Magnesium is the fourth-most abundant mineral in the body, with approximately 60 per cent of it found in bone and 30 per cent in skeletal and cardiac muscle. Magnesium is also found in the blood and body fluids. It is involved in over 300 biochemical reactions in the body and is crucial for energy production, muscle function, protein synthesis and insulin metabolism. This makes it of critical importance for physical performance. Yet magnesium is one of the most common nutritional deficiencies seen in athletes, resulting in reduced performance, lactic acid buildup, muscle cramping and poor recovery.
Magnesium is vital for the conversion of glycogen to glucose – the body’s main fuel during exercise. Without sufficient levels the body switches to anaerobic metabolism, resulting in a buildup of lactic acid and associated muscle soreness and spasms. This means if you are low in magnesium you are likely to feel tired and lack energy.
Magnesium also influences protein metabolism, making it important for strength and power as well as recovery. Research published in the Journal of Nutrition suggests that even small shortfalls in magnesium intake can seriously impair athletic performance.
If you’re concerned about bone health it’s worth remembering that while calcium is important it does nothing without adequate levels of magnesium and vitamin D. Magnesium activates cellular enzyme activity, allowing the body to convert vitamin D into its active form to help with calcium absorption and bone building.
Magnesium, together with calcium, is essential for optimal muscle function. A deficiency in magnesium can result in muscle and nerve twitches, spasms and cramping. Heavy exercisers often experience a buildup of lactic acid, shin splints and painful muscles during and after exercise. Having sufficient magnesium helps speed up recovery, reduce fatigue and avoid injuries.
Low magnesium levels will decrease your insulin sensitivity, making it harder for you to lose fat and get lean. So if you are looking to change your body composition make sure you’re getting enough.
Magnesium deficiency is common, with runners and people who exercise regularly at a greater risk of because of its role in energy production and metabolism. It is also lost through sweat during exercise, and in urine. Several studies, including one published in the American Society for Clinical Nutrition, have revealed many athletes, particularly women, are failing to consume sufficient magnesium in their diet.
Top food sources of magnesium include unrefined whole grains, such as wholemeal bread and wholegrain cereals, green leafy vegetables, nuts and seeds (especially pumpkin seeds), peas, beans and lentils. Some fish, such as halibut and mackerel, are also good sources. Drinking water can be an important source of magnesium, especially “hard water”. But even if you have a healthy diet you may not be getting enough – you would need to eat more than nine bananas to meet the recommended daily amount.
The UK recommended intake for magnesium is 300mg for men and 270mg for women. The recommended intake can also be expressed in mg/kg and is roughly 6mg per kg of body weight. So if you weighed ten stone (63kg) this would be 378mg magnesium per day. Your daily needs may be higher if you exercise. And you do.