Abstract

PALHA, Cátia; GOUVEIA, Miguel  and  FERNANDES, Sara Guimarães. Oral magnesium supplementation in muscle cramp prevention: evidence-based review. Rev Port Med Geral Fam [online]. 2020, vol.36, n.1, pp.36-42. ISSN 2182-5173.  https://doi.org/10.32385/rpmgf.v36i1.12533.

Aim: Evidence review on the efficacy of oral magnesium supplementation in the prevention of muscle cramps without associated pathology, in adults. Data sources: National Guideline Clearinghouse, Canadian Medical Association Practice Guidelines Infobase, Guidelines Finder, The Cochrane Library, DARE, Bandolier, Evidence-Based Medicine Online, and PubMed. Methods: On 4^th July 2018, using the MeSH terms ‘Muscle Cramp’, ‘Magnesium’ and ‘Magnesium Compounds’, we searched for meta-analyses, systematic reviews, randomized controlled trials (RCT), observational studies and clinical guidelines published in Portuguese, Spanish, and English. To assign levels of evidence (LE) and strength of recommendations, the Strength of Recommendation Taxonomy (SORT) scale of the American Academy of Family Physicians was used. Results: We found 47 articles, of which five met the inclusion criteria: one meta-analysis (LE 2), three systematic reviews (LE 2) and one RCT (LE 2). No studies related to exercise-associated cramps were found. Studies are consensual in the apparent lack of efficacy of the magnesium in the prevention of idiopathic muscle cramps. As for the pregnancy-associated cramps, the evidence is inconsistent. However, the use of small samples, short follow-up periods and the heterogeneity of methodologies (population, supplement type, posology, and outcomes) compromise the extrapolation and reduce the strength of the conclusions obtained. Conclusion: According to the evidence found, oral magnesium supplementation in the general population seems to be ineffective in preventing idiopathic muscle cramps (SORT B), therefore, with no evidence to support its routine prescription in clinical practice. In pregnancy-associated cramps, the evidence of oral magnesium supplementation is unclear (SORT B). To achieve more robust conclusions, higher quality RCT is needed, with more homogeneous methodologies.

Keywords : Muscle cramp; Magnesium; Magnesium compounds.

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