ARS | Publication request: Influence of Dietary Sulfur-Containing Amino Acids on the Bioavailability to Rats of Zinc in Corn Kernels

Submitted to: Nutrition Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 12, 1996
Publication Date: N/A

Interpretive Summary: Improving the bioavailability of zinc in cereal grains and grain-based food products is critical because cereals will become increasing important sources of zinc as people understand the USDA food pyramid and accept current dietary recommendations calling for increased consumption of cereals and other plant foods. Cereal grains and grain-based products provide only about 13% of the zinc consumed by people in the USA, and much of the zinc may not be absorbed because of antinutritional factors in the diet. The present study indicates that zinc bioavailability may be enhanced up to 33% by dietary supplements of methionine or cysteine, which are indispensable amino acids that contain sulfur. These amino acids increased the absorption of dietary zinc provided either as an inorganic salt or that which occurred naturally in corn kernels. Selection of seeds and grains with increased amounts of methionine may overcome the adverse effects of antinutrients on zinc bioavailability and thereby increase the nutritional value of the foods and improve the nutritional health of people.

Technical Abstract: A whole-body radioassay method was used to assess effects of supplemental dietary amino acids on absorption by rats of zinc in kernels of two corn varieties labeled either intrinsically or extrinsically with 65Zn. Corn genotypes were normal corn (Nor-corn) with one row of cells in the aleurone layer of the kernel and a variety (Mal-corn) that had multiple rows of cells in the aleurone. In experiment 1, rats fed a basal diet containing 15% soy protein absorbed 64% of the 65Zn provided extrinsically in test meals. When provided test meals containing intrinsically labeled Nor-corn or Mal-corn kernels, the rats absorbed 64 and 57% of the intrinsic 65Zn, respectively. In rats fed diets containing supplemental lysine, methionine, or both lysine and methionine, absorption of extrinsic 65Zn averaged 69, 82, and 86% of the dose, respectively. In experiment 2, rats fed the basal diet absorbed 57 and 53% of the intrinsic 65Zn in Nor-corn or rMal-corn kernels, respectively, but rats fed supplemental methionine or crysteine absorbed 73% of the intrinsic 65Zn provided in either the Nor- corn or Mal-corn kernels. Supplemental sulfur-containing amino acids fed to marginally zinc deficient rats enhanced the absorption of 65Zn provided either extrinsically as zinc sulfate or intrinsically in corn kernels.