Magnesium is an essential mineral for every organ, muscle and bone in the body. Mineral-depleted soil has greatly contributed to magnesium deficiency in the United States, where it is estimated that 68 percent of Americans are lacking in the element. Magnesium supplements are an effective way to prevent deficiency, and there are many to choose from. As a supplement, magnesium is always bound to other compounds, such as sulfur and oxygen, which affects bioavailability and absorbability.
Functions of Magnesium
Magnesium ions are essential to all cells because they interact with phosphate to influence nucleic acids, which are the building blocks of DNA and RNA. In addition, over 300 enzymes need magnesium for their metabolic actions, as cited by "Biochemistry of Human Nutrition." Bones also need magnesium, along with other minerals and vitamins, to maintain their strength and form. Further, muscles need magnesium for proper function, especially the relaxation phase.
Magnesium Requirements and Deficiency
The National Institutes of Health state the recommended daily intake, or RDA, of magnesium is 420 mg for men and 320 mg for non-pregnant women. In healthy adults, serum levels of magnesium should be between 0.7 and 1.0 mmol/L. Symptoms of magnesium deficiency include nausea, fatigue, muscle cramps and possibly restless leg syndrome. Long-term deficiency contributes to asthma, diabetes and osteoporosis and may lead to seizures, abnormal heart beats and coronary spasms, as cited in "Human Biochemistry and Disease."
Magnesium Supplements
Numerous types and forms of magnesium supplements are available, including liquids, injectables and tablets. Magnesium can be chelated, which means attached to an organic acid, such as citrate, or non-chelated. Non-chelated forms include magnesium oxide and magnesium sulfate and are considered less absorbable than are chelated varieties. In addition to preventing deficiency, magnesium supplements are used medicinally as laxatives and antacids and to reduce excessive nerve excitation and blood vessel spasm.
Magnesium Oxide
Magnesium oxide is a non-chelated supplement almost always taken as a tablet and considered safe for long-term use. It contains the highest amount of elemental magnesium per tablet of any magnesium supplement at 60 percent, according to the National Institutes of Health. High amounts of elemental magnesium theoretically increase bioavailability, although magnesium oxide is not absorbed well in the intestines, at only a 4 percent rate. Thus, a 500 mg tablet of magnesium oxide contains 300 mg of elemental magnesium, although only 12 mg or so is absorbed. The remaining magnesium stays in the intestines for a while, creating a strong laxative affect.
Magnesium Sulfate
Magnesium sulfate is most commonly found in tablets containing other minerals and vitamins. By itself, it can be administered intravenously in hospitals to treat pre-eclampsia in pregnant women, convulsions and childhood acute kidney inflammation. Magnesium sulfate is also safe to use long term as a dietary supplement, although it contains only 10 percent elementary magnesium, which is the lowest of any magnesium supplement. Thus, a 500 mg tablet of magnesium sulfate contains only 50 mg of elemental magnesium. Its absorption rate is slightly better than that of magnesium oxide, but not nearly as efficient as magnesium citrate. Magnesium sulfate is a primary ingredient in Epsom salt and also has strong laxative effects.
References
- "Nutrition and Public Health"; Sari Edelstein; 2006
- "Biochemistry of Human Nutrition"; George Gropper; 2000
- National Institutes of Health: Office of Dietary Supplements: Dietary Reference Intake for Magnesium
- "Human Biochemistry and Disease"; Gerald Litwack; 2008
- National Institutes of Health: Office of Dietary Supplements: Percentage of Elemental Magnesium
- "Harrison's Principles of Internal Medicine"; A. Fauci et al.; 2008
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