Effects of methionine, cystine and taurine on plasma cholesterol level in rats fed a high cholesterol diet.

Abstract

Currently it is recognized that the plasma cholesterol concentration is significantly influenced by the kind and amount of dietary protein in experimental animals and humans.1>2) Earlier experiments demonstrated that sulfur-containing amino acids (SAA) such as methionine, cysteine, and cystine have cholesterol-lowering effects in rats fed a low protein diet containing cholesterol.3) However, the effects of dietary proteins on plasma cholesterol levels cannot be explained simply by the amount of total SAA contained in the proteins, because, for instance, the plasma cholesterol concentration of animals fed soy protein diets is always lower than that of animals fed milk casein diets4) although the casein contains more total SAA than soy protein. Milk casein is a unique protein among many dietary proteins since a large portion of the total SAAis methionine and the cystine content is extremely low.5)