Do Omega Fatty Acids Cause Prostate Cancer?

July 15, 2013

Do Omega Fatty Acids Cause Prostate Cancer? 

 Reference:  Brasky, J Natl Cancer Institute July 11, 2013 

 Headlines! Fish Oil causes prostate cancer.  Oh, dear.  Now what?  Is it real?  What did they find?  Here are the details.   After screening 800 men that went on to develop prostate cancer versus 1300 men that didn’t, comparison of blood omega-3 fatty acid levels showed that the men who had higher blood levels had a 43% increased chance of developing prostate cancer and 71% chance of getting aggressive prostate cancer.  The blood level indexes were in the range of 3.2% for the low group and 5.7% in the higher group.  It seems to have been a well-designed study that has lots of statistical power to it.  What to make of it?  It certainly made the headlines. 

 Here is my take on it and how to consider it.  First of all, it was an epidemiological study showing association, not causation.  Lots of other unintended forces could be going on in the background.  A similar epidemiological association view of prostate cancer could be to look at Japanese. They eat about 8 times the amount of omega 3 fatty acids.   They should all be dead from prostate cancer.  In North America, Caucasians have 63 deaths per 100,000 lives and African Americans have 102 deaths.  Japanese have 10 deaths per 100,000 lives.  Hmmm. 

Secondly, the index levels of omega-3 weren’t very high.  A level of 5.7% isn’t that high.  In the Framingham study, folks not taking omega-3s had a 5.2% index and those taking it had 7.5%.  Framingham didn’t show an epidemic of prostate cancer in the high consumption group, even with a much higher index. How about relative risk from the beneficial effect of fish oil on heart disease compared to prostate cancer?   American men die at 7.4 times the rate from heart disease than they do from prostate cancer (even though 60% of us have it on autopsy at death at age 80).   

If fish oil reduces risk of heart disease by a conservative 10% (considering the recent NEJM article downplaying the value of fish oil) and increases prostate cancer by 50%, the beneficial ratio would still 4.4 times more chance of heart disease over prostate cancer, still leading to relative benefit.   This is a crude analysis, but you get the gist. Finally, there are about 5-6 studies that also show the opposite finding including some by Brasky himself with Grapeseed oil (another omega 3).  His interest in omega fatty acids is real and he certainly has been looking.  What to make of this careful and well-designed study? 

 WWW. What Will Work for Me?  This is how science works.  It’s uncomfortable.  We find new ideas only by publishing well-designed research and following the conclusions.  My hunch is that this is a blind alley with confounding factors not considered playing a role. Vitamin D wasn’t measured, for example.  I’m still taking my two grams of DHA and EPA a day.  I’m not getting too worried yet.  The Japanese also eat natto and get huge amounts of K2 by so doing.  That I can’t do.  I’m just taking my K2 supplement.  Maybe that’s why they don’t have prostate cancer.  We’ll see.   But it caught my attention.   

 Pop Quiz 

 1.  Braskey found, in a well designed study, that men who had the highest omega-3 index had a 41% increased risk of developing prostate cancer.  T or F                   Answer:  T.  In a nutshell.

 2.   This study proves that prostate cancer is caused by eating too much fish?  T or F              Answer:  False in the strongest terms.  It's an association study.  Many other confounding factors could be making the effect 

 3.   Japanese men have much more prostate cancer than American men and eat much more fish.  T or F                         Answer:   False.  They have about 15% of the prostate cancer we have in America, suggesting an opposite conclusion to this study.  They do eat a lot more fish. 

 4.   American men's risk for prostate cancer is greater than their risk for heart disease.  T or F Answer:  False.  It's much lower.  50% of American men die from heart disease.  Prostate cancer is number 1 for men, but still not as common as heart disease. 

 5.  You should stop taking fish oil.  T or F                        Answer:  False, but you should pay attention. This study could be opening the door to a new idea.

The column was written by Dr. John Whitcomb, Brookfield Longevity, Brookfield, WI.