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Effects of age and sex on dietary protein requirement: Comparison of stable isotope and nitrogen balance data at protein intakes that span the range of adequacy
Author(s) -
Conley Travis Blair,
Lim Eunjung,
Yarasheski Kevin E.,
Campbell Wayne W.
Publication year - 2011
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.25.1_supplement.983.24
Subject(s) - nitrogen balance , leucine , nitrogen , chemistry , postprandial , zoology , protein metabolism , metabolism , endocrinology , biology , amino acid , biochemistry , organic chemistry , insulin
Research suggests changes in leucine oxidation (leu ox ) with feeding may reflect protein requirement of adults. This study assessed the relationship between leucine kinetics and nitrogen balance. 34 younger (n=18, 22–46 y) and older (n=16, 63–81 y) men and women completed three 18‐d trials with protein intakes of 0.50, 0.75, or 1.00 g protein•kg BW −1 •d −1 . Postabsorptive (PA) and postprandial (PP) leucine kinetics were quantified using 1‐[ 13 C]leucine. Nitrogen balance was determined using nitrogen data from food composites and urine and fecal collections. Protein requirement was estimated from nitrogen balance data via linear regression of protein intake with inverse prediction. Age and sex did not affect protein requirement. Among all subjects and protein intakes, nitrogen balance was correlated with PP leu ox (r = 0.39) (P<0.05 for all results), PP leucine balance (r = 0.60), net leucine balance (r = 0.49) and the change in leu ox from the PA to PP state (r = 0.49). At the highest protein intake, the change in leu ox from the PA to PP state was inversely correlated with protein requirement (r = −0.39). Collectively, these findings associate feeding induced changes in leucine oxidation with nitrogen balance based estimates of protein requirement and support a comparable protein requirement among younger and older adults. Grant Funding Source : NIH RO1 AG15750, UL1 RR025761 , and RR000954 , and USDA 98‐35200‐6151, Ingest Behav Res Ctr.