Study type: Randomized controlled trialConfidence: Moderate

Effects of Zinc Magnesium Aspartate (ZMA) Supplementation on Training Adaptations and Markers of Anabolism and Catabolism

Wilborn CD, Kerksick CM, Campbell BI, Taylor LW, Marcello BM, Rasmussen CJ, Greenwood MC, Almada A, Kreider RB

Year2004

Sample sizen=42

JournalJournal of the International Society of Sports Nutrition

AuthorsWilborn CD, Kerksick CM, Campbell BI, Taylor LW, Marcello BM, Rasmussen CJ, Greenwood MC, Almada A, Kreider RB

Evidence is still building up

Summary

A double-blind RCT in 42 resistance-trained men matched for lean body mass, given either a dextrose placebo or ZMA before bed for 8 weeks alongside a standardized resistance training program. Zinc/magnesium status, total/free testosterone, IGF-1, growth hormone, cortisol, the cortisol/testosterone ratio, muscle/liver enzymes, 1RM strength, muscular endurance, and body composition were all assessed, and none showed a significant difference versus placebo.

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DOI: 10.1186/1550-2783-1-2-12

Key Findings

Key findings

Key point

1
No significant between-group differences in total/free testosterone, IGF-1, growth hormone, cortisol, or the cortisol/testosterone ratio
2
No significant difference versus placebo in 1RM strength or muscular endurance
3
No significant between-group difference in body composition (lean mass, body fat %)
4
A comparatively large (n=42), double-blind RCT combined with 8 weeks of actual resistance training
5
Participants were zinc-replete (fasting zinc and magnesium within normal ranges); the authors limit their conclusion to resistance-trained males with normal zinc status

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Related Research

Related research

Randomized controlled trial

Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement

European Journal of Clinical Nutrition, 2009

A placebo-controlled trial in 14 healthy, regularly exercising men (22–33) whose baseline dietary zinc intake (11.9–23.2 mg/day) already met requirements. Participants took a high-dose zinc supplement (ZMA) or placebo between dinner and bedtime for 8 weeks, and serum total/free testosterone plus the urinary excretion pattern of testosterone and selected steroid hormone metabolites were measured. No significant changes were found in serum total or free testosterone, nor in the urinary metabolite excretion pattern.

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Articles featuring this study

Research vs Bro-science
Do ZMA and zinc really boost testosterone? Lore vs research
ZMA — a portmanteau for its ingredients, Zinc, Magnesium, and vitamin B6 — has been sold since the late 1990s on the promise of raising testosterone and building muscle. It's still a staple on gym shelves and supplement sites today. We line up the claim that 'ZMA or zinc raises testosterone and gains' against the research.
Hirotsugu Yoshimura

Last checked: 2026-07-25