With the recent news linking fish oil to prostate cancer, I understandably felt compelled to dig a little deeper, especially as I knew the mass media would not. After all, how could it be that omega-3s, the increasingly popular panacea, had a macabre side? I took the news with a pinch of salt, and I think I was right to. Here’s why…
The study showing the link (not causative) between omega-3 supplementation and prostate cancer incidence was epidemiological in nature. That is to say, researchers took people with prostate cancer, and those without, and measured their blood omega-3 levels. On the whole, they found that those with prostate cancer also had higher blood (serum) omega-3 levels. I’ve addressed the well-known flaws in epidemiology before ( just for fun, here’s a news article from the BBC reporting almost the exact opposite finding), so I’ll leave the data analysis to this article, which does a good job highlighting the particular holes in the study. Essentially, the best this type of study can do is link 2 phenomena, not say that one causes the other. Do read the article, it’s a good one. My favourite quote?
“It is quite common for people diagnosed with prostate cancer to supplement with fish oil, as it is commonly touted to be cancer-protective”.
So hang on, you tell people with cancer to take fish oil, they take it, then you’re surprised when a study finds that people with cancer have higher levels of omega-3s in their blood? This is proved by the text in the study’s abstract, where they find that “Risk of high-grade cancer was associated with high intake of polyunsaturated fats”.
Around the world the headlines sing: “Omega-3s linked to prostate cancer”. Yes, those men with cancer ate more fish oil, as many people with cancer are told to do, and consequently had more omega-3s in their blood too. And you somehow think that it’s the fish oils causing the cancer? No, no. No! After allsupplementation is known to drastically change serum levels of omega-3s in the blood. So how can we not follow the tantalisingly clear logic train and at least doubt the idea that omega-3s are carcinogenic? Well, I think we can.
To summarise what you should think of this study’s findings, I’d like to quote Kurtis Frank from examine.com “This study and no other studies in existence can currently be used to say that fish oil causes prostate cancer. If anything, this study begets a plethora of questions in regards to the relationship between prostate cancer and omega-3 but proves nothing.”
So, yes to the old adage “more research needs to be done”, but I for one interpret the weight of scientific evidence as vastly in favour of omega-3 supplementation.
For those people who have cancer and are popping fish oil pills in the hope that it will help, should know that a previous study found no correlation between fish oil supplementation and cancer. Only that study didn’t make mainstream headlines, because it’s a null finding, and they’re boring. So pop away, most studies say it won’t make things any worse. For example, here’s a May 2013 meta-analysis (more trustworthy than epidemiological studies) which shows that prostate cancer risk is lower with higher blood levels of omega-3 fats.
More relevant to most people than finding they have cancer, is actually dieing of it. Indeed, if we’re talking about mortality, then this 2010 meta analysis found that omega-3s do indeed reduce your chances of death from prostate cancer, we just can’t yet say if they’ll stop you from getting the cancer in the first place, or if they’ll help you live longer in general.
You should always seek the advice of your personal medical practitioner, but in the all too common event that your diet doesn’t provide you with enough omega-3s, I strongly urge you not to put the fish oil supplements down. They’re doing you a lot more good than harm! That said, make sure any oils you take are good quality, and stored in a dark bottle away from light and heat to prevent rancidity.
Disagree? Let me know. Leave a comment in the section below.