L Carnitine Side Effects & Risks L carnitine is primarily synthesized in the liver from the amino acids lysine and methionine through a series of four enzymatic reactions, with the liver and kidneys converting the precursor butyrobetaine into active JCI l Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans L'carnitine prevents metabolic steatohepatitis in obese diabetic KK'A^{y< sup> mice}