Choose supplements from reliable manufacturers that certify the supplement is free from contamination with mercury, PCBs, dioxins or pesticides.
Only take fish oil supplements under the supervision of your doctor if you have type-2 diabetes, as it may cause increases in blood sugar levels.
Some preliminary research shows that fish oil supplements may increase the risk for prostate cancer, according to Harvard Medical School, which recommends getting your omega-3 fats from whole foods, such as fish, instead of supplements. The potential benefits from omega-3 fats may be due to the combination of nutrients in fish, rather than just the omega-3 fats in the fish oil.
Omega-3 supplements may have an anti-inflammatory effect, helping to reduce pain in a similar way to NSAIDs, according to a study published in Surgical Neurology in April 2006. They may also help decrease leg aches caused by problems with blood flow to the extremities, although research results in this area are still preliminary and conflicting.