| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Body Composition Independent RCTs (e.g., Wilborn et al., 2004) examined ZMA's effect on lean body mass and fat mass in resistance-trained males and found no significant changes in body composition compared to placebo over 8 weeks of supplementation. The original industry-funded study suggested favorable changes, but this has not been independently replicated. | Improves (the measure goes up) | Small effect | 55 people |
Supplement
ZMA is a combination of zinc, magnesium and vitamin B6, nutrients the body uses for enzyme activity, muscle function and hormone signaling. The evidence is limited for sleep quality, where trials of the magnesium part found modest improvements, especially in older adults and people low in magnesium, though that benefit belongs to magnesium generally, not ZMA itself. Independent trials in well-nourished trained men found no clear difference in testosterone, strength or body composition.
- Updated
- How we grade
- Best evidence
- Grade C
- Conditions studied
- 3
- Outcomes
- 5
- Graded outcomes
- 0014
Evidence by condition
- Strong
- Moderate
- Limited
- Very limited
General
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Sleep Quality The magnesium component of ZMA has modest evidence from multiple human trials supporting improved sleep quality, particularly in older adults and those with low magnesium status. However, this benefit is attributable to magnesium supplementation broadly, not the specific ZMA formulation. No controlled trials have demonstrated that ZMA provides superior sleep benefits compared to equivalent doses of magnesium alone. | Improves (the measure goes up) | Small effect | ||||
| Testosterone Levels One industry-funded RCT (Brilla & Conte, 2000) in NCAA football players reported increased free and total testosterone with ZMA supplementation. However, multiple independent RCTs in resistance-trained males who were not zinc/magnesium deficient found NO significant effect on testosterone levels. The original positive finding has not been replicated by independent researchers, and the evidence overall does not support a testosterone-boosting effect in replete individuals. | Improves (the measure goes up) | Small effect | 100 people |
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Muscle Strength The original patent-holder-funded study reported strength gains in football players supplemented with ZMA. Independent RCTs (e.g., Wilborn et al., 2004) found no significant improvements in muscle strength, power output, or training adaptations compared to placebo in resistance-trained men with adequate zinc and magnesium status. Strength benefits appear limited to individuals correcting an underlying zinc or magnesium deficiency. | Improves (the measure goes up) | Small effect | 85 people |
Aerobic Exercise Performance
- Aerobic Exercise Performance: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Aerobic Exercise Performance Independent studies in trained athletes have found no significant improvement in aerobic exercise performance metrics with ZMA supplementation when participants had adequate baseline zinc and magnesium levels. Any performance benefits observed in other trials are attributed to correcting pre-existing mineral deficiencies rather than a pharmacological effect of the ZMA formulation itself. | Improves (the measure goes up) | Small effect | 50 people |
Body Composition
- Body Composition: improves
Key findings
- Sleep QualityImproves (the measure goes up)
- Testosterone LevelsImproves (the measure goes up)
- Muscle StrengthImproves (the measure goes up)
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- Grade C
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