Many consumers buying over-the-counter omega-3 fatty acid supplements may be getting rancid pills, according to a new study published Sept. 7 by researchers at the George Washington University. Derived from plants (algae) as well as seafood (fish, krill, etc.) , omega-3 supplements—sometimes labeled as fish oil—are often taken because of research that suggests they may provide health benefits.

Rancidity is measured by the amount of oxidation of the oil in the supplement. As supplements become more oxidized, the nutritional benefits delivered to the consumer are reduced.

“Our study suggests many of these supplements are not fresh—and thus may not provide a potential health benefit,” says Leigh A. Frame, associate professor of clinical research & leadership at the GW School of Medicine & Health Sciences and senior author of the study. “The findings also suggest consumers are not getting what they paid for.”

The article, “A Multi-Year Rancidity Analysis of 72 Marine and Microalgal Oil Omega-3 Supplements,” was published in the Journal of Dietary Supplements.

Higher levels of omega-3 have been associated with a wide range of benefits to multiple organs, including the brain and eyes, but the most common reason for its popularity with consumers is to help the cardiovascular system.

The researchers conducted six years of tests on 72 of th