually increase DHA status in the blood the same way omega-3 supplementation can.
  • The “highest levels of serum DHA” reported here were based on percentage of fatty acids—not absolute value. Here’s a great explanation of why percentage-based measurements may be misleading in studies like these.

Another major study, the European Prospective Investigation into Cancer and Nutrition, also found a slight (but non-statistically-significant) link between prostate cancer and DHA levels in the bloodbut at the same time, found zero association between dietary fish fat and the disease. And as I wrote in the post on Mark’s Daily Apple, nearly all previous studies have shown fish consumption to have either a neutral or protective association with prostate cancer. Blood levels of DHA and dietary intake don’t seem to follow the same pattern in relation to this disease.

That said: I’m pretty weary of long-term mega-dosing of fish oil for other reasons. Thanks to all their double bonds, omega-3s are relatively unstable and prone to oxidation, just like other polyunsaturated fats. It’s quite possible that the anti-inflammatory benefits appearing short term could eventually collide with a new set of problems that take longer to appear: those stemming from oxidative stress. Moderate supplementation probably won’t cause harm, but regularly taking huge doses of fish oil should probably be done with caution. The best strategy for achieving a great omega-3/omega-6 ratio is reducing your intake of high-omega-6 foods like grains and industrial oils, rather than simply chugging back more omega-3 to compensate.

Edit: Paul at Perfect Health Diet has a more technical discussion of omega-3s, angiogensis, and cancer that does make DHA seem a little fishy. Highly worth reading!



  1. It appears the lesson here (once again) is that it’s way better to get nutrients from food than from supplements. However, I’d also want to know how the Omega 3 fatty acids were extracted from the actual fish and refined before I condemned all Omega 3 supplements. For example if they were extracted at high heat or with chemical solvents, that would be quite different from eating fish cooked at home at normal cooking temperatures, etc. Thanks again, Denise (and Paul and Mark) for keeping us informed.

    1. Good question/comment regarding the extraction/refining of fish oil. Much more intelligent commentary than my faggot ex-grandson “RichD” could have come up with.

  2. Oh, and one more thing to consider: how long have those supplements been sitting around prior to being consumed, especially given, as you point out, how unstable all the polyunsaturated fatty acids are. We would eat the actual fish within a few days at most from when they were caught, or else freeze them, whereas the supplements could have been sitting around, potentially exposed to heat, light, etc. for weeks or months before being consumed in the study. So much to think about!

  3. With no seed oils or chicken in the diet (or grains obviously), eating a diet of mainly ruminants and just a single pound of fish per week would bring your omega 6:3 ratios into perfect balance. The animals could even be grain fed. Although the fish would have to be wild caught as farmed fish have significantly less omega 3 content.

  4. Yes, Denise I saw this too. I featured this on my blog 3 days back.

    This just goes to show what Urgelt of YouTube says. ALL food is a minefield. ALL food ( animal and plant) carries risk. ALL dietary decisions are a risk.

    Science currently just does not know nearly enough about nutrition. We do not even understand human cellular metabolism that well- only bits and fragments.

    Take care,


  5. “That said: I’m pretty weary of long-term mega-dosing of fish oil for other reasons.”

    What do YOU consider mega-dosing? Or moderate dosing?

    1. On a long term basis: I’d say 1 – 2 grams a day is probably fine for most people, 5 grams is starting to push your luck, and the 30 – 60 grams I’ve seen some people take is downright risky.

      1. I would say not only downright risky but downright dirty! if you know what I mean? yay!! Denise is back!

      2. Personally I think that we can only handle a certain amount of PUFA’s.
        So 5g/day omega-3 with 20 g PUFAs would create an oxidation level very hard to handle, whereas 30 g saturated fat per day would possibly handle more. MY cent.

        1. Eh, but why do I know? I am a dick-sucking fag and a worthless piece of shit that sucks my grandfather’s dick.


  6. In my opinon the main argument against the omega 3 FA is the fact that some of the healthiest cultures around the world consume small amounts animal foods including fish and the majority of total weekly calories consist of wide variety of unrefined plant based material. In John Robbins book Healthy at 100, he presents the research on the worlds longest living and healthiest peoples such as, the Hunzan’s, Abkhasians , Okinawans and Vilcabamban’s. The average individual in these cultures lives to 110 years of age, happy, vibrant, active and coherent. They consume low fat plant based diets, with little or no meat.

 For example, the Vilcabambans enjoy organically-grown fruits and vegetables along with whole grains for plenty of fiber. They eat meat only about once a month, and their diet is low in fat, including omega-3.

    1. But what about Iceland where people eat tons of animal products and have the third best longevity in the world despite some pretty dire factors like poor sunlight and way too much calcium (I think dairy products are only good to a point, you can get too much calcium).

      And what say you to the notion that the Okinawans that life the longest eat the most animal foods?

      I feel as if some folks have spun the whole low-fat quasi-vegan longevity diet thing the wrong way and omitted important information.

    2. Getting one’s nutrition information from Robbins and the other vegan disciples, is like getting one’s news from Fox. It’s all from one, highly partison side. I wouldn’t take it as gospel without examining other sources. (Perhaps the first red flag would be the claim that they live to an average age of 110. So that means they commonly live to 120 and older? Well, the oldest living person is 114, so that’s doubtful.)

      1. How do you know for ABSOLUTE FACT how old the oldest living person is? Touche, you fuckin dumbass fag. Go lick the shit out of your grandmother’s ass then clean the garage and mow the lawn you fuckin bitch.

  7. The possibility of excess omega-3 causing illnesses reminded me of one China study correlation: Fish and Liver cancer. Denise, you explained it before caused by hepatitis infection (
    Interestingly, in material made by M. A. Crawford it was explained it caused by aspergillus flavus (, page 31 in ppt).
    It seems that everyone (me too) wants to avoid explanation that liver cancer could be caused by excess omega-3. The text in perfect health site about alcohol and omega-3 seems to support this possibility, however.
    Any reason to look if china study supports omega-3 & liver cancer connection?

    1. The China Study is of absolutely no scientific use at all.

      Well perhaps they are of minor anthropological interest.

  8. Interesting wrinkle in this study was pointed out by a commenter:

    78% of the people in the study were on finasteride, a very nasty ( but profitable drug which targets DHT metabolism to slow baldness (“Propecia”) and shrink the prostate (“Proscar”).

    As Paul Jaminet points out ( , “The finasteride arm had 78% more high-grade cancers than the placebo arm.”

    So was it a study on fish oil causing cancer? Or a study on finasteride causing cancer attempting to shift the blame onto fish oil?

    Jaminet further comments, “Unfortunately the study doesn’t report the level-response relationship between DHA and high-grade cancers separately in the finasteride and placebo arms – only in the two groups combined. I see this as a failure of the reviewers and an embarrassment to the authors.”

  9. from communicated with the researcher, Dr. Theodore Brasky, to understand the implications. He explained that the study did not reflect supplement use and that a soon-to-be-published study of by him shows no association between fish oil supplement use and prostate cancer risk. He also noted that other research has found fish consumption to be associated with a large reduction in late state or fatal prostate cancer (Szymanski, Am J Clin Nutr 2010).

    1. Yet numerous studies supposedly show that nut consumption reduces mortality from heart disease and as well as all-cause mortality. Are they all wrong? Or could there be things in nuts that override any downside to their high Omega 6 content?

  10. “Will Omega-3s Boost Your Risk of Prostate Cancer?”

    Yes but regular masturbation ameliorates it. I figure it’s a wash. 🙂 Best of both worlds.

  11. Deniese, I heard about your book on Mark Sessions site, I’m eager to see that. Love your work.

    Ray Peat has a pretty comprehensive article on fish oil toxicity. He extends this toxicity mechanism to a lot of poly/unsaturated fats as well. He gives a good history lesson on how these products are born and pushed on us through marketing.

  12. My take on this is that polyfats and transfats, being complex things to metabolise, tend to accumulate in people with poor fat metabolism.
    You need functioning mitochondria, plenty of carnitine, good micronutient levels to metabolise polytransfats. You actually convert polyfats to transfats in order to burn them like sat fats, and this is pretty much the only way (bar peroxidation) to adjust their levels. It’s a significantly more complicated process than the repetitive shuttle burning of SFAs. So accumulation is a symptom of disease, (perhaps, for example, reductive stress from mitochondrial disfunction is the driver), not always the cause.

  13. And if the transfats were natural CLA from dairy, or maybe other naturally occurring transfats, that would be protective against cancer.

  14. My take on this: Animal/fish based omega 3 (AO3) can be bad in excess, sometimes….
    I avoid omega 6 and vegetable based omega 3 and INCREASE saturated fat like tallow and butter, and the AO3. I reason that we probably have “room” for only so much unsaturated fats or PUFAs, as these fats easily become rancid both outside the fridge and inside our bodies.

    Too much TOTAL PUFAs and our antioxidation mechanisms will likely be overloaded , with surely a quite unhealthy result. We can only handle so much pufas and since we know that the AO3 are the good boys as they improve cell membrane fluidity etc., i.e. they do the opposite to “clogging up”, the AO3s are the ones to be picked.

    Simply by taking out the questionable pufas from the diet it means more room for the better pufas, the ones we want to benefit from.
    That could well mean that poor health inflicted by excess pufas can be restored quicker by combining fully SATURATED fats with MORE omega 3. I mean such amounts of omega 3 that could have deteriorating effects, IF COMBINED with other pufas.
    Ray Peat means that the PUFAS are best kept when “embedded” in saturated fats. Then “rancidity chain reactions” , if they really occur, are naturally prevented. Best of both worlds so, stability and functionality combined. Tallow for long lasting and AO3 for fluidity.
    My few cents.

  15. Has anyone followed the work of Brian Peskin on essential oils?
    His thesis is that we have the wrong end of the stick. The REAL essential oils are alpha linollenic acid (ALA) and linoleic acid (LA), which he calls the parent essential oils (PEOs). These are the important components, while DHA and EPA are derivative compounds of very limited relevance to our bodies, and harmful at the excessive doses in such as fish oil.

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