Ask The Supp Guru Special Edition: Does Fish Oil Cause Prostate Cancer?

Just when you thought that the case for fish oil supplementation was airtight, along comes a study connecting essential fatty acids with prostate cancer.
Q

Hey Jim, you recommend fish oil in all of your Bodybuilding.com trainers. Now I hear it might cause prostate cancer. What's up?

I've been getting bombarded the last few days on Twitter, Facebook, and Instagram by people who want to know whether or not omega-3 fats cause prostate cancer. This is due to a brand new study that suggests—or "confirms," depending on which headline you read—that they do.

Here's my take: This "study" is completely bogus. I'll get into the details in a second, but I wanted to be sure to call B.S. as quickly and clearly as possible. Sorry to be blunt, but it angers me when scientists publish weak statistical correlations that cause the media to get the public in a tizzy over the fake dangers of supplements.

Now that I have gotten that off my chest, let's take a closer look at what makes this phony news story stink to high heaven.

Wait, What Study?

The study in question, published in the Journal of the National Cancer Institute by researchers from the Fred Hutchinson Cancer Research Center, claims that men with higher blood levels of omega-3 fats had more than a 70 percent greater risk in developing high-grade prostate cancer, an almost 45 percent increase in the risk of low-grade prostate cancer, and almost a 45 percent increase in the risk for all prostate cancers. The lead author was quoted as saying, "We've shown once again that use of nutritional supplements may be harmful."

Note that he doesn't warn against eating salmon, which is also very high in omega-3 fats. No, he warns against supplements. And when he says "We've shown once again," he is referring to a 2011 study by the same researchers which concluded that men with the highest levels of the omega-3 DHA (docosahexaenoic acid) had 2.5 times the risk of developing high-grade prostate cancer compared to men with the lowest levels.

These are big conclusions for him to draw when numerous other studies have shown that omega-3 fats actually reduce the risk of cancers, including prostate cancer. For this one lab to find the complete opposite means that we should approach this study carefully and look closely at how its conclusions were reached. And sure enough, neither it nor the 2011 study stands up to basic criticism.

Something Smells Fishy

First off: On its face, the conclusions from this study don't match up with basic real-world medical stats. If omega-3 fats were causing prostate cancer, you would expect that countries with the highest fish intake would have the highest rates of prostate cancer. You would also expect that the countries with the lowest fish intake would have the lowest rates of prostate cancer. And yet the opposite is far closer to the truth.

But let's look at the flaws of this study in particular. For starters, the actual blood levels of omega-3 fats that separated the patients into groups were very small. The blood levels of omega-3 fats in the patients that were considered to have a higher risk of prostate cancer were 4.66 percent. The blood levels of omega-3 in the control group were 4.48 percent. That's a change of less than 0.2 percent! This is a miniscule difference and should be considered statistically insignificant. But if you run enough different statistical tests —and particularly if you're simply aiming to confirm your anti-supplement bias —you can eventually find one that helps you show "significance."

An equally glaring problem with the study is that the researchers did not give subjects omega-3 supplements, or even a diet high in fatty fish like salmon. All they did was take old data from previous studies, look at the level of omega-3 fats in the patients' blood, and run selective statistics to show that there was a relationship to the rate of prostate cancer. It did not determine how the levels were increased—very slightly increased—and yet the lead author jumped to the wild conclusion that omega-3 supplements are harmful.

Confused Conclusions

"The researchers did not give subjects omega-3 supplements, or even a diet hight in fatty fish like salmon. All they did was take old data from previous studies."

This is called "correlation," and it does not prove a cause-and-effect relationship. It simply shows a relationship, and in this case, it's a pretty flimsy one. In fact, several prominent research scientists have already stated that they are surprised that this study by the Fred Hutchinson Cancer Research Center team was even published in the Journal of the National Cancer Institute because it was so flawed.

Up in Smoke

Here's another interesting relationship that the researchers found in their 2011 study, but which you won't hear them talking about. At the same time they were concluding that omega-3 fats somehow increased the risk of cancer, their stats indicated that men who smoke have a significantly lower risk of prostate cancer than non-smokers.

They also "discovered" in the new study that the men who had the highest blood levels of trans fat had a 50 percent reduction in the risk of prostate cancer!

Yes, that's trans fat—the most evil fat of them all. How could anyone believe that trans fats could reduce the risk of prostate cancer? It's even sillier than believing that omega-3 fats could increase the risk of prostate cancer.

Image of fish oil gel tabs
"It angers me when scientists publish weak statistical correlations that cause the media to get the public in a tizzy over the fake dangers of supplements"

So if you really listened to the conclusions of the two studies by the Fred Hutchinson Cancer Research Center, then you should avoid fatty fish like salmon and stop taking fish oil to keep your omega-3 fat levels low. Instead, eat packaged foods and dine at fast food restaurants to increase your trans fat intake, and after your meal, be sure to light up a cancer stick.

Sound like a smart plan? No, it doesn't. So don't listen to these clearly flawed "studies" that should never have been published in the first place. Do what you know works and keep supplementing with fish oil. It can increase muscle growth, aid fat loss, enhance joint health, boost brain function and mood, and reduce inflammation, all of which can help to reduce the risk of heart disease and many cancers. And that's just the short list of the benefits.

References (and I use the term "references" lightly)
  1. Brasky, T. M., et al. Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the Select Trial. Journal of the National Cancer Institute. In press, 2013.
  2. Brasky, T. M, et al. Serum phospholipid fatty acids and prostate cancer risk: results from the prostate cancer prevention trial. Am J Epidemiol. 2011 Jun 15; 173(12):1429-39.