Minerals and trace elements - Magnesium
Magnesium is an essential mineral present in all human tissues, especially in bone. It has both physiological and biochemical functions and has important interrelationships with calcium, potassium and sodium. It is needed for the activation of many enzymes (for example enzymes concerned with the replication of DNA and the synthesis of RNA) and for parathyroid hormone secretion, which in involved in bone metabolism. It is also needed for muscle and nerve function.
Nutritional deficiency is rare and characterised by progressive muscle weakness and neuromuscular dysfunction. Mild hypomagnesaemia (low blood magnesium) is common in severely ill patients, alcoholics and those with malabsorption disorders.
In contrast, intakes of magnesium that are judged to be too low are quite common in the UK. Despite magnesium being available in a wide range of foods, one in five women aged 19-34 years and more than half of teenage girls have intakes below the LRNI (51% of 11-14 age group and 53% of 15-18 age group) and more than 20% of boys aged 11-14 years are also at risk of low intakes.
There is no evidence that large dietary intakes are harmful to humans with normal kidney function. However, regular intake of high dose supplements can result in diarrhoea and may also result in raised blood levels of magnesium with associated adverse effects.
Magnesium is present in both plant and animal cells and is the mineral in chlorophyll, the green pigment in plants, and so is widely available. Sources include green leafy vegetables, nuts, bread, fish, meat and dairy products.
© British Nutrition Foundation