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Variable Intensity Exercise Increases Protein Requirements in Active Male and Female Adolescents as Determined by the Indicator Amino Acid Oxidation (IAAO) Technique
Author(s) -
Brooks Jahmal C,
Volterman Kim A,
West Daniel W,
CourtneyMartin Glenda,
Pencharz Paul B,
Moore Daniel R
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.652.11
Subject(s) - phenylalanine , ingestion , zoology , amino acid , medicine , intensity (physics) , physical activity , lean body mass , chemistry , biology , physical therapy , body weight , biochemistry , physics , quantum mechanics
Adolescence is characterized by the greatest increase in linear growth and accrual of fat‐free mass (FFM) during the life cycle. This growth spurt is optimized by adequate energy and protein intake. Active adolescents also display a greater FFM than their sedentary peers with the sexual dimorphism of puberty leading to a greater total gain in males than females. Given current evidence which suggest that protein requirement is higher in active adults than their sedentary counterparts, we aimed to determine the protein requirements of active, growing adolescents by utilizing the minimally invasive Indicator Amino Acid Oxidation (IAAO) technique. Fourteen active male (n=7; 13±0.6 years; 171±2.8 cm; 57.3±4.2 kg; 48.4±5.0 kg FFM; 0.3±0.2 years from peak height velocity (PHV); means±95% CI) and female (n=7; 11±0.4 years; 159±3.3 cm; 51.6±8.1 kg; 41.5±6.7 kg FFM; 0.5±0.4 years from PHV; means±95% CI) participants each underwent 6 metabolic trials that included an acute bout of a variable intensity exercise (modified Loughborough Intermittent Shuttle Test) followed by the ingestion of 8 hourly meals providing a variable amount of protein (0.2 – 2.67 g·kg −1 ·d −1 ), 6 g·kg −1 of carbohydrate, and sufficient energy to match habitual intake. Protein was provided as crystalline amino acid mixtures modeled on the basis of egg protein, with the exception of tyrosine (40 mg·kg −1 ·d −1 ) and phenylalanine (30.5 mg·kg −1 ·d −1 of which 5.46 mg·kg −1 was L‐[ 13 C] phenylalanine over the final 4 drinks). After the determination of breath 13 CO 2 enrichment by continuous‐flow isotope ratio mass spectrometry and CO 2 production by indirect calorimetry, the estimated average requirement (EAR) was determined from the breakpoint of the 13 CO 2 excretion (F 13 CO 2 ) after application of a bi‐phase linear regression. Preliminary analysis of F 13 CO 2 revealed breakpoints of 1.53 g·kg −1 ·d −1 (r 2 = 0.57) and 1.34 g·kg −1 ·d −1 (r 2 = 0.69) for males and females respectively. When normalized to FFM, the breakpoints were 1.97 ± 0.33 g·kg FFM −1 ·d −1 (r 2 = 0.68) and 1.45 ± 0.22 g·kg FFM −1 ·d −1 (r 2 = 0.63) for males and females, respectively. The breakpoints derived herein exceed current estimated breakpoint values using the IAAO method for sedentary adults and children (0.93 g·kg −1 ·d −1 , and 1.3 g·kg −1 ·d −1 respectively). Adjusting for the upper 95% CI, a recommended dietary allowance (RDA) was determined to be 1.83 g·kg −1 ·d −1 and 1.54 g·kg −1 ·d −1 for males and females respectively. Our estimate of the RDA in active adolescents exceeds the current protein RDA based on the factorial estimate of nitrogen balance for adolescents (0.9 g·kg −1 ·d −1 ), suggesting that variable intensity exercise increases daily protein requirements in active adolescents (and especially males) to potentially support greater FFM development and/or the replenishment of exercise‐induced oxidative losses. Support or Funding Information Supported by the Ajinomoto Innovation Alliance Program.