Alpha lipoic acid, or thioctic acid, is synthesized in the body from amino acid methionine. Plays an antioxidant function and participates as a cofactor in cellular energy supply, activating the mitochondrial enzymes pyruvate dehydrogenase and alpha-ketoglutarate, the first involved in the oxidation of pyruvate, otherwise reduced to lactic acid, the second in the oxidation of alpha-ketoglutarate, an important intermediate of cellular breathing and metabolism of amino acids. In food is found in meat (example: liver) and in yeast.