Men - did you see any of the headlines last week about fish oil causing prostate cancer? If so, I hope you didn’t swear off salmon and throw away your Omega-3 capsules. The evidence the headlines were based on is pretty flimsy.
In an observational study published July 10 in the Journal of the National Cancer Institute, data from the SELECT Selenium and Vitamin E Cancer Prevention Trial were extracted to examine a possible link between omega-3 levels in blood and prostate cancer risk. A positive association was found with DHA, one of the fish oil Omega-3 EFAs and both low-grade and high-grade prostate cancer (44% and 71% increase respectively).
These numbers sound pretty significant, but are they? First of all, correlation does not necessarily mean causation. The lowest risk of prostate cancer in this study happened to correlate with the highest trans fatty acid levels, but no one is even suggesting that TFAs, with well-known harmful effects, prevent cancer.
Blood levels of EFAs depend on your most recent meal, not on long term eating habits, which is not included in the data. So we don’t know how much fish, if any, the men in this study ate or if they took omega-3 supplements.
The total omega-3 levels, as a percent of total blood lipids, in both groups was quite low – 3.66% in the group who got cancer and 3.62% in the group who didn’t, and the difference very slight. Yet Japanese men, who consume 8 times as much omega-3s as Americans, have a much lower prostate cancer rate.
The researchers in this study did not control for age, race or diet and other known risk factors may not have been completely accounted for. Of the men who got cancer, 53% were smokers, 64% regularly consumed alcohol and 80% were overweight or obese.
The overwhelming majority of valid studies – larger and much better designed – show that omega-3s lower cancer risk, including prostate cancer. One study from Harvard School of Public Health which followed 20,000 men for over 22 years found that men who ate fish 5 or more times per week had a 48% lower risk of prostate cancer death than those who ate fish less than once a week. And a 30 year study from Sweden concluded that eliminating fish from your diet could increase your risk of prostate cancer by up to 300%. Now that’s significant!
The only way to explain the study’s conclusions - and the news stories that promoted them – is a desire for sensational headlines and a strong anti-supplement bias. And I don’t think I’m stretching it here. One of the researchers, Alan Kristy, was quoted: “We’ve shown once again that use of nutritional supplements may be harmful.” Baloney! What they have shown is that following nutritional advice from mainstream media may be harmful.
Dr. Jonny Bowden in Huffington Post
Dr. Michael Murray
Dr Robert Rountree, Chief Medical Officer at Thorne Research, in Dr Nalini blog
For more information on this or other natural health topics, stop in and talk to Stan; for medical advice consult your licensed health practitioner.