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The Effect of ZMA on Testosterone and Body Composition

Daniel Brady | December 5, 2012 in Supplements
Generic ZMA Advertisement

ZMA (Zinc Magnesium Aspartate) claims to improve strength, body composition and testosterone. We will look at the evidence to see which of these claims, if any, are true. Read on for the results.

To the left is an example of a ZMA promotional chart. It shows substantial improvements in testosterone and strength. So that is the benefit the customer should expect to receive, right? Not when we look at the evidence.

Study 1 – No Strength or Testosterone Improvement, but Small Body Composition Improvements

This study found no improvement in testosterone or strength after 8 weeks, but saw small improvements in body composition in both FFM (Free Fat Mass) and BF% (Body Fat Percentage).[1]

ZMA FFM and Fody Fat Percentage

Study 2 – No Testosterone Improvement

This study shows no improvement in testosterone levels in people with a zinc sufficient diet.[2] This suggests that the promotional charts are not showing the results from average people, but are instead showing the results from zinc deficient people.


Magazines or products showing significant improvements in testosterone, strength and body composition from ZMA are biased and likely showing misleading charts and results. ZMA seems ineffective unless you’re zinc deficient, which can be found out by blood test. Read up on other supplements that will provide you with better improvements, for example Creatine and BCAAs.

  1. Effects of Zinc Magnesium Aspartate (ZMA) Supplementation on Training Adaptations and Markers of Anabolism and Catabolism. Colin D. Wilborn, Chad M. Kerksick, Bill I. Campbell, Lem W. Taylor, Brandon M. Marcello, Christopher J. Rasmussen, Mike C. Greenwood, Anthony Almada, & Richard B. Kreider []
  2. Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement. K Koehler, M K Parr, H Geyer, J Mester and W Schänzer []

Daniel has a strong interest in evidence supported fitness training, preparation and supplementation. His goal is to provide clear information that simply works. He's currently 16 kg of muscle above his starting weight (7kg in the past 12 months), and targeting a continued growth rate of 5kg+ per year.
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