Omega-3 and Prostate Disease

Chapter summary

Fish oils seem to give some benefit against prostate cancer in some research, but a 2013 study said fish oil supplements increased rates.
To decide, look at better-designed trials and weigh the other benefits.
The author, who is hard on supplements, admits he took fish oil for eczema-prone skin. A friend takes it for depression. He suspects some of the benefit comes from the decision to “do something positive”.

Higher blood levels of long-chain omega-3 fats (EPA, DPA, DHA) were linked to a 43% higher risk of prostate cancer and a 71% higher risk of the aggressive form.
It compared 834 men who developed prostate cancer (156 aggressive) with 1,393 men who did not. All were in the SELECT trial of selenium and vitamin E.
SELECT itself found selenium alone cut absolute risk by 20%, selenium plus vitamin E by 60%, and high-dose vitamin E alone raised risk by 160%.

Concern: Long-chain omega-3 fats are the most easily peroxidised fats. Peroxidation makes toxic aldehydes that can mutate DNA, and oxidised DHA may promote blood vessel growth that feeds tumours.
Critics of the study: Prof Anthony D’Amico says the study “really cannot make the conclusion that it’s trying to”. It shows an association, not cause and effect, and did not adjust for known predictors of prostate cancer. The result is a weak association. Other commentators, including the Alliance for Natural Health, called it flawed.
Inuit evidence: Inuit have high omega-3 levels and extraordinarily low prostate cancer rates, which argues against harm, though many other factors differ.
The author’s verdict: The evidence is just not conclusive.

Omega-3s are touted as brain boosters but do not appear to slow mental decline.
Eric Ammann (University of Iowa) analysed blood omega-3 in 2,100 women aged 60 to 80 without dementia. Over six years they were tested on memory, fluency, spatial ability and other skills.
There was no difference in cognition, or in rate of decline, between women with high and low omega-3.
Omega-3 research is confounded. Most diets contain some, and people who eat lots of fish and nuts tend to be affluent and health-conscious.

Moderation. If you take it because you believe it helps your mood, that is part of the “mind” leg of the stool.
Do not expect it to change a prognosis.
Eat more green leafy vegetables or an extra shellfish serving a week.
If you have a specific condition, test it on your symptoms: use it, stop it, start again, and measure.

Brasky, T. et al. (2013) Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial. J Natl Cancer Inst 105(15):1132-41.
Brasky, T. et al. (2011) Serum phospholipid fatty acids and prostate cancer risk: results from the Prostate Cancer Prevention Trial. Am J Epidemiol.
Lippman, S. et al. (2009) Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the SELECT trial. JAMA 301:39-51.
Spector, P. (2013) Something fishy about omega-3s: prostate cancer, fish oil and panaceas. Huffington Post.
Alliance for Natural Health Europe. A tide of evidence washes away flawed fish oil prostate cancer study.
Botelho, A. (2013) Fish oils don’t boost brain power. New Scientist 2936.