Optimization of insulin-mediated creatine retention during creatine feeding in humans.
The aim of this study was to determine whether creatine ingested in combination with relatively small quantities of essential amino acids, simple sugars, and protein would stimulate insulin release and augment whole-body creatine retention to the same extent as a large bolus of simple sugars. Seven young, healthy males underwent three randomized, 3-day experimental trials. Each day, 24-h urine collections were made, and on the second day participants received 5 g creatine + water (creatine trial), 5 g creatine + approximately 95 g dextrose (creatine + carbohydrate) or 5 g creatine + 14 g protein hydrolysate, 7 g leucine, 7 g phenylalanine, and 57 g dextrose (creatine + protein, amino acids, and carbohydrate) via naso-gastric tube at three equally spaced intervals. Blood samples were collected at predetermined intervals after the first and third naso-gastric bolus. After administration of the first and third bolus, serum insulin concentration was increased by 15 min (P < 0.05) in the creatine + carbohydrate and creatine + protein, amino acids, and carbohydrate trials compared with creatine alone, and plasma creatine increased more following creatine alone (15 min, P < 0.05) than in the creatine + carbohydrate and creatine + protein, amino acids, and carbohydrate trials. Urinary creatine excretion was greater with creatine alone (P < 0.05) than with creatine + carbohydrate and creatine + protein, amino acids, and carbohydrate. Administration of creatine + protein, amino acids, and carbohydrate can stimulate insulin release and augment whole-body creatine retention to the same extent as when larger quantities of simple sugars are ingested.
Pittas
G
G
Centre for Integrated Systems Biology and Medicine, School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK. gpittas@hotmail.com
Hazell
M D
MD
Simpson
E J
EJ
Greenhaff
P L
PL
D000328:Adult; D000596:Amino Acids / Q000008:administration & dosage; D003401:Creatine / Q000378:metabolism* / Q000494:pharmacology*; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage*; D004311:Double-Blind Method; D005947:Glucose / Q000008:administration & dosage; D006801:Humans; D007328:Insulin / Q000097:blood*; D008297:Male; D012016:Reference Values; D055815:Young Adult
D000596:Amino Acids; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D007328:Insulin; D005947:Glucose; D003401:Creatine