A Research Letter in last week’s Journal of the American Medical Association reported that blood levels of trans fatty acids, a substance with known adverse metabolic effects, fell 56 percent between 2000 and 2009. The study compared trans fat levels in adult white men in samples from the NHANES studies, a periodic assessment of the heath and well-being of a representative sample of the US population. In 2003, the US Food and Drug Administration required that food companies declare the trans fatty acid content on the nutrition label of foods and dietary supplements. In addition, some community and state health departments have required restaurants to limit TFAs and reductions have been shown in supermarket and restaurant products.