Absurd Study Claims Omega-3 Fats Raise Prostate Cancer Risk
July 31, 2013 |
By Dr. Mercola
Omega-3 rich fish oil is one of the most well-researched substances on the market. Its wide ranging health benefits have been repeatedly proven, and animal-based omega-3 is one of the few supplements I recommend for virtually everyone to improve overall health.But omega-3 fat, naturally found in salmon and krill, which are both excellent sources, has received some undeservedly bad press coverage lately. You may have seen some of the following headlines:
- Link Between Omega-3 Fatty Acids and Increased Prostate Cancer Risk Confirmed (Science Daily1)
- Omega-3 Supplement Taken By Millions 'Linked to Aggressive Prostate Cancer' (Huffington Post2)
- Men who take omega-3 supplements at 71% higher risk of prostate cancer(NY Daily News3)
- Omega-3 supplements may trigger prostate cancer (Nursing Times4)
- Hold the salmon: Omega-3 fatty acids linked to higher risk of cancer (Time Magazine5)These headlines are perfect examples of gross misreporting of science by the media, and it is instances like this that demonstrate why you cannot trust the conventional press to keep you informed about health. In the words of Jonny Bowden,6 PhD, CNS, the media’s reporting on this particular study is “disgraceful, incompetent, and scientifically illiterate.” I couldn’t agree more.
'Omega-3 Fats Involved in Prostate Tumorigenesis,' Researchers Claim
The study raising all this hoopla was published in the Journal of the National Cancer Institute7 on July 10. This case-cohort study8 examined associations between omega-3 levels in blood and prostate cancer risk among participants in the "Selenium and Vitamin E Cancer Prevention Trial," also known as SELECT.9The researchers concluded that men with higher blood concentrations of animal-based (marine-derived) omega-3s had a 44 percent increased risk of developing low-grade prostate cancer compared to those with the lowest levels.Specifically, higher blood levels of the omega-3 fat DHA correlated to higher prostate cancer risk, while no correlation was found for EPA and ALA. They also had a 71 percent higher risk of developing high-grade prostate cancer.The “grade” refers to the level of abnormality found in the cancer cells.10 The more abnormal the cells appear, the higher the grade of the cancer. Based on these correlations, the researchers concluded that “these fatty acids are involved in prostate tumorigenesis.” But just how did they reach that conclusion?According to Time Magazine:11“The study measured omega-3 blood levels in the participating men, and did not include information on the volunteers’ eating habits, so researchers could not differentiate between the effects of fatty acids from fish from those of supplements. However, the overwhelming majority of the participants did not take fish oil supplements.Based on the results, [lead author, Theodore] Brasky says that men with a family history of prostate cancer should discuss with their doctor whether fish oil supplements are safe for them, since these pills tend to contain concentrated doses of omega-3.Supplements contain between 30% to 60% of a serving of fish, and if a fish oil supplement is taken every day, that adds up to a lot of daily fish oil. Brasky also suggested that men cut down on their fatty fish intake, though not eliminate it entirely.”Folks, this is some of the most absurd advice I’ve seen in a long time. How they could possibly come to the conclusion that omega-3 supplements might be dangerous based on this study is a mystery in and of itself. Correlation is not the same as causation, first of all.Secondly, no omega-3 supplements were actually given in this study. In fact, most participants reportedly did not take them. Another immediate tip-off that something’s awry is the finding that participants who had the highest levels oftrans fats in their blood had the lowest risk for prostate cancer... As Dr. Bowden writes in his Huffington Post12 rebuttal:“How do you explain the fact that reporter after reporter and news outlet after news outlet conveniently equated higher blood levels of DHA with 'fish oil supplement taking?'There’s almost no other explanation other than a strong anti-supplement bias and a desire for shocking headlines. And any doubt about the objectivity of the researchers should have been abandoned after one of them—Dr. Alan Kristy—told reporters,13 'We’ve shown once again that use of nutritional supplements may be harmful.'”Indeed, Dr. Kristy sounds like a spokesperson for Senator Durbin’s hypocritically idiotic supplement bill, which threatens the supplement industry by granting the FDA more power to regulate supplements as if they were drugs, potentially putting supplement companies out of business.
Do Omega-3s Raise Men’s Prostate Cancer Risk? Hardly!
Foods rich in omega-3 fats have previously been shown to prevent prostate cancer from spreading. One such clinical study (opposed to the featured study, which was observational and therefore cannot establish causality) was published in theBritish Journal of Cancer14 in 2006. This study found that while omega-6 fats (the kind found in most vegetable oils) increased the spread of prostatic tumor cells into bone marrow, the spread of cancer cells was blocked by omega-3 fats, suggesting that a diet rich in omega-3 fats could potentially inhibit the disease in men with early stage prostate cancer.A more recent meta-analysis15 of available research, published in 2010, found that fish consumption was associated with a 63 percent reduction in prostate cancer-specific mortality, even though no association between fish consumption and a significant reduction in prostate cancer incidence could be found. GreenMedInfo.com16 recently discussed this topic as well, listing a number of additional studies that have shown fish/fish oil/omega-3 to be beneficial against prostate cancer.As pointed out by Denise Minger,17 previous research18 has shown that the higher blood levels of DHA found in the featured study is not necessarily indicative of higher fish consumption. In fact, low-fat diets can increase DHA levels in much the same way omega-3 supplementation can. According to previous research:“Plasma phospholipid fatty acids have the potential to function as a surrogate measure of the potential effects of diet on a whole range of cell membrane lipids... This difference in fatty acid levels after the consumption of similar proportions but varied content of fatty acids suggests competition among the lipid series [(n-3), (n-6), (n-7) and (n-9)] for the enzymes of elongation and desaturation.When the relative supply of (n-3) fatty acids is abundant, these fatty acids are preferentially desaturated and elongated relative to (n-6) fatty acids)...In summary... free fatty acid compositions are responsive to total dietary fat content. Specifically, the consumption of a low fat diet promotes an increase in the level of total and highly unsaturated long-chain (n-3) fatty acids and a decrease in the total (n-6) content of plasma phospholipid and cholesteryl ester fatty acids. The observed modifications in phospholipid and cholesteryl ester fatty acids in response to a low fat diet are similar to those observed when (n-3) fatty acids of plant or animal origin are fed.”
Why DHA Levels in Featured Study May Be Meaningless...
Furthermore, the featured study reported DHA levels based on percentage of total fatty acids rather than the absolute value, which in and of itself can be quite misleading,19 as it actually obscures any real differences. Dr. Bowden illustrates the dilemma well with the following analogy:“Would you like 90 percent of all the money Mr. Jones has or 10 percent of all the money Mr. Smith has?”How could you possibly tell how much money those percentages of total represent, unless you know how much money Mr. Jones and Mr. Smith each have to begin with? As explained in a 2009 commentary published in the American Journal of Clinical Nutrition,20 the only time percentage of total might be meaningful is when the total fatty acid content is identical for all subjects, which it undoubtedly was not in this case.As stated by Dr. Bob Roundtree, MD:21“Considering the extensive body of literature that supports the anti-inflammatory effects of omega-3 fatty acids, there is no credible biological mechanism, nor is one suggested in the article, that would explain why these essential fatty acids might increase tumorigenesis.”
Confounding Factors Ignored
Another problem with studies looking at correlations only, is that the factor you’re looking at may only be a minor player, or completely irrelevant, compared to other factors. For example, in this case:22
- 53 percent of the subjects with prostate cancer were smokers
- 64 percent of the cancer subjects regularly consumed alcohol
- 80 percent of the cancer subjects were overweight or obeseAccording to a 2011 study published in PLoS One,23 aggressive prostate cancer was associated with obesity. More recently, a cohort study published in Cancer Epidemiology, Biomarkers & Prevention24 in April of this year found that men who were overweight or obese increased their risk of prostate cancer by 57 percent—a percentage that falls right smack in the middle of that 44-71 percentage range attributed to high DHA serum levels in the featured study. And this association between obesity and prostate cancer held for all cases— low-grade and high-grade, early stage and late, nonaggressive and aggressive prostate cancer........