What Is ZMA?
ZMA, or zinc magnesium aspartate, is a dietary supplement containing zinc, magnesium, and vitamin B6 that typically comes in pill, capsule, or powder form.Supplement manufacturers also sometimes include additional vitamins, minerals, and other ingredients in ZMA supplements to differentiate their products from others on the market.
Notably, there’s nothing unique about the zinc, magnesium, or vitamin B6 in ZMA—you can get these vitamins and minerals from your diet.
For example, meat, fish, and seafood are good sources of zinc; magnesium-rich foods include nuts, seeds, leafy greens, and whole grains; and fish, organ meats, starchy vegetables, and fruits (except citrus fruits) contain high levels of vitamin B6.
ZMA supplements are popular among the health and fitness crowd because many believe they boost testosterone levels and athletic performance, aid sleep and weight loss, and improve immune function.
ZMA: Benefits
Here are the most commonly claimed benefits of ZMA and what science says about each.ZMA and Testosterone
Research shows that eating too little zinc and magnesium suppresses testosterone production.As such, supplement manufacturers claim that ZMA—which typically contains high doses of zinc and magnesium—can help boost your “T” levels.
To support this stance, they often cite a study conducted by scientists at Western Washington University, in which football players who took ZMA daily for 7 weeks increased their testosterone by ~32% and insulin-like growth factor 1 (a hormone that promotes muscle growth) by ~4%.
While this seems like proof of ZMA’s T-boosting properties, there are two reasons to doubt these findings.
First, a supplement company that produced a ZMA supplement funded and conducted the research. While this isn’t a guarantee of scientific malpractice, it’s sensible to wait until a disinterested third party verifies the results before accepting them unreservedly.
This point is even more pertinent given that the supplement company in question, BALCO, had a history of unethical behavior. For example, its owner, Victor Conte, who also co-authored the study, was later imprisoned for distributing performance-enhancing drugs to athletes.
Second, most other studies show that ZMA has no effect on testosterone levels.
Thus, ZMA probably isn’t the “testosterone booster” supplement sellers claim. That said, if you currently don’t eat many zinc- and magnesium-rich foods, your T levels probably aren’t as high as they could be.
If this is the case for you, taking ZMA (or any multivitamin containing zinc and magnesium) could help you maintain healthier testosterone levels, though it won’t increase your testosterone beyond what’s possible naturally the way anabolic steroids might.
ZMA and Sleep
Supplement sellers often claim that the zinc and magnesium in ZMA enhance recovery by helping you fall asleep faster and improving your sleep quality.There’s little high-quality evidence that this is true, though.
Some observational studies show that people who sleep poorly tend to be zinc deficient, whereas those who sleep well usually have higher zinc levels. Importantly, these studies don’t show that having high or low zinc levels causes good or poor sleep, only that “zinc status” and sleep quality correlate.
Other studies in malnourished children and elderly people in long-term care show that taking vitamin supplements containing zinc improves sleep duration and sleep quality. Likewise, a study published in Molecular Nutrition & Food Research showed that people who ate zinc-rich foods slept better than those who took a placebo.
In all of these experiments, the participants consumed supplements and food containing vitamins and minerals besides zinc, making it impossible to say how much the zinc contributed to their improved sleep.
Studies investigating magnesium’s effect on sleep are marginally more promising.
For example, research shows that magnesium activates your parasympathetic nervous system (the network of nerves that control your body’s ability to relax), which may promote calm at bedtime and help you fall asleep faster.
Other research shows that magnesium interacts with your brain’s gamma-aminobutyric acid (GABA) receptors, preventing chemical messages from being passed from neuron to neuron and helping to reduce stress and induce sleep.
Furthermore, taking magnesium may increase melatonin, the hormone that regulates your sleep-wake cycle.
In one study published in the Journal of Research, elderly insomniacs who took magnesium daily for 8 weeks fell asleep faster and significantly increased melatonin and sleep duration compared to those who took a placebo.
Overall, we don’t have enough high-quality evidence to draw firm conclusions about how zinc and magnesium affect sleep. Until more tightly controlled human trials show a benefit, it’s probably not sensible to invest in ZMA as a sleep supplement.
ZMA and Athletic Performance
Many people believe ZMA boosts athletic performance, but there’s little evidence this is the case.Aside from the dubious study conducted by the BALCO supplement company that found football players who took ZMA (and definitely not steroids) for 7 weeks increased quadriceps strength by ~10% and power by ~13-to-15% relative to those who took a placebo, there are only two other studies that suggest the magnesium in ZMA is an “ergogenic aid” for weightlifters.
One found that taking magnesium for a week helped weightlifters increase their bench press one-rep max by 17%, though this effect disappeared when they took it longer (4 weeks). This led the researchers to conclude that magnesium probably doesn’t provide long-term performance benefits.
The other was conducted by the same research team at Western Washington University that helped Victor Conte devise the BALCO study. In it, researchers had 26 inexperienced weightlifters take magnesium or a placebo daily and train their legs 3 times weekly for 8 weeks.
The results showed that those who took magnesium increased their quad strength by ~26%, whereas the weightlifters who took a placebo increased their quad strength by only ~11%.
Similarly to the BALCO study, however, the research was funded by a supplement company that sells a magnesium supplement. Again, this isn’t proof that the researchers fudged the data, but it increases the likelihood that financial interest colored the results.
The only other study to investigate ZMA’s effect on weightlifting performance was published in the Journal of the International Society of Sports Nutrition. The researchers had 42 experienced weightlifters with healthy zinc and magnesium levels take ZMA or a placebo for 8 weeks and train 4 times weekly.
The results showed that taking ZMA had no effect on strength gain, muscle endurance, or cycling sprint performance, nor did it increase testosterone, insulin-like growth factor 1, growth hormone, muscle gain, or fat loss.
Some research suggests magnesium may contribute to better endurance performance, though methodological flaws plague the supporting studies, making them difficult to trust. For example, most use supplements containing magnesium alongside other compounds and don’t report whether the participants were magnesium deficient at the beginning of the trial.
Still, the weight of the evidence goes in the opposite direction, with most studies showing that magnesium doesn’t affect athletic or endurance performance.
Another argument ZMA zealots use to convince people of ZMA’s performance-boosting benefits is that intense training schedules and restrictive dieting leave many athletes zinc and magnesium deficient, which may hinder their performance.
This doesn’t prove that ZMA improves performance, though. Rather, it may eliminate nutrient deficiencies that might prevent you from performing at your best.
At bottom, there’s no high-quality evidence that ZMA boosts athletic performance, especially if you’re not zinc or magnesium deficient.
ZMA and Immune Function
Zinc, magnesium, and vitamin B6 play essential roles in immune function.For example, zinc promotes wound healing, magnesium reduces inflammation, and vitamin B6 helps your body fight infection.
As such, supplement companies often market ZMA as an “immune support” supplement.
However, provided you eat a healthy diet containing plenty of zinc- and magnesium-rich foods, such as meat, fish, nuts, seeds, and leafy greens, ZMA probably won’t boost immune function further.
That said, if your diet contains few of these foods, supplementing with ZMA (or any multivitamin) may help your immune system function better.
ZMA and Weight Loss
Although no studies show that ZMA aids weight loss, many people take the results of observational research on zinc and magnesium as indications that ZMA will help you lose weight.This is a mistake.
These studies only show that obese people are more likely than leaner people to be zinc deficient and that those who eat a magnesium-rich diet tend not to be obese, not that taking zinc and magnesium supplements helps you lose weight.
More tellingly, the results from two large meta-analyses of randomized controlled trials (the “gold standard” of scientific research) show that zinc and magnesium supplements have no effect on weight loss.
Thus, there’s no reason to add zinc and magnesium to your fat-loss supplement stack.
