SATURDAY, April 30 (HealthDay News) -- Aspirin's ability to prevent potentially deadly blood clots may be hindered by elevated levels of fatty acids in the bloodstream, a new study suggests.

It's common for doctors to prescribe aspirin as a blood thinner for patients at high risk of a heart attack. Aspirin inhibits the activity of the COX-1 enzyme, which plays a role in blood clot formation.

It's known that free fatty acids -- released into the bloodstream during the breakdown of fat cells -- also inhibit COX-1 activity.

In this study, researchers looked at the effect that two fatty acids -- oleic acid and palmitic acid -- have on aspirin's effectiveness in preventing clots. Oleic acid is found in various animal and vegetable fats, and palmitic acid is one of the most common saturated fats found in plants and animals.

The researchers found that both types of fatty acids interfered with aspirin's ability to reduce the risk of clots, according to an American Heart Association news release.

The study was to be presented Saturday at the American Heart Association's Arteriosclerosis, Thrombosis and Vascular Biology 2011 Scientific Sessions in Chicago.

Because this study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.

More information

The U.S. Food and Drug Administration has more about the use of aspirin to prevent heart attack or stroke.