The mice [exposed to bacteria that increase risk of colitis and colon cancer] that had received medium and high dosages of the omega-3 fatty acid developed late-stage colon cancer, the researchers found. The other mice did not.
Fenton said the results show a high dose of fish oil beyond what you'd normally get from a healthy Diet
has the potential to suppress the immune response to a virus or bacteria if you already have a compromised immune system.
And for sufferers of inflammatory bowel disease, high doses of fish oil could increase the severity of inflammation, possibly leading to the development of abnormal and even cancerous cells, she said.
Most people don't get a lot of omega-3 acids in their diets, Fenton said, even though the acids are known to lower triglycerides and reduce the risk of cardiovascular disease. When supplements are taken in moderation to make up for deficiencies, they can be good for health.
But the danger comes when too much is taken by people who don't need supplementation, she said.