It is estimated that many Americans do not get enough magnesium. Magnesium is the fourth most abundant mineral in the body (after calcium, phosphorus, and sulfur) and is essential for good health – especially of the heart, muscles and kidneys.

The mineral enables proper muscle and nerve functioning. It steadies heart rhythm, regulates blood sugar levels and blood pressure, and keeps bones strong. It may even protect against cardiovascular disease and immune system dysfunction.

Magnesium is sometimes used as a laxative for constipation and as an antacid for indigestion. Studies have indicated that magnesium supplements may help prevent or shorten the duration of migraine headaches. A 2010 study by researchers at the Massachusetts Institute of Technology and Tsinghua University in Beijing found that it improved short- and long-term memory.

As magnesium moves through the body, it helps neutralize stomach acid and move stool through the intestines, where it is absorbed and transported via the blood to cells and tissues throughout the body. Excess magnesium is excreted through the kidneys.

A balanced and varied diet will usually provide needed nutrients, including magnesium. Foods high in fiber tend to also be high in magnesium, such as dark green leafy vegetables, broccoli, squash, beans, peas, nuts, seeds, unrefined grains, and soy products. Tap water contains magnesium – “hard” water contains more minerals, including magnesium, than “soft” water – as does dairy products, meats, chocolate, and coffee.

The recommended dietary allowance of magnesium is 400 to 420 milligrams (mg) for adult men; 310 to 320 for adult women. For example, foods with magnesium benefits include:

3 ounces halibut 90 mg
½ cup cooked spinach 75 mg
1 ounce mixed nuts, dry roasted 65 mg
Shredded wheat cereal (2 rectangles) 55 mg
1 potato, baked with skin 50 mg
1 yogurt 45 mg
½ cup brown rice 40 mg
1 banana 30 mg
1 cup whole milk 24 mg

Signs of magnesium deficiency are rare, and tend to occur in stages. Initial symptoms may include hyperexcitability, muscle weakness, and sleepiness. Later symptoms include loss of appetite, insomnia, poor memory, fatigue, and muscle twitching. More advanced cases of magnesium deficiency may involve symptoms of muscle cramps, seizures, a rapid heartbeat, and personality changes. In severe cases, delirium, numbness, and hypocalcemia (low levels of calcium in the blood) may occur.

Magnesium deficiency is more likely among the following people and conditions:

• Older adults. The body’s ability to absorb minerals and nutrients declines with age. Studies have shown that older adults have lower blood levels of magnesium than younger adults.
• High-fat diet. People who eat foods high in fat tend to absorb less magnesium.
• African Americans. Black people tend to have lower levels of magnesium than people in other racial groups.
• Diabetics. Hyperglycemia is associated with an increased loss magnesium in urine.
• Alcoholics. Lower magnesium levels have been noted in people who substitute alcohol for food.
• Gastrointestinal disorders. People with malabsorptive conditions, such as Crohn’s disease and gluten sensitivity, may have an impaired ability to absorb magnesium. In addition, chronic vomiting or diarrhea can cause a magnesium deficiency.
• Certain medications. Some medicines can impair the body’s ability to absorb magnesium. These include diuretics, antibiotics, and some cancer medications.

Magnesium supplements generally contain another substance, such as a salt. They should be taken with meals; on an empty stomach, the supplements can cause diarrhea. In some cases, intravenous magnesium replacement may be required.

People with kidney disease should consult a doctor before taking magnesium as they may not be able to adequately excrete excess magnesium.

Too much magnesium may result in diarrhea and abdominal cramps.