Background: Knowledge of essential amino acid requirements in infants is important because excessive intake of protein can lead to increased long-term morbidity such as obesity. A deficient intake may lead to suboptimal growth and impaired neurodevelopment. The current recommended branched-chain amino acid requirements in infants aged 0-1 mo are based on the amino acid content of human milk. Objective: We quantified the requirements for isoleucine, leucine, and valine for term neonates by using the indicator amino acid oxidation method with [1-13C]phenylalanine as the indicator. Design: Fully enterally fed term infants received randomly graded amounts of isoleucine (5-216 mg · kg-1 · d-1), leucine (5-370 mg · kg -1 · d-1), or valine (5-236 mg · kg -1 · d-1) as part of an elemental formula. Data are expressed as means ± SDs. Results: Eighty-three Asian, term neonates (mean ± SD birth weight: 3.3 ± 0.4 kg; gestational age: 39.4 ± 1.3 wk) were studied at a postnatal age of 13 ± 5 d. Mean requirements for isoleucine, leucine, and valine (measured in boys only) were 105 mg · kg-1 · d-1 (r2 = 0.61, P < 0.001), 140 mg · kg-1 · d-1 (r 2 = 0.26, P < 0.01), and 110 mg · kg-1 · d-1 (r2 = 0.35, P = 0.001), respectively. Conclusions: Current human milk-based recommendations for isoleucine and valine in term infants aged 0-1 mo are correct. However, the current recommendation for leucine (166 mg · kg-1 · d-1) is higher than the mean requirement of 140 mg · kg-1 · d-1 that we determined in this study. This trial was registered at www.trialregister. nl as NTR1610
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