Fish Oil Supplements Linked to Prostate Cancer | Health Blog

Date: 07/20/2013    Written by: Hiyaguha Cohen

Fish Oil Harmful to Prostate?

Men's health issues

Like OJ Simpson, who went from being a media darling to a media devil overnight, fish oil has experienced a rapid nosedive in reputation. Until recently, everyone who cared about health popped fish oil supplements daily, but then a series of studies cast doubt on whether that was a wise thing to do.  First, back in 2011, a study proposed a link between high levels of omega-3s and prostate cancer. Then a few months ago, we reported research that concluded that Omega-3 supplements, for all the hype, actually did zilch to protect health. Now, a new study "apparently" corroborates the earlier research indicating that fish oil may significantly increase the risk of one of the most prevalent men's health issues: prostate cancer.1

The 2011 prostate study found that men with the highest levels of DHA--which is the supposedly heart-healthy type of omega-3 found in fish--developed prostate cancer at two-and-a-half times the rate of those with the lowest levels. And those with the highest levels of synthetic, manmade, trans-fatty acids (those bad-for-you fats that lead to heart disease) somehow magically reduced the risk of aggressive prostate cancer by half. In other words, what's naturally good for the heart apparently isn't good for the prostate. And what's synthetically bad for the heart is good for the prostate. Or to put it yet another way, some experts contend that although omega-3 may reduce inflammation, at the same time, it possibly increases oxidative stress to DNA, which creates ripe circumstances for cancer to develop. When you think about it, that's pretty astonishing. It's only one step away from Woody Allen's Sleeper, in which doctors in the future determine that cigarettes and ice cream sundaes are powerful health enhancers.

The new study, just published in the Journal of the National Cancer Institute, reinforced the 2011 study, concluding that men with high levels of omega-3s have a 43 percent increased risk of developing prostate cancer and a 71 percent increased chance of developing the most aggressive forms of prostate cancer. The 2,227 subjects included 834 men who had prostate cancer and 1,393 men who did not. Of the 834 who had prostate cancer, 156 had a particularly aggressive type.

One of the chief conclusions experts seem to have drawn from this research is that people should stop taking omega-3 supplements right away. And some of these experts imply that that if fish oil supplements aren't good for you, other supplements also may be harmful. For instance, study co-author, Dr. Alan Kristal who is an epidemiologist at the Fred Hutchinson Public Health Center in Seattle, said, "We've shown once again that the use of nutritional supplements may be harmful. Why would you do it [take fish oil supplements]? Americans have been sold a complete bill of goods on supplements. I think the message increasingly is that these are not good for you."

Andrew Vickers, a statistician specializing in prostate cancer at Memorial Sloan-Kettering Cancer Center, chimes in, "The problem comes when you take components of a diet and put it in a pill."2

The irony here is that the study did not actually track what the subjects ate or which supplements they took. Instead, the researchers simply analyzed blood samples to measure the levels of fatty acids they contained, and then they observed that the samples with the highest levels of fatty acids seemed to belong to subjects with the highest rates of prostate cancer. No information about the overall lipid profiles of those who had prostate cancer was provided.

In fact, the blood samples were taken from men participating in another study--which was seriously flawed--that analyzed the effects of selenium and vitamin E in prostate cancer. Even more ironic is the fact that when asked, the vast majority of the subjects claimed they did not take omega-3 supplements at all. And so it's quite unclear why the subjects with prostate cancer had elevated fatty acid levels in the first place. It could be that they ate more fish; it could be they took more supplements of other kinds. The only thing that "appears" to be clear is that elevated omega-3 levels do seem to be associated with increased risk of prostate cancer…at least according to the two cited studies. Then again, it's theoretically possible that prostate cancer interferes with the body's ability to process omega-3s, and that it's the cancer causing the high levels of omega-3s rather than the other way around.

Before throwing fish overboard because two studies seemingly came to the same conclusion, though, it's important to note that this study and the 2011 study did not actually independently corroborate each other. They were conducted by the same team. It's also worth noting that  almost every conclusion they came to flies in the face of everything we know about fats and cancer. For example, the current study "found" that omega-6 fatty acids were associated with a lower risk of prostate cancer, which contradicts almost all previous research. In fact, other studies have found that excessive omega-6 fatty acids contribute to the risk of prostate cancer. Certainly no other study has corroborated  their stunning conclusion that synthetic trans fatty acids are cancer protective.

If you're confused about whether to take your omega-3s, at the least take note that it may be a different story for preventing cancer in women. In the study we reported a few months ago, women taking omega-3 supplements had an 18-percent lower incidence of death and hospital admissions compared to those taking the placebo, although men showed no benefit at all.

If you do want to keep supplementing with marine-based omega-3's, you might want to consider switching over to krill oil because, as Jon Barron noted in a previous blog, "Krill oil contains phospholipids specially integrated with omega-3 essential fatty acids. This unique structure provides important cell membrane building blocks in the right ratios for use by the body."

While the studies continue, your best bet is to stick to the Mediterranean Diet. Even though fish is a staple in that regimen, one study after another confirms that the Mediterranean Diet confers substantial health benefits and adds longevity. Since the Mediterranean Diet relies on fresh fruits, nuts and vegetables combined with very little meat, dairy, or processed food, and since incorporating fish as a staple in that context seems to not be a problem, the natural conclusion would be that heavy fish intake may only be troublesome in the context of an otherwise unbalanced diet.


Jon Barron notes that the referenced studies are seriously flawed and should not necessarily be taken at face value. He points out that there are far more studies that show that omega-3 fatty acids are actually prostate cancer protective. For example, a 2009 study out of UC San Francisco found that men with high genetic risk of prostate cancer who ate high omega-3 fish such as salmon had a 63% reduced risk of developing the disease. That study also found that men who consumed little to no fish incurred a fivefold increased risk of developing advanced prostate cancer. The researchers concluded that omega-3's might decrease inflammation in the prostate and slow the progression of cancer by having an effect on the gene.3

These results were reflected in a 2010 study that found no "reduction" in prostate cancer incidence from omega-3 fatty acids, but did find a stunning 63% decrease in prostate cancer-specific mortality.4

Likewise, a 2012 study out of Harvard found that eating oily fish regularly can significantly increase your chance of surviving prostate cancer. The findings, which were published in the American Journal of Epidemiology found patients who regularly ate the highest amounts of omega-3 fish oil were between 34 to 40 per cent less likely to die from the disease.5

Most notably, though, studies which have specifically tracked a large population of men over an extended period of time to specifically determine whether or not the consumption of high omega-3 foods was prostate cancer protective or not have confirmed it is. For example, a population-based prospective cohort study that tracked 6272 Swedish men over 30 years found that those who ate no fish had a two-fold to three-fold higher frequency of prostate cancer versus those who ate moderate or high amounts of fatty fish.6

In the end, the most startling conclusion of the study is that people should stop taking omega-3 supplements right away -- a conclusion immediately echoed by a number of commenting doctors. Understand, doctors are smart people; but just because someone's smart doesn't mean they can't say stupid things. How can you possibly come to the conclusion from this study that people should stop taking omega-3 fatty acid supplements when the study itself points out that the vast majority of the subjects claimed they did not take omega-3 supplements at all?

  • 1. Crane, Misti. "Study: Fish oil might increase prostate cancer risk." 11 July 2013. The Columbus Dispatch. 12 July 2013.
  • 2. Groden, Claire. "Hold the Salmon: Omega-3 Fatty Acids Linked to Higher Rate of Cancer." 11 July 2013. Time. 12 July 2013.
  • 3. Adam C. Reese, Vincent Fradet, John S. Wittea. "Omega 3 Fatty Acids, Genetic Variants in COX-2 and Prostate Cancer." J Nutrigenet Nutrigenomics. 2009 October; 2(3): 149--158
  • 4. Szymanski KM, Wheeler DC, Mucci LA. "Fish consumption and prostate cancer risk: a review and meta-analysis." Am J Clin Nutr 2010;92:1223-33.
  • 5. Epstein M, Kasperzyk L, Mucci LA, et al. Dietary Fatty Acid Intake and Prostate Cancer Survival in Örebro County, Sweden. American Journal of Epidemiology. Published online July 10, 2012.
  • 6. Terry P, Lichtenstein P, Feychting M, Ahlbom A, Wolk A. "Fatty fish consumption and risk of prostate cancer." Lancet. 2001 Jun 2;357(9270):1764-6.

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    Submitted by Kevin on
    July 28, 2013 - 7:31pm

    Great points made!

    Submitted by Justine Johnstone on
    August 13, 2013 - 9:50am

    I understand that all the men in the SELECT study actually had very LOW levels of omega 3s in their blood. The ones with more aggressive cancers had slightly highER levels than those with less aggressive cancers but they were still much lower than the levels considered to be healthy. So it's not correct to say - as many of the second-hand reports did - for example, that they had 'elevated' or 'high' levels of omega 3s. Is this your understanding too?

    Submitted by BaselineFoundation on
    August 13, 2013 - 12:32pm

    It’s a question of semantics. They were elevated relative to others in the study, but, as you suggest, not particularly elevated in terms of what is normally recommended. However, the bigger issue is that most of the people with “elevated” levels indicated that they did NOT take supplements—which leaves open the question of how their levels got elevated and what their ratios of omega-6 to omega-3 were. For example, if they were elevated because they consumed a large amount of conventional vegetable oils and corn fed meat, then the problem is not likely to lie in the elevated omega-3’s in the blood—they’d just be the canary in the coal mine—but in the high levels of omega-6’s that came along with it, not to mention the high levels of synthetic growth hormones in the meat.

    Again, since the majority of the participants didn’t take supplements, any interpretation of the study results would depend ENTIRELY on how the levels got elevated. If you don’t have that information (and they don’t), you have nothing.

    Submitted by Bruce on
    December 13, 2017 - 12:56pm

    I know this is really old but it is worth noting as LEF pointed out there was only one blood test for blood lipids. One! Maybe the day before some of them had some fish and that was the only time for the next six months and the ones slightly higher might overall be much lower. These fake announcements of the harm related to supplement use are irresponsible. Bad medicine.

    Submitted by Elizabeth on
    August 13, 2013 - 1:28pm

    Do you really expect me to believe that a "cancer study" done by conventional doctors is realiable........a study that was published in the Cancer Journal. It is a known fact that "studies" can be done in a way that will produce the desired outcome. AND.....most conventional doctors do not WANT any other treatment than destroy-slash-and-burn. That's how doctors & Big Pharma makes milions.
    I consider this "study" to be flawed. You also provide no information on the validity of Omega 3's from other sources. Since your previous article stating that there is no nutritional difference between organic food & non-organic foods, which is absolutely incorrect, I am sceptical about your viewpoints.

    Submitted by BaselineFoundation on
    August 13, 2013 - 3:12pm

    Hi Elizabeth, are you actually reading the articles…or just the titles?  As it says in the article you complain about, ”Jon Barron notes that the referenced studies are seriously flawed and should not necessarily be taken at face value. He points out that there are far more studies that show that omega-3 fatty acids are actually prostate cancer protective.”

    As for the issue of organic VS conventional, we have repeatedly written multiple times about the flaws in the studies that claim there is no difference between organic and conventional. Here’s a sampling.

    And most notably,

    As the ancient Romans used to say, “Res Ipsa loquitur.” The articles speak for themselves.  I think you and the staff here have the same viewpoints!

    Submitted by Elizabeth on
    August 13, 2013 - 4:24pm

    I DO APOLOGIZE about my recent comments. It is true that I did not read the entire document. After reading halfway thru the document, I submitted my comments. Afterwards, I went to the full article again and saw that I "jumped the gun" and commented before reading it fully and noticed more complete info further down in the article. At that point, I wished I had not commented because my comments were not fair.
    As for organic foods......I am only familiar with probably the first article written on that subject......have not seen the other articles you referrenced. Thanks for that info.
    Am glad to know that your staff and people like me are "on the same page" and you are keeping us current on what is important and valid.

    Submitted by BaselineFoundation on
    August 13, 2013 - 4:37pm

    Hi Elizabeth,

    No problem, I am glad that we are all on the same page.  Thanks for reading our articles!


    Submitted by PeterB on
    August 13, 2013 - 8:33pm

    This is a good survey. As you say, studies that didn't even assess participants' omega-3 intake can't possibly justify the advice to stop taking them.

    But taking fish-oil supplements is not the same as eating fish, even "high omega-3 fish such as salmon" as described in the first paragraph of the Addendum above. Some of the other components of fish (trace elements, for example) may also confer significant health benefits, whether independently of the omega-3s or in synergy with them. So studies of people's fish consumption (even oily fish consumption) can't definitively prove anything about omega-3 supplements. If the summary here is accurate, the 2009 study mentioned appears to make this error of treating fish consumption and omega-3 supplementation as if they were equivalent.

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