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Plasma Free Amino Acids of Children Consuming as Diet with Uneven Distribution of Protein Relative to Energy¹

Instituto de Investigacion Nutricional, Lima, Peru, and Departments of Pediatrics (School of Medicine) and International Health (School of Hygiene and Public Health), The Johns Hopkins University, Baltimore, Maryland 21205

Adequate N retention and growth have been demonstrated in children consuming diets in which the total daily protein is fed in a single meal, energy intake being spread over a 14 hour period. To elucidate how adequate protein nutriture continues when protein is not consumed in parallel to energy, plasma free amino acids were measured in 11 children fed a casein-modified cow's milk based diet providing all protein (6.4% of calories) in one feeding, while energy was evenly distributed among five feedings. Children were fed at 0800 hours, 1200 hours, 1500 hours (protein-containing meal), 1900 hours, and 2200 hours. Fasting plasma aminograms were determined in all 11 children. During a long-term growth study with the diet, six children had additional determinations 3 and 4 hours after the first feeding on the same day on which the fasting sample was obtained; samples prior to and 3 and 4 hours after the 1500 hour feeding were obtained on a different day. In a seventh child, all six samples were obtained on a single day. Fasting values for total amino acids (TAA), total essential amino acids (TEAA) and TEAA/TAA, Val, Ile and Pro were elevated in most cases, a pattern seen in children fed high protein diets. The 1100 hour and 1200 hour samples showed a marked decrease in TAA, TEAA and TEAA/TAA. A further drop at 1500 hour produced a pattern characteristic of protein deficiency. Following the protein containing meal, TAA increased 50–100%, TEAA 100–200%, with disproportionate increases in Leu, Ile, Val and Pro. The persistence of this pattern in some cases up to 17 hours suggested that EAA were available for protein synthesis when additional energy was subsequently consumed. An aminogram characteristic of protein deficiency was seen only 18–20 hours after the last protein intake.

KEY WORDS: • plasma amino acids • infant nutrition • dietary protein distribution

¹ Supported by Research Grant AM-09980 and Research Fellowship 1F22 AM-03252-01 from the National Institutes of Health, U.S.P.H.S., by a grant from the Nutrition Foundation, and by Research Contract csd/2946 with the Agency for International Development, U.S. Department of State.

² Address reprint requests to Dr. William MacLean, School of Hygiene and Public Health, Room 6021, 615 North Wolfe Street, Baltimore, Maryland 21205.

Manuscript received 14 July 1975.