Does dietary creatine supplementation play a role in skeletal muscle metabolism and performance?
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing mechanistic and trial data without systematic review methodology
PubMed 10919967 · doi:10.1093/ajcn/72.2.607S
What was done
This narrative review synthesized human trial and metabolic data examining the effects of dietary creatine monohydrate supplementation (typically 20 g/d for 5–6 days) on skeletal muscle total creatine and phosphocreatine concentrations, anaerobic ATP resynthesis, and performance during short-term, high-intensity exercise.
What was found
Ingestion of creatine monohydrate at 20 g/d for 5–6 days increased skeletal muscle total creatine concentration by approximately 25 mmol/kg dry mass, with approximately 30% stored as phosphocreatine. Muscle creatine uptake positively correlated with performance improvements in repeated bouts of maximal exercise. Doses exceeding 20–30 g/d for 5–6 days showed no additional benefit. Individuals with baseline muscle total creatine near 150 mmol/kg dry mass showed no uptake, phosphocreatine resynthesis, or performance improvements. Loss of ATP during heavy exercise decreased despite increased work output. Creatine uptake was enhanced when combined with exercise and carbohydrate ingestion.
Why it matters
It clarifies the metabolic basis of creatine's ergogenic effect—enhanced ATP resynthesis via phosphocreatine availability—and establishes an upper biological ceiling where individuals with high baseline muscle creatine do not benefit from supplementation.
Limits
The abstract describes a narrative review without systematic search criteria or reported participant sample sizes. Effects are specific to short-term, high-intensity anaerobic exercise and 5–6 day loading protocols, with no data on long-term outcomes or non-athletic clinical populations.
Cited by
- supports Creatine supplementation increases intramuscular phosphocreatine, which maintains ATP levels during muscle contractions and delays reliance on slower energy pathways.