Fish Oil Increases IBD, Colon Cancer Risk

EAST LANSING, Mich.New research from Michigan State University reveals dietary intake of high doses of fish oil induces severe colitis and colon cancer in mice. The findings further support establishing a dose limit for docosahexaenoic acid (DHA), one of the omega-3 fatty acids present in fish oil, particularly in people suffering from chronic conditions such as inflammatory bowel diseases, the researchers said.

We found that mice developed deadly, late-stage colon cancer when given high doses of fish oil," said Jenifer Fenton, a food science and human nutrition researcher at MSU. More importantly, with the increased inflammation, it only took four weeks for the tumors to develop."

The findings, published in the journal Cancer, 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. The study mice were prone to inflammatory-like bowel disease; inflammation is an important risk factor for many types of cancers, including colon cancer.

Our findings support a growing body of literature implicating harmful effects of high doses of fish oil consumption in relation to certain diseases," Fenton said. Currently, there is a call by academics and the food industry to establish dietary guidelines for omega-3 consumption. This is primarily motivated by the fact that most Americans are deficient in omega-3 fatty acids, and there is substantial evidence supporting the beneficial effects of the consumption."

She said the findings were surprising because DHA has been shown to have some anti-inflammatory properties.

"We hypothesized that feeding fish oil enriched with DHA to mice would decrease the cancer risk; we actually found the opposite. These mice were less equipped to mount a successful immune response to bacteria that increased colon tumors," she said, adding that people should not avoid fish oil; what the research shows is needed are guidelines on dosing.