Magnesium Intake in Physically Active People

Magnesium is the fourth most abundant mineral and the second most abundant as a divalent cation at the intracellular level in the human body. This mineral participates in approximately 800 reactions linked to neuromuscular, cardiovascular and hormonal functions. The human body stores ~50% of magnesium in the bones, less than 1% in the blood, and about the remaining 50% in the cells of body ^tissues.1 Approximately 40% of bone mass is made up of magnesium, with the magnesium/calcium ratio being a determining factor for bone health and integrity.² In fact, an imbalance between these two minerals can accelerate the processes of demineralization of bones. The skeletal muscles store ~27% of the body's magnesium, being an essential element to produce energy, promote post-exercise recovery processes both at the muscular level and the central nervous system.¹

Magnesium deficiencies are rare, because it is found in a wide variety of foods, and the body has an effective storage system for this mineral in the kidneys, intestines and especially in the reserves of bone tissue. Insufficient magnesium levels in humans can be due to gastric disorders (diarrhea), excessive use of diuretics, high alcohol consumption or in certain cases due to insufficient dietary intake, such as when following extremely hypocaloric diets in athletes who must lose weight, (e.g. wrestlers, gymnasts, dancers, etc.). The symptoms associated with magnesium deficiency are apathy, muscle weakness, muscle dysfunctions such as cramps, especially in the feet, decreased post-workout recovery capacity, mental fatigue, irritability, lack of concentration, cardiac arrhythmias, elevated blood pressure. ³

Because of its role in energy production and storage, muscle function, and maintaining blood sugar levels, magnesium has been studied as an ergogenic aid for physically active people, including athletes.

Requirements.

The recommended daily intake of magnesium is 400 to 420 mg for men and 310 to 320 for women aged 14 to over 70 years of age, while in children it could be somewhat higher.⁴

Dietary sources.

Magnesium is present in nuts, legumes, seafood, green leafy vegetables, soybean flour, wheat germ and milk. Between 30% and 50% of magnesium would be absorbed in adults who ingest 90 mg of magnesium per meal. However, its absorption is influenced by different factors such as a high level of dietary fibre, especially from magnesium-poor sources such as spinach, chard, soy or cereals. ²

Magnesium and Physical Activity.

Although increased magnesium losses from urine and sweat have been reported, especially during long-term exercise, these losses should not be harmful in people who maintain a balanced and energy-adequate diet. However, in sports specialties such as swimming, where the impact of gravity is significantly reduced, the need for a higher intake of magnesium combined with dry strength training is an important factor in attenuating the loss of bone mineral density in athletes who perform many hours of training in the aquatic environment. ¹

Magnesium as a dietary supplement

As a dietary supplement, it is marketed in combination with other micronutrients (vitamins and minerals) as well as with calcium and phosphorus or in isolated form in the form of salts such as citrate, aspartate, lactate, chloride, sulfate, oxide, acetate, gluconate, magnesium chelates combined with amino ^acids2. Although formats with creatine or in cream form have also been analyzed. ⁵

Organic forms of magnesium such as citrate and aspartate have shown greater absorption so they are preferred over inorganic forms such as magnesium oxide which have a laxative effect. ² Recently, it has been proposed to include in magnesium supplements a mixed salt composed of magnesium cations with citrate and malate anions. This salt would provide between 12 and 15% magnesium with a maximum daily intake of 250 ^mg.6

Taking magnesium supplements would not improve the effects of exercise on strength or muscle mass gains. ^1,5 However, an insufficient intake from the diet can harm and limit adaptations to training. ⁵ In fact, its intake as a dietary supplement would be intended to avoid magnesium deficiencies when very restrictive hypocaloric diets are carried out during hard and prolonged training periods (e.g. bodybuilders, combat sports, dancers, or gymnasts) or when excessive amounts of alcoholic beverages are ingested. ⁵ Although most human studies have been carried out in physically active young people and only a few in older ^people7 or with animals, recent research suggests that magnesium intake in periods of aging favors protein synthesis, attenuates muscle mass loss, improves tissue regeneration and strength levels, as well as attenuates muscle loss in older people with symptoms of sarcopenia. ⁸

Supplementation protocols

Recommended doses range from > 6 to 8 mg per kg of body weight per day (~500 to ~700 mg). These doses have been associated with significant increases in magnesium in muscle cells, reaching optimal levels of saturation that could be associated with improvements in muscle function. ^5,9 Supplementation periods should last between 4 and 7 weeks.¹⁰

Because it is an alkaline element, it should not be consumed with meals but at least 1 hour before or after. Excess magnesium from the diet may not be absorbed, especially when its levels are normal. However, their intake above the needs does not seem to cause any health problems, except in people with kidney disorders. ²

Conclusions

Current scientific evidence suggests that magnesium supplementation would not exert an ergogenic effect on physical performance beyond those achieved by training. ^1,2,5,7 However, in people with low magnesium levels due to insufficient dietary intake in relation to physiological demands, supplementation may be of great help in maintaining muscle function. ^5,10

AUTHOR

Fernando Naclerio

Professor of Strength Training and Sports Nutrition
Institute for Lifecourse Development, Centre for Exercise Activity and Rehabilitation School of Human Sciences. University of Greenwich, United Kingdom.
Email: f.j.naclerio@gre.ac.uk

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BIBLIOGRAPHIC REFERENCES

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8. Liu S, Zhang L, Li S. Advances in nutritional supplementation for sarcopenia management. Front Nutr. 2023; 10(4). doi:10.3389/fnut.2023.1189522
9. Brilla LR, Haley TF. Effect of magnesium supplementation on strength training in humans. J Am Coll Nutr. 1992; 11(3):326-329. doi:10.1080/07315724.1992.10718233
10. Heffernan SM, Horner K, De Vito G, Conway GE. The role of mineral and trace element supplementation in exercise and athletic performance: a systematic review. Nutrients. 2019; 11:696. doi:10.3390/nu11030696