Consumer Reports put more than a dozen popular brands to the test.
Many take fish-oil capsules every day. Fish-oil supplements are omega-3s, and those are important for your heart health.
Consumer Reports tested 15 top-selling brands purchased in the New York metropolitan area.
"All did have the amount of omega-3 fatty acids promised on the label," said Dr. John Santa, Consumer Reports. "And the levels of dioxin-like PCBs and other contaminants were below the limits set by the US Pharmacopoeia."
But with four brands, at least one sample had total PCB levels in amounts that could require warning labels under a strict California law.
And with Kirkland Signature's enteric-coated capsules, the coating didn't disintegrate properly. That can give a fishy aftertaste.
However, Consumer Reports did find nine brands that met all the quality standards.
Of those, the least-expensive is Wal-Mart's Spring Valley brand. The recommended dose costs just 17 cents per day.
"Omega-3 fatty acids can reduce the risk of heart attacks and stroke," said Dr. Santa. "But most people can get enough by eating fatty fish at least twice a week."
That includes salmon and sardines.
But for those who don't like fish, many wonder about dosage, as seemingly all the manufacturers have a different take on it.
Many health experts recommend that it's safe to take between 1,000 and 2,500 milligrams a day.