Last week I received several messages from clients asking ‘What do you think of this?”. All of them contained the same link to a story that was being widely reported in the media;
“Taking omega 3 fish oil supplements may increase the risk of aggressive prostate cancer by 70%,” Daily Mail
You can read more details about the study and some of the conclusions they drew, here.
I advise many of my clients to supplement with a quality omega 3 fish oil for numerous health benefits. It’s one of the few supplements that I believe in and take myself. This study went against much of the research I’ve read, so it obviously caught my interest..
A book by Ben Goldacre called ‘Bad Science’ instantly sprung to mind. The book looks at how the media interprets and reports scientific research to the public. It looks at how statistics can be manipulated and how the media has a long history of misrepresenting scientific research.
It did make me wonder. Was this another case of the media promoting a scare story to be controversial? Did the research actually back up the claims? Well with all these things, the devil is ALWAYS in the details…
The study itself
This was an epidemiological study. Researchers picked an outcome (prostate cancer) and investigated what may have led to that outcome (in this case omega-3 levels of patients who had whats called high grade prostate cancer).
This type of study can not determine cause and effect. This means that it is impossible (and irresponsible) to conclude that fish or fish oil supplementation causes an increase in risk for prostate cancer, contrary to the media reports last week. The authors of the research themselves admit they don’t know why omega 3’s – which normally display anti-cancer effects accords the board – would promote prostate cancer.
At best the study could only show a correlation between omega 3’s and prostate cancer. It might also manage to show a correlation between prostate cancer and watching Baywatch. But to conclude that watching Baywatch is any way the cause of prostate cancer would be irresponsible to say the least.
Furthermore, this study did not measure mortality. When looking at mortality, fish oil seems to be associated with reduced mortality (1). Fish Oil did not help prevent prostate cancer, but it reduced your chances of dying from it.
Lets delve into the details a bit further..
The method used for analysis of omega 3 levels was a single blood test, taken when the subjects entered the study. The problem is that single blood tests are not an accurate way of measuring omega 3 levels. A single test is simply an acute measure of omega 3 intake, which would be effected by eating a single fish meal or taking a fish oil supplement. It is not an accurate assessment of long term intake, which would be by far the most important measurement.
This acute aspect is important, since fish oil supplementation can drastically change serum levels of omega 3’s in the blood. It is quite common for people diagnosed with prostate cancer to supplement with fish oil, as it is commonly touted to be cancer-protective (which would mean that prostate cancer precedes fish oil supplementation).
The most this study is able to show is that prostate cancer is associated with higher omega-3 ratios in your blood. In no way does it show or prove any cause for prostate cancer, or suggest a reason why the levels of omega 3’s are high in the first place.
Omega 3 has been shown to reduce mortality, and is often recommended as a supplement to cancer sufferers. This could well be the reason for the high omega 3 ratios in those subjects.
Some of the methodology of the study was flawed, in particular the method used to measure omega 3 levels in the blood of the subjects.
There is a pletherare of research showing numerous health benefits of taking an omega 3 fish oil supplement, some of which we will explore in this blog in the coming months. But remember, it is a supplement, not a magic pill. It is no substitute for a healthy diet containing a variety of fish.
(1) Szymanski, K M; Wheeler D C; Mucci, L A (2010) Fish consumption and prostate cancer risk: a review and meta-analysis. American Journal of Clinical Nutrition, 92 (5) 1223-33