Increasing evidence supports a role of magnesium (Mg) in skeletal muscle function. However, no systematic review or meta-analysis has summarized data on Mg supplementation in relation to muscle fitness in humans. Thus, this study aimed to quantitatively assess the effect of Mg supplementation on muscle fitness. A meta-analysis and systematic review. Medline database and other sources were searched for randomized clinical trials through July 2017. Studies that reported results regarding at least one of the following outcomes: leg strength, knee extension strength, peak torque, muscle power, muscle work, jump, handgrip, bench press weights, resistant exercise, lean mass, muscle mass, muscle strength, walking speed, Repeated Chair Stands, and TGUG were included. Measurements of the association were pooled using a fixed-effects model and expressed as weighted mean differences (WMDs) with 95% confidence intervals (95% CIs). Fourteen randomized clinical trials targeting 3 different populations were identified: athletes or physically active individuals (215 participants; mean age: 24.9 years), untrained healthy individuals (95 participants; mean age: 40.2 years), and elderly or alcoholics (232 participants; mean age: 62.7 years). The beneficial effects of Mg supplementation appeared to be more pronounced in the elderly and alcoholics, but were not apparent in athletes and physically active individuals. The results of the meta-analysis suggested that no significant improvements in the supplementation group were observed regarding isokinetic peak torque extension [WMD = 0.87; 95% CI = (-1.43, 3.18)], muscle strength [WMD = 0.87; 95% CI = (-0.12, 1.86)] or muscle power [WMD = 3.28; 95% CI = (-14.94, 21.50)]. Evidence does not support a beneficial effect of Mg supplementation on muscle fitness in most athletes and physically active individuals who have a relatively high Mg status. But Mg supplementation may benefit individuals with Mg deficiency, such as the elderly and alcoholics.
Keywords: dietary supplements; magnesium; muscle fitness; muscle strength.