The Natural Fish Oil Concentrate used in this softgel is manufactured under strict quality control standards.It is tested to be free of potentially harmful levels of contaminants (i.e. mercury, heavy metals, PCB's, dioxins, and other contaminants). Those who experience nausea or reflux from other fish oils should find this enteric coated, odor controlled softgel easier to tolerate. From the FDA's website: Supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease.