Last week, the mainstream press reported a study that linked consumption of fish oil to prostate cancer. A closer look at the study, however, calls the headline into question. The results were taken from a study that was designed to answer the association between selenium and vitamin C and cancer risk. The study was not initially designed to study the link between omega 3 oils and prostate cancer risk. The researchers included one (just one) measurement of blood levels of omega 3 oils. It is always dangerous to use a study designed for a specific purpose, such as selenium and vitamin C intake and cancer risk in general to answer a specific question about another factor such as fish oil consumption. One measurement in time gives no information about any subject's daily intake in a disease that takes years to develop. The difference between the two groups, those with increased risk and the control was 4.66% vs. 4.48%. This is at best a weak correlation and not causation. There was no information as to whether the omega 3 intake was from supplements or from eating fish. If from supplements, was it from capsules which don't become rancid, or from bottled fish oil which can become rancid and form carcinogenic compounds known as epoxides? If in supplement form, was it distilled fish oil in which carcinogens are removed? If these subjects obtained their omega 3 oils from eating fish, was there something in the fish that was itself carcinogenic? These results conflict with countless epidemiological studies that consistently show a low incidence of cancer in people from countries like Japan where fish consumption is high.
These days we have too much research by press release and two much waring between the conventional medical-industrial complex and the alternative medical-industrial complex. It is best not to rely one just one study about anything and to check into who funded the study. Be skeptical of all studies until you have researched the research yourself or rely on the judgement of a trusted physician. It is also useful to read both sides of the argument online and use your best judgement to decide. Not every supplement in every amount is going to be indicated for all patients at all times. It just ain't that simple, headlines notwithstanding.