In a study involving 1,455 people with colorectal cancer and 1,455 without the disease (the controls), researchers found that the cancer patients consumed lower amounts of omega-3 PUFAs and its main components, docosahexaenoic and eicosapentaenoic acids, than did the cancer-free controls.

People with the highest level of omega-3 PUFAs in their diets had 37-percent lower odds of colorectal cancer compared with people with the lowest level. "The omega-3 fatty acids that had the strongest associations were the ones present in oily fish -- eicosapentaenoic acids and docosahexaenoic," Theodoratou and co-author Dr. Harry Campbell noted in written comments to Reuters Health.

The odds of colorectal cancer was 41 percent lower in people with the highest docosahexaenoic intake and 37 percent lower in those with the highest eicosapentaenoic acids intake, compared with people with the lowest intake of these individual PUFAs.

"These associations remained constant after several corrections and adjustments of the statistical models," Theodoratou and Campbell noted. They caution, however, that more study is needed "before we can conclude that omega-3 fatty acids may protect against colorectal cancer."

"During the study, some of the people were regularly consuming supplements rich in omega-3 fatty acids such as cod liver oil products. But when we added the supplementary to the dietary omega-3 intake we did not find a stronger protective effect than the dietary effect alone," according to Theodoratou and Campbell.

As mentioned, there was no association between intake of omega-6 PUFAs and colorectal cancer risk. This is likely due to the different biologic action of omega-6 and omega-3 PUFAs.

Omega-6 PUFAs have been shown to boost concentrations of chemicals in the body that promote the development of colon cancer, whereas omega-3s are rapidly incorporated into cell membranes and exert several anti-cancer actions.

People with colorectal cancer were also found to have diets high in saturated, monounsaturated and trans fatty acids mainly found in meat and savory products, but these associations did not have a significant bearing on colorectal cancer risk in adjusted models.

SOURCE: American Journal of Epidemiology July 15, 2007.

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