title: L-Arginine but not L-glutamine likely increases exogenous carbohydrate oxidation during endurance exercise.
abstract: The addition of L-arginine or L-glutamine to glucose-electrolyte solutions can increase intestinal water, glucose, and sodium absorption in rats and humans. We evaluated the utility of L-arginine and L-glutamine in energy-rehydration beverages through assessment of exogenous glucose oxidation and perceptions of exertion and gastrointestinal distress during endurance exercise. Eight cyclists rode 150 min at 50% of peak power on four occasions while ingesting solutions at a rate of 150 mL 15 min(-1) that contained (13)C-enriched glucose (266 mmol L(-1)) and sodium citrate ([Na(+)] 60 mmol L(-1)), and either: 4.25 mmol L(-1) L-arginine or 45 mmol L(-1) L-glutamine, and as controls glucose only or no glucose. Relative to glucose only, L-arginine invoked a likely 12% increase in exogenous glucose oxidation (90% confidence limits: ± 8%); however, the effect of L-glutamine was possibly trivial (4.5 ± 7.3%). L-Arginine also led to very likely small reductions in endogenous fat oxidation rate relative to glucose (12 ± 4%) and L-glutamine (14 ± 4%), and relative to no glucose, likely reductions in exercise oxygen consumption (2.6 ± 1.5%) and plasma lactate concentration (0.20 ± 0.16 mmol L(-1)). Effects on endogenous and total carbohydrate oxidation were inconsequential. Compared with glucose only, L-arginine and L-glutamine caused likely small-moderate effect size increases in perceptions of stomach fullness, abdominal cramp, exertion, and muscle tiredness during exercise. Addition of L-arginine to a glucose and electrolyte solution increases the oxidation of exogenous glucose and decreases the oxygen cost of exercise, although the mechanisms responsible and impact on endurance performance require further investigation. However, L-arginine also increases subjective feelings of gastrointestinal distress, which may attenuate its other benefits.
authors: School of Sport and Exercise, The Institute of Food, Nutrition, and Human Health, Massey University, PO Box 756, Wellington, New Zealand. d.s.rowlands@massey.ac.nz
authors: David S
authors: DS
authors: Rowlands
authors: Jim
authors: J
authors: Clarke
authors: Jackson G
authors: JG
authors: Green
authors: Xiaocai
authors: X
authors: Shi
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001120:Arginine / Q000008:administration & dosage*; D001642:Bicycling / Q000502:physiology*; D050260:Carbohydrate Metabolism / Q000187:drug effects / Q000502:physiology*; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000378:metabolism*; D004311:Double-Blind Method; D005973:Glutamine / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D010084:Oxidation-Reduction / Q000187:drug effects; D010807:Physical Endurance / Q000187:drug effects / Q000502:physiology*
chemical_list: D004040:Dietary Carbohydrates; D005973:Glutamine; D001120:Arginine