The evidence to support the effectiveness of ZMA as an anabolic compound come from a 1999 study published by Brilla LR, Conte V (1999). “A novel zinc and magnesium formulation [ZMA] increases anabolic hormones and strength in athletes”. Sports Medicine, Training and Rehabilitation Journal. Results were also published in Medicine and Science in Sports and Exercise, Vol. 31, No. 5, May 1999

In the study Dr. Brilla reported that supplementation with ZMA improved the strength and free testosterone levels of NCAA football players by 250%. In the study one group of players was given the ZMA nightly for eight weeks while a second group received a placebo. The ZMA group showed an increase of 11.6% in their leg strength as measured using a Biodex isokinetic dynamometer. The placebo group showed only a 4.6% increase.

Dr. Brilla hypothesized, “The muscle strength increases may have been mediated by the anabolic hormone increases in the ZMA group. The ZMA group had 30% increases in free and total testosterone levels compared to 10 percent decreases in the placebo group… The ZMA group also had a slight increase in insulin-like growth factor-1 (IGF-1) levels compared to a 20 percent decrease in the placebo group. This study shows that anabolic hormone and muscle strength increases can be induced in already strength-trained athletes by using a novel zinc-magnesium preparation.”

Unfortunately all is not as rosy as it may seem. It is well known that many people in the U.S. are deficient in both zinc and magnesium and that both are necessary for proper hormone production and protein synthesis. Even more telling is that athletes requirements for the two minerals are even greater than the average person. A closer look reveals that the zinc and magnesium levels in the athletes blood was already low at the beginning of the study almost to the point of deficiency. Of course additional training would have lower those values even more for the placebo group while the ZMA group would bring their zinc and magnesium up to normal levels. It is well documented that zinc plays an important role in testosterone production and protein synthesis. And magnesium is crucial to protein synthesis.

One might also take note that the study was funded by SNAC Systems Inc. who hold the patent on ZMA and that one of the studies authors (V. Conte) is a partial owner in this company.

Finally, another study [2] in 2004 found that ZMA has no effect on strength or hormone levels. Wilborn Colin D. et al (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.

One finding about ZMA that does hold true is its claims for better sleep. Users typically report much deeper sleep along with very vivid dreams when taking ZMA. It is possible that this is a side effect from the increased hormone levels brought on by the body no longer being deficient in zinc and magnesium or perhaps ZMA does have some effect on the sleep cycle. That would prove promising for this mineral supplement as many important hormones, including human growth hormone, are produced and released in greatest quantities at night while sleeping.