Identification of TMAO producer phenotype and hostdietgut dysbiosis by carnitine challenge test in human and germ free mice Gut Did you know L carnitine, a vital amino acid, is naturally produced by your body and found in various foods? While acetyl L carnitine (ALCAR) can be a beneficial supplement for some, most people get Intestinal microbiota metabolism of l carnitine, a nutrient in red meat, promotes atherosclerosis Nature Medicine When to take L carnitine: Dosage, forms, and side effects