The importance of Magnesium in the diet and its relevance to Sports Performance

By Sarah Mortimer (HPN graduate) 

Magnesium is one of the most talked about minerals and justifiably so; it is involved in over 300 enzymatic reactions in the human body (1) including energy production pathways hence its potential relationship to sports performance. These energy pathways mentioned involve the uptake of oxygen into the muscle, the ATP (adenosine tri-phosphate) pathway as well as the electrolyte balance4 another important aspect affecting sports performance.

Undoubtedly Magnesium is a very important mineral but is supplementation necessary or can we obtain enough from our diet? Also does being physically active increase the need for the mineral therefore warranting supplementation?
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Rich dietary sources of Magnesium include whole unrefined grains, nuts, seeds, cocoa, and green leafy vegetables (2). Generally, foods like these, higher in natural fibres are also high in Magnesium, highly refined foods are a poorer source. A natural whole and unprocessed way of eating should meet the Recommended daily intake of Magnesium of between 310 – 420mg/day for adults. Magnesium can be lost via sweat thus increasing the need for dietary or supplemental magnesium in the diet of athletes.
Depletion in athletes may impair energy metabolism and ability to sustain physical activity (3). There is some evidence that magnesium deficiency may impair exercise performance by increasing the effects of oxidative stress when exercising at a high intensity (4). A deficiency of Magnesium increases the need for oxygen during exercise and therefore reduces the efficiency and output because of its impact on muscle relaxation (6).
One study of Magnesium supplementation showed with 8mgs of Magnesium per kilo of body weight per day the subjects (physically active students) experienced increases in endurance performance and decreased oxygen consumption during standardized, sub-maximal exercise (7). A larger study (8) which tested the serum Magnesium of 1,453 individuals demonstrated that higher levels were associated with greater muscle integrity and function as tested by various strength and power exercises.
The link between muscle cramps and Magnesium deficiency is also well known, results are mixed but many studies show a decrease in the frequency of cramping when supplementing with Magnesium. The results seem to be fast acting, one study showing improvement in competitive swimmers within 3 days (8). Although not shown to improve performance Magnesium has also been known to improve stress levels and sleep quality which may help with general wellbeing and human performance.

Another potential benefit of Magnesium is related to strength and power which has implications not only for sports performance but also to general wellbeing; maintenance of muscle mass being especially important as we age. It is suggested that dietary Magnesium conserves age-related loss of skeletal muscle mass and power in women of all ages (10).
If participating in a weight classified sport the likelihood of Magnesium deficiency may be heightened as a consequence of rapid weight loss and dehydration when trying to achieve a weight class. This has been shown to affect strength and power scores in Judo athletes the study suggesting supplementation particularly during times of weight loss (11).
Dosage for Magnesium supplementation seems to be between 300-600mg/day although some studies were much higher working with 8-10mg/kg of body weight per day (5). Magnesium in the form of Magnesium citrate seems to be slightly more absorbable than other forms (9).
The effect of exercise on Magnesium requirements and utilization, and the effect of Magnesium deficiency and supplementation on performance during exercise have been reviewed numerous times. It does remain unclear as to whether the benefits seen of Magnesium supplementation are due to the reversal of a deficiency or because of the actions of Magnesium itself (5). Supplementation may be of some benefit especially to physically active individuals as their needs may be higher given losses of Magnesium via sweat, and also if reducing weight. The negative effects of a deficiency on performance may warrant supplementation in athletes or a review of the current diet to make sure the natural sources of Magnesium are being consumed on a regular basis. 

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References:
1. Long, S, Romani A.M. (2014). Role of Cellular Magnesium in Human Diseases. Austin J Nutr Food Sci. Nov 18;2(10). pii: 1051.

2. Blaszczyk U; Duda-Chodak A, (2013) Magnesium: its role in nutrition and carcinogenesis.
Roczniki Państwowego Zakładu Higieny 64(3):165-71
3. Caroline H. Bohl , Stella L. Volpe (2002). Magnesium and Exercise Critical Reviews in Food Science and Nutrition . Vol. 42, Iss. 6.
4. Forrest H Nielsen, Henry C Lukaski. (2006). Update on the relationship between magnesium and exercise. Magnesium Research; 19 (3): 180-9
5. Nica, A. S., Caramoci, A., Vasilescu, M., Ionescu, A. M., Paduraru, D., & Mazilu, V. (2015). Magnesium supplementation in top athletes - effects and recommendations. Sports Medicine Journal / Medicina Sportivâ, 11(1), 2482-2494.

6. Bergstrom M, Hultman E (1988). Energy cost and fatigue during intermittent electrical stimulation of human skeletal muscle, J Appl Physiol,; 65: 1500-1505.
7. Brilla LR, Gunter KB (1995). Effect of magnesium supplementation on exercise time to exhaustion, Med Exerc Nutr Health; 4: 230-233.

8. McDonald R1, Keen CL (1988). Iron, zinc and magnesium nutrition and athletic performance, Sports Med.; 5(3): 171-84.
9. Walker AF, Marakis G, Christie S, et al. (2003). Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnes Res;16:183-91.
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10. Welch, A. A., Kelaiditi, E., Jennings, A., Steves, C. J., Spector, T. D., & MacGregor, A. (2015). Dietary Magnesium Is Positively Associated with Skeletal Muscle Power and Indices of Muscle Mass and May Attenuate the Association Between Circulating C-Reactive Protein and Muscle Mass in Women. Journal Of Bone And Mineral Research: The Official Journal Of The American Society For Bone And Mineral Research, doi:10.1002/jbmr.2692
11. Matias, C. N., Santos, D. A., Monteiro, C. P., Silva, A. M., Raposo, M. F., Martins, F., & ... Laires, M. J. (2010). Magnesium and strength in elite judo athletes according to intracellular water changes. Magnesium Research: Official Organ Of The International Society For The Development Of Research On Magnesium, 23(3), 138-141. doi:10.1684/mrh.2010.0217