Magnesium is an essential mineral present in tiny amounts in the body. It has many different roles, including helping to make bone and other tissues, converting food to energy, and aiding in the activity of more than 300 enzymes (chemicals that regulate various bodily functions).

Between 50 percent and 75 percent of the body’s magnesium is found in the bones. Most of the remainder is found in the muscles and soft tissue, with a tiny fraction present in the blood. Some of magnesium’s other roles in the body include maintenance of nerve and muscle cells, helping the immune system function properly and holding calcium in tooth enamel, which helps prevent dental caries.

The majority of adults in the United States do not receive the recommended levels of magnesium from their diets. Magnesium found in drinking water helps to make up this deficit, and magnesium deficiency is rare.

Consuming excessive amounts of magnesium usually does not cause problems in healthy people. However, it can be potentially fatal in people who cannot excrete the extra magnesium due to kidney problems.

Magnesium is found in many different types of food. Dark green vegetables such as spinach are rich in magnesium because it is present in the center of the chlorophyll molecules that give the vegetable its color. Other good sources of magnesium include certain fruits, legumes, nuts and whole grains.

Magnesium supplements are available in both over-the-counter and prescription formulations. They sometimes are recommended by physicians for people who have certain health conditions.