Please see my Author's Note sidebar, below.
Prostate cancer is a leading cause of death among men in the United States.
Some 230,000 American men will be diagnosed this year, and more than 29,000 will die from it.
Sadly, the remarkably misleading conclusions of a prostate cancer study published last summer caused men pointless confusion and concern … and scared them away from healthful fish and fish oil.
Most major news outlets simply repeated its authors' alarmist and unsupported, distorted conclusions … lazily and uncritically.
Monday, January 13, 2014
This article left an unclear impression of the evidence on omega-3s and prosate cancer.
I should have noted that several prior epidemiological studies found that men with high-grade prostate cancer also had higher blood levels of omega-3 DHA or EPA from fish or fish oil or of omega-3 ALA from green plants and some seeds (Crowe FL 2008; Brasky TM et al. 2011; Brasky TM et al 2013).
However, many epidemiological studies have not linked higher omega-3 levels to increased risk, or linked them to reduced risk (Gann PH et al. 1994; Godley PA et al. 1996; Harvei S et al. 1997; Newcomer LM et al. 2001; Männistö S et al. 2003; Laaksonen DE et al. 2004; Chavarro JE et al. 2007; Ukoli FA et al. 2009).
And, as many experts said in critiquing the flawed conclusions of a 2012 evidence review
... which focused on epidemiological studies involving men diagnosed with prostate cancer ... those men may have been eating more fish or taking more fish oil in hope of curbing the course of their disease.
And the seemingly negative studies were epidemiological investigations, not controlled clinical trials.
As described in this article, a new clinical trial from UCLA adds good evidence suggesting a protective role for a low-fat diet rich in omega-3s.
As a controlled (albeit small and short-term) clinical trial, it has considerable scientific credibilty ... although it concerns the progression. not the prevention of prostate cancer.
And it is supported by human and lab research into how omega-3s affect known risk factors for prostate cancer.
Still, we need large, controlled clinical trials to gain a clear, definitive picture.
In that study, researchers from Ohio State University analyzed omega-3 levels in blood samples from participants in a clinical trial testing vitamin supplements against prostate cancer.
They found a very slight statistical link between higher omega-3 DHA blood levels and the risk of aggressive prostate cancer … and issued clearly unjustified, context-free conclusions and recommendations.
Experts in prostate cancer and omega-3s quickly pointed out the fatal flaws in the authors' conclusions, as we reported in “Fishy Prostate News
For example, Harvard prostate cancer specialist Anthony D'Amico, M.D., called the Ohio State team's findings “extremely weak and possibly false.”
Importantly, that flawed analysis contradicted, very unconvincingly, the overwhelming majority of prior research.
Overall, the evidence from cells, animals, and human studies supports the likely, plausible prospect that omega-3-rich diets help protect men's prostates from cancer and/or slow its spread (e.g., “Positive Omega-3/Prostate Trial
Since most men who die from prostate cancer do so very late in life, slowing its growth could be tantamount to preventing death or disability from the disease.
Before reviewing the latest good news about omega-3s and prostate cancer, let's look at the California-based 2011 trial behind the encouraging new findings.
UCLA study found omega-3s protective
Three years ago, California-based scientists reported positive results from a clinical trial testing the effects of omega-3 supplements in men undergoing radical prostatectomy (Aronson WJ et al. 2011).
As they wrote, ample evidence suggests that omega-3s discourage prostate cancer, while the average American's excessive intake of omega-6 fats (from cheap vegetable oils) raises the risk and lethality of prostate cancer: “Pre-clinical studies suggest [that] lowering dietary fat and decreasing the ratio of omega-6 to omega-3 polyunsaturated fatty acids decreases the risk of prostate cancer development and progression.”
They conducted a randomized clinical trial to test the effect of reducing dietary fat intake and men's' omega-6:omega-3 intake ratio.
Men undergoing radical prostatectomy were randomly assigned to one of two diets for four to six weeks prior to surgery:
- Standard American Diet: high-fat (40 percent of calories) diet with an omega-6:3 ratio of 15:1
- Omega-3 Diet: low-fat (15 percent of calories) diet plus 5 grams of fish oil, with an omega-6:3 ratio of 2:1
The Standard American diet's fat sources were typical of the American diet, featuring high levels of omega-6 fats from corn oil, and low levels of omega-3s from fish.
Encouragingly, prostate cancer spread less among the men who ate the low fat Omega-3 Diet.
And the men on the Omega-3 Diet showed beneficial changes in the cell membranes of both the healthy cells and the cancer cells:
- Higher levels of (anti-inflammatory) omega-3 fatty acids (from their diet's fish oil)
- Lower levels of the (pro-inflammatory) omega-6 fatty acids (from their diet's corn oil)
Chronic, unhealthful inflammation fuels cancers, and the body uses omega-3 fatty acids to moderate and end inflammation.
With some exceptions, the omega-6 fats abundant in seeds, nuts, and most vegetable oils generally sustain inflammation.
And this outcome prompted the authors to call for more study: “These results support further studies evaluating reduction of dietary fat with fish oil supplementation on modulating prostate cancer biology.” (Aronson WJ et al. 2011)
Now, further analysis of data from this California-based 2011 study offers more evidence that seafood-source omega-3s are allies against prostate cancer … not risk factors for it.
New California trial supports omega-3s' protective potential
Deeper analysis of data from the 2011 California-based clinical trial further undermines the credibility of the deeply flawed, alarmist Ohio State study published last summer (Galet C et al. 2013).
The prostate cancer patients assigned to the Omega-3 Diet (low-fat diet 5 grams of fish oil) daily showed key benefits, versus the control group eating a standard American diet:
- Lower levels of pro-inflammatory substances in their blood
- Lower scores on a measure used to predict cancer recurrence, called CCP
According to lead author William Aronson, M.D., lowering the cell cycle progression (CCP) score may help prevent prostate cancers from becoming more aggressive:
“CCP scores were significantly lower in the prostate cancer in men who consumed the low-fat fish oil diet ... This is of great interest, as the CCP score in prostate cancer is known to be associated with more aggressive disease ...” (UCLAHS 2013)
His team also found that men on the low-fat Omega-3 Diet had lower blood levels of pro-inflammatory substances associated with cancer.
As Aronson said, when they found lower blood levels of a pro-inflammatory agent called LTB4 in the Omega-3 group, as well as lower CCP scores, “... we discovered a completely novel finding that one of the receptors for LTB4 is found on the surface of prostate cancer cells.” (UCLAHS 2013)
In other words, the low-fat Omega-3 Diet lowered levels of a previously unknown promoter of prostate cancer ... one that the California team unmasked for the first time.
“These studies are showing that, in men with prostate cancer, you really are what you eat,” Aronson said. “The studies suggest that by altering the diet, we may favorably affect the biology of prostate cancer.” (UCLAHS 2013)
The study was funded by the National Institutes of Health (NIH).
Based on their results, Aronson will start a prospective, randomized trial in 100 men, next year.
The volunteers will eat their usual diet or to a low-fat, omega-3-enriched diet, and will receive a prostate biopsy at the beginning of the trial and again one year later.
Aronson's team will then measure markers in the prostate biopsy tissue to check for cell growth and CCP (cancer growth) scores.
We'll let you know how that turns out.
In the meantime, the evidence clearly supports the idea that fish-source omega-3s help protect prostate health.
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