The supplement industry is constantly churning with innovation, remixes of existing supplements, rebrands of old trends, and new use cases based on the latest science. It's not uncommon for a new supplement to start gaining popularity, but if you find a name you haven't encountered before, it's important to research what it actually is.
One I recently came across is the ZMA supplement. It has been sweeping through certain groups of supplement users, particularly athletes, bodybuilders, and other fitness groups. As such, you have some expectations for what it might be trying to accomplish. I've always viewed exercise as one of the core pillars of health, so anything that can support beneficial exercise without putting undue strain on the body can be a good thing.
So, I decided to do some digging and see what the science says about ZMA supplements.
Table of Contents
What are ZMA Supplements?
ZMA is a catchy name for Zinc Magnesium Aspartate. Before you start looking into chemical structures or anything, though, it's worth noting that this isn't just one substance; it's three.
Specifically, ZMA supplements are a mixture of zinc, magnesium, and vitamin B6. The word "aspartate" in the name comes from one of the more common forms of magnesium used in the mixture, magnesium aspartate. Interestingly, while I've written extensively about the different forms of magnesium, magnesium aspartate wasn't on my radar.
Each ingredient in ZMA is presumed to have certain benefits. The questions I want to answer are:
- Why do people take ZMA supplements?
- What are the specific benefits of each ingredient, as backed by science?
- Are there benefits to taking the mixture in ZMA form?
- Should you consider taking ZMA supplements?
Read on while I dig deeper into each of these questions.
Why Do People Take ZMA Supplements?
ZMA supplements are most common with workout enthusiasts and fitness gurus. The theory is that each ingredient is one that benefits some element of fitness, such as digestion, energy, metabolism, recovery from exercise, and muscle growth.
Often, bodybuilders, weightlifters, and other fitness proponents are taking these kinds of supplements already. They may be part of a daily regimen, a pre-workout mixture, or a post-workout recovery mix. Lumping them together into one supplement helps condense two or three products into one instead.
ZMA proponents also claim that the supplement can boost testosterone levels (besides being a sex characteristic, testosterone is important for muscle growth), improve sleep quality, and build strength. The real question, though, is what the research says, if there's any research to be found.
First, let's go through each of the three ingredients and look at their known benefits. Then, we'll look at the three together and see if there are any additional factors to consider.
What Are the Benefits of Zinc?
Zinc is a naturally occurring trace mineral that is considered essential – your body needs it but can't produce it, so you need to get it from food sources. It's used in cellular metabolism across over 300 enzymatic processes in the body. It's also used to enhance immune function, in the synthesis of DNA, in the creation of protein, in wound healing, and in the development of the body throughout pregnancy through adolescence.
The recommended daily intake of zinc ranges from about 2mg in infants up to 8-11 mg (depending on gender) in adults. Foods rich in zinc include oysters (which have nearly 300% of your recommended daily intake per serving), beef, fortified cereals, seeds, cheese, and dairy. Zinc deficiency is relatively rare and can cause alopecia, delayed growth in children, a weakened immune system, and reproductive problems in adults.
Excessive zinc levels in adults are considered to be any intake over 40mg per day. High zinc intake can lead to headaches, dizziness, vomiting, loss of appetite, and gastric issues. Ongoing high levels can interfere with copper absorption, lower good cholesterol levels, and can even disrupt magnesium absorption. All of these, chronically, can lead to worse problems down the line.
ZMA supplements usually include somewhere around 30 mg of zinc, which, when added to normal dietary intake, can put you very close to the danger zone.
What Are the Benefits of Magnesium?
Magnesium is abundant in the body, available naturally in many foods, and fortified into others. It's a common addition to many supplements, and it's fairly well-known what it does throughout the body. Magnesium is used for hundreds of enzymatic reactions, in muscle synthesis and nerve function, for blood sugar and blood pressure control, and for energy production. It's used in the development of bone and the creation of DNA,
The recommended daily intake of magnesium ranges from 30 mg in infants up to around 320-420 mg in adults.
Magnesium is very well-studied, but that level of scrutiny hasn't actually given us much insight. Millions of people – as much as half of all Americans – may be chronically deficient in magnesium, and many of the "benefits" of magnesium may just be treating that deficiency. It's also very difficult to accurately test magnesium levels without very invasive bone tests, which are almost never necessary.
All of that said, there are some observed benefits of magnesium supplements. Some studies have shown it having benefits on cardiac function, lower risk of stroke and heart disease, and better management of diabetes. However, other studies have not shown the same benefits, so there's a lot of uncertainty. You can read a deeper analysis of magnesium in my coverage elsewhere.
As far as magnesium aspartate specifically, one study showed a mild benefit to hypertension, and a small rat study ( from 40 years ago) showed no benefit to short-term exercise but reported a longer-term benefit on muscle performance.
ZMA supplements usually use magnesium aspartate, which is a magnesium salt with aspartic acid, an amino acid. It's relatively unstudied, and there isn't much conclusive evidence of its benefits; in fact, different kinds of ZMA mix it with magnesium oxide as well.
While the FNB's upper limit of magnesium is only 350 mg per day, ZMA supplements generally include 450mg. That said, adverse effects of excess magnesium are generally only observed at significantly higher levels – more than 10x that amount – and there isn't much risk of anything more than some digestive upset from taking these supplements.
What Are the Benefits of Vitamin B6?
Vitamin B6 is a water-soluble vitamin, which means that it's easy for the body to excrete excess. B6 is used as a coenzyme for over 100 bodily functions and is used in cognitive development, neurotransmitter synthesis, metabolism and protein usage, immune function, and hemoglobin formation.
The recommended daily intake of vitamin B6 is around 1.5-1.7mg per day for adults, and it's commonly found in many dietary sources. B6 deficiency is rare and is associated with end-stage renal disease, as well as developmental problems in infants and children.
As mentioned, because B6 is water-soluble, it's very difficult to get too much of it. Even common energy drinks have 2,500% of your recommended daily intake. ZMA supplements often have around 10-11 mg, which is 650% of your RDI.
Does ZMA Have Benefits Beyond the Ingredients?
Most of the benefits of the ingredients in ZMA come from the usual game of telephone; a study looks at what the ingredient does and finds it plays a role in supporting, say, muscle growth; someone else reads that and decides it means taking more of it means more muscle growth, and someone else uses that information in marketing the ingredient as an athletic supplement. Typically, while the associations are there, the effects are usually minor.
With ZMA specifically, have there been any studies looking into what it can do?
A study from 2000 in the Journal of Exercise Physiology looked at 27 football players over two months and found that daily ZMA supplements significantly increased muscle strength and power, as well as testosterone levels. However, a similar study looking at 42 men performing resistance training found no benefits over a placebo. It's also worth mentioning that the study that did show benefits was also partially written by, and funded by, an individual who owns a company producing ZMA supplements, so there's a conflict of interest to consider.
A common claim with ZMA is that it can improve sleep quality and exercise performance. A small study on 16 trained men evaluated exercise performance and fatigue levels after mild sleep deprivation and found no benefit from taking the supplement. This doesn't show any potential long-term benefits – or lack thereof – but it does indicate mild or nonexistent short-term benefits. Another study with 19 trained men also showed relatively little potential benefit.
As far as testosterone goes, ZMA supplements often claim an increase in testosterone production, which is correlated to more muscle growth and strength. A 2007 study looked at serum testosterone and urinary testosterone excretion and found no significant effects among those who already consume enough zinc in their diets.
All of these studies are very small, and while they're usually well-formulated, they don't necessarily have statistical significance. However, in general, they point towards tempered expectations, not bold claims.
Overall, while zinc and magnesium have been shown to improve fatigue levels and promote testosterone levels individually, there's no significant evidence showing that they're any better together than separately. Additionally, it may be just as likely that the benefits come from giving supplements to populations who are normally deficient rather than providing a tangible benefit to those who already have adequate intake.
Should You Consider Adding ZMA Supplements to Your Diet?
In large part, the choice is yours. However, I will add a few points of caution to consider.
First of all, while there are no serious adverse effects associated with too much vitamin B6 and very little with excess magnesium, maintaining excess zinc levels can have serious long-term consequences. Since ZMA supplements put you right at that edge, you have to be aware that the rest of your diet may also contain zinc and make sure you aren't going overboard.
This is doubly true if you're big into fitness and have a whole regimen of supplements you take. If any of those other supplements also include zinc, magnesium, or vitamin B6, it can put you well into the danger zone or at least be wasting you a lot of money taking supplements well above the levels that provide any known benefit.
On my end, I always promote a healthy diet first and supplements second. Supplements aren't going to solve your problems on their own unless your problems are diagnosed deficiencies. They can potentially support certain goals, but the best situation is one where you're eating a healthy and balanced diet and using supplements to make up for small gaps in your nutritional profile. That's what I use my own MicroVitamin for, which I developed to meet my needs.
For reference, my MicroVitamin does include Vitamin B6 (1.275mg, or 75% of your RDI), Zinc (8.25mg, or 75% of your RDI), and Magnesium (126mg, or 30% of your RDI). However, these amounts are much lower than what a ZMA supplement includes, and MicroVitamin includes much more besides.
As always, just because I take a specific nutrient or supplement doesn't mean you should as well. Always consult with your doctor and make health decisions based on your specific circumstances and goals.
Sources:
- Zinc Fact Sheet for Health Professionals: https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/
- Magnesium Fact Sheet for Health Professionals: https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/
- Vitamin B6 Fact Sheet for Health Professionals: https://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional/
- Reduction of blood pressure with oral magnesium supplementation in women with mild to moderate hypertension: https://pubmed.ncbi.nlm.nih.gov/8017327/
- Effects of potassium + magnesium aspartate on muscle metabolism and force development during short intensive static exercise: https://pubmed.ncbi.nlm.nih.gov/3988415/
- Effects of a Novel Zinc-Magnesium Formulation on Hormones and Strength: https://www.asep.org/asep/asep/BrillaV2.PDF
- Effects of Zinc Magnesium Aspartate (ZMA) Supplementation on Training Adaptations and Markers of Anabolism and Catabolism: https://pubmed.ncbi.nlm.nih.gov/18500945/
- Effects of Supplementing Zinc Magnesium Aspartate on Sleep Quality and Submaximal Weightlifting Performance, following Two Consecutive Nights of Partial Sleep Deprivation: https://pubmed.ncbi.nlm.nih.gov/38257144/
- Effects of an Acute Dose of Zinc Monomethionine Asparate and Magnesium Asparate (ZMA) on Subsequent Sleep and Next-Day Morning Performance (Countermovement Jumps, Repeated Sprints and Stroop Test): https://pubmed.ncbi.nlm.nih.gov/39125347/
- Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement: https://pubmed.ncbi.nlm.nih.gov/17882141/
