The Natural Fish Oil Concentrate used in this softgel is molecularly distilled and 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 digest. The Fish Oil Concentrate is primarily derived from sardines, anchovies and mackerel.