Magnesium: What you need to know

Magnesium plays important roles in both the structure and the function of the human body, which contains about 35 grams of this element with over 60 percent found in the skeleton, 27 percent in muscle, about 7 percent in other tissue and cells. 

Magnesium is involved in hundreds of essential metabolic reactions such as energy production, synthesis of essential molecules like nucleic acid and proteins, formation of bone, cell membranes and chromosomes. Magnesium affects transport of ions like potassium and calcium across cell membranes. 

Magnesium can interact with other nutrients like zinc, fiber, protein, vitamin D and calcium.  Too much of supplemental form of zinc may affect absorption of magnesium.  High intake of fiber can also reduce magnesium utilization, so can low intake of protein and active form of vitamin D or calcitriol.  That is, high protein, vitamin D and low fiber intakes may increase utilization of magnesium. 

Magnesium deficiency is rare in healthy individuals.  At risk are people with conditions like gastrointestinal disorders (prolonged diarrhea, Crohn's disease, malabsorption syndromes, celiac disease, surgical removal of part of the intestine), renal disorders (diabetes mellitus and chronic use of certain diuretics) and chronic alcoholism. Older people are more likely magnesium deficient. 

Magnesium deficiency may raise risk of a number of diseases or health conditions including hypertension (high blood pressure) and cardiovascular disease.  Sufficient magnesium may help prevent these conditions. 

Magnesium may also help treat diseases.  Supplementation of this element in dosage of 485 mg per day has been found in trials to lower blood pressure.   

High dose intravenous magnesium sulfate has been used to prevent eclamptic seizures that are associated with preeclampsia-eclampsia late in pregnancy and during labor.  The element is believed to relieve cerebral blood vessel spasm and increase blood flow to the brain. 

This element may also be used to reduce risk of death in patients who have suffered heart attack or myocardial infarction.  Other potential applications include treatment of diabetes, osteoporosis, migraine headaches and asthma. 

The dietary allowance for magnesium recommended by The Food and Nutrition Board of the Institute of Medicine is about 400 mg per day for adult men and 310 mg per day for adult women.  Infants, children, adolescents, pregnant women and breast feeding women also get a recommended dietary allowance for the nutrient. But it does not really serve much of a guideline because you simply cannot measure the nutrition in your diet and don’t really know whether you are magnesium deficient. 

One large survey of U.S. men and women shows that intake of magnesium by Americans (320 mg per day for men and 230 mg per day for women) is far below the recommended dietary allowance. Older people have even lower intake of the nutrient. 

To have sufficient magnesium, food consumers should eat more plant-based foods including green leafy vegetables, unrefined grains and nuts.   Foods high in magnesium include 100% bran cereal, oat bran, shredded wheat, brown rice, almonds, hazelnuts, peanuts, lima beans, spinach, Swiss chard, molasses, and banana. 

In addition, magnesium may be obtained through supplementation.  Magnesium supplements can be magnesium oxide, magnesium gluconate, magnesium chloride, and magnesium citrate among others. 

Dietary intake of magnesium rarely results in any toxic effects. But magnesium supplements may.  One symptoms of excessive intake of supplemented magnesium is diarrhea.  Because of this, magnesium salts may actually be used as a laxative. People with certain conditions like impaired kidney function may be more vulnerable to the toxicity of the element.

By David Liu davidl at foodconsumer dot org