Fish oil — long encouraged by doctors as a supplement to support heart and joint health, among other benefits — induced severe colitis and colon cancer in mice in research led by Michigan State University and published October 2010 in the journal Cancer Research.
Don’t take this the wrong way though, this study seems to serve more as a reminder too much of anything can be bad for you. It’s also nice to contrast the information we hear, which is usually positive related to fish oil — omega-3 fatty acids. The fact of the matter is that the amount of omega-3 fatty acids we need for optimal functioning is still not known, so don’t go crazy with the supplements.
Fenton cautions people may not need to avoid fish oil; what the research shows is needed are guidelines on dosing. With any nutrient, there is a “bell curve” effect. On the left of the curve are those deficient in a nutrient; on the right are those in excess.
She said people already receiving enough omega-3 fatty acids through their normal diet and foods have no need for added supplementation.