Sarah Renaghan, M.S.
Magnesium – what does it do for – or to – us? As an essential trace element, it is vital to the human body. Magnesium facilitates over 300 enzymatic reactions in the human body in the areas of energy metabolism, electrolyte and ion balance, cell signaling, and protein synthesis, all of which relate to physical activity and fitness.
Magnesium plays both a direct and indirect role in the body’s physiological response to exercise conditions. Exercise increases production of both sweat and urine, and thus loss of electrolytes including magnesium, but the body’s magnesium stores become redistributed to meet the increased muscle metabolism needs. The nutrient allows for the direct regulation of muscle contraction/ relaxation by regulating calcium flux and energy-producing molecules (ATP). Indirectly, it supports multiple enzymes in the glycolytic pathway and oxidative metabolism throughout the body. Because of increased energy needs during exercise and sports, low magnesium levels limit performance.
The redistribution during exercise is temporary and shifts back to restore plasma concentrations and meet the needs of damaged muscle tissue. Proper magnesium levels in the skeletal muscle alleviate oxidation/ inflammation, prevent mitochondrial swelling, promote proper cellular signaling and regulate electrolyte/ ion flux; a deficiency worsens the negative effects of exercise.
How much is enough to avoid deficiency? The Recommended Daily Allowance (RDA) values for 19-31 year old men and women are 400 and 310mg/day, respectively; for 31 and older, those values increase to 420 and 320mg/day. Dietary sources of magnesium include green leafy vegetables, whole grains, fish, nuts, legumes and soy. Consuming magnesium-rich whole foods brings in other minerals, many of which interact beneficially. Certain food combinations increase magnesium absorption (i.e. vitamin D) while others may decrease it (i.e. fiber, protein).
What about too much magnesium or not enough? Excess magnesium levels scarcely ever occur with dietary consumption but may occur with non-dietary products such as supplements, laxatives and antacids and can be serious. Another cause of toxicity is poor renal function; the kidneys are unable to filter out excess magnesium. All that being said, exercise may increase body magnesium requirements by 10-20% so consuming greater than the RDA through food sources would likely prevent deficiency. Individuals with poor renal function, especially related to kidney disease or diabetes, should consult with a physician prior to increasing intake of magnesium. There is a tolerable upper intake limit for supplemental forms of magnesium (350mg/day for adults). Oral magnesium supplements are typically used; magnesium gluconate has been shown to have highest absorption. Topical solutions may also be used for direct absorption into skin and often used for localized pain relief.
Magnesium poor diets may lead to deficiencies. Refined carbohydrates, dairy, and meat are magnesium-poor food sources and thus, diets high in these foods may lead to deficiencies. Deficiencies are most common in sports when athletes are on calorie-restricted diets for weight-class sports (i.e. wrestling). Symptoms of deficiency include muscle weakness, neuromuscular dysfunction, muscle cramping/ spasms, decreased immune function and impaired response to oxidative damage and stress. Deficiency-related impairments in sport performance include reduced exercise capacity and endurance, increased heart rate and oxygen uptake during submaximal exercise, impaired neuromuscular function, fatigue, cramping, and impaired immune function/recovery. Supplementation has not been shown to improve performance in individuals with adequate magnesium status but may improve exercise performance resulting from a magnesium-deficient diet.
Altogether, adequate magnesium levels maximize sports and exercise performance. With heavy physical activity, supplements may help maximize performance and avoid both exercise-related harmful effects and magnesium deficiency effects but – they must be used with care and only by those with normal renal function.
For further reading
- Kass LS, Skinner P, Poeira F. A pilot study on the effects of magnesium supplementation with high and low habitual dietary magnesium intake on resting and recovery from aerobic and resistance exercise and systolic blood pressure. J Sports Sci Med. 2013(12): 144-150. Accessed on 28 June 2013. Retrieved from http://www.jssm.org/vol12/n1/20/v12n1-20text.php.
- Kies CV, Driskell JA. Sports Nutrition: Minerals and Electrolytes. CRC Press, 1995: 152-169. http://www.crcpress.com/product/isbn/9780849379161
- Nielsen FH, Lukaski HC. Update on the relationship between magnesium and exercise. Magnes Res. 2006 Sep;19(3):180-9. Accessed on 20 June 2013. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/17172008.
- Office of Dietary Supplements, National Institutes of Health. Dietary Supplement Fact Sheet: Magnesium. Reviewed 13 July 2009. Accessed on 1 July 2013. Retrieved from http://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/.
- Swaminathan R. Magnesium metabolism and its disorders. Clin Biochem Rev. 2003 May;24(2):47-66. Accessed on 25 June 2013. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/18568054.