In brief:
- ZMA consists of zinc, magnesium and vitamin B6 and is popular for supporting recovery and sleep.
- The evidence for raising testosterone is weak — the benefits show up mainly in people who are deficient in these minerals.
- Athletes who train intensively often have a magnesium and zinc deficiency, so ZMA may be justified in their case.
- With a balanced diet, the added effect of ZMA is likely to be limited.
ZMA is a dietary supplement that combines three components: zinc (usually as monomethionine aspartate), magnesium (as aspartate) and vitamin B6 (as pyridoxine). ZMA is marketed mainly to athletes to improve recovery, raise sleep quality and support testosterone levels. In this article we look at what independent studies actually show.
What is ZMA and how does it work?
The patented ZMA formula usually contains 30 mg of zinc, 450 mg of magnesium and 10.5 mg of vitamin B6 in a single daily dose. The concept is based on the idea that during intense training the body loses both zinc and magnesium through sweat, and replenishing these minerals together supports hormonal balance and recovery.
Magnesium is involved in regulating over 300 enzymatic reactions, including protein synthesis and energy production (NIH ODS, 2023). Zinc is needed for testosterone synthesis, supporting immune function and wound healing — this was also confirmed by the EFSA scientific panel when it assessed the health claim (EFSA, 2009). Vitamin B6 supports the bioactivity of both minerals and takes part in amino acid metabolism.
Does ZMA raise testosterone and athletic performance?
This is ZMA’s most controversial claim. The original study (Brilla & Conte, 2000) in American football players showed that 8 weeks of ZMA use raised testosterone levels by 33% and IGF-1 levels by 3.6%, and increased muscle strength compared with the placebo group. However, the study was funded by the manufacturer, BALCO, which creates a significant conflict of interest.
An independent randomized study (Wilborn et al., 2004) reached the opposite result: in trained men with normal zinc levels, ZMA had no statistically significant effect on testosterone, IGF-1 or body composition over 8 weeks. This clearly suggests that the effect of ZMA depends primarily on whether the user has a deficiency.
As for magnesium, a link has been found between low magnesium levels and lower testosterone in people who train. In one study (Cinar et al., 2011), testosterone levels rose in athletes who received magnesium, both at rest and after a training load, compared with the placebo group — it is important to note here that the participants probably had a mild magnesium deficiency before the study.
For comparison: What is creatine and how does it work — creatine is a supplement whose effectiveness is backed by strong independent studies that have been replicated many times. For ZMA the evidence base is much weaker and the results are mixed.
When is using ZMA justified?
The real benefit of ZMA shows up mainly in three situations.
Mineral deficiency in athletes. People who train intensively have an increased risk of magnesium and zinc deficiency, because these minerals are lost through sweat and the body’s requirement is higher (Volpe, 2015). In this case, supplementation is evidence-based.
Sleep quality. Magnesium has shown a positive effect on sleep quality, especially in older adults and people under chronic stress (Abbasi et al., 2012). Taking ZMA before going to sleep may help people with low magnesium levels.
Immune function and recovery. Zinc supports the normal functioning of the immune system and wound healing (EFSA, 2009).
That said, ZMA is no substitute for balanced nutrition. For people who get enough zinc and magnesium from food, the supplement adds little benefit.
How to take ZMA safely and correctly?
Manufacturers recommend taking ZMA on an empty stomach 30–60 minutes before going to sleep, because calcium competes with magnesium for absorption. This means ZMA should not be combined with dairy products or calcium supplements at the same time.
According to NIH ODS, the tolerable upper intake level for zinc in adults is 40 mg per day (NIH ODS, 2023). The zinc content of a standard ZMA dose stays below that, but with long-term use you need to make sure your total zinc intake from all sources does not exceed the safety limit — chronic overdosing can interfere with copper absorption.
What is creatine and how does it work covers a supplement that is often combined with ZMA — they act through different mechanisms and do not interfere with each other’s absorption.
References
- Brilla LR & Conte V (2000). Effects of a Novel Zinc-Magnesium Formulation on Hormones and Strength. J Exerc Physiol Online. 3(4):26–36.
- Wilborn CD et al. (2004). Effects of Zinc Magnesium Aspartate (ZMA) Supplementation on Training Adaptations and Markers of Anabolic and Catabolic Hormone Status During a High-Intensity Training Program. J Int Soc Sports Nutr. 1(2):12–20. DOI: 10.1186/1550-2783-1-2-12
- Cinar V et al. (2011). Effects of magnesium supplementation on testosterone levels of athletes and sedentary subjects at rest and after exhaustion. Biol Trace Elem Res. 140(1):18–23. PMID: 20352370
- Abbasi B et al. (2012). The effect of magnesium supplementation on primary insomnia in elderly: A double-blind placebo-controlled clinical trial. J Res Med Sci. 17(12):1161–1169. PMID: 23853635
- Volpe SL (2015). Magnesium and the Athlete. Curr Sports Med Rep. 14(4):279–283. PMID: 26166051
- NIH Office of Dietary Supplements (2023). Zinc — Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/
- EFSA Panel on Dietetic Products, Nutrition and Allergies (2009). Scientific Opinion on health claims related to zinc. EFSA Journal. 7(9):1229. DOI: 10.2903/j.efsa.2009.1229
Frequently asked questions
What is ZMA?
ZMA is a supplement that contains zinc (as monomethionine aspartate), magnesium (as aspartate) and vitamin B6. It is used mainly to support athletes’ recovery, sleep and hormonal balance.
Does ZMA raise testosterone?
The evidence is mixed. An early study funded by the manufacturer showed a positive effect, but an independent study (Wilborn et al., 2004) found no statistically significant effect in men with normal levels. The effect is more likely in people who have a magnesium or zinc deficiency.
When should you take ZMA?
It is recommended to take it fasted, 30–60 minutes before going to sleep. Avoid consuming calcium-rich foods or supplements at the same time, as calcium interferes with magnesium absorption.
Is ZMA safe?
At standard doses, ZMA is generally safe. For adults, the safe upper limit for zinc is 40 mg per day (NIH ODS). If you use it long term, make sure your total zinc intake from all sources does not exceed this limit, as chronic overdosing can interfere with copper absorption.
Is ZMA suitable for vegetarians and vegans?
Most ZMA products are plant-based and suitable for vegetarians and vegans, but always check the composition of the specific product. Vegans often have lower zinc levels (zinc is absorbed less well from plant foods), which is why ZMA may be especially relevant for this group.
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