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What you should know about: Magnesium

Many Americans take magnesium supplements, which are sometimes marketed as super pills that help a long list of ailments including muscle tension, low energy, and trouble sleeping. But think twice before you reach for this mineral in pill form. “The main reason to take this is a documented low body magnesium, usually identified by a low blood level,” says Dr. Bruce Bistrian, chief of clinical nutrition at Beth Israel Deaconess Medical Center and professor of medicine at Harvard Medical School.

Magnesium amounts in food

1 ounce dry roasted almonds

80 milligrams

½ cup frozen spinach (cooked)

78 milligrams

¾ cup bran flakes cereal

64 milligrams

1 medium baked potato w/skin

48 milligrams

½ cup canned kidney beans

35 milligrams


Magnesium is one of the body’s most abundant minerals and is an important part of hundreds of functions, including maintaining muscle and nerve function, as well as a steady heartbeat, healthy immune system, and strong bones.

The National Institutes of Health reports that most older adults in the United States don’t get the proper amount of magnesium in their diets. But Dr. Bistrian says magnesium deficiency is very rare. “The kidney has an extraordinary ability to reduce magnesium loss in the urine, and thus achieve magnesium balance on a wide variety of intakes,” he explains.


Supplements are helpful in people who are unable to absorb magnesium from food, such as people who have poorly controlled diabetes, kidney problems, alcoholism, or chronic digestive problems. Sometimes medicines—such as some diuretics, antibiotics, and cancer drugs—can interfere with magnesium absorption, making a supplement necessary.

But what about the claims that magnesium supplements can improve energy, sleep cycles, and body aches? Dr. Bistrian is skeptical. “There’s no evidence to my knowledge that it would be effective for these symptoms,” he says.

What you should do

If you’re concerned about low magnesium, ask your doctor for a blood test. A normal blood level range is 1.7 to 2.2 milligrams per deciliter (mg/dL).

To maintain a healthy magnesium level, Dr. Bistrian says it’s best to get the mineral from food, especially high-fiber foods including dark, leafy green vegetables, unrefined grains, and legumes. The recommended dietary allowance (RDA) of magnesium from food is 420 milligrams (mg) per day for men ages 50 and older and 320 mg per day for women ages 50 and older. The RDA for magnesium from a supplement is lower: 350 mg per day for men and women.

Too much magnesium from a supplement or from magnesium-containing drugs, such as antacids or laxatives, may cause diarrhea—but that’s often the desired effect. There are no known adverse effects of magnesium intake from food.

Posted by: Dr.Health

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