Magnesium or ZMA: what is the difference

Magnesium is one of the most popular minerals among people who train, and ZMA is one of the best-known complexes where magnesium is a component. Despite the similarity of names on labels, these are products with different logic: in the first case you choose a specific form and dose of magnesium, in the second you get a ready-made mix with zinc and vitamin B6. The editorial team explains the difference.

The role of magnesium in the body

Magnesium takes part in hundreds of enzymatic reactions. The most important of them for an athlete is working with ATP: in the cell the energy molecule effectively functions as a complex with magnesium. Without it, muscle contraction, protein synthesis and nerve impulse transmission are impossible.

The mineral also regulates the work of ion channels, in particular it blocks NMDA receptors at rest and affects calcium channels. It is with this that its significance for neuromuscular excitability, muscle relaxation and, partly, sleep is associated.

The bulk of magnesium is stored in the bones and muscles, while less than one percent of the total stores is in the blood serum. Because of this, a normal blood test does not always rule out a shortfall in the tissues.

The recommended intake of magnesium for adults is approximately 310–420 mg per day depending on sex and age. A significant part of this amount a person should get from food, and supplements only complement the diet.

Forms of magnesium in supplements

Separate magnesium supplements are produced in many forms: oxide, citrate, glycinate (bisglycinate), malate, lactate, chloride, taurate, L-threonate. They differ in elemental magnesium content, solubility and effect on digestion.

Oxide contains a lot of elemental magnesium but is absorbed worse and more often acts as a laxative. Citrate is soluble and well absorbed, but in large doses it also loosens the stool. Glycinate is usually gentler on the intestines, so it is often chosen for evening intake.

The ability to choose the form is the key advantage of separate magnesium. A person with sensitive digestion takes glycinate, a person prone to constipation takes citrate, and one to whom price matters takes more affordable salts.

The dose of separate magnesium is also easy to adjust: from 100–200 mg as a supplement to a good diet up to larger amounts on a doctor's recommendation in the case of a confirmed shortfall.

How ZMA differs

ZMA is a ready-made combination, in the classic version of which magnesium is represented by aspartate in an amount of about 450 mg, zinc by mono-L-methionine and aspartate (about 30 mg), as well as vitamin B6 (10–11 mg). The form of magnesium here has been chosen for you.

The amount of magnesium in ZMA exceeds the upper limit recommended for supplements — 350 mg per day for adults. This limit is set precisely because of the risk of diarrhea, not because of systemic toxicity, but it is worth taking into account.

Another difference is the interaction of components. Studies of mineral balance have shown that very high doses of zinc can reduce magnesium absorption. At ZMA doses this effect is most likely small, but the combination of two competing minerals in one capsule is itself not ideal from the point of view of absorption.

Therefore, the magnesium in ZMA is not «better» magnesium but simply one component in a fixed mix that can be appropriate only under certain conditions.

Evidence base

For separate magnesium there are randomized studies on sleep. Abbasi et al. (2012) reported an improvement in insomnia indicators in older people who took magnesium. The systematic review by Mah and Pitre (2021) rated the quality of evidence as low, although the direction of the effect was favorable.

Regarding athletic performance the data is mixed: reviews indicate that correcting a magnesium shortfall can improve performance, but in people with normal status additional magnesium provides no noticeable benefit.

For ZMA the key works concern hormones and strength. The initial positive study by Brilla and Conte (2000) was not confirmed by Wilborn et al. (2004), who found no effect on testosterone, IGF-1, body composition or strength.

Thus, magnesium has a modest but real evidence base for certain goals, while ZMA as a combination has mainly a marketing story with one dubious positive study.

Safety and signs of a shortfall

A magnesium shortfall may manifest as muscle cramps, twitching, fatigue, irritability and heart rhythm disturbances. However, these symptoms are nonspecific, so self-diagnosis by them is unreliable.

The risk groups for a shortfall are people with gastrointestinal diseases, type 2 diabetes, chronic alcohol use, as well as patients who take proton pump inhibitors or some diuretics for a long time.

• Do not take magnesium supplements without a doctor in chronic kidney disease.
• Separate the intake of magnesium and tetracycline and fluoroquinolone antibiotics.
• Take into account magnesium in multivitamins and heartburn remedies.
• Loose stools are a signal to reduce the dose or change the form.

With ZMA, questions of zinc safety are added to this: prolonged intake of doses exceeding the upper limit can cause copper deficiency. Therefore the safety of the complex must be assessed by all components, not just by magnesium.

Editorial conclusions

Magnesium and ZMA differ primarily in the possibility of choice: separate magnesium allows you to select the form and dose, while ZMA provides a fixed mix with a high dose of magnesium, zinc and vitamin B6.

For sleep support and correcting a magnesium shortfall, a separate product is usually a more precise tool. ZMA makes sense only when both minerals are needed.

The hormonal promises associated with ZMA have not been confirmed by independent studies, so a product should be chosen according to real needs.

We also recommend our materials on the forms of magnesium, on the comparison of zinc and ZMA and on melatonin and magnesium for sleep.

References

1. de Baaij JH, Hoenderop JG, Bindels RJ. Magnesium in man: implications for health and disease. Physiol Rev. 2015;95(1):1–46.
2. Institute of Medicine. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, DC: National Academy Press; 1997.
3. Abbasi B, Kimiagar M, Sadeghniiat K, et al. The effect of magnesium supplementation on primary insomnia in elderly: a double-blind placebo-controlled clinical trial. J Res Med Sci. 2012;17(12):1161–1169.
4. Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a systematic review & meta-analysis. BMC Complement Med Ther. 2021;21(1):125.
5. Nielsen FH, Lukaski HC. Update on the relationship between magnesium and exercise. Magnes Res. 2006;19(3):180–189.
6. Spencer H, Norris C, Williams D. Inhibitory effects of zinc on magnesium balance and magnesium absorption in man. J Am Coll Nutr. 1994;13(5):479–484.
7. Wilborn CD, Kerksick CM, Campbell BI, et al. Effects of zinc magnesium aspartate (ZMA) supplementation on training adaptations and markers of anabolism and catabolism. J Int Soc Sports Nutr. 2004;1(2):12–20.