Magnesium is the eighth most abundant element in the Earth’s crust by mass.1 Proposed as an element by Scottish physician Joseph Black in 1755, the name is derived from Magnesia, a district of Eastern Thessaly in Greece where compounds of this element occur naturally.2,3
Magnesium is the fourth most common mineral in the human body after calcium, sodium, and potassium.4 On average there is around 21-28 g of magnesium in the body consisting of 53% found in bones, 27% in muscles, 19% in soft tissues, and less than 1% in the serum.4 Magnesium is a cofactor in more than 300 enzymatic reactions contributing to protein synthesis, energy production, muscle contraction and relaxation, normal neurological function and regulation of vascular tone, heart rhythm, blood glucose, blood pressure and bone formation.4
Magnesium is widely distributed in plant and animal foods and in beverages, but its consumption has decreased significantly due to changes in dietary habits.5 Green leafy vegetables, such as spinach, legumes, nuts, seeds, and whole grains, are good sources as well as foods containing dietary fibre.5 However, food processing (such as refining grains in ways that remove the nutrient-rich germ and bran) substantially contributes to reduced magnesium uptake.5
The daily recommended intake (RDI) of magnesium for adults in Australia is around 300–400 mg/day.6 However, evidence confirms that nearly two-thirds of the population in the western world are not achieving the recommended daily allowance for magnesium, causing magnesium deficiencies (hypomagnesaemia) which contribute to various health conditions such as coronary artery disease and osteoporosis.7
For example, approximately 50% of Americans were found to consume less than the Estimated Average Requirement (EAR) for magnesium.8 In Germany, the intake of magnesium was determined to be only half of the recommended allowance.9 A French study found that 71.7% of males and 82.5% of females aged 4-82 had an inadequate magnesium intake.10
In 2011-12, an Australian health survey by the Australian Bureau of Statistics found that one in three people aged 19-50 did not meet their requirements for magnesium.11
GLUCOSE METABOLISM AND GLYCOLYSIS
Glucose which is the Greek word for ‘sweet’ is the primary source of energy within the body and the need for glucose increases during exercise.12 This is because exercise involves movement of many muscles and muscles are one of the biggest users of glucose.
Glycolysis is a process which breaks down glucose in order to extract the energy for cellular metabolism. Magnesium’s role in this process as a cofactor is extremely important for enzymes that are involved in the production cellular energy to help fuel the body, especially during and after exercise.13
MAGNESIUM AND EXERCISE
1. Energy production
During exercise, carbohydrates are broken down sequentially into glucose to provide energy and support during muscle movement.13
As glucose metabolism and glycolysis for energy production is dependent on cellular magnesium status, insufficient magnesium supply in the body can impair energy production.13 Also, exercise may result in magnesium deficiency because of increased magnesium excretion in sweat and urine.7
A study which examined the effects of dietary magnesium restriction on biochemical responses during submaximal exercise found that low levels of magnesium may disrupt the body’s ability to efficiently use energy stores.14 These findings indicated that dietary magnesium depletion can be induced in otherwise healthy women resulting in increased energy needs which adversely affected cardiovascular function during exercise.14
2. Muscle function
Magnesium is involved in many processes that affect muscle function including oxygen uptake and electrolyte balance.15 In response to exercise, magnesium gets transported to locations where energy production is taking place and participates in the process of energy metabolism where it also assists in the maintenance of normal muscle contraction and relaxation.13
There is evidence that marginal magnesium deficiency can impair exercise performance and thereby intensify the negative consequences of strenuous exercise such as oxidative stress.15 Oxidative stress is an imbalance of free radicals and antioxidants in the body which can damage cells and tissues, contributing to the development of many diseases.16 In addition to this, some studies have indicated an improvement on exercise performance in individuals supplemented with magnesium although a strong causal relationship has not yet been established.13,17-19
Magnesium is an essential mineral involved in energy metabolism, cardiorespiratory and muscle functions. It has been documented that the general western population including physically active individuals have insufficient magnesium intakes which could compromise the efficiency of energy metabolism as well as physical performance during exercise.
Therefore, it is important that individuals meet their RDI for magnesium6 (320 mg for women and 420 mg for men) in order to help maintain general health and wellbeing, especially when exercising.
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6. NHMRC Committee. Nutrient Reference Values for Australia and New Zealand Including Recommended Dietary Intakes: Magnesium. Commonwealth of Australia 2006.
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11. Australian Health Survey: Usual Nutrient Intakes, 2011-12.
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13. Zhang Y, Xun P, Wang R, Mao L and He K. Can magnesium enhance exercise performance. Nutrients 2017; 9: 946.
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15. Nielsen FH and Lukaski HC. Update on the relationship between magnesium and exercise. Magnes Res 2006; 19(3): 180-189.
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18. Lukaski, HC. Magnesium, zinc, and chromium nutrition and athletic performance. Can J Appl Physiol 2001; 26: S13–S22.
19. Kass LS, Skinner P and 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.