Articles by Dr. Erdman are for informational purposes, and are not to be taken as specific medical advice.
On July 10th, the headline read, “Men Might Want
to Shun Fish oils, Study Shows.” This new study from the Fred Hutchinson Cancer
Research Center supposedly shows a link between increased EPA/DHA levels in the
blood and prostate cancer risk. Given all the positive health effects linked to
fish oil intake, this study definitely seems out of step with previously shown
benefits.
As I have said before, always try to find out more about who
did the study, how it was performed and if it has been repeated by others. I am
no expert in these activities, but I have found a great article written by an
expert, Dr. Michael Murray. He is a leading authority on natural medicine, and
has written over 30 books on health and nutrition. Much of the following
information is attributed to this article: “How a SELECTed Bad Study Became Big
News,” written on July 12, 2013, and published online at GreenMedinfo.com.
Dr. Murray says the pedigree of this study is impressive. It
was published in the Journal of the National Cancer Institute and was conducted
by researchers at the Fred Hutchinson Cancer Center in Seattle, WA. Yet, the
data used is from the much maligned Selenium and Vitamin # Cancer Prevention
Trial, or SELECT. That is the problem.
The SELECT study was a large clinical study that attempted
to determine whether vitamin E could prevent prostate cancer. This study was, again,
out of step with other studies showing positive prostate cancer reduction with
vitamin E, in that it showed a 17% increase in prostate cancer in men who took
vitamin E. That is just not shown in any other study.
Dr. Anthony Victor D’Amico, MD, who has a doctorate from MIT,
says this: “The study really cannot make the conclusion that it’s trying to,
because these types of studies are not cause and effect; that is, if you take
fish oil you’re going to get an aggressive or some kind of prostate cancer.”
A study such as this, where they review and measure only
blood samples taken and analyzed without removing other known predicators of
prostate cancer; and where they have no knowledge of whether or not these men
ever took fish oil or ate fish, draws a weak correlation, at best.
Dr. Murray brings up multiple important considerations about
this study. First, it is not consistent with other studies showing the positive
benefits of fish oil. This study did not include information or documentation
of fish or fish oil intake in the study group. This study was not initially set
up to evaluate these factors, hence its relevance is not as significant as
studies designed to specifically determine the impact of omega 3 fatty acids on
prostate cancer risk.
Again in this study there is no evidence that anybody in
this study took fish oil supplements or even ate fish. They only measured
plasma levels EPA/DHA, not how they got there. In usual circumstances, plasma
levels of EPA/DHA reflect very recent intake and are a poor marker of long term
omega 3 intake. Maybe those who showed prostate cancer recently increased their
intake of omega 3’s to help them recover from it.
Without a dietary history, a racial breakdown, and other
known prostate cancer risk factors being accounted for, there is no way of
knowing that these findings are more than mere association, not cause and
effect, as these authors are trying to intimate.
So, what do we know about fish oil and prostate cancer from
other studies actually done to measure this link? A meta-analysis of all
previously conducted studies shows some better conclusions for fish oil and
prostate cancer. A 30 year study of 6,272 Swedish men showed those who ate NO
fish had a two to three fold increase risk of prostate cancer. Another study,
of 22 years, found that fish consumption greater than five times per week
reduced the risk of dying from prostate cancer by 36%. A 12 year Harvard study
involving 47,882 men showed that for every 500mg of marine fat ingested per
week, there was a decrease of risk of developing metastatic prostate by 24%. And
finally, a study of 47,866 men with no history of cancer initially, aged 40-75, followed over 14 years,
showed those with the highest intake of EPA/DHA, had a 26% reduced risk of
prostate cancer.
Based on the facts presented, do not quit taking fish oil. All fish oil is not created equally. This is one supplement that you must ensure purity and quality, or it is actually bad for you to take. Make sure it is excellent quality; fresh, not rancid (80% on superstore shelves are!); and not contaminated with unwanted things like heavy metals and pesticides. Cheap fish oil is usually not good fish oil! 1,000mg daily, for men, is recommended, If you are trying to treat one of the 60 ailments fish oil has been proven to help, you should consume at least 3,000mg daily.