Urinary creatine and methylamine excretion following 4 x 5 g x day(-1) or 20 x 1 g x day(-1) of creatine monohydrate for 5 days.
Level 2 - randomized trial
Individual crossover trial evaluating dosing strategies in healthy humans.
PubMed 19437189 · doi:10.1080/02640410902838237
What was done
In a crossover study, 9 male participants completed two 5-day creatine monohydrate supplementation regimens separated by a 6-week washout period: 4 x 5 g/day vs. 20 x 1 g/day (both totaling 20 g/day). Twenty-four-hour urine samples were collected on 2 baseline days, during 5 days of supplementation, and for 2 days post-supplementation. Creatine was measured using high-performance liquid chromatography and methylamine using gas chromatography.
What was found
Urinary creatine excretion was significantly lower with 20 x 1 g/day (49.25 ± 10.53 g) than with 4 x 5 g/day (62.32 ± 9.36 g; P < 0.05). Total methylamine excretion over days 3–7 (n = 6) was also significantly lower with 20 x 1 g/day (8.61 ± 7.58 mg) compared to 4 x 5 g/day (24.81 ± 25.76 mg; P < 0.05).
Why it matters
Dividing creatine intake into smaller, more frequent doses reduces urinary loss and byproduct excretion, suggesting higher retention for the same total daily dose.
Limits
The sample size was very small (n = 9 total, n = 6 for methylamine), conducted exclusively in males, and the abstract does not state whether treatment order was randomized. Direct muscle creatine content was not measured.
Cited by
- supports A study showed that consuming 1 g of creatine every 30 minutes up to a 20 g total dose resulted in greater bodily creatine retention than a bolus dose.