Magnesium is one of the most abundant minerals in the human body. All of the enzymes in the human body that utilize or synthesize ATP require the presence of magnesium ions for their catalytic actions (ATP, or adenosine triphosphate is basically the currency of energy transfer in the body). Therefore, we need magnesium to ensure our bodies can continue to make energy.
Many people don’t get enough magnesium (only 30% of Americans meet the daily requirements.) As magnesium is used to make energy, deficiencies can lead to reduced capacity to exercise, impaired performance, poor recovery post-exercise, and feeling tired and low in energy.
In addition to cellular energy production, Magnesium also has a role in muscle contraction and relaxation. Low magnesium levels are associated with an increased incidence of muscle cramps (because magnesium helps the muscle relax – no magnesium, no relaxation.) If you tend to cramp in training or in races, supplementing your diet with magnesium, particularly in the week before a race, might benefit you.
A recent study of swimmers taking magnesium supplements for training and competition found those taking 65mg of magnesium experienced an 86% reduction in cramps. Benefits were seen in as early as 3 days of supplementation.
A depletion in magnesium post-exercise can also be associated with structural damage to muscles, so replenishing magnesium levels may aid in muscle recovery. Magnesium is also a co-factor for the production of Insulin-like growth factor (IGF-1), which assists in the growth and strength of muscles.
Magnesium is found in a number of sports supplements, but not all of them. For example, Staminade powder contains magnesium, while Powerade does not. As magnesium is usually the number one electrolyte depleted after a marathon, I think it is important to choose supplements that do contain magnesium.
The RDI for Magnesium in Australia is 400-420mg for men and 310-320mg for women. However, excess consumption has not been shown to lead to toxic effects, as excess magnesium is excreted in faeces, urine and sweat, and doesn’t accumulate in the body. However, excess consumption can lead to diarrhoea. Epsom salts (magnesium sulfate) have long been used as a laxative.
Dietary sources of magnesium include nuts, spices, cocoa, unprocessed cereals, green leafy vegies, peas, beans and shellfish.
Magnesium supplements are also reasonably cheap and can be of particular benefit during periods of heavy training or in the week or so before a race, particularly races in hot climates (as sweating helps deplete magnesium levels quicker).