ROME, ITALY. The presence of benign polyps (adenomas) is a significant risk factor for full-blown colon or rectal cancer. Animal studies have shown that the omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) inhibit the development of colon cancer and epidemiological studies have shown that fish consumption is inversely proportional with the incidence of colon cancer. Encouraged by these findings, researchers at the Catholic University of Rome set out to determine if fish oil supplementation would inhibit the development of benign polyps, the precursors of colon cancer.
Their study involved 34 men and 26 women who had just undergone surgery to remove benign polyps from their colon. The patients were divided into 4 groups. Group 1 was supplemented with 1.4 grams of EPA and 1.1 grams of DHA per day, group 2 with 2.7 grams of EPA and 2.4 grams of DHA, group 3 with 4.1 grams of EPA and 3.6 grams of DHA while group 4 received placebo capsules containing mainly olive oil. Biopsy samples from the lower part of the colon lining and blood samples were taken and analyzed at the start of the trial and 30 days later at the end of the supplementation period. Overall, patients in the fish oil groups experienced a significant decline in the number of abnormal cells in their colon lining as compared to members of the placebo group. Further analysis showed that the reduction in the number of abnormal cells was limited to patients who had a large number of abnormal cells at the beginning of the trial. The researchers also noted a very significant increase in EPA and DHA levels and a significant drop in arachidonic acid level in the biopsy samples from the fish oil supplemented patients.
A separate 6-month trial involving 15 patients taking 1.4 grams per day of EPA and 1.1 grams per day of DHA also showed a significant drop in the number of abnormal colon lining cells. The researchers conclude that low-dose supplementation with fish oils inhibit the proliferation of abnormal cells (a precursor to polyps) in patients at risk for colon cancer and that this effect can be maintained with long- term treatment. They caution that it may be advisable to increase vitamin E intake during fish oil administration.
Anti, Marcello, et al. Effects of different doses of fish oil on rectal cell proliferation in patients with sporadic colonic adenomas. Gastroenterology, Vol. 107, December 1994, pp. 1709-18