Although magnesium is present in many foods, it usually occurs in small amounts. As with most nutrients, daily needs for magnesium cannot be met from a single food. Eating a wide variety of foods, including five servings of fruits and vegetables daily and plenty of whole grains, helps to ensure an adequate intake of magnesium. The table of food sources of magnesium suggests many dietary sources of magnesium. Water can provide magnesium, but the amount varies according to the water supply.
Hard water contains more magnesium than soft water.
Even though dietary surveys suggest that many Americans do not consume magnesium in recommended amounts, magnesium deficiency is rarely seen in the United States in adults. Gastrointestinal problems, such as malabsorption disorders, can cause magnesium depletion by preventing the body from using the magnesium in food. Healthy adults who eat a varied diet do not generally need to take a magnesium supplement. Extra magnesium may be required by individuals with conditions that cause excessive urinary loss of magnesium, chronic malabsorption, severe diarrhea and steatorrhea, and chronic or severe vomiting. Doctors routinely monitor magnesium levels of individuals who take these medicines and prescribe magnesium supplements if indicated.