Creatine Supplementation Increases Total Body Water Without Altering Fluid Distribution.
Level 2 - randomized trial
Individual randomized controlled trial
What was done
Thirty-two resistance-trained adults (16 men, 16 women) were randomized to receive either creatine monohydrate or a sucrose placebo for 28 days (loading: 25 g/day for 7 days; maintenance: 5 g/day for 21 days). Muscle creatine concentration was measured via percutaneous needle biopsy of the vastus lateralis. Total body water (TBW), extracellular water (ECW), and intracellular water (ICW) were measured via deuterium oxide and sodium bromide dilution analyses before supplementation, after the loading phase, and after the maintenance phase.
What was found
The abstract reports no numerical values, effect sizes, or confidence intervals. It reports that the creatine group experienced statistically significant increases in muscle creatine concentration, body mass, and TBW, while fluid distribution across compartments was not altered. The placebo group experienced a small but statistically significant increase in TBW only.
Why it matters
The study demonstrates that body mass gains and water retention from creatine supplementation occur proportionately across fluid compartments rather than causing abnormal extracellular fluid retention or edema.
Limits
The abstract reports zero numerical data or effect sizes. The sample size is small (32 participants total, split across two arms and sexes), and findings in young, resistance-trained individuals may not generalize to other populations or clinical cohorts.
Cited by
- contradicts A creatine loading phase (20-30 g/day for 5-7 days) acutely increases water retention for 3-5 days, after which maintenance dosing of 3-5 g/day moves the water intracellularly into muscle.