Improve omega 3 to 6 ratio to protect the prostate

10th June 2010

All men need to look after their prostate gland and improving the omega-3 to omega-6 ratio in the diet may cut prostate cancer risk

Over half a million news cases of prostate cancer are diagnosed every year world wide, and the cancer is the direct cause of over 200,000 deaths.

The incidence of the disease is also increasing with a rise of 1.7 per cent over 15 years.

However a new study lead by researcher Professor William Aronson at the David Geffen School of Medicine at UCLA, adds to a growing body of evidence linking an increased omega-3 to omega-6 intake ratio to improved health and prevention of prostate cancer can now be added to that list.

Earlier this year, researchers from the Paterson Institute, a cancer research institute funded by British charity Cancer Research UK and affiliated with the University of Manchester reported that omega 6 fats increased the spread of prostate tumour cells into bone marrow, while omega-3 fatty acids were seen to block this invasion (British Journal of Cancer, doi: 10.1038/sj.bjc.6603030).  This new research, published in the new issue of the journal Clinical Cancer Research (Vol. 12, Issue 15), suggests that changing the ration of omega-3 to omega-6 in the typical Western diet might reduce prostate cancer tumor growth rates and PSA levels. 

Prostate specific antigen (PSA) is a protein that is used as a marker for the disease – higher levels are associated with a higher risk of prostate cancer.  A special mouse model was used for hormone-sensitive prostate cancer that is said to closely mirror the disease in humans. The mice were divided into two groups, one fed a diet 20 percent fat with a healthy one-to-one ratio of omega-6 to omega-3 fatty acids, while the second group of mice was fed the same diet but with the fat derived from mostly omega-6 fatty acids.  At the end of the intervention period, the researchers reported that tumour cell growth rates had decreased by 22 per cent and PSA levels by 77 per cent in the group receiving a healthier balance of fatty acids compared with the group that received predominantly omega-6 fatty acids.  “This study strongly suggests that eating a healthier ratio of these two types of fatty acids may make a difference in reducing prostate cancer growth, ,” said Aronson.

Omega 6 fats are found in corn, safflower and other vegetable oils, nuts, seeds, and red meats. Corn oil is the backbone of the American diet.  We consume up to 20 times more omega-6 fatty acids in our diet compared to omega-3 acids,” explained Aronson. 

The most likely mechanism for the tumour reductions, say the researchers, is the role of metabolites of omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and the omega-6 acid, arachidonic acid.  These three fatty acids compete to be converted by cyclooxgenase enzymes (COX-1 and COX-2) into prostaglandins, which can become either pro-inflammatory and increase tumour growth, or anti-inflammatory and reduce growth.  Aronson and his co-workers found that levels of the pro-inflammatory prostaglandin (PGE-2) were 83 per cent lower in tumours in the omega-3 group than in mice on the predominantly omega-6 fatty acid diet.  This suggests that higher levels of DHA and EPA may lead to development of more anti-inflammatory prostaglandins.

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