Creatine vs Glycine
Both are commonly discussed for muscle & recovery. Creatine has the stronger research base (strong evidence), while Glycine is rated moderate.
Evidence last reviewed May 2026
Evidence
🟢Strong Evidence
🟡Moderate Evidence
Research says
Research agrees
Research agrees
Expert mentions
161
3 recommend
176
3 recommend
Studies
20
referenced
20
referenced
Study dose
3000–5000mg
The majority of reviewed trials and meta-analyses used maintenance doses in the 3–5 g per day range of creatine monohydrate, with loading protocols (typically 20 g/day for 5–7 days) used in some studies but considered unnecessary for long-term saturation by expert consensus. Higher doses have been studied in specific clinical contexts but are not typical for general health or performance goals.
3000–15000mg
Sleep studies primarily used 3g (3000mg); the GlyNAC RCT and broader therapeutic reviews reference ranges up to 9–15g daily depending on the health outcome studied. Higher doses have been used in metabolic and aging contexts without notable adverse effects reported.
Best timing
MorningEveningPre-workoutPost-workoutWith foodEmpty stomach
EveningEmpty stomach
Who recommends
Caution
Generally safe
Generally safe
Creatine
Key findings
- ·Multiple meta-analyses consistently show creatine supplementation combined with resistance training increases muscle hypertrophy and strength gains in adults under 50.
- ·A meta-analysis of RCTs found creatine supplementation improved memory performance in healthy individuals, supporting a role in cognitive function beyond athletic performance.
- ·A dedicated meta-analysis on renal outcomes found no evidence of kidney damage from creatine supplementation in healthy populations at standard doses.
Evidence gaps
- ·Evidence in specific populations — including women across the lifespan, children and adolescents, and older adults — is based largely on moderate-quality narrative reviews rather than large, well-controlled trials.
- ·The magnitude and durability of cognitive benefits remain uncertain; most cognitive research is shorter-term and the clinical significance of memory improvements in non-deficient, healthy adults is unclear.
Glycine
Key findings
- ·A randomized clinical trial of GlyNAC (glycine + N-acetylcysteine) in older adults found improvements in glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, and physical function, supporting glycine's role as a key substrate for glutathione synthesis.
- ·Glycine is a well-established biochemical precursor to glutathione, creatine, and collagen — three molecules with broad relevance to aging, muscle function, and tissue integrity.
- ·Glycine may be conditionally essential in older adults and under high physiological demand, as endogenous synthesis appears insufficient to meet total-body requirements in these contexts.
Evidence gaps
- ·Most clinical evidence for glycine uses combination products (e.g., GlyNAC, gelatin + vitamin C), making it impossible to determine how much of the observed benefit is attributable to glycine alone versus co-ingredients.
- ·Long-term supplementation trials in diverse human populations are lacking; existing studies are largely short-term and focused on older adults or athletes, leaving gaps for other demographics including those with chronic disease.