Fishy science

File this one squarely under “what will they think of next?”

In case you haven’t already heard, a controversial study recently made some major headlines. The claim: A group of scientists have “confirmed” a link between long-chain omega-3s–in other words, fish oil–and an increased risk of prostate cancer.

I know, I know. I’ll just let that sink in for a minute. Because I realize how utterly ridiculous it sounds.

These researchers were quick to pat themselves on the back for proving (and I quote) “once again that use of nutritional supplements may be harmful.” So, let’s take a closer look at their study, shall we?

Here are the details, in a nutshell: Researchers looked at data from SELECT–the Selenium and Vitamin E Cancer Prevention Trial. As the name suggests, this trial was designed to assess whether selenium or vitamin E reduces the risk of prostate cancer.

That’s right–fish oil wasn’t even on the original study’s radar. Nevertheless, this team decided to analyze the omega-3 status of 834 men with prostate cancer. Then they compared results with 1,393 randomly selected study participants… and voilà!

They found that men with the highest levels of omega-3s had a 44 percent higher risk of low-grade prostate cancer. And a 71 percent higher risk of high-grade prostate cancer.

In fact, compared to men with lower omega-3 levels, these subjects had a 43 percent higher risk of prostate cancer in any form.

Now… where to begin here? I guess we should get the technical stuff out of the way first.

Observational studies, by their very design, can only reveal potential associations. They cannot indicate any sort of cause and effect relationship. And therefore, no firm conclusions can be made from their results… ever.

Furthermore, only a double-blind, placebo-controlled study can prove whether an observed association is legitimate–and not just an isolated fluke.

This study met neither of those criteria. Period. End of discussion.

Now, on to some less technical, more obvious problems with this study’s conclusion–holes that industry experts wasted no time pointing out.

Let’s say for a minute that fish oil does raise prostate cancer risk. Wouldn’t men be dropping like flies in countries like Sweden and Japan–places that are famous for their hearty seafood consumption? And, alternatively, wouldn’t areas with the lowest fish consumption be benefitting from significant protection?

(Hint: They’re not.)

But that’s not even the worst part. The scariest thing here is that, although the researchers were quick to blame dietary supplements, there is no evidence that anybody in this study even took fish oil. In fact, these researchers have no idea how the participants consumed their omega-3’s.

Furthermore, the difference between the two groups’ fatty acid levels was miniscule–4.66 percent in the cancer groups versus 4.48 percent in the supposedly lower-risk control.

You mean to tell me that a .2 percent difference in omega-3 levels–which could easily be achieved by simply scarfing down some tuna salad before a blood draw–can raise your risk of cancer by 71 percent???

Please. Neither of these measurements is even abnormal. And they certainly don’t erase the volumes of research that actively support the use of fish oil as a powerful weapon against prostate cancer.

In just about every other study that’s seen the light of day, high omega-3 status–whether from eating fish or taking supplements–has been linked to a lower incidence of cancer. And that includes prostate cancer.

In fact, one 2010 meta-analysis showed that eating a lot of fish lowers your risk of being diagnosed with prostate cancer–and of dying from the disease–by more than 60 percent.

If people want to miss out on this incredible benefit because of one deeply flawed study, they can be my guest. But while they’re at it, they ought to trade in their fish oil for a pack of cigarettes and a six-pack.

Why? Among this study’s other “observations”: Non-smokers had more aggressive prostate cancer. And so did men who consumed less than one drink a day.

I don’t imagine I have to say much more than that. It’s amazing to me that this paper was even accepted for publication–not to mention that it received the attention that it did. These are supposed to be “peer-reviewed” studies, in which a competent panel of professionals validates the credibility of the results.

But I guess any research that tears down nutritional supplements gets a green light now. No matter how absurd–even laughable–it is.

Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial. J Natl Cancer Inst. 2013 Jul 10. [Epub ahead of print]
Gray, Nathan. “Experts slam omega-3 link to prostate cancer as ‘scaremongering.'” 12 July 2013.