Blood plasma levels of trans fats among American adults fell sharply since federal rules mandating the declaration of trans fats took effect.

Research illustrating the change was published in a recent issue of Amber Waves published by the U.S. Department of Agriculture. The Department noted that between 2005 and 2010, many food manufacturers reformulated their products to eliminate or reduce trans fat content, in part by because of the labeling requirements.

Researchers from the Economic Research Service of the USDA explored whether dietary advice and food product reformulations resulted in decreased intake of trans fat, comparing blood plasma levels between 1999 and 2010.

Overall, the E.R.S. found blood plasma levels of trans fats fell 53% from 1999-2000 to 2009-10.

“The decline in blood plasma levels of a type of trans fat often found in partially hydrogenated oils was greater (58.6%) than the decline in blood plasma levels of a trans fat often found in dairy products (51.3%),” the USDA said.

An association between higher trans fat levels and elevated risk of cardiovascular disease makes the decrease important, the USDA said. The association is thought to stem from the contribution of trans fats in raising LDL cholesterol.