NOW DHA-500 is double strength, moleculary distilled, and enteric coated. This fish oil concentrate is manufactured under strict quality control standards. It is tested to be free of potentially harmful levels of contaminants such as PCBs, dioxins, mercury and other heavy metals. Those who experience nausea or reflux from other fish oils should find this enteric-coated, odor-controlled softgel easier to tolerate. Supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease.