Written by Ioannis Nikitidis, Medical Doctor, Dietitian and Nutritionist
The Magnesium role in human body
Magnesium (Mg) is the second most abundant mineral after potassium and serves as a co-factor in more than 300 enzymatic reactions, including energy production. (1) Magnesium is an essential element that regulates membrane stability and neuromuscular, immune, cardiovascular and hormonal functions and is an important cofactor in many metabolic reactions. The Dietary Reference Intake (RDI) for magnesium for adults is 310(females) to 420(males) mg/day. (2) Some of the most common food sources of magnesium are: Pumpkin seeds, wholegrains breads and cereals, green leafy vegetables, lean meat, legumes, nuts, milk, yogurt and tofu. (3)
Interest in potential adverse effects of physical activity on magnesium status among sports medicine specialists began with the diagnosis of magnesium deficiency in a female tennis player who was experiencing frequent episodes of muscle spasms associated with prolonged outdoor exercise. (4) There are studies indicating that prolonged endurance exercise like marathon running in contrast to short-term, high-intensity exercise, decreased plasma and serum magnesium concentrations. This decrease is usually temporary and returns to baseline within a day. It has been attributed to the movement of magnesium into other body compartments and an increase in excretion through urine and sweat. In case the decrease in serum magnesium is not temporary, it may indicate that exercise increases the magnesium requirement to a point where intake is inadequate and thus results in a sub clinical or deficient status. (5)
Magnesium deficiency and supplementation
Although studies have shown that oral magnesium intake does not appear to have any beneficial effects in athletes with adequate magnesium, supplementation may benefit performance in individuals who are magnesium deficient.
(6) According to a study, a marginal magnesium-deficiency was found to impair exercise performance in untrained postmenopausal women. Specifically, heart rate and oxygen consumption increased significantly during submaximal exercise when the women were supplemented with 150 mg of magnesium versus 320 mg/d. Moreover, there are studies reporting that magnesium supplementation resolved muscle cramps and spasms in strenuously exercising individuals. Furthermore, in a study of young men participating for seven weeks in a strength-training program and consuming about 250 mg magnesium/day, a greater increase in peak knee-extension torque was found in those fed an additional 250 mg/day than those fed a placebo. Additional studies indicate that magnesium supplementation leads to decreased serum ammonia concentration which in turn means a better use of energy and carbohydrates during exercise and thus a beneficial response of an exercising individual with a low magnesium status. In a study among 100-yard male and female swimmers, dietary magnesium has been found to be a significant predictor of performance improvement. (5)
The relation between magnesium and glucose metabolism
Mg is directly involved in glucose metabolism and this might be one of the factors contributing to its performance enhancing effects during exercise. Thus, the enhancement of exercise performance by Mg could be related to glucose availability and regulation. It is widely known that exercise needs the integration of several systems in the whole body.
For example, the muscle-skeletal system responds to the action and the circulatory system needs to increase the cardiac output for supporting more oxygen and other related compounds. Brain and spinal cord control, plan, and regulate the motor commands. Several studies have investigated glucose changes only in the blood, muscle, or brain to study systemic effects of exercise. Therefore, exploring the glucose changes in the blood, muscle, and brain simultaneously is important to understand the systemic changes. In addition, effects of Mg on the dynamic glucose changes in the blood, muscle, and brain remain unclear and at times controversial. Furthermore, obtaining samples from multiple locations in an exercising animal is always an analytical challenging. (1)
In an animal study (2014), researchers tried to explore the effects of Mg on the dynamic changes in glucose and lactate levels in the muscle, brain and blood of exercising rats. They concluded that Mg possibly enables the provision of an adequate glucose source by increasing glucose availability and facilitating the clearance of lactate. An integral system for the simultaneous determination of dynamic changes in glucose and lactate in the blood, muscle, and brain of exercising rats was established. (1)
In a study (2014) among male volleyball players, researchers evaluated the influence of magnesium supplementation on the physical performance. It was reported that decreases in lactate production and significant increases (of up to 3 cm) in countermovement jump and countermovement jump with arm swing values were detected in the experimental group following magnesium supplementation, but not in the control group. Additionally, it was concluded that magnesium supplementation improved anaerobic metabolism, even though the players were not magnesium-deficient. (7)
The importance of magnesium in pre-workout and during workout
~ Written by Ioannis Nikitidis, Medical Doctor, Dietitian and Nutritionist
3) Dr Louise Burke & Greg Cox. The complete guide to food for sports performance - Peak nutrition for your sport. 3rd Edition, Allen& Unwin, 2010