Myth busting: does magnesium prevent muscle cramps?

Claudio Viecelli

4/6/2025

Translation: Jessica Johnson-Ferguson

Strength training is far more than just building muscle. It’s like medicine for your body, as it can help prolong a healthy life expectancy [1–6]. In this series, we take a critical look at widespread myths. This time we’re looking at muscle cramps and magnesium.

Cramps are sudden, painful contractions of muscles. They can last from anything between a few seconds and several minutes and are usually palpable. While sometimes associated with illnesses, they generally occur without a recognisable cause, which makes them a bit of a medical mystery. We still don’t fully understand the mechanism behind cramps. There are indications that the problem is rooted in the motor neurons, the nerve cells and the muscle fibres controlled by these nerve cells [7]. This theory is supported by the existence of certain neuromuscular diseases that are associated with spasms and typically affect the motor neurons, such as amyotrophic lateral sclerosis, better known as ALS. Certain metabolic diseases (e.g. liver failure), medications (diuretics and beta-agonists) and haemodialysis can also promote muscle cramps [8,9].

However, muscle cramps often occur without a serious underlying illness. Elderly people, pregnant women and athletes who reach their limits are particularly affected. Cramps associated with physical exertion occur during or immediately after intense exercise and usually affect the muscle groups that were previously strained [10]. In contrast, cramps associated with pregnancy or advanced age often occur in the legs or feet – especially during longer periods of rest, such as at night in bed. These cases are referred to as resting cramps or nocturnal leg cramps. Resting cramps later in life are quite common. In a study from the UK, one third of men and women over the age of 50 said they had experienced at least one resting cramp in the last two months. Of those affected, 40% reported having three or more cramps per week. Six per cent even said they suffered from resting cramps every night [11].

Magnesium is often recommended in these cases. It even holds the third place in the sales ranking of vitamins and food supplements in the Galaxus shop. But what is magnesium? Magnesium’s an essential mineral and plays an important role in numerous bodily functions. For example, in muscle contraction and the regulation of neuron excitability [12,13].

My colleague Anna Sandner explains in detail why the human body needs magnesium:

Magnesium and your muscles

Magnesium is the fourth most abundant mineral in the human body and occurs naturally in foods such as dark leafy greens, pulses, nuts, seeds and unrefined cereal products. Magnesium supplements are widely available and can be bought without a prescription. Many are advertised specifically for the prevention of cramps. These supplements usually consist of magnesium salts combined with various substances including citrate, lactate or sulphate. They’re usually sold as tablets, but are also available in liquid or soluble powder form. In the body, magnesium is mainly absorbed in the small intestine. This occurs either by passive diffusion or by active transport, although a smaller percentage of the magnesium is absorbed the higher the dose [14].

Magnesium influences muscle function by competing with calcium, which is necessary for muscle contraction. Calcium is released from the sarcoplasmic reticulum and binds to specific proteins to trigger contraction [15]. Magnesium can bind to the same binding sites as calcium, but its effect is weaker [15]. At rest, the magnesium concentration in the muscle cells is around 10,000 times higher than that of calcium. [15]. At rest, magnesium binds to all binding sites in the muscles and is only displaced after the release of calcium before a contraction. If too little magnesium is present, less calcium is needed to displace magnesium, which can lead to increased excitability and manifest itself in cramps and spasms.

Literature on the matter

The literature on the subject is inconclusive. There’s little evidence that magnesium relieves muscle cramps in the majority of people [16]. A 2012 meta-analysis of the studies published up to that time showed no significant reduction in the number of cramps after treatment with magnesium [17].

In contrast, however, a meta-analysis from 2002 showed that magnesium could be beneficial for muscle cramps during pregnancy [18]. However, as the sample sizes were relatively small, these studies should be taken with a pinch of salt. Large-scale studies would be necessary to clarify the benefits of magnesium. A meta-analysis published a few years ago, which included 11 studies, also matches the above statements [19]. There’s not much evidence to suggest that magnesium reduces the frequency or severity of cramps in older people.

References

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2. Westcott WL. Resistance training is medicine: Effects of strength training on health. Curr Sports Med Rep. 2012;11: 209–216. doi:10.1249/JSR.0b013e31825dabb8

3. Booth FW, Roberts CK, Laye MJ. Lack of exercise is a major cause of chronic diseases. Compr Physiol. 2012;2: 1143–1211. doi:10.1002/cphy.c110025.Lack

4. Pedersen BK, Saltin B. Exercise as medicine - Evidence for prescribing exercise as therapy in 26 different chronic diseases. Scand J Med Sci Sport. 2015;25: 1–72. doi:10.1111/sms.12581

5. Sawan SA, Nunes EA, Lim C, McKendry J, Phillips SM. The Health Benefits of Resistance Exercise: Beyond Hypertrophy and Big Weights. Exerc Sport Mov. 2023;1. doi:10.1249/ESM.0000000000000001

6. Shailendra P, Baldock KL, Li LSK, Bennie JA, Boyle T. Resistance Training and Mortality Risk: A Systematic Review and Meta-Analysis. Am J Prev Med. 2022;63: 277–285. doi:10.1016/J.AMEPRE.2022.03.020

7. Miller TM, Layzer RB. Muscle cramps. Muscle and Nerve. 2005;32: 431–442. doi:10.1002/mus.20341

8. McGee SR. Muscle Cramps. Arch Intern Med. 1990;150: 511–518. doi:10.1001/archinte.1990.00390150025005

9. Garrison SR, Birmingham CL, Koehler BE, McCollom RA, Khan KM. The effect of magnesium infusion on rest cramps: Randomized controlled trial. Journals Gerontol - Ser A Biol Sci Med Sci. 2011;66 A: 661–666. doi:10.1093/gerona/glq232

10. Schwellnus MP, Drew N, Collins M. Muscle Cramping in Athletes-Risk Factors, Clinical Assessment, and Management. Clin Sports Med. 2008;27: 183–194. doi:10.1016/j.csm.2007.09.006

11. Naylor JR, Young JB. A general population survey of rest cramps. Age Ageing. 1994;23: 418–420. doi:10.1093/ageing/23.5.418

12. Nielsen FH, Lukaski HC. Update on the relationship between magnesium and exercise. Magnes Res. 2006;19: 180–189.

13. de Baaij JHF, Hoenderop JGJ, Bindels RJM. Magnesium in man: Implications for health and disease. Physiol Rev. 2015;95: 1–46. doi:10.1152/physrev.00012.2014

14. Graham LA, Caesar JJ, Burgen AS. Gastrointestinal absorption and excretion of Mg 28 in man. Metabolism. 1960;9: 646–659.

15. Greising SM, Gransee HM, Mantilla CB, Sieck GC. Systems biology of skeletal muscle: Fiber type as an organizing principle. Wiley Interdiscip Rev Syst Biol Med. 2012;4: 457–473. doi:10.1002/wsbm.1184

16. Sebo P, Cerutti B, Haller DM. Effect of magnesium therapy on nocturnal leg cramps: A systematic review of randomized controlled trials with meta-analysis using simulations. Fam Pract. 2014;31: 7–19. doi:10.1093/fampra/cmt065

17. Garrison SR, Allan GM, Sekhon RK, Musini VM, Khan KM. Magnesium for skeletal muscle cramps. Cochrane database Syst Rev. 2012;2012: CD009402. doi:10.1002/14651858.CD009402.pub2

18. Luo L, Zhou K, Zhang J, Xu L, Yin W. Interventions for leg cramps in pregnancy. Cochrane Database Syst Rev. 2020;2020. doi:10.1002/14651858.CD010655.pub3

19. Garrison SR, Korownyk CS, Kolber MR, Allan GM, Musini VM, Sekhon RK, et al. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev. 2020;2020. doi:10.1002/14651858.CD009402.pub3

Claudio Viecelli

Biologe

claudio.viecelli@keyoniq.com

Molecular and Muscular Biologist. Researcher at ETH Zurich. Strength athlete.

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