Hundreds of thousands of Eskimos Can’t be Wrong.... Just over a week ago, the big headline health story was that fish oil supplementation could increase the risk of prostate cancer. Given all of the positive health benefits linked with fish oil intake and coupled with the fact so many people now take additional fish oil supplements, it’s not surprising that such “findings” should receive huge press coverage. Moreover, it has got plenty people talking – and a lot of them to me! So I’ve been digging around this week to try and find out more; initially I was quite dismayed when I discovered that the research had been carried out by one of the world’s leading cancer research institutes, the Fred Hutchinson Cancer Centre, based in Seattle. However, on closer examination of the study, there are numerous issues that suggest that not only might the conclusion be wrong, but that the study design was completely flawed. Firstly the study was not designed to look at the relationship between omega-3 fatty acid intake and prostate cancer - its primary focus was to look at selenium and vitamin E. The trial, known as SELECT (the Selenium and Vitamin E Cancer Prevention Trial), was a very large clinical study that attempted to determine whether vitamin E could prevent prostate cancer. Previous studies had shown 50 IU of vitamin E to be protective against prostate cancer, but the SELECT study chose to use 400 IU of synthetic vitamin E. Results showed that the subjects taking this synthetic vitamin E had a 17% higher risk of prostate cancer compared to the control group. In the new analysis, researchers measured the levels of fats in the blood of participants and concluded that men with the highest concentrations of EPA, DPA and DHA-(three fatty found in fish oil)-had an increased risk of prostate cancer. Specifically, they reported a 71% increased risk of high-grade prostate cancer, a 44% increased risk of low-grade prostate cancer and an overall 43% increased risk for total prostate cancer in a subset of patients with the highest level of these omega-3 fatty acids. Enough to convince most people to immediately swing by the nearest bin and ditch their fish oil capsules along with any salmon or tuna steaks they may have had lurking in the freezer! But, before you start hurling those supplements at the bin, just consider the following. If the study conclusions were correct then aggressive prostate cancer would be an increased health risk for men in countries with even moderate fish consumption. In fact, many studies have shown the opposite effect with prostate cancer rates being lowest in populations with relatively high dietary intakes of fish oil such as Japanese and Mediterranean communities. Furthermore, prostate cancer is virtually unheard of amongst the Inuit Eskimos – I think they eat quite a bit of fish don’t they? Some other important points to consider are: • This study is absolutely not consistent with other studies which have been designed to look specifically at the relationship between fish oil and various types of cancer. • This study did not examine or even document the intake of fish or fish oil supplements amongst participants. • This study was not designed to evaluate causative relationships between fish oil intake and cancer. • There is no evidence that anybody in this study took fish oil supplements or even ate fish! • The data may reflect existing cancer activity rather than a causative association. Without dietary history or documentation of fish oil use there is no way of knowing. For example, men recently diagnosed with prostate cancer may have subsequently decided to increase their fish oil consumption, having read that this can improve their long-term health outcome. This would raise their blood plasma concentrations but if they already had cancer before they started supplementing clearly this is not a causative relationship!! But, on a positive note, this study is more than likely to lead to a proliferation of more research and that has surely got to be a good.
Posted on: Fri, 19 Jul 2013 14:11:32 +0000
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