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Nutritional Value of Normal, Opaque-2 and Sugary-2 Opaque-2 Maize Hybrids for Infants and Children

2. Plasma Free Amino Acids¹

Instituto de Investigacion Nutricional, Apartado 55, Miraflores (Lima), Peru and Gastroenterology and Nutrition Unit, Department of Pediatrics, School of Medicine, The Johns Hopkins University, Baltimore, MD 21205

Plasma free amino acids of convalescent malnouished infants and children were determined before the 3 and 4 hours after the first meal of the 27th day of maize endosperm (E) or whole kernel (WK) meal consumption. Three varieties of E—normal, opaque-2 (o₂) or sugary-2 opaque-2 (su₂o₂)—had been consumed in six different sequences during consecutive 9-day periods by six subjects; the same protocol was followed for the corresponding WK meals. Plasma aminogram was expected to reflect the effects of 28 days of maize consumption and 8 days of the last variety consumed, particularly the latter. The significantly poorer absorptions of nitrogen (N) from the E meals were reflected in lower fasting molar ratios of total essentials to total amino acids (TEAA/TAA = 0.192 versus 0.229 for WK). Fasting leucine/TEAA molar ratio was consistently elevated, notably after normal maize. With the exception of one very low (0.067) and one moderately low (0.120) lysine/TEAA ratio, fasting values did not suggest a first-limiting amino acid. Striking postprandial falls singled lysine out as first-limiting in five, possibly six, studies, tryptophan in two studies (normal E and su₂o₂ WK) and probably isoleucine in one o₂ WK study. In two studies (su₂o₂ E and normal WK), lysine and tryptophan seemed equally limiting. The improved lysine and tryptophan contents of o₂ and su₂o₂ maize still leave one or both of these, and possibly isoleucine, as potentially first-limiting for small children.

KEY WORDS: • plasma free amino acids • opaque-2 maize • sugary-2 opaque-2 maize

¹ Supported by Research Contract AID/ta-C-1286 with the Agency for International Development, U.S. Department of State, by Research Grant HD-10111 from the National Institutes of Health, U.S.P.H.S. and by a grant from the Middendorf Foundation, Baltimore, MD.

Manuscript received 5 September 1979.