Dietary intake of polyunsaturated fatty acids (PUFAs) has been associated with risk of colorectal cancer, with omega–6 PUFAs increasing and omega–3 PUFAs decreasing risk. Most studies, however, have relied on questionnaires to assess consumption of fatty acids, and results have been inconsistent.

Harvey Murff, MD, and colleagues have studied a blood–based biomarker of PUFA intake. They evaluated the association between red blood cell membrane PUFA content and adenomas in patients who participated in the Tennessee Colorectal Polyp Study, a large colonoscopy–based case–control study.

The investigators reported in the British Journal of Nutrition that higher levels of arachidonic acid (an omega–6 PUFA) were associated with an increased risk of colorectal adenomas. Higher levels of two omega–3 PUFAs (DPA and EPA) were associated with a reduced risk of adenomas and advanced adenomas.

Since more than 95 percent of colorectal cancers develop from adenomas, the findings support increased consumption of omega–3 PUFAs, found in fish oils, and decreased consumption of arachidonic acid, found predominantly in meat, for colorectal cancer prevention.