NOW Foods DHA 500 mg Softgels The Natural Fish Oil Concentrate used in this softgel is manufactured under strict quality control standards. It is tested to be free of detectable levels of potentially harmful contaminants (i.e. mercury, heavy metals, PCB"s, dioxins, and other contaminants). Consumption of Omega-3 fatty acids may reduce the risk of coronary heart disease. FDA evaluated the data and determined that, although there is scientific evidence supporting the claim, the evidence is not conclusive.