Magnesium

Other Name(s):

magnesium carbonate, magnesium citrate, magnesium hydroxide, magnesium oxide, magnesium sulfate

General Description:

Magnesium is an essential element involved in the proper functioning of more than 300 enzymes. It is required for nerve and muscle activity, and to regulate the electrical and muscular activity of the heart. Magnesium is found in many over-the-counter antacids and laxatives. Because magnesium is found in many food sources, magnesium deficiency is rare.

Magnesium has many functions in the body. Important actions include activating enzymes involved in reactions in the ATP/phosphate energy cycle and carbohydrate metabolism, participating in nerve conduction, helping regulate nerve irritability and helping regulate muscle irritability.

Magnesium plays an essential role in the formation and structure of bone and tooth enamel. It is required to convert protein, carbohydrates and lipids into energy, and it aids in the synthesis of protein, RNA and DNA. Magnesium is involved in the breakdown (metabolism) of many substances in the body.

Medically Valid Uses:

Magnesium, particularly in the form of magnesium sulfate or magnesium citrate, is used as a laxative and bowel evacuant. Magnesium citrate is typically given to cleanse the bowel before taking X-rays, CT scans or MRIs of the abdomen.

Magnesium is also used to prevent and treat hypomagnesemia (low magnesium levels). In hospitals, magnesium is used to treat pre-eclampsia and eclampsia, conditions occurring during pregnancy and immediately after delivery.

In conjunction with calcium, vitamin D and parathyroid hormone, magnesium is essential for the production of healthy bone tissue and tooth enamel. Magnesium supplements may be prescribed to treat certain heart conditions, such as heart attack, heart rhythm abnormalities, cardiac surgery, congestive heart failure and digitalis poisoning. It may also be used during cardiac surgery.

Unsubstantiated Claims:

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Magnesium is claimed to be useful in maintaining the health of muscles, bone and nerve tissues. It may help nervous conditions by fighting anxiety as a natural tranquilizer. It may help with depression, induce sleep in people suffering from insomnia and relieve PMS. It is said to prevent muscle cramps, muscle weakness and fatigue. Magnesium is also claimed to prevent heart disease, arteriosclerosis (hardening of the arteries) and high triglyceride levels.

Recommended Intake:

As indicated below, magnesium is measured in milligrams (mg). The DRI is the Dietary Reference Intake.

Group

DRI

Infants (0 to 6 months)

30 mg

Infants (6 months to 1 year)

75 mg

Children (1 to 3 years)

80 mg

Children (4 to 8 years)

130 mg

Boys (9 to 13 years)

240 mg

Girls (9 to 13 years)

240 mg

Boys (14 to 18 years)

410 mg

Girls (14 to 18 years)

360 mg

Men (19 to 30 years)

400 mg

Women (19 to 30 years)

310 mg

Men (31+ years)

420 mg

Women (31+ years)

320 mg

Pregnant women

+ 40 mg

Breast-feeding women

No change

Magnesium supplements come in many forms. Each form has a different percentage of magnesium. Magnesium oxide and magnesium hydroxide contain the highest concentrations of magnesium, with magnesium gluconate and magnesium gluceptate containing the lowest.

Dosage is expressed either as the amount of magnesium present or the percentage of magnesium in the preparation. Be sure to read the label carefully to see if it expresses the amount of elemental magnesium or the total weight of the compound. The equivalent amount of elemental magnesium can be calculated by multiplying the percentage of magnesium in the preparation by ten. Thus, 1 gram of magnesium oxide contains 60.3 percent of magnesium, or 603 mg.

To prevent diarrhea, magnesium supplements should be taken with food.

Increased need for magnesium occurs in people with diabetes, malabsorption syndrome or kidney disease, or in people who regularly take diuretics (water pills). Vomiting or diarrhea, especially over a long period of time, can deplete the body's magnesium. Burns over large areas of the body, extreme athletic performance or moderate-to-heavy use of alcohol may also increase magnesium requirements. Athletes who restrict calories may require magnesium supplements.

 

Food source

Nutrient content per 100 grams

Cashews

267 mg

Almonds

252 mg

Brewer's yeast

231 mg

Peanuts

181 mg

Peanut butter

178 mg

Pistachios

158 mg

Walnuts

134 mg

Kidney beans

132 mg

Dried figs

82 mg

Beet tops

71 mg

Milk

70 mg

Lima beans

66 mg

 

Because magnesium is present in almost all foods, diets deficient in magnesium are rare. Signs of deficiency may include weakness, confusion, muscle tremor, lack of coordination, personality changes, gastrointestinal disorders and loss of appetite (resulting in pathological thinness).

Side Effects, Toxicity and Interactions:

Taking too much magnesium can result in diarrhea (the most common side effect), low blood pressure (hypotension), irregular heartbeats (arrhythmias) and muscle weakness. Severe nausea and vomiting can also result.

Magnesium supplements may be dangerous for people with kidney failure, chronic renal failure or impaired kidney function. Supplements may also be dangerous if you have a heart block.

Women who are pregnant or breast-feeding should consult a physician before taking any mineral supplements.

Magnesium is used in many antacid formulations and can cause diarrhea. Taking magnesium preparations with food may reduce the symptoms.

Additional Information:

Click here for a list of reputable Web sites with general information on nutrition.

References:

  1. Behrman RE, Kliegman RM, Nelson EE, Vaughan VC, eds. Nelson Textbook of Pediatrics. 14th ed. Philadelphia, PA: W.B. Saunders Co.; 1992.

  2. Braunwald E, Isselbacher KJ, Petersdorf RG, Wilson JD, Martin JB, Fauci AS, eds. Harrison's Principals of Internal Medicine. 11th ed. New York, NY: McGraw-Hill; 1987.

  3. Smolin LA, Grosvenor MB. Nutrition Science and Applications. 2nd ed. Sanders College Publishing; 1997.

  4. Magnesium. Facts and Comparisons. St Louis, MO: Facts & Comparisons; 1991.

  5. USP DI 19th ed. Englewood, CO: Micromedex Inc.; 1999

  6. Wiesmann HP, Tkotz T, Joos U. Magnesium in newly formed dentin mineral of rat incisor. J Bone Miner Res. 1997;12(3):380-3.

  7. Tucker KL, Hannan MT, Chen H, Cupples LA, Wilson PW, Kiel DP. Potassium, magnesium, and fruit and vegetable intakes are associated with greater bone mineral density in elderly men and women. Am J Clin Nutr. 1999;69(4):727-36.

  8. Rude RK, Kirchen ME, Gruber HE, Stasky AA, Meyer MH. Magnesium deficiency induces bone loss in the rat. Miner Electrolyte Metab. 1998;24(5):314-20.

  9. Clarkson PM, Haymes EM. Exercise and mineral status of athletes: calcium, magnesium, phosphorus, and iron. Med Sci Sports Exerc. 1995;27(6):831-43.

  10. Shils ME. Magnesium. In: Shils ME, Olson JA, Shike M, eds. Modern Nutrition in Health and Disease. 8th ed. Philadelphia, PA: Lea & Febiger; 1994:164-184.

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