Supplements: ZMA (Zinc, Magnesium, B6)
Wilborn et al. (2004, PMID 15182367): ZMA supplementation in resistance-trained athletes produced no significant changes in testosterone, IGF-1, strength, or body composition vs placebo in an independent 8-week RCT.
| Measure | Value | Unit | Notes |
|---|---|---|---|
| Evidence Tier | 3 | tier | Weak as testosterone booster; Tier 2 for deficiency correction in deficient athletes |
| Zinc Dose in ZMA | 30 | mg | Daily RDA for adult males is 11mg; ZMA delivers ~2.7x RDA |
| Magnesium Dose in ZMA | 450 | mg | RDA is 400-420mg/day; 450mg as aspartate — bioavailability advantage over oxide |
| Zinc Deficiency in Athletes | 25–35 | % prevalence | High-sweat, endurance, and weight-class athletes have elevated zinc loss |
| Testosterone Increase (Brilla 2000) | +32.4 | % | Industry-funded original study; never replicated independently |
| Testosterone Increase (Wilborn 2004) | no significant change | — | Independent 8-week RCT in trained athletes — null result |
ZMA has a fascinating origin story and a straightforward scientific verdict: it corrects mineral deficiencies in athletes who have them, but does not boost testosterone or performance in athletes who are already replete.
The Origin
Victor Conte created ZMA as a proprietary blend combining zinc monomethionine aspartate (30mg), magnesium aspartate (450mg), and pyridoxine B6 (10.5mg). Conte and Brilla published a study in 2000 (PMID 10861344) showing that NCAA football players taking ZMA for 8 weeks saw a +32.4% increase in testosterone and +3.6% increase in IGF-1, with significant strength gains. The supplement industry embraced it immediately.
The Replication Problem
Wilborn et al. (2004, PMID 15182367) conducted an independent 8-week RCT in resistance-trained men. Result: no significant changes in serum testosterone, IGF-1, body composition, or strength compared to placebo. This is the study that matters for evaluating ZMA’s claims in the training context — it has no financial conflict of interest.
Deficiency vs. Supplementation
| Claim | Evidence if Deficient | Evidence if Replete | Better Alternative | Verdict |
|---|---|---|---|---|
| Testosterone increase | Tier 2 — corrects to normal range | No effect (Wilborn 2004) | Check serum zinc/magnesium first | Deficiency-dependent |
| IGF-1 increase | Tier 3 | No effect | Adequate total protein | No benefit if replete |
| Strength gains | Tier 2 — corrects impaired recovery | No effect | Adequate mineral intake | Deficiency-dependent |
| Sleep quality | Tier 2 (magnesium component) | Tier 2–3 | Magnesium glycinate alone | Partial — magnesium helps |
| Immune function | Tier 2 (zinc deficiency) | No effect | Dietary zinc sources | Deficiency-dependent |
Why Zinc Deficiency Is Common in Athletes
Zinc is lost in sweat — roughly 0.5–1.3mg per hour of intense exercise. Athletes restricting calories, endurance athletes logging high weekly volumes, and weight-class athletes periodically cutting weight are at meaningful risk of suboptimal zinc status. Estimates suggest 25–35% of these populations have insufficient intake.
When zinc deficiency suppresses testosterone (via impaired LH signaling and Leydig cell function), correcting it brings testosterone back toward normal range. This is not boosting — it is restoration.
The Magnesium Question
The 450mg magnesium aspartate in ZMA overlaps with the well-supported use of magnesium for sleep quality and muscle relaxation. Magnesium’s GABAergic effects are reasonably documented (Tier 2). If sleep is the primary goal, magnesium glycinate (200–400mg) has superior bioavailability to aspartate and is substantially cheaper than ZMA.
Practical Guidance
Test before supplementing. A serum zinc and RBC magnesium panel costs less than a 30-day ZMA supply. If you are replete, ZMA provides no testosterone benefit. If you are deficient, ZMA will help — but standalone zinc and magnesium give you more precise dosing at lower cost.
Related Pages
Sources
- Brilla LR, Conte V. Effects of a novel zinc-magnesium formulation on hormones and strength. J Exerc Physiol Online. 2000;3(4):26-36. PMID 10861344
- Wilborn CD, et al. Effects of Zinc Magnesium Aspartate (ZMA) Supplementation on Training Adaptations and Markers of Anabolism and Catabolism. J Int Soc Sports Nutr. 2004;1(2):12-20. PMID 15182367
- Córdova A, et al. Influence of 8 Weeks of Zinc Supplementation on Sleep Quality, Rest and Recovery. Nutrients. 2019;11(11):2529. PMID 31671868
Frequently Asked Questions
Does ZMA increase testosterone?
Only if you are deficient in zinc or magnesium. The original Brilla & Conte (2000, PMID 10861344) study showed a +32.4% testosterone increase, but was conducted by Victor Conte — who later became infamous as the BALCO lab founder — and was never independently replicated. Wilborn et al. (2004, PMID 15182367) found no significant testosterone changes in trained athletes in an independent 8-week trial.
Who actually benefits from ZMA?
Athletes with suboptimal zinc or magnesium status — approximately 25–35% of high-sweat athletes. Zinc is lost in sweat, and endurance athletes and those in weight-class sports restricting calories often have insufficient intake. If you are deficient, correcting that deficiency with zinc + magnesium will normalize testosterone to its genetically expected range. ZMA does not produce supraphysiological testosterone.
Does ZMA help sleep?
The magnesium component may improve sleep quality independently of testosterone effects. Magnesium's role in GABAergic signaling and muscle relaxation has Tier 2 evidence for sleep improvement. The zinc component has weaker evidence for sleep. If sleep is your goal, a standalone magnesium supplement (glycinate form, 200–400mg) is better studied and cheaper than ZMA.
Is Victor Conte's involvement relevant to evaluating ZMA?
Yes, contextually. Conte developed ZMA as a proprietary product and conducted the original supporting study. He later founded BALCO Laboratories, central to the 2003 steroid scandal involving Olympic athletes. This history underscores why independent replication — which found null results — is critical when evaluating industry-originated research.
Should I take ZMA or just zinc and magnesium separately?
If you have a specific reason to address zinc or magnesium deficiency, standalone supplements give you more dosing flexibility at lower cost. Magnesium glycinate (200–400mg before bed) and zinc (10–25mg with food, away from calcium) cover the same physiological territory. ZMA's B6 content is not a meaningful addition for most people with adequate diet.