Magnesium
Organic magnesium is important in both plant and animal life. Chlorophylls are
magnesium-centered porphyrins. The adult daily nutritional requirement, which is
affected by various factors including gender, weight and size, is 300-400
mg/day. Many enzymes require the presence of magnesium ions for their catalytic
action, especially enzymes utilizing ATP. Inadequate magnesium intake frequently
causes muscle spasms, and has been associated with cardiovascular disease,
diabetes, high blood pressure, anxiety disorders and osteoporosis. Acute
deficiency is rare.
The DRI upper tolerated limit for supplemental magnesium is 350 mg/day. The most
common symptom of excess magnesium is diarrhea. Infants should not be given
magnesium supplements.
Green vegetables such as spinach provide magnesium because the center of the
chlorophyll molecule contains magnesium. Nuts, seeds, and some whole grains are
also good sources of magnesium.
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 magnesium content of refined foods is usually low. Whole-wheat bread, for
example, has twice as much magnesium as white bread because the magnesium-rich
germ and bran are removed when white flour is processed. 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. Dietary surveys
do not estimate magnesium intake from water, which may lead to underestimating
total magnesium intake and its variability.
Following are some foods and the amount of magnesium in them:
- spinach (1/2 cup) = 80 milligrams (mg)
- peanut butter (2 tablespoons) = 50 mg
- black-eyed peas (1/2 cup) = 45 mg
- milk, low fat (1 cup) = 40 mg
