Role of L carnitine in exercise training: Anti inflammatory, antioxidant, and metabolic interactions ScienceDirect L Carnitine 3000mg per dose Zenement Food Supplements L Carnitine has become one of our top 5 sellers the last few years and when you review the research, you can see why. L carnitine is a supplement probably more well known if L carnitine is a naturally occurring amino acid structure that is made in the human brain, liver, and kidneys. L carnitine plays a critical role in energy production, as it converts fat into energy.