EAST LANSING, Mich., Oct. 6 (UPI) -- In a study of mice, U.S. researchers found high doses of fish oil induced severe colitis and colon cancer -- a finding researchers described as "surprising."
Study leader Jenifer Fenton, a food science and human nutrition researcher at Michigan State University, said the researchers hypothesized feeding fish oil enriched with docosahexaenoic acid to mice prone to inflammatory-like bowel disease would decrease their cancer risk.
"We actually found the opposite," Fenton said in a statement. "We found that mice developed deadly, late-stage colon cancer when given high doses of fish oil -- more importantly, with the increased inflammation, it only took four weeks for the tumors to develop."
The study, published in the journal Cancer Research, found an increase in the severity of the cancer and an aggressive progression of the cancer in not only the mice receiving the highest doses of DHA but those receiving lower doses as well.
However, Fenton cautioned people may not need to avoid fish oil -- with any nutrient, there is a "bell curve" effect, with those on the left deficient in a nutrient and those on the right in excess.
"Currently, there is a call by academics and the food industry to establish dietary guidelines for omega-3 consumption," Fenton said. "Most Americans are deficient in omega-3 fatty acids, and there is substantial evidence supporting the beneficial effects of the consumption."
The findings support a growing body of literature implicating the harmful effects of high doses of fish oil in relation to certain diseases, Fenton added.