Peer review

A strain of maize, homozygous for the recessive mutant gene,opaque-2, is higher in lysine and tryptophan and has a better balance between leucine and isoleucine than other hybrid lines. Four levels of this corn, 300, 250, 200, and 150 g, were administered to healthy adult human subjects. The regression of daily nitrogen balance on amount of corn consumed was linear and highly significant (P< 0.01). The equation was Ŷ= 4.10X– 943 when Ŷ is nitrogen balance in milligrams and X is grams of corn. Five of six subjects were in nitrogen equilibrium or positive balance when they consumed 300 g ofopaque-2corn and most subjects were in equilibrium with 250 g, but one large man required 350 g. The requirement was related to body size. Supplementation of 200 g of this corn with lysine or tryptophan alone improved nitrogen retention in only one female subject whose requirement for corn was low, whereas methionine did not enhance retention by any subject.Opaque-2maize, therefore, should be a valuable source of protein for population groups who regularly consume large amounts of corn.

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