Harvard team finds fish fats cut risk in men eating ample fish fats in place of aspirin
by Craig Weatherby
Adding to the impressive pile of evidence linking higher omega-3 intake to lower colon cancer risks comes a study that clarifies these fish-borne fats’ protective power in comparison with aspirin.
Worldwide, colorectal cancer accounts for about one in ten cancers. But the highest rates by far occur in the developed world, while people in Asia and Africa enjoy the lowest risk.
Low-dose daily aspirin is strongly linked to reductions in colorectal cancer rates, as are marine-source omega-3s.
And both preventive agents appear to work in part via their impacts on different stages in the metabolic pathways that yield inflammation.
Harvard team finds high omega-3 intake comparable to aspirin
Dr. Megan Hall of Harvard University’s School of Public Health lead a team that included nutritional epidemiologist Walter Willet, M.D.: the renowned researcher we heard speak at Dr. Andrew Weil’s 2006 Nutrition & Health Conference.
Their team measured omega-3 levels in the blood of 178 men with colorectal cancer (cases) and 282 healthy people (controls).
When the Harvard group analyzed data from the men who were not taking aspirin, they found that the men with the highest blood levels of omega-3s were 66 percent less likely to have colorectal cancer, compared with the men showing the lowest omega-3 blood levels (The researchers’ results took into account potential confounding factors, such as smoking, when making their calculations).
They also found that the risk of colon cancer among all of the men – those taking aspirin and those not taking it -- was 40 percent less among those who had the highest omega-3 blood levels, versus the men with the lowest levels. However, this outcome was not deemed statistically significant.
Among the men taking aspirin, the researchers detected no additional risk reduction in those with relatively high blood levels of omega-3s. This isn’t surprising, given the similar ways in aspirin and omega-3s prevent cancer-fueling inflammation described below.
Why omega-3s and aspirin cut colon cancer risks
The growth of many common cancers, including colorectal tumors, is fueled by chronic, silent inflammation in the body: a state common among Americans and one created by their diets, which are too high in omega-6 fats and too low in omega-3s.
Aspirin works against silent inflammation by inhibiting an enzyme (COX-1) needed to produce messenger chemicals called prostaglandins.
Fish fats work against unnoticed inflammation by promoting production of anti-inflammatory prostaglandins. In other words, omega-3s leave COX enzymes unaffected, but the balance of prostaglandins the COX enzymes produce is a function of the fats in our cell membranes.
So when our diets are balanced properly between omega-6 to omega-3 fats (about a 3:1 ratio), the body tends toward an inflammation–neutral state.
When your cell membranes contain omega-3s in abundance—instead of omega-6 fats from vegetable oils and meats— the bulk of prostaglandins that our COX enzymes produce will tip toward the inflammation-moderating kinds.
Instead of the low omega-6 to omega-3 dietary ratio that humans adapted to during eons of hominid evolution, people in America and some other industrialized Western countries consume 15 to 40 times more omega-6s than omega-3s.
For more on the colon-protective powers of omega-3s—and those of vitamin D and EV olive oil—search our newsletter archive for “colon” and “colorectal”.
- Hall MN, Campos H, Li H, Sesso HD, Stampfer MJ, Willett WC, Ma J. Blood levels of long-chain polyunsaturated Fatty acids, aspirin, and the risk of colorectal cancer. Cancer Epidemiol Biomarkers Prev. 2007 Feb;16(2):314-21.