BADALONA, SPAIN. Several epidemiological studies have shown that high fat diets are associated with an increased risk of colon cancer. Other studies have shown that diets rich in fish and fish oil supplements are protective against colon cancer. Spanish medical researchers have released the results of a major study aimed at determining if and how polyunsaturated fatty acids play a role in the progression of adenomas (benign polyps) to full-blown colon cancer. The study involved 27 patients with sporadic benign polyps of the rectum or colon, 22 patients with cancer of the colon or rectum, and 12 subjects with a normal colon. The researchers measured the fatty acid profile of blood plasma and biopsy samples of the lining of the colon from both diseased and normal areas. They found no differences between polyp patients and patients with a normal colon as far as plasma profile and normal colon lining profile was concerned. However, there was a significant difference between the fatty acid profile of normal colon tissue and diseased colon tissue in adenoma patients. Diseased lining tissue was found to have higher levels of linoleic acid, dihomogammalinolenic acid, and eicosapentaenoic acid (EPA) and lower levels of alpha-linolenic and arachidonic acids. There was also a very significant stepwise reduction in EPA content of diseased colon lining from the benign polyp stage progressing to the most severe colon cancer stage.
The researchers concluded that there are significant changes in the levels of n-3 and n-6 fatty acids early on in the sequence leading from benign polyps to colon cancer and speculate that these changes might participate in colon cancer progression. They recommend further work to investigate the benefits of long-term dietary manipulation in view of the finding that taking low-dose fish oil supplements normalizes the cell proliferation pattern in patients with sporadic polyps.
Fernandez-Banares, F., et al. Changes of the mucosal n3 and n6 fatty acid status occur early in the colorectal adenoma-carcinoma sequence. Gut, Vol. 38, 1996, pp. 254-59