Optimization of insulin-mediated creatine retention during creatine feeding in humans.
Level 2 - randomized trial
Randomized crossover trial in humans
PubMed 20035494 · doi:10.1080/02640410903390071
What was done
Seven young, healthy men completed three randomized, 3-day crossover trials. On the second day of each trial, participants received one of three treatments via naso-gastric tube at three equally spaced intervals: 5 g creatine + water; 5 g creatine + approximately 95 g dextrose; or 5 g creatine + 14 g protein hydrolysate, 7 g leucine, 7 g phenylalanine, and 57 g dextrose. Blood samples were collected after the first and third bolus, and 24-hour urine collections were measured daily to assess whole-body creatine retention.
What was found
Serum insulin concentration increased by 15 minutes (P < 0.05) in both the creatine + carbohydrate and creatine + protein/amino acids/carbohydrate trials compared with creatine alone. Plasma creatine increased more following creatine alone at 15 minutes (P < 0.05) than in either combination trial. Urinary creatine excretion was greater with creatine alone than with either combination trial (P < 0.05). Specific numerical values for blood concentrations and urinary excretion were not reported in the abstract.
Why it matters
Combining protein hydrolysate and essential amino acids with moderate carbohydrate stimulates insulin-mediated whole-body creatine retention as effectively as a large simple-sugar dose, allowing lower sugar intake during creatine supplementation.
Limits
The sample size was very small (n = 7) and limited to young healthy males. Treatments were administered via naso-gastric tube rather than normal oral ingestion, and intramuscular creatine levels were not directly measured.
Cited by
- supports Taking creatine with food or carbohydrates increases its absorption via insulin-mediated mechanisms.