Recommended Nutrient Intakes for Vitamin and Minerals

Magnesium

Functions

Magnesium is important for over 300 reactions in the body. Over half of the body's magnesium is found in the bone, with the remainder in muscles and soft tissue and a small amount (about 1%) in the extracellular fluid.

Magnesium is an integral part of the inorganic structure of bones and teeth.  In soft tissue, magnesium forms part of the protein-making machinery and is necessary for energy metabolism. It is a catalyst in the reaction that adds the last phosphate to ATP.

Magnesium is required for the metabolism of protein, glucose, fat, nucleic acids. With calcium it is involved in muscle contraction and blood clotting. Calcium promotes the processes whereas magnesium inhibits them. Also the interaction between calcium and magnesium helps regulate lung function.

Magnesium holds calcium in tooth enamel and may help prevent dental caries.

Magnesium also supports the immune system.

Recommended Intakes

Table: Recommended Intakes for Magnesium (mg/day)

Food Sources

Magnesium is present in both animal and plant cells and also in the mineral chlorophyll. Green vegetables, cereals, legumes, animal products, nuts, seafood, chocolate and cocoa are good sources of magnesium.

Deficiency

By itself, magnesium deficiency is rare. Magnesium deficiency can develop with alcohol abuse, protein malnutrition, renal or endocrine disorders, in diseases that cause prolonged vomiting or diarrhoea, malabsorption disorders, and with the use of diuretics.

Magnesium deficiency can cause tetany, impair the central nervous system and may cause hallucinations. Low levels of magnesium can increase the risk of cardiac arrythmias and cardiac arrest. Also, with magnesium deficiency the walls of the arteries and capillaries undergo visible changes and tend to constrict. The magnesium ion seems to be critical to heart function and may protect against hypertension and heart disease.

Toxicity

It appears that large doses of magnesium are not harmful to humans with normal renal function. It is almost impossible to cause hypermagnesaemia from food sources. Large amounts of magnesium salts (Epsom salts) have a cathartic effect.