Muscle Cramps: Does Magnesium Really Work?

A Cochrane review published in September 2020 assessed 11 randomised controlled trials to determine if magnesium supplementation was effective in reducing the incidence of skeletal muscle cramps. 10 out of the 11 trials used oral magnesium supplementation as prevention for muscle cramps. Assessment of 735 individuals found no evidence that magnesium supplementation was effective in the prevention of muscle cramps. Three trials assessed magnesium in prevention of muscle cramps during pregnancy, but results were conflicting across all three studies(1).

It is important to note that the studies included assessed magnesium in the prevention of idiopathic muscle cramps (i.e. cramps occurring without a clear cause), as well as cramps in pregnancy and cramps in people with liver disease. The review did not assess exercise-associated muscle cramps as no clinical trials were found assessing this condition. So what about magnesium supplementation for exercise?

According to the Australian Institute of Sport (AIS), current evidence suggests that magnesium supplementation does not confer any performance benefits for athletes that have sufficient dietary intake and magnesium supplementation therefore is not recommended(2). However, it can be difficult for some people to know if they're getting enough dietary magnesium.

According to the Australian Bureau of Statistics, the 2011 - 2012 National Nutrition and Physical Activity Survey found that one in three Australians over the age of two did not meet their Estimated Average Requirement (EAR) for daily intake of Magnesium, with 37% of males and 34% of females not meeting the requirement from their diet. The results of this national survey revealed that 72% of females and 61% of males aged 14 to 18 did not meet the EAR(3). So could this potentially be grounds for athletes to consider supplementing with magnesium?

While RCTs to date suggest there is no significant benefit of taking magnesium for the prevention of muscle cramps in the general population, athletic individuals may be more susceptible to muscle cramps and very little data exists to evaluate the magnesium intake and status in this population. Given that many athletes report subjective improvement in muscle cramping symptoms while using magnesium supplements, in the presence of data indicating that a significant proportion of the population may have insufficient magnesium intake from diet alone, it may be beneficial for active individuals to test magnesium supplementation on an individual basis to determine if they benefit from its use.

References:
1. Garrison S, Korownyk C, Kolber M, Allan G, Musini V, Sekhon R et al. Magnesium for skeletal muscle cramps. Cochrane Database of Systematic Reviews [Internet]. 2020;. Available from: https://www.cochranelibrary.com/
2. Australian Institute of Sport (AIS) https://www.ais.gov.au/
3. Australian Health Survey: Usual Nutrient Intakes, 2011-12 financial year [Internet]. Australian Bureau of Statistics. 2021 [cited 17 May 2021]. Available from: https://www.abs.gov.au/statistics/health/
Muscle Cramps - Does Magnesium Really Work?

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