ATLANTA — Blood levels of trans fatty acids (T.F.A.s) in white adults in the United States declined 58% between 2000 and 2009, according to a study conducted by the Centers for Disease Control and Prevention. The current study provides information for white adults only, and additional C.D.C. studies are under way to examine blood trans fatty acids in other adult race and ethnic groups, children, and adolescents.

The C.D.C. researchers selected participants from the National Health and Nutrition Examination Survey (NHANES) years 2000 and 2009 to examine trans-fatty acid blood levels before and after the Food and Drug Administration’s 2003 regulation, which took effect in 2006, requiring manufacturers of food and some dietary supplements to list the amount of trans fats on the Nutrition Facts Panel of the product label. The researchers said this is the first time the C.D.C. has been able to measure trans fats in human blood.

“The 58% decline shows substantial progress that should help lower the risk of cardiovascular disease in adults,” said Christopher Portier, director of the C.D.C.’s National Center for Environmental Health. “Findings from the C.D.C. study demonstrate the effectiveness of these efforts in reducing blood T.F.A.s and highlight that further reductions in the levels of trans fats must remain an important public health goal.”

The C.D.C. studied four major trans fatty acids to provide a reasonable representation of trans fatty acids in blood: elaidic acid, linoelaidic acid, palmitelaidic acid, and vaccenic acid. The study measured trans fatty acids in 229 fasting adults from the 2000 NHANES and 292 from 2009 NHANES. The study found the overall decrease in trans-fatty acids was 58%. For specific trans-fatty acids, decreases were: elaidic acid (63%), linoelaidic acid (49%), palmitelaidic acid (49%), and vaccenic acid (56%).