A new study has found that regular and long-term consumption of omega-3 fatty acids and oily fish can slash the risk of developing colorectal cancer by up to 40 per cent.
Over an impressive 22 years of study, both omega-3 and fish intake were associated with cancer risk reduction in the colon and rectum, according to findings by researchers from Harvard and Columbia University.
The research adds to the ever-growing list of healthy benefits linked to omega-3 fatty acids, such as aiding cognitive function, protecting the heart against cardiovascular disease, and reducing the risk of certain cancers.
In terms of colorectal cancer, a disease responsible for about 492,000 deaths each year around the world, the potential benefits have only been investigated in a small number of studies.
According to a recent meta-analysis by researchers from Wageningen University in the Netherlands, the overall body of science indicates that the incidence of colorectal cancer may be cut by 12 per cent by consuming more fish per week. In addition, for every additional serving of fish consumed per week the risk of developing the cancer could be cut by four per cent, stated the meta-analysis in the American Journal of Epidemiology.
Assessing the results
In terms of the Harvard-Columbia University study, Megan Hall and her fellow researchers followed 21,376 men participating in the Physicians’ Health Study (PHS) trial (started in 1982) for an average of 22 years. The men’s intake of fish, and subsequently omega-3 fatty acid intake, was calculated from an abbreviated food-frequency questionnaire.
Over the course of the study, 500 cases of colorectal cancer were diagnosed. In terms of fish intake, the highest average intake was associated with a 40 per cent reduction in the risk of colorectal cancer. In addition, this link was relevant for both colon and rectal cancers.
When the scientists focussed on omega-3 fatty acid consumption, they found similar associations, with the highest intakes linked to a 26 per cent reduction in colorectal cancer risk, compared to the lowest average intake.
Commenting on the findings Hall said: “Our results from this long- term prospective study suggest that intakes of fish and long-chain n- 3 fatty acids from fish may decrease the risk for colorectal cancer”.
Different omega-3, different effects
A study published last year in the American Journal of Epidemiology (Vol. 166, pp. 1116-1125) reported that different omega-3 fatty acids conferred different levels of protection. Indeed, increased intake of eicosapentaenoic acid (EPA) was associated with a 41 per cent reduction in risk, while docosahexaenoic acid (DHA) was associated with a 37 per cent reduction in risk, comparing highest against lowest average intakes.
It has previously been proposed that omega-3 fatty acids may inhibit the omega-6 arachidonic acid (AA) cascade that has been linked to cancer formation and cell proliferation.
Metabolism of fatty acids produces compounds called prostaglandins, which can be either pro- or anti-inflammatory. The prostaglandins derived from omega-3 fatty acids are said to be anti-inflammatory and may protect against the development of cancer, while prostaglandins derived from omega-6 fatty acids, like AA, are proposed to be pro- inflammatory.
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