Zinc monomethionine aspartate and magnesium aspartate, or ZMA, is a supplement comprised of zinc, magnesium, and vitamin B6. Individually, zinc and magnesium are involved in several physiological processes affecting exercise and it is thought that the combined supplement can improve athletic performance. In theory, zinc and magnesium may enhance anabolic hormones and improve adaptations to resistance training. (Wilborn 2004, Sport Ireland Institute 2009)
The reasoning behind ZMA supplementation is based on the idea that athletes may suffer from zinc and magnesium deficiency, which has a negative effect on muscular adaptations and exercise performance (Deuster 2013). Deficiencies in zinc and magnesium aspartate lead to decreased testosterone and insulin-like growth factor (Mason 2012). Supplementing ZMA is thought to increase testosterone levels and therefore increase muscular strength (Sport Ireland Institute 2009).
There has been some evidence that demonstrates improved anabolic hormone profile and muscle function with supplemental ZMA use in already strength-trained NCAA football players (Brilla 2000). However, a study by Wilborn (2004) examining ZMA effects on training adaptations in forty-two resistance trained men showed "no significant effects on total and free testosterone, IGF-1, growth hormone, cortisol, the ratio of cortisol to testosterone, or muscle and liver enzymes in response to training." There were also no significant improvements in 1-RM strength or muscular endurance.
ZMA use for anabolic purposes is not well supported by current evidence (Deuster 2013). ZMA supplementation does not appear to affect anabolic or catabolic responses to resistance training, body composition, or training adaptations (Wilborn 2004). ZMA is classified as a group C supplement, meaning there is no definitive evidence of beneficial effects and The International Society of Sports Nutrition reports that ZMA effects on muscle building is not known (Mason 2012).
ZMA supplementation could, however, provide benefits to athletes with deficiencies. A meta-analysis evaluating the dietary zinc intake and zinc status in athletes demonstrated that "athletes are at risk of suboptimal zinc status despite higher dietary zinc intake" (Chu 2018). The role of zinc in energy metabolism and the loss of zinc through sweat during exercise may increase the need for zinc in athletes (Chu 2018).
Current evidence does not support ZMA supplementation so no dosing guidelines can be provided. Overall, ZMA does not seem to increase testosterone levels or cause additional strength adaptations from resistance training. It has yet to be determined whether ZMA provides ergogenic effect in populations with low zinc and magnesium status, so further investigation is warranted. (Sport Ireland Institute 2009)
Brilla LR, Conte V (2000). Effects of a Novel Zinc-Magnesium Formulation on Hormones and Strength. Journal of Exercise Physiology Online, 3(4), 26-36.
Chu A, Holdaway C, Varma T, Petocz P, Samman S (2018). Lower serum zinc concentration despite higher dietary zinc intake in athletes: A systematic review and meta-analysis. Sports Medicine, 48(2), 327-336.
Deuster PA, Hodgson AB, Stear SJ, Burke LM, Castell LM (2013). A–Z of nutritional supplements: Dietary supplements, sports nutrition foods and ergogenic aids for health and performance: Part 46. British Journal of Sports Medicine, 47(12), 809-810.
Mason BC, Lavallee ME (2012). Emerging Supplements in Sports. Sports Health, 4(2), 142–146.
Sport Ireland Institute. (2009). Zinc and ZMA Retrieved April 2, 2019, from https://static1.squarespace.com/static/53296b1be4b0f59c2976d2c8/t/554b7ab3e4b0b316215374b1/1431009971379/Zinc
Wilborn CD, Kerksick CM, Campbell BI, Taylor LW, Marcello BM, Rasmussen CJ, Greenwood MC, Almada A, Kreider RB (2004). Effects of zinc magnesium aspartate (ZMA) supplementation on training adaptations and markers of anabolism and catabolism. Journal of the International Society of Sports Nutrition, 1(2), 12-20.