Potential Adverse Effects of L Carnitine Marnys Ever heard of Fish Odor Syndrome? Its a rare condition where the body cant break down trimethylamine a compound found in foods like fish, eggs, and beans. This leads to a strong, fish like smell L Carnitine Linus Pauling Institute Oregon State University What are the benefits and side effects of L carnitine (Levocarnitine)? When a 12 month old boy in Portugal developed an unexpected and persistent smell similar to rotting fish, his parents were unsettled. The child appeared healthy, showed no signs of infection, and behaved normally.