L-carnitine plays a critical role in transporting long-chain fatty acids into mitochondria where they are oxidized to produce energy. It is produced in the liver and kidneys from amino acids but is also obtained through meat consumption. L-carnitine supplementation may benefit male infertility, aging, physical performance, end-stage renal disease, type 2 diabetes, cardiovascular disease, and peripheral arterial disease. Side effects are mild but include nausea and "fishy" odor and it may interact with blood thinners.