A just-published article in the American Journal of Epidemiology reports a very clear negative correlation between colorectal cancer and omega-3 consumption. It describes the results of a case-control study done in Scotland from 1999 to 2006. The investigators hoped to recruit all cases of colorectal cancer coming for surgery in Scotland; they managed to recruit about half of them and ended up with about 1500 “cases.” Each case was paired with a healthy control matched for age, sex, and residence. Then they compared the diets of the two groups. This is the approach that first linked smoking and lung cancer. Lung-cancer patients were more likely to smoke than other types of patients.
In the Scotland study, there was no correlation between cancer and overall fat consumption, but there was a very clear correlation with omega-3 fat consumption: more omega-3, less cancer. There was no correlation with omega-6 fat consumption. The conclusions remained the same after they combined their results with four previous similar studies.