10 Mechanisms by Which Amino Acids May Enhance Mineral Absorption in Animals

Abstract

Both macro- and trace minerals of the diet face similar barriers to their absorption. Minerals residing in the lumen of the GI tract, whether it be the rumen, stomach, small or large intestine of an animal, have to cross the apical and basolateral membranes of enterocytes or perhaps the tight junctions between cells of the epithelium layer to enter the interstitial space below the epithelium. Once there they can diffuse into the venous blood of the GI tract in order to reach the cells of the body requiring the minerals for various functions. Considerable evidence suggests that amino acids can enhance the absorption of minerals, particularly the trace minerals. However, the exact mechanisms by which amino acids enhance mineral absorption remain elusive. In this presentation, the role dietary amino acids may play in forming ionic and hydrogen bonds with trace minerals to enhance their solubility over the absorptive epithelium is discussed. In addition, minerals covalently bonded to amino acids have been utilized as a means of enhancing trace mineral absorption, particularly for Cu, Fe, Zn and Mn. These forms of trace minerals can be more effectively absorbed than traditional sulfate forms of these minerals. It has been suggested the amino acid bonding to the trace mineral works by preventing formation of insoluble mineral complexes with dietary chelators within the lumen of the GI tract. It has also been suggested that the amino acid -mineral complex can utilize the more efficient amino acid transporters to cross the apical membrane of the enterocytes instead of the usual mineral transport mechanisms for each mineral. The evidence for each of these mechanisms will be discussed along with the possible repercussions these mechanisms might have on mineral requirements of the animal.