R. A. Koeth et al., “Intestinal Microbiota Metabolism of L–Carnitine, a Nutrient in Red Meat, Promotes Atherosclerosis,” Nature Medicine 19, no. 5 (May 2013): 576–85; W. H. Tang et al., “Intestinal Microbial Metabolism of Phosphatidylcholine and Cardiovascular Risk,” New England Journal of Medicine 368, no. 17 (April 25, 2013): 1575–84.