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Amino Acids. 2016 Jul;48(7):1707-16. doi: 10.1007/s00726-016-2241-0. Epub 2016 Apr 30.

Determination of the safety of leucine supplementation in healthy elderly men.

Author information

1
Department of Pediatrics, University of British Columbia, Vancouver, Canada.
2
Division of Geriatric Medicine, Department of Medicine, Vancouver General Hospital, University of British Columbia, Vancouver, Canada.
3
Department of Pediatrics, University of British Columbia, Vancouver, Canada. relango@cfri.ubc.ca.
4
Child and Family Research Institute, BC Children's Hospital, Vancouver, Canada. relango@cfri.ubc.ca.
5
School of Population and Public Health, University of British Columbia, Vancouver, Canada. relango@cfri.ubc.ca.

Abstract

Leucine, a branched-chain amino acid (BCAA), has been shown to stimulate muscle protein synthesis, and thus has been proposed to prevent age-related muscle atrophy (sarcopenia). Therefore, leucine supplementation may have potential benefits in elderly populations to preserve muscle mass. The tolerable upper intake level (UL) for leucine intake in young men has recently been determined to be 500 mg kg(-1) day(-1), and increases in blood ammonia concentrations were seen at intake levels above 500 mg kg(-1) day(-1); the UL for leucine in elderly is unknown. The objective of the current study was to determine the safety of leucine supplementation in healthy elderly men. Six healthy elderly men (72.2 ± 3.5 years) received graded stepwise increases in leucine intakes ranging from 50 to 750 mg kg(-1) day(-1), on eight separate study days. Plasma and urinary biochemical variables, including blood ammonia, and an oral primed-continuous protocol of L-1-(13)C-Leucine was performed. Blood ammonia concentrations above normal values (35 µmol/L) were observed at leucine intakes >550 mg kg(-1) day(-1). Leucine oxidation measured as a F(13)CO2 (rate of label tracer oxidation) increased with increasing leucine intakes and started to plateau after 450 mg kg(-1) day(-1). Two-phased linear regression analysis of the F(13)CO2 data revealed a breakpoint of 431 mg kg(-1) day(-1) (R (2) = 0.73), suggesting that the upper limit to oxidize leucine was reached at that point. Taking the data together the upper limit for leucine intake in healthy elderly could be set similar to young men at 500 mg kg(-1) day(-1) or ~35 g/day for an individual weighing 70 kg.

TRIAL REGISTRATION:

ClinicalTrials.gov NCT02095080.

KEYWORDS:

Ammonia; Elderly; Leucine; Oxidation; Upper limit

PMID:
27138628
DOI:
10.1007/s00726-016-2241-0
[Indexed for MEDLINE]

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