Magnesium is an element (Mg) with an atomic weight of 24.312 and the atomic number 12. In its elemental form, magnesium is a light, silver-white metal. It is a cation, which means that its ion has a positive charge. Of the cations in the human body, magnesium is the fourth-most abundant. Ninety-nine percent of the body's magnesium is contained within its cells: about 60% in the bones, 20% in the muscles, 19%–20% in the soft tissue, and 1% circulates in the blood. Important to both nutrition and medicine, magnesium, like calcium and phosphorus , is considered a major mineral. Magnesium in its carbonate and sulfate forms has been used for centuries as a laxative. The name of the element comes from Magnesia, a city in Greece where large deposits of magnesium carbonate were discovered in ancient times.
Magnesium is an important element in the body because it activates or is involved in many basic processes or functions, including:
- cofactor for over 300 enzymes
- oxidation of fatty acids
- activation of amino acids
- synthesis and breakdown of DNA
- immune function
- interactions with other nutrients, including potassium , vitamin B6, and boron
Magnesium has a number of general uses, primarily in standard allopathic medicine, but also in some alternative therapies.
The Food and Nutrition Board of the National Academy of Sciences has established the following dietary reference intakes (DRIs) and tolerable upper limits (ULs) for magnesium: Infants and children 0–6 months, 30 mg; 7–12 months, 75 mg; 1–3 years, 80 mg; 4–8 years, 130 mg; 9–13 years 240 mg. Males 14–18 years, 410 mg; 19–30 years, 400 mg; over 30 years, 420 mg. Females 14–18 years, 360 mg; 19–30 years, 310 mg; over 30 years, 320 mg. The ULs apply only to magnesium taken as a dietary supplement or given for medical reasons, since no toxicity from magnesium occurring naturally in foods has been reported. The ULs for magnesium are: 1–3 years, 65 mg; 4–8 years, 110 mg; 9 years and over, 350 mg.
Good dietary sources of magnesium include nuts; dried peas and beans; whole grain cereals such as oatmeal, millet, and brown rice; dark green vegetables; bone meal; blackstrap molasses; brewer's yeast ; and soy products. Dark green vegetables are important sources of magnesium because it is the central atom in the structure of chlorophyll. Drinking hard water or mineral water can also add magnesium to the diet.
A severe magnesium deficiency in a healthy person is unusual because normal kidneys are very efficient in keeping magnesium levels balanced. This condition, called hypomagnesemia, is usually caused either by disease (kidney disease, severe malabsorption, chronic diarrhea, hyperparathyroidism , or chronic alcoholism ) or as a side effect of certain medications, most commonly diuretics, cisplatin (a cancer medication), and a few antibiotics. The symptoms of hypomagnesemia include disturbances of the heart rhythm, muscle tremors or twitches, seizures, hyperactive reflexes, and occasional personality changes (depression or agitation). A patient with hypomagnesemia may also produce Chvostek's sign, which is a facial spasm caused when the doctor taps gently over the facial nerve. This condition of painful intermittent muscle contractions and spasms is known as tetany. Hypomagnesemia can be treated with either oral or intravenous preparations containing magnesium.
Magnesium toxicity (hypermagnesemia) is rare because excessive amounts are usually excreted in the urine and feces. Most cases of hypermagnesemia are caused by overuse of dietary supplements containing magnesium. The symptoms of magnesium toxicity include central nervous system depression, muscle weakness, fatigue , and sleepiness. In extreme cases, hypermagnesemia can cause death. It can be treated with intra-venous calcium gluconate along with respiratory support. Severe hypermagnesemia can be treated by hemodialysis or peritoneal dialysis.
Standard medical practice
DIAGNOSIS. The levels of magnesium in a patient's blood or body fluids can help diagnose several illnesses. A high magnesium level in the blood may indicate kidney failure, hypothyroidism , severe dehydration, Addison's disease, or overingestion of antacids containing magnesium. A low blood level of magnesium may indicate hypomagnesemia. Because 99% of the body's magnesium is contained in its cells, blood tests can only measure the approximately 1% of magnesium that is extra-cellular (circulating in the bloodstream). This makes it difficult to diagnose low magenesium levels.
Fortunately, magnesium levels in urine can also aid diagnosis. High levels of urinary magnesium may indicate overconsumption of supplemental magnesium, overuse of diuretics, hypercalcemia (too much calcium in the body), hypophosphatemia (too little phosphate in the body), or metabolic acidosis (high blood acid levels). Low levels of magnesium in the urine may point to hypomagnesemia or hypocalcemia (too little magnesium or calcium in the body), an underactive parathyroid gland, or metabolic alkalosis (high blood alkaline levels).
TREATMENT. Magnesium is used to treat tachycardia (excessively rapid heartbeat) and low levels of electrolytes (chloride, potassium, and sodium ). It helps manage premature labor, and can be given prophylactically to prevent seizures in toxemia of pregnancy . In 2002, a major international study verified the effectiveness of magnesium sulfate in preventing eclampsia, a potentially fatal seizure condition in pregnant women. Not only is it effective, but at a cost of about $5 per patient, it proves less expensive as well.
Magnesium helps control seizures resulting from hypomagnesemia associated with alcoholism, Crohn's disease , or hyperthyroidism . Magnesium injections are also used to treat acute asthma attacks.
Magnesium preparations may be given as antacids in the treatment of peptic ulcers and hyperacidity. They are also given as laxatives for the short-term relief of constipation or to empty the patient's bowel prior to surgery or certain diagnostic procedures. Magnesium hydroxide is used to treat patients who have been poisoned by mineral acids or arsenic.
Magnesium in the form of magnesium sulfate is known as Epsom salts. It can be taken by mouth as a laxative, but is also used externally to reduce tissue swelling, inflammation, and itching from insect bites, heat rash, or other minor skin irritations. Epsom salts can be applied to the affected skin or body part in moist compresses, or dissolved in warm bath water.
Recent research indicates that magnesium deficiency may contribute to atherosclerosis (hardening of the arteries), as well as to necrotizing enterocolitis (NEC), a sometimes-deadly inflammation that destroys the bowel in premature infants. Magnesium may also be useful in treating attention-deficit hyperactivity disorder (ADHD) and migraine headaches.
HOMEOPATHY. Phosphate of magnesia is a staple homeopathic remedy, called Magnesia phosphorica (Mag. phos.) It is recommended for symptoms that are relieved by the application of warmth and gentle pressure, such as hiccups accompanied by colic in infants, menstrual cramps that are relieved when the woman bends forward, and abdominal pain without nausea and vomiting . Patients who benefit from Mag. phos. are supposedly less irritable or angry in temperament than those who need Colocynthis or Chamomilla.
NATUROPATHY. Naturopaths emphasize the importance of proper food selection and preparation to obtain an adequate supply of nutrients in the diet. They maintain that modern methods of agriculture promote overcropping and soil depletion, which they believe reduces the amount of magnesium (and other minerals) available from food grown in that soil. The processing and refining of wheat and rice, which discards the magnesium contained in the bran, wheat germ , or rice husks, also reduces the amount of magnesium in these foods. For these reasons naturopaths often recommend organic produce, which they believe contains higher levels of minerals, and suggest that they not be overcooked or boiled in too much water. In addition, this water, or "pot liquor," is often rich in magnesium that cooks out of the vegetables. It should not be discarded but saved for use in soups or stews.
Many naturopaths believe that the official government recommended daily allowance (RDA) of magnesium is too low. They think that it should be doubled to about 600 or 700 mg daily for adults. Most recommend the use of dietary supplements containing magnesium to make up the difference.
Naturopathic practitioners regard magnesium to be important in the relief or cure of the following conditions:
- Mitral valve prolapse: Magnesium deficiency may lower the body's ability to repair defective connective tissue, including defective mitral valves.
- Certain psychological conditions, including apathy, decreased ability to learn, memory loss , and confusion.
- Kidney stones : Magnesium increases the solubility of certain calcium compounds that form kidney stones if they are not excreted in the urine.
- Hypertension: Hypertensive people often have lower levels of magnesium within their cells than people with normal blood pressure.
- Angina pectoris: Magnesium is thought to relax spastic arteries and help prevent arrhythmias.
- Osteoporosis : Many osteoporosis patients have low levels of magnesium in their bodies.
- Premenstrual syndrome (PMS) and menstrual cramps: Some women report relief from the symptoms of PMS when taking magnesium supplements.
- Naturopaths also treat asthma, epilepsy, autism , hyperactivity, chronic fatigue syndrome , noise-induced hearing loss, insomnia , and stress-related anxiety with supplemental magnesium.
Naturopaths generally recommend supplemental magnesium for people with high blood cholesterol , post-menopausal women, women taking birth control pills, diabetics, people who eat a lot of fast food or other highly processed food, and people who drink alcohol. Many nutrition experts recommend supplements that contain a balanced ratio of calcium to magnesium, usually two parts of calcium to one of magnesium. People who increase their calcium intake should increase their dose of magnesium (and phosphate) as well, because they work together and complement each other.
Some naturopaths recommend taking magnesium in the form of an aspartate or a citrate, arguing that these compounds are more easily absorbed by the body than magnesium carbonate or magnesium oxide. Others prefer magnesium chelated (combined with a metallic ion) with amino acids. Magnesium can also be obtained from herbal sources, such as red raspberries.
Standard medical preparations
Magnesium hydroxide is a common over-the-counter antacid, available as either a tablet or liquid. Most antacid tablets contain about 200 mg of magnesium hydroxide; liquid magnesium hydroxide is sometimes called milk of magnesia. Magnesium carbonate works as a cathartic or laxative when combined with citric acid to produce magnesium citrate; it is often flavored with lemon or cherry to make it more pleasant to swallow. Magnesium sulfate (in the form of Epsom salts) is available over the counter, usually in half-pound or pound boxes. Epsom salts are small whitish or colorless crystals that dissolve easily in water and have a bitter or salty taste.
Magnesium for intravenous dosage is prepared as a sulfate in a 50% solution. In general, intravenous administration of magnesium is reserved for patients with such serious symptoms as seizures, preeclampsia or eclampsia of pregnancy, acute asthma attacks, or severe cardiac arrhythmias. Magnesium sulfate can also be given by intramuscular injection.
Preparations containing magnesium should not be given as laxatives to patients with kidney disease, nausea and vomiting, diarrhea, abdominal pain, rectal bleeding, symptoms of appendicitis , or symptoms of intestinal obstruction or perforation. In addition, these preparations should not be used routinely to relieve constipation, as the patient may become dehydrated, lose calcium from the body, or develop a dependence on them. Antacids containing magnesium should be used with caution in patients with kidney disease.
Magnesium preparations taken internally may cause hypermagnesemia, especially with prolonged use; electrolyte imbalance; and abdominal cramps when taken as a laxative. Milk of magnesia occasionally produces nausea or diarrhea. There are no known side effects of Epsom salts when used externally.
Milk of magnesia will decrease the patient's absorption of chlordiazepoxide, digoxin, isoniazid, quinolones, or tetracycline antibiotics. Because it increases the gastrointestinal tract's mobility, magnesium can also decrease the absorption (and thereby the effectiveness) of many other drugs and supplements as well. Magnesium sulfate, if given intravenously, is incompatible with calcium gluceptate, clindamycin, dobutamine, polymyxin B sulfate, procaine, and sodium bicarbonate.
Baron, Robert B., MD, MS. "Nutrition." In Current Medical Diagnosis & Treatment 2000. Edited by Lawrence M. Tierney, Jr., MD, et al. New York: Lange Medical Books/McGraw-Hill, 2000.
Beers, Mark H., MD, and Robert Berkow, MD, eds. The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 1999.
Burton Goldberg Group. Alternative Medicine: The Definitive Guide. Fife, WA: Future Medicine Publishing, Inc., 1995.
Murray, Michael, ND, and Joseph Pizzorno, ND. Encyclopedia of Natural Medicine. Rocklin, CA: Prima Publishing, 1991.
Okuda, Toshihiro, MD, PhD, Kiyoshi Kurokawa, MD, MACP, and Maxine A. Papadakis, MD. "Fluid & Electrolyte Disorders." In Current Medical Diagnosis and Treatment 2000, edited by Lawrence M. Tierney, Jr., MD et al. New York: Lange Medical Books/McGraw-Hill, 2000.
Russell, Percy J., and Anita Williams. The Nutrition and Health Dictionary. New York: Chapman & Hall, 1995.
"Help for Eclampsia." American Medical News (June 17, 2002): 32.
American Association of Naturopathic Physicians. P. O. Box 20386. Seattle, WA 98112.
Committee on the Scientific Evaluation of Dietary Reference Intakes. Institute of Medicine (1997) Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, DC: National Academy Press, 1997.
Homeopathic Pharmacopoeia of the United States. P. O. Box 2221. Southeastern, PA 19399-2221. (610) 783-5124. Fax: (610) 783-5180. Publishes and distributes the Homeopathic Pharmacopoeia of the U.S., which defines the contents of homeopathic remedies and other preparations.
Rebecca J. Frey, PhD
Teresa G. Odle
Magnesium (Mg) is an element belonging to the alkaline earth metal group. It participates in over 300 metabolic reactions, is crucial for life and health and isMagnesium
|Age||Recommended Dietary Allowance (mg)||Tolerable Upper Intake Level of Dietary Supplements (mg)|
|Children 0–6 mos.||30 (AI)||Not established|
|Children 7–12 mos.||75 (AI)||Not established|
|Children 1–3 yrs.||80||65|
|Children 4–8 yrs.||130||110|
|Children 9–13 yrs.||240||350|
|Boys 14–18 yrs.||410||350|
|Girls 14–18 yrs.||360||350|
|Men 19–30 yrs.||400||350|
|Women 19–30 yrs.||310||350|
|Men 31≤ yrs.||420||350|
|Women 31≤ yrs.||320||350|
|Pregnant women 18≥ yrs.||400||350|
|Pregnant women 19–30 yrs.||350||350|
|Pregnant women 31≤ yrs.||360||350|
|Breastfeeding women 18≥ yrs.||360||350|
|Breastfeeding women 19–30 yrs.||310||350|
|Breastfeeding women 31≤ yrs.||320||350|
|Cereal, 100% bran, ½ cup||129|
|Oat bran, ½ cup, dry||96|
|Halibut, cooked, 3 oz.||90|
|Almonds, roasted, 1 oz.||80|
|Cashew nuts, roasted, 1 oz.||75|
|Spinach, cooked, ½ cup||75|
|Swiss chard, cooked, ½ cup||75|
|Beans, lima, cooked, ½ cup||63|
|Shredded wheat, 2 biscuits||54|
|Peanuts, roasted, 1 oz.||50|
|Black-eyed peas, cooked, ½ cup||43|
|Brown rice, cooked, ½ cup||40|
|Beans, pinto, cooked, ½ cup||35|
|AI = Adequate Intake|
|mg = milligram|
(Illustration by GGS Information Services/Thomson Gale.)
the fourth most common mineral in the body. In the body, it forms ions that have an electric charge of +2. Humans must meet their needs for magnesium from their diet. Magnesium is found mainly in plants and in some drinking water.
Magnesium is necessary for many cellular reactions critical to maintaining life. It plays a role in:
- strengthening bones
- synthesizing new deoxyribonucleic acid (DNA; genetic >material)
- synthesizing proteins
- muscle contraction
Dietary supplement —A product, such as a vitamin, mineral, herb, amino acid, or enzyme, that is intended to be consumed in addition to an individuals diet with the expectation that it will improve health
Diuretic —A substance that removes water from the body by increasing urine production
Electrolyte —Ions in the body that participate in metabolic reactions. The major human electrolytes are sodium (Na+), potassium (K+), calcium (Ca 2+), magnesium (Mg2+), chloride (Cl-), phosphate (HPO4 2-), bicarbonate (HCO3-), and sulfate (SO4 2-).
Glucose —A simple sugar that results from the breakdown of carbohydrates. Glucose circulates in the blood and is the main source of energy for the body.
Ion —An atom or molecule that has an electric charge. In the body ions are collectively referred to as electrolytes.
Mineral —An inorganic substance found in the earth that is necessary in small quantities for the body to maintain health. Examples: zinc, copper, iron.
Osteoporosis —A condition found in older individuals in which bones decrease in density and become fragile and more likely to break. It can be caused by lack of vitamin D and/or calcium in the diet.
Ribonucleic acid (RNA) —A molecule that helps decode genetic information (DNA) and is necessary for protein synthesis
Serum —The clear fluid part of the blood that remains after clotting. Serum contains no blood cells or clotting proteins, but does contain electrolytes.
Triglycerides —A type of fat found in the blood. High levels of triglycerides can increase the risk of coronary artery disease
Type 2 diabetes —Sometimes called adult-onset diabetes, this disease prevents the body from properly using glucose (sugar).
- nerve impulse transmission
- conversion of nutrients into energy
- movement of ions across cell membranes
- regulation of blood glucose (sugar) levels
- regulation of blood pressure
- protecting the body against cardiovascular disease
Magnesium is in chlorophyll, the pigment that makes plants green. Humans absorb magnesium from food as it passes through the small intestine. The kidneys normally regulate how much magnesium is in the blood, and any excess magnesium is excreted in urine. Magnesium levels can be measured with a blood test.
When magnesium dissolves in body fluids, it becomes an electrolyte. Electrolytes are ions that have an electric charge. Magnesium is a cation, or positively charged ion, with an electric charge of +2, meaning it has lost two of its negatively charged elections. Other important electrolytes in the body are sodium (Na+ ), potassium (K+), calcium (Ca 2+), and the negatively charged ions chloride (Cl-), phosphate (HPO 4 2-), bicarbonate (HCO3-), and Sulfate (SO 4 2-). Multiple electrolytes are involved in most metabolic reactions. These electrolytes are not evenly distributed within the body, and their electric charge and uneven distribution are what allow many chemical reactions to occur. About 50-60% of the 25 grams of magnesium in an adult’s body, is in the bones. About 25% is in muscle cells, 6–7% in other cells, and less than 1% outside cells (e.g. in extracellular fluid or in blood serum).
Magnesium is involved in many reactions. One of the most important is in synthesizing adenosine tri-phosphate (ATP ), the molecule that supplies most of the energy to drive cellular metabolism. Magnesium is also required to create new DNA, Ribonucleic acid (RNA ), and proteins. The electrical charge of the magnesium ion is important in regulating the transmission of nerve impulses, muscle contraction, and the movement of nutrients and other electrolytes in and out of cells. Magnesium also has an effect on the way calcium is deposited in bones. It makes bone structurally more dense and stronger.
Normal magnesium requirements
The United States Institute of Medicine (IOM ) of the National Academy of Sciences has developed values called Dietary Reference Intakes (DRI s) for many vitamins and minerals. The DRI s consist of three sets of numbers. The Recommended Dietary Allowance (RDA ) defines the average daily amount of the nutrient needed to meet the health needs of 9,798 of the population. The Adequate Intake (AI ) is an estimate set when there is not enough information to determine an RDA. The Tolerable Upper Intake Level (UL ) is the average maximum amount that can be taken daily without risking negative side effects. The DRI s are calculated for children, adult men, adult women, pregnant women, and breastfeeding women.
The IOM has not set RDA s for magnesium in children under one year old because of incomplete scientific information. Instead, it has set AI levels for this age group. The RDA s for magnesium are the amount that has been determined to prevent deficiency. However, based on recent findings about the relationship between magnesium, diabetes, and cardiovascular disease, there is some debate over whether this represents the optimum amount for health. RDA s and ULs for magnesium are measured in milligrams (mg). There are no UL s for magnesium that is obtained from food and water. All magnesium ULs apply to dietary supplements only.
The following list gives the daily RDA s and IA s and UL s for magnesium for healthy individuals as established by the IOM.
- children birth–6 months: AI 30 mg; UL not established; All magnesium should come from breast milk, fortified formula, or food.
- children 7–12 months: AI 75 mg; UL not established; All magnesium should come from breast milk, fortified formula, or food.
- children 1–3 years: RDA 80 mg; UL 65 mg
- children 4–8 years: RDA 130 mg; UL 110 mg
- children 9–13 years: RDA 240 mg; UL 350 mg
- boys 14–18 years: RDA 410 mg; UL 350 mg
- girls 14–18 years: RDA 360 mg; UL 350 mg
- men 19–30 years: RDA 400 mg; UL 350 mg
- women 19–30 years: RDA 310 mg; UL 350 mg
- men age 31 and older: RDA 420 mg; UL 350 mg
- women age 31 and older: RDA 320 mg; UL 350 mg
- pregnant women 18 years and younger: RDA 400 mg; UL 350 mg
- pregnantwomen 19–30years: RDA 350mg;UL 350mg
- pregnant women 31 years and older: RDA 360 mg; UL 350 mg
- breastfeeding women 18 years and younger: RDA 360 mg; UL 350 mg
- breastfeeding women 19–30 years: RDA 310 mg; UL 350
- breastfeeding women 31 years and older: RDA 320 mg; UL 350 mg
Sources of magnesium
Chlorophyll, the pigment that makes plants green, contains magnesium. Good natural sources of magnesium include dark green vegetables such as spinach and Swiss chard. Other vegetables high in magnesium are lima beans, black-eyed peas, almonds, cashew nuts, and peanuts. Whole grains contain a lot of magnesium, but processing removes most of it. Therefore brown rice is a good source of magnesium, but white rice is not. Whole wheat flour has more magnesium than white flour, and wheat bran and oat bran have more than either type of flour. Some water that is high in minerals (hard water) has a significant amount of magnesium; the amount varies widely depending on location. Magnesium is also found in many multivitamins and is available as a single-ingredient supplement. The amount of magnesium available to the body from dietary supplements varies depending on the molecule in which magnesium is found. Common forms of magnesium in dietary supplements include magn! esium oxide, magnesium gluconate, magnesium citrate, and magnesium aspartate. Some antacids contain a significant amount of magnesium hydroxide. The best way to get an adequate amount of magnesium is to eat a healthy diet high in green vegetables and whole grains.
The following list gives the approximate magnesium content for some common foods:
- 100% bran cereal, ½ cup: 129 mg
- oat bran, ½ cup dry: 96 mg
- shredded wheat, 2 biscuits: 54 mg
- halibut, cooked 3 ounces: 90 mg
- almonds, roasted, 1 ounce: 80 mg
- cashew nuts, roasted, 1 ounce:75 mg
- peanuts, roasted, 1 ounce: 50 mg
- spinach, cooked, ½ cup: 75 mg
- Swiss chard, cooked, ½ cup: 75 mg
- lima beans, cooked, ½ cup: 63 mg
- black-eyed peas, cooked, ½ cup: 43 mg
- pinto beans, cooked, ½ cup: 35 mg
- brown rice, cooked, ½ cup: 40 mg
Magnesium excess and deficiency
Magnesium excess is called hypermagnesemia. This condition is rare. It occurs most often in people with severe kidney disease (end-stage renal failure), when the kidney can no longer remove magnesium ions from the blood. Another common cause is human error in calculating the amount of intravenous (IV) fluids containing magnesium to give to seriously ill patients in the hospital. Abuse of antacids and laxatives containing magnesium hydroxide can also result in hypermagnesemia. Symptoms of hypermagnesemia (in increasing severity )include nausea, vomiting, lightheadedness, muscle weakness, loss of deep tendon reflexes, low blood pressure, irregular heart rhythms, coma, and death.
Hypomagnesemia, or low levels of magnesium are estimated to occur in about 2 of the American population, in 1,020 of hospitalized patients, and in up to 60 of patients in intensive care. Anywhere between 30 and 80 of people with alcoholism have hypomagnesemia, as do about one-fourth of people with diabetes.
Magnesium deficiency can be caused either by insufficient intake or excessive excretion of magnesium. Causes of insufficient intake include digestive disorders that interfere with the absorption of magnesium (e.g. Crohns disease, celiac disease, inflammatory bowel syndrome), malnutrition with a limited diet of green vegetables, alcoholism (alcohol is substituted for food), and anorexia nervosa (self-starvation). Some causes of excessive excretion of magnesium include kidney failure, diabetes, use of some diuretic drugs, and some hormone disorders of the parathyroid gland.
The kidneys are the main regulator of magnesium. People with kidney disease should not take magnesium supplements.
Pregnant women should discuss their magnesium needs with their healthcare provider. Many pregnant women have low levels of magnesium but should use supplements only under medical supervision. Low magnesium levels are thought to contribute to preeclampsia and eclampsia and possibly to increase the risk of early labor.
People undergoing surgery should tell their anesthesiologist if they are taking magnesium supplements, antacids, or laxatives because magnesium increases the muscle-relaxing effects of certain anesthetics.
Certain drugs and conditions can cause an excessive loss of magnesium. These include:
- cisplatin, a drug used in cancer treatment
- diuretics (water pills)
- fluoride poisoning
Certain drugs may be less effective when taken with magnesium supplements. These include some antibiotics, and digoxin, a heart medication. Iron may be absorbed more poorly in the presence of magnesium.
Some minerals decrease the absorption of magnesium. These include calcium, manganese, and phosphate. Boron appears to increase magnesium levels.
No complications are expected from magnesium obtained from food and water. Potential complications related to excess use of magnesium supplements or from inadequate levels of magnesium are discussed above.
The safety of magnesium supplements in children has not been investigated. Breastfeeding women should avoid magnesium supplements and children should be encouraged to meet their magnesium requirements by eating a healthy diet high in green vegetables and whole grains and low in fat.
Cohen, Jay S. The Magnesium Solution for Migraine Headaches. Garden City Park, NY: Square One, 2004.
Dean, Carolyn. The Magnesium Miracle: Discover the Essential Nutrient That Will Lower the Risk of Heart Disease, Prevent Stroke and Obesity, Treat Diabetes, and Improve Mood and Memory. New York: Ballantine Books, 2007.
Fragakis, Allison. & The Health Professionals Guide to Popular Dietary Supplements. Chicago: American Dietetic Association, 2003.
Lieberman, Shari and Nancy Bruning. The Real Vitamin and Mineral Book: The Definitive Guide to Designing Your Personal Supplement Program, 4th ed. New York: Avery, 2007.
Pressman, Alan H. and Sheila Buff. The Complete Idiots Guide to Vitamins and Minerals, 3rd ed. Indianapolis, IN: Alpha Books, 2007.
Seelig, Mildred S. and Andrea Rosanoff. The Magnesium Factor. New York: Avery, 2003.
He, Ka, Liu Kiang, Martha L. Daviglus et al. “Magnesium Intake and Incidence of Metabolic Syndrome Among Young Adults.” Circulation113, no. 13 (April 4, 2006):1675-1682. <http://circ.ahajournals.org/cgi/content/abstract/113/13/1675>
van Dam, Rob M., Frank B. Hu, Lynn Rosenberg, et Al. “Dietary Calcium and Magnesium, Major Food Sources, and Risk of Type 2 Diabetes in U.S. Black Women.” Diabetes Care 29, no 10 (2006):2238-43. <http://care.diabetesjournals.org/cgi/content/abstract/29/10/2238:>
American Heart Association. 7272 Greenville Avenue, Dallas, TX 75231. Telephone: (800) 242-8721. Website: <http://www.americanheart.org>
Linus Pauling Institute. Oregon State University, 571 Weniger Hall, Corvallis, OR 97331-6512. Telephone: (541) 717-5075. Fax: (541) 737-5077. Website: <http://lpi.oregonstate.edu>
Office of Dietary Supplements, National Institutes of Health. 6100 Executive Blvd., Room 3B01, MSC 7517, Bethesda, MD 20892-7517 Telephone: (301)435-2920. Fax: (301)480-1845. Website: <http://dietary-supplements.info.nih.gov>
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Note: This article, originally published in 1998, was updated in 2006 for the eBook edition.
Magnesium is the second element in Group 2 (IIA) of the periodic table a chart that shows how chemical elements are related to each other. The elements in Group 2 are known as the alkaline earth elements. Other elements in that group include beryllium, calcium, strontium, barium, and radium.
Compounds of magnesium have been used by humans for centuries. Yet, the element itself was not isolated until 1808. The long delay occurred because magnesium forms very stable compounds. That means that such compounds do not break down very easily.
Magnesium is the seventh most abundant element in the Earth's crust. It also occurs in large amounts dissolved in ocean waters.
Group 2 (IIA)
Alkaline earth metal
Large amounts of magnesium are used to make alloys. An alloy is made by melting or mixing two or more metals. The mixture has properties different from those of the individual metals. Magnesium alloys are quite light, yet very strong. This property makes them useful in the construction of airplanes and space-craft.
About 70 percent of the magnesium compounds produced in the United States are used in the manufacture of refractory materials. A refractory material is one that can withstand very high temperatures by reflecting heat. Refractory materials are used to line the ovens that maintain high temperatures. The remaining 30 percent of magnesium compounds are used in agriculture, construction, industrial, and chemical operations.
Discovery and naming
Compounds of magnesium are very abundant in the Earth. Dolomite, or calcium magnesium carbonate (CaMg(CO32, is an example. Dolomite has been used as a building material for centuries.
The allure of Epsom salts
P erhaps the best know magnesium compound is magnesium sulfate (MgSO4). It is popularly known as Epson salts.
One of the earliest stories about Epsom salts dates back to 1618. The town of Epsom, in Surrey, England, was suffering from a severe drought. A farmer named Henry Wicker brought his cattle to drink from a water hole on the town commons (central park). But the cattle would not drink the water. Wicker was surprised because he knew they were very thirsty. He tasted the water himself and found that it was very bitter.
The bitterness was due to magnesium sulfate in the water. This compound became known as Epsom salts.
People soon learned that soaking in the natural waters that contained Epsom salts made them feel better. The salts seemed to have properties that soothed the body. Before long, soaking in these waters became very popular.
Today, Epsom salts are used in bath water. They relax sore muscles and remove rough skin. Many people believe the salts have the same relaxing effect as hot springs. Some gardeners even believe that sprinkling Epsom salts in the garden helps flowers and vegetables grow!
Careful studies of magnesium and its compounds began in the middle 1700s. Scottish physician and chemist Joseph Black (1728-99) carried out some of the earliest experiments on magnesium compounds. He reported on his research in an article that became famous. Black is sometimes given credit for "discovering" magnesium because of his work with the element.
By 1800, chemists knew that magnesium was an element. But no one had been able to prepare pure magnesium metal. Magnesium holds very tightly to other elements in its compounds. No one had found a way to break the bonds between magnesium and these other elements.
In 1808, English chemist Humphry Davy (1778-1829) solved the problem by passing an electric current through molten (melted) magnesium oxide (MgO). The current caused the compound to break apart, forming magnesium metal and oxygen gas:
Davy used this method to discover a number of other elements. (See sidebar on Davy in the calcium entry in Volume 1.) Like magnesium, these elements form compounds that are very difficult to break apart. An electric current provides the energy to break these compounds down into their elements.
The name magnesium goes back many centuries. It was selected in honor of a region in Greece known as Magnesia. The region contains large supplies of magnesium compounds.
Magnesium is a moderately hard, silvery-white metal. It is the lightest of all structural metals. These metals are strong enough to be used to build buildings, bridges, automobiles, and airplanes.
Magnesium is easily fabricated. Fabrication means shaping, molding, bending, cutting, and working with a metal. Metals must be fabricated before they can be turned into useful products. Metals that are strong, tough, or hard are not easily fabricated. They must be converted to an alloy. A metal that is more easily fabricated (such as magnesium) is combined with them.
Magnesium is a fairly active metal. It reacts slowly with cold water and more rapidly with hot water. It combines with oxygen at room temperature to form a thin skin of magnesium oxide. It burns with a blinding white light at higher temperatures. Magnesium reacts with most acids and with some alkalis. An alkali is a chemical with properties opposite those of an acid. Sodium hydroxide (common lye such as Drano) and lime-water are examples of alkalis.
Magnesium also combines easily with many non-metals, including nitrogen, sulfur, phosphorus, chlorine, fluorine, bromine, and iodine. It also reacts readily with a number of compounds, such as carbon monoxide (CO), carbon dioxide (CO2, sulfur dioxide (SO2, and nitric oxide (NO).
Occurrence in nature
The abundance of magnesium in the Earth's crust is estimated to be about 2.1 percent. That makes it the sixth most common element in the earth. It also occurs in seawater. A cubic mile of seawater is estimated to contain up to six million tons of magnesium.
There are many naturally occurring minerals of magnesium. Some of the most important are dolomite; magnesite, or magnesium carbonate (MgCO3; carnallite, or potassium magnesium chloride (KMgCl3; and epsomite, or magnesium sulfate (MgSO4.
The largest producer of magnesium ores is Turkey. Other large producers are North Korea, China, Slovakia, Austria, and Russia. The amount of magnesium produced in the United States is not reported in order to protect trade secrets.
Magnesium produced in the United States comes from three sources: seawater, brine, and mines. Seawater is processed to obtain magnesium by companies in California, Delaware, Florida, and Texas. Magnesium is obtained from brine in Michigan and Utah. Brine is water that is even saltier than seawater. Finally, some magnesium compounds are taken from mines in Nevada, North Carolina, and Washington.
There are three naturally occurring isotopes of magnesium: magnesium-24, magnesium-25, and magnesium-26. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope.
One radioactive isotope of magnesium, magnesium-28, also exists. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive. Magnesium-28 has no important commercial uses.
Magnesium is prepared by one of two methods. The first method is similar to the method used by Davy in 1808. An electric current is passed through molten (melted) magnesium chloride:
The second method involves reacting magnesium oxide with ferrosilicon. Ferrosilicon is an alloy of iron and silicon. When magnesium oxide and ferrosilicon react, free magnesium metal is formed.
Although most cameras now use electronic flashes, magnesium metal is often contained in cameras that use flash bulbs. A thin strip of magnesium metal is inside the bulb. When the flash is ignited, the magnesium strip catches fire. It burns with a very bright white light. The light from the bulb illuminates a scene for the photograph.
A common use of magnesium metal is in fireworks. Most firework displays include some brilliant flashes of very white light. Those flashes are produced by the burning of magnesium metal.
Magnesium is commonly alloyed with other metals. Magnesium and aluminum, for instance, are two metals that combine to form alloys that are very strong and resistant to corrosion (rust). But they weigh much less than steel alloys with similar properties.
Strength and low density are important properties in the manufacture of airplanes, automobiles, metal luggage, ladders, shovels and other gardening equipment, racing bikes, skis, race cars, cameras, and power tools. A typical magnesium alloy contains about 90 percent magnesium, 2 to 9 percent aluminum, and small amounts of zinc and manganese.
The largest single use of magnesium compounds is in refractories. Other magnesium compounds are used in the following categories:
medicine: pain killer and fever reducer (magnesium acetylsalicylate); antacid to neutralize stomach acid (magnesium hydroxide; magnesium phosphate; magnesium silicate); laxative to loosen the bowels (magnesium carbonate; magnesium chloride; magnesium citrate; magnesium hydroxide; magnesium lactate; magnesium phosphate); antiseptic to kill germs (magnesium borate; magnesium salicylate; magnesium sulfate); sedative to help one get sleep (magnesium bromide)
production of glass and ceramics: magnesium fluoride; magnesium oxide
mothproofing of textiles: magnesium hexafluorosilicate
fireproofing wood for construction: magnesium phosphate
manufacture of paper: magnesium sulfite
Magnesium is essential for good health in both plants and animals. It forms part of the chlorophyll molecule found in all green plants. Chlorophyll is the molecule in green plants that controls the conversion of carbon dioxide and water to carbohydrates, such as starch and sugar. Plants that do not get enough magnesium cannot make enough chlorophyll. Their leaves develop yellowish blotches as a result.
Magnesium is found in many enzymes in both plants and animals. An enzyme is a catalyst in a living organism. It speeds up the rate at which certain changes take place in the body. Enzymes are essential in order for living cells to function properly. It is difficult not to get enough magnesium in one's daily diet. It is found in nuts, cereals, seafoods, and green vegetables. Most people have no problem getting the 300 to 400 milligrams of magnesium recommended in the daily diet.
Magnesium forms part of the chlorophyll molecule found in all green plants.
A lack of magnesium can occur, however. For example, alcoholics and children in poor countries sometimes develop a magnesium deficiency. In such cases, magnesium deficiency may cause a person to become easily upset or overly aggressive.
On the other hand, it is also possible to be exposed to too much magnesium. For example, inhaling magnesium powder can produce irritation of the throat and eyes, resulting in a fever. In large doses, magnesium can cause damage to muscles and nerves. It can eventually result in loss of feeling and paralysis (inability to move parts of the body).
Such conditions are rare. They are likely to occur only among people who have to work with magnesium metal on a regular basis.
Magnesium (Mg) is one of the most abundant structural metals (those metals used to build things), ranking third behind iron and aluminum. Magnesium compounds are found in mineral rocks such as dolomite and magnesite, while the Earth’s oceans contain a practically unlimited supply of the metal in the form of dissolved magnesium chloride. One cubic mile of sea-water holds some six million tons of the element. The lightest of all the structural metals, magnesium (atomic number 12) is about one-third lighter than aluminum and gives more strength and stiffness per pound than any other common metal.
Magnesium is a moderately hard, silvery white metal, the lightest of all structural metals. The element is easily molded, bent, cut, and otherwise fabricated. Magnesium’s melting point is about 1,204°F (651°C), its boiling point is around 1,994°F (1,090°C), and its density is 1.005 ounces per cubic inch (1.738 grams per cubic centimeter). It is a solid at room temperature.
Magnesium is an active metal that reacts slowly with cold water and more rapidly with hot water. It reacts with oxygen at room temperature to form a thin skin of magnesium oxide (MgO) that protects the underlying metal from further oxidation. At higher temperatures, magnesium reacts vigorously with oxygen to produce a blinding white light. The metal also reacts with most acids and with some strong alkalis. It combines easily with many non-metals, including nitrogen, sulfur, phosphorus, and the halogens. It also reacts with a number of compounds, such as carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2), and nitric oxide (NO).
The abundance of magnesium in the Earth’s crust is estimated to be about 2.1%, making it the sixth most common element in Earth. Its estimated crustal abundance is 0.37 ounces per pound (2.33 x 104 milligrams per kilogram). It also occurs in seawater, usually as magnesium chloride (MgCl2). Its estimated oceanic abundance is 0.17 ounces per gallon (1.29 x 103 milligrams per liter). According to some estimates a cubic mile of seawater may contain up to six million tons of magnesium metal.
Magnesium compounds such as Epsom salts were first prepared in the late 1600s and early 1700s. For a while, the oxide compound (magnesia) was confused with lime (calcium carbonate), until Scottish physicist and chemist Joseph Black (1728–1799) discovered the difference between the two substances in 1754. English chemist Sir Humphry Davy (1778–1829) demonstrated in 1808 that magnesia was the oxide of a new metal, which he named magnesium, but the element was not isolated until twenty years later, when French chemist Antoine Alexandre Brutus Bussy (1794–1882) combined dry magnesium chloride with potassium to produce the metal in its pure form. Using electrolysis, English physicist and chemist Michael Faraday (1791–1867) obtained magnesium from magnesium chloride in the 1830s. Then, in 1852, German chemist Robert Wilhelm Bunsen (1811–1899) developed an electrolytic cell for producing large quantities of magnesium. For the next sixty years, German chemists further developed Bunsen’s cell and pioneered in the production and use of magnesium. The element is relatively easy to extract from seawater by electrolysis, which splits the chloride compound and produces magnesium metal and chlorine gas. By 1909, Germany was manufacturing magnesium commercially, and the United States began producing magnesium during World War I, eschewing German imports.
During the war, magnesium was used in incendiary bombs, which ignite and burn upon impact, as well as flares and tracer bullets. Powdered magnesium burns with a dazzling white flame, a property of the metal Bunsen had demonstrated in the 1850s. This quality has been exploited in many other products, such as fireworks, and the metal is used in photography to provide a brilliant flash for lighting purposes.
Magnesium’s light weight is its most valuable attribute, however. When World War II began in 1939, Germany was well-positioned to use magnesium for aircraft construction and other military applications. In response, U.S. companies stepped up their magnesium manufacturing efforts, resulting in a dramatic increase in magnesium production in the United States; it peaked in 1943 at nearly 184,000 tons. In addition to electrolytic extraction of magnesium from seawater, the element can be produced from mineral rocks by various thermal processes. These methods use a reducing agent such as ferrosilicon to break down magnesium compounds and form vapors of magnesium, which are then distilled into crystals and melted.
Today, many automotive manufacturers in Europe and the United States are using or testing vehicle parts made of magnesium alloys—mixtures of magnesium and other metals, most often aluminum. Magnesium’s light weight will become more critical as automakers try to meet new vehicle mileage standards. Because magnesium is easily cast into complex structures, automakers could also reduce the number of parts needed and streamline the assembly process. Some manufacturers already use magnesium alloys in vehicle bodies and frames.
Magnesium alloys are also used in a host of other products, such as sports equipment, for which light weight is an advantage. Baseball catchers’ masks, skis, racecars, and horseshoes are made with magnesium alloys. Consumer goods such as ladders, portable tools, electronic equipment, binoculars, cameras, furniture, and luggage also benefit from magnesium’s light weight. Other applications make use of its ability to absorb vibration. Magnesium is an important element from a biological standpoint as well. Scientists have learned that magnesium ions aid in the digestive process, and several magnesium compounds are active ingredients in medicines such as milk of magnesia (magnesium hydroxide) and Epsom salts (magnesium sulfate). In plants, magnesium is even more critical—it is a component of chlorophyll, the green pigment that converts the sun’s energy, in the form of light, into food. Magnesium’s position in the chlorophyll molecule, which is similar to that of iron in hemoglobin, was discovered by Richard Willstätter in the early 1900s. This was the first clue to magnesium’s importance as a plant nutrient; before, scientists thought that it was an impurity. Since then, agricultural fertilizers for magnesium-deficient soils have greatly increased crop yields.
Magnesium is essential for good health in both plants and animals. It forms part of the chlorophyll molecule that catalyzes the conversion of carbon dioxide and water to carbohydrates in green plants. Plants that do not get enough magnesium do not manufacture an adequate amount of chlorophyll, and their leaves tend to become yellow.
Magnesium also occurs in enzymes needed by animals. The amounts required are so small that magnesium deficiency diseases are rare. In some areas, however, people with poor diets may not get the magnesium they need, producing symptoms such as extreme agitation or aggressiveness.
Overexposure to magnesium is also rare, but may occur and, if it does, may produce health problems. For example, people who work around magnesium metal may inhale the fumes, experiencing symptoms such as irritation of the throat and eyes, damage to muscles and nerves, and loss of feeling and paralysis.
A mineral found in the fluid that surrounds cells, magnesium (Mg) is an essential component of more than 300 enzymes that regulate many body functions. Imbalances occur when the blood contains more or less magnesium than it should.
Magnesium is necessary for the formation and functioning of healthy bones, teeth, muscles, and nerves. It converts food into energy, builds proteins, and is instrumental in maintaining adequate levels of calcium in the blood. Magnesium helps prevent cardiovascular disease and irregular heartbeat, reduces the risk of bone loss (osteoporosis ), and increases an individual's chance of surviving a heart attack. It may also help prevent stroke and lessen the effects of existing osteoporosis.
Fish, dairy products, leafy green vegetables, legumes, nuts, seeds, and grains are especially good sources of magnesium, but varying amounts of this mineral are found in all foods. Some is stored in the kidneys, and excess amounts are excreted in the urine or stools.
Magnesium deficiency (hypomagnesemia) or excess (hypermagnesemia) is rare, but either condition can be serious.
Causes and symptoms
Magnesium deficiency most often occurs in people who have been fed intravenously for a long time, whose diet does not contain enough magnesium, or who are unable to absorb and excrete the mineral properly.
Secreting too much aldosterone (the hormone that regulates the body's salt-fluid balance), ADH (a hormone that inhibits urine production), or thyroid hormone can cause hypomagnesemia.
Other factors associated with hypomagnesemia include:
- Loss of body fluids as a result of stomach suctioning or chronic diarrhea
- Cisplatin (a chemotherapy drug)
- Long-term diuretic therapy
- Hypercalcemia (abnormally high levels of calcium in the blood)
- Diabetic acidosis (a condition in which the body's tissues have a higher-than-normal acid content)
- Complications of bowel surgery
- Chronic alcoholism
- Severe dehydration.
People who have hypomagnesemia usually experience loss of weight and appetite, bloating, and muscle pain, and they pass stools that have a high fat content. Also, they may be listless, disoriented, confused, and very irritable. Other symptoms of hypomagnesemia are:
- Muscle weakness
- Irregular heart beat
- Delusions and hallucinations
- Leg and foot cramps
- Muscle twitches
- Changes in blood pressure.
Severe magnesium deficiency can cause seizures, especially in children.
Neonatal hypomagnesemia can occur in premature babies and in infants who have genetic parathyroid disorders or who have had blood transfusions. This condition also occurs in babies born to magnesium-deficient mothers or to women who have:
- Diabetes mellitus
- Hyperparathyroidism (overactive parathyroid glands)
- Toxemia (a pregnancy-related condition characterized by high blood pressure and fluid retention).
Hypermagnesemia is most common in patients whose kidneys cannot excrete the magnesium they derive from food or take as medication. This condition can also develop in patients who take magnesium salts, or in healthy people who use large quantities of magnesium-containing antacids, laxatives, or analgesics (pain relievers).
Magnesium poisoning can cause severe diarrhea in young people, and mask the symptoms of other illnesses. Very high overdoses can lead to coma. The risk of complications of magnesium poisoning is greatest for:
- Elderly people with inefficient kidney function
- Patients with kidney problems or intestinal disorders
- People who use antihistamines, muscle relaxants, or narcotics.
Severe dehydration or an overdose of supplements taken to counteract hypomagnesemia can also cause this condition.
People who have hypermagnesemia may feel flushed and drowsy, perspire heavily, and have diarrhea. Breathing becomes shallow, reflexes diminish, and the patient becomes unresponsive. Muscle weakness and hallucinations are common. The patient's heart beat slows dramatically and blood pressure plummets. Extreme toxicity, which can lead to coma and cardiac arrest, can be fatal.
Blood tests are used to measure magnesium levels.
The goal of treatment is to identify and correct the cause of the imbalance. Oral magnesium supplements or injections are usually prescribed to correct mild magnesium deficiency. If the deficiency is more severe or does not respond to treatment, magnesium sulfate or magnesium chloride may be administered intravenously.
Doctors usually prescribe diuretics (urine-producing drugs) for patients with hypermagnesemia and advise them to drink more fluids to flush the excess mineral from the body. Patients whose magnesium levels are extremely high may need mechanical support to breathe and to circulate blood throughout their bodies.
Intravenously administered calcium gluconate may reverse damage caused by excess magnesium. Intravenous furosemide (Lasix) or ethacrynic acid (Edecrin) can increase magnesium excretion in patients who get enough fluids and whose kidneys are functioning properly.
In an emergency, dialysis can provide temporary relief for patients whose kidney function is poor or who are unable to excrete excess minerals.
Because imbalances may recur if the underlying condition is not eliminated, monitoring of magnesium levels should continue after treatment has been completed.
Most people consume adequate amounts of magnesium in the food they eat. Dietary supplements can be used safely, but should only be used under a doctor's supervision.
Hypermagnesemia— An abnormally high concentration of magnesium in the blood.
Hypomagnesemia— An abnormally low concentration of magnesium in the blood.
"Mineral Guide." CNN Page. May 2, 1998. 〈http://www.cnn.com/HEALTH〉.
magnesium (măgnē´zēəm, –zhəm), metallic chemical element; symbol Mg; at. no. 12; at. wt. 24.3050; m.p. about 648.8°C; b.p. about 1,090°C; sp. gr. 1.738 at 20°C; valence +2. In 1808, Sir Humphry Davy discovered magnesium in its oxide, although it is not certain that he isolated the metal. Pure magnesium was isolated substantially by A. A. B. Bussy in 1828 by chemical reduction of the chloride. Magnesium was first isolated electrolytically by Michael Faraday in 1833.
Magnesium is a ductile, silver-white, chemically active metal with a hexagonal close-packed crystalline structure. It is malleable when heated. Magnesium is one of the alkaline-earth metals in Group 2 of the periodic table. It reacts very slowly with cold water. It is not affected by dry air but tarnishes in moist air, forming a thin protective coating of basic magnesium carbonate, MgCO3·Mg(OH)2. When heated, magnesium powder or ribbon ignites and burns with an intense white light and releases large amounts of heat, forming the oxide, magnesia, MgO. A magnesium fire cannot be extinguished by water, since water reacts with hot magnesium and releases hydrogen. Magnesium reacts with the halogens and with almost all acids. It is a powerful reducing agent and is used to free other metals from their anhydrous halides.
Magnesium forms many compounds. The oxide, hydroxide, chloride, carbonate, and sulfate are commercially important. They are used in ceramics, cosmetics, fertilizers, insulation, leather tanning, and textile processing. Epsom salts (magnesium sulfate heptahydrate, MgSO4·7H2O), milk of magnesia (magnesium hydroxide, Mg(OH)2), and citrate of magnesia are used in medicine. Magnesium reacts with organic halides to form the Grignard reagents of organic chemistry.
Magnesium is the eighth most abundant element in the earth's crust but does not occur uncombined in nature. It is found in abundance in the minerals brucite, magnesite, dolomite, and carnalite. It is also found (as the silicate) in asbestos, meerschaum, serpentine, and talc. Magnesium chloride is found in seawater, brines, and salt wells. Mineral waters often contain salts of magnesium; the magnesium ion imparts a bitter flavor. Magnesium is a constituent of the chlorophyll in green plants and is necessary in the diet of animals and humans.
Two methods of producing magnesium commercially are used. The principal method is the electrolysis of fused magnesium chloride, which is used in the extraction of magnesium from seawater (the principal source) and from dolomite. In recovery from seawater, the magnesium is precipitated as magnesium hydroxide by treatment with lime (calcium oxide) obtained from oyster shells. The hydroxide is collected and treated with hydrochloric acid to form the chloride. The chloride is fused and electrolyzed, forming magnesium metal and chlorine gas. The molten metal is cast into ingots for further processing; the chlorine gas is made into hydrochloric acid and is reused to form magnesium chloride. About 1 lb of magnesium is recovered from each 100 gal of seawater; the oceans are a virtually inexhaustible source of this metal. A second method of magnesium production, called the ferrosilicon process, involves the reduction of magnesium oxide (prepared by calcining dolomite) with an iron-silicon alloy.
Magnesium is a commercially important metal with many uses. It is only two thirds as dense as aluminum. It is easily machined, cast, forged, and welded. It is used extensively in alloys, chiefly with aluminum and zinc, and with manganese. Magnesium alloys were used as early as 1910 in Germany. Early structural uses of magnesium alloys were in aircraft fuselages, engine parts, and wheels. They are now also used in jet-engine parts, rockets and missiles, luggage frames, portable power tools, and cameras and optical instruments. Duralumin and magnalium are alloys of magnesium. The metal is also used in pyrotechnics, especially in incendiary bombs, signals, and flares, and as a fuse for thermite. It is used in photographic flashbulbs and is added to some rocket and missile fuels. It is used in the preparation of malleable cast iron. An important use is in preventing the corrosion of iron and steel, as in pipelines and ship bottoms. For this purpose a magnesium plate is connected electrically to the iron. The rapid oxidation of the magnesium prevents the slower oxidation and corrosion of the iron.
Magnesium (Mg) is one of the most abundant structural metals (those metals used to build things), ranking third behind iron and aluminum . Magnesium compounds are found in mineral rocks such as dolomite and magnesite, while the Earth's oceans contain a practically unlimited supply of the metal in the form of dissolved magnesium chloride. One cubic mile of seawater holds some six million tons of the element. The lightest of all the structural metals, magnesium (atomic number 12) is about one-third lighter than aluminum and gives more strength and stiffness per pound than any other common metal.
Magnesium compounds such as Epsom salts were first prepared in the late 1600s and early 1700s. For a while, the oxide compound (magnesia) was confused with lime (calcium carbonate ), until Joseph Black discovered the difference between the two substances in 1754. Humphry Davy demonstrated in 1808 that magnesia was the oxide of a new metal, which he named magnesium, but the element was not isolated until twenty years later, when French chemist Antoine Bussy (1794-1882) combined dry magnesium chloride with potassium to produce the metal in its pure form. Using electrolysis , Michael Faraday obtained magnesium from magnesium chloride in the 1830s. Then in 1852, Robert Bunsen developed an electrolytic cell for producing large quantities of magnesium. For the next sixty years, German chemists further developed Bunsen's cell and pioneered in the production and use of magnesium. The element is relatively easy to extract from seawater by electrolysis, which splits the chloride compound and produces magnesium metal and chlorine gas. By 1909, Germany was manufacturing magnesium commercially, and America began producing magnesium during World War I, eschewing German imports.
During the war, magnesium was used in incendiary bombs, which ignite and burn upon impact, as well as flares and tracer bullets. Powdered magnesium burns with a dazzling white flame, a property of the metal Bunsen had demonstrated in the 1850s. This quality has been exploited in many other products, such as fireworks, and the metal is used in photography to provide a brilliant flash for lighting purposes.
Magnesium's light weight is its most valuable attribute, however. When World War II began in 1939, Germany was well-positioned to use magnesium for aircraft construction and other military applications. In response, American companies stepped up their magnesium manufacturing efforts, resulting in a dramatic increase in magnesium production in the United States; it peaked in 1943 at nearly 184,000 tons. In addition to electrolytic extraction of magnesium from seawater, the element can be produced from mineral rocks by various thermal processes. These methods use a reducing agent such as ferrosilicon to break down magnesium compounds and form vapors of magnesium, which are then distilled into crystals and melted.
Today, many automotive manufacturers in Europe and America are using or testing vehicle parts made of magnesium alloys—mixtures of magnesium and other metals, most often aluminum. Magnesium's light weight will become more critical as automakers try to meet new vehicle mileage standards. Because magnesium is easily cast into complex structures, automakers could also reduce the number of parts needed and streamline the assembly process. Some manufacturers already use magnesium alloys in vehicle bodies and frames.
Magnesium alloys are also used in a host of other products, such as sports equipment, for which light weight is an advantage. Baseball catchers' masks, skis, race cars, and horseshoes are made with magnesium alloys. Consumer goods such as ladders, portable tools, electronic equipment, binoculars, cameras, furniture, and luggage also benefit from magnesium's light weight, and other applications make use of its ability to absorb vibration. Magnesium is an important element from a biological standpoint as well. Scientists have learned that magnesium ions aid in the digestive process, and several magnesium compounds are active ingredients in medicines such as milk of magnesia (magnesium hydroxide) and Epsom salts (magnesium sulfate ). In plants, magnesium is even more critical—it is a component of chlorophyll , the green pigment that converts the Sun 's energy , in the form of light, into food. Magnesium's position in the chlorophyll molecule , which is similar to that of iron in hemoglobin, was discovered by Richard Willstätter in the early 1900s. This was the first clue to magnesium's importance as a plant nutrient; before, scientists thought that it was an impurity. Since then, agricultural fertilizers for magnesium-deficient soils have greatly increased crop yields.
Magnesium is the eighth most abundant element found within the human body; a 190-lb (86 kg) person possesses approximately 1 oz (23 gr) of magnesium in various places. Approximately 50% of the mineral is stored in the bone structures, and approximately 50% is located within various cells, and organ and tissue structures. One percent of all of the body's magnesium is contained within the cardiovascular system. Magnesium plays a role in more than 300 of the biochemical reactions that are essential to human performance, ranging from the maintenance of the skeletal structure and organ health to the function of the cardiovascular and central nervous systems.
While pure magnesium is an element found on the periodic table, it is not obtained in its natural state from the Earth due to its chemical composition, which makes magnesium react with a number of other elements to form compounds, particularly those involving oxygen, sulphur, and hydrogen. The active ingredient in the bitter water first discovered in an English well in the early 1600s, which later became known as the tonic, Epsom salts, is magnesium sulphate, or MgSO4. The popular digestive aid, Milk of Magnesia, also uses magnesium in its composition.
Magnesium is an important component of chlorophyll, the chemical that makes living plants green. For this reason, many of the excellent dietary sources of magnesium are plant products such as green vegetables, most whole grains, beans, and nuts. Well water that is drawn from ground that has a significant mineral composition, sometimes referred to as hard water, will usually contain significant amounts of magnesium. Magnesium is typically contained in foods that also have significant amounts of potassium and dietary fiber.
As foods are digested, any magnesium is absorbed into the body through the small intestine. The magnesium not processed into the body is excreted through the kidneys in urine. It would be difficult to consume magnesium in quantities sufficient to induce a toxic reaction; magnesium deficiency is a far more important dietary issue. The recommended daily allowance (RDA) of magnesium is 420 mg per day for a male over 30 years of age; the RDA for a 30-year-old female is 320 mg per day.
While calcium, in combination with vitamin D, is the most significant mineral presence in the construction and the maintenance of the human bones, magnesium plays a significant role in the transport of calcium to the required areas of bone development. The combined operation of trace minerals, including magnesium, is a preventative in the onset of osteoporosis, a common bone density disease, especially among post-menopausal women.
Magnesium is also a factor in the manner in which the skeletal muscles respond to the directions transmitted by the central nervous system. Although less crucial in this respect than sodium or potassium, magnesium is necessary in the manner in which signals are sent to working muscles during exercise.
Magnesium plays an important role in the determination of blood sugar (glucose) levels, as well as the manner in which proteins ingested through food are synthesized by the body. In a related fashion, magnesium also acts in the regulation of heartbeat and the functions of the immune system. As with the many influences of magnesium on the metabolisms of the human body, magnesium is not usually the lead actor, but works in a supporting capacity.
Magnesium levels within the body can be influenced by a number of factors, in addition to the obvious failure to consume sufficient magnesium-rich foods. Medications that possess a diuretic quality have been established as contributing to a negative impact on the body's ability to retain magnesium. The medications that are particularly reactive to magnesium in this fashion are those used in the treatment of disorders such as Crohn's disease, a serious illness of the intestinal system. In a similar fashion, the excess consumption of caffeine has the effect of reducing magnesium stores within the body.
A magnesium deficiency will not be manifested in a sudden or dramatic physical fashion. The early symptoms of a magnesium deficiency may include a loss of appetite, generalized weakness, and fatigue. If the condition worsens, the person will experience difficulties in concentration (similar to other electrolytic disruptions in the body), and ultimately, low levels of both calcium and potassium will occur. The most effective way to restore low levels of magnesium is by way of improved diet, especially through green vegetables and whole grains. In some circumstances, the levels may be increased through the use of magnesium supplements. Given the nature of the element, magnesium can be restored to its appropriate concentration in the body within a number of days. Magnesium is a component of a number of dietary and training supplements, in a variety of compounds.
Magnesium was first recognized as an element by Joseph Black in 1755. In 1808 Sir Humphry Davy isolated the element, and in 1831 H. Bussy devised a method for producing it. Magnesium, in its combined states, is readily abundant and is the eighth most common element in Earth's crust. Magnesium metal is silvery white in color.
The most common method for producing elemental magnesium is in fused salt electrolytic cells, wherein magnesium chloride (MgCl2) is decomposed by applying a voltage to elemental magnesium and chlorine gas. The magnesium chloride feed is obtained directly from seawater or from magnesium oxide deposits containing magnesite or dolomite. In these cases, the oxide is first chlorinated prior to electrolysis. Another method is to produce magnesium directly from the oxide by reducing the oxide with silicon under vacuum. The resultant Mg vapor is condensed to recover Mg metal. This process is carried out in vacuum retorts and is known as the Pidgeon process.
The principal uses of Mg are for alloying with aluminum, for desulphurizing steel and pig iron, and for nodularizing the graphite in cast irons. Recently, researchers have focused on using Mg alloys to produce lightweight components in automobiles. As a result, Mg usage in vehicles is steadily increasing.
Compounds of magnesium, including the hydroxide, the chloride, the citrate, and the sulfate, are used in the medical field. Magnesium is an important element in both animal and plant life. On average, adults require a daily intake of about 300 milligrams (0.011 ounces) of magnesium.
see also Alkaline Earth Metals; Black, Joseph; Davy, Humphry; Inorganic Chemistry.
Kramer, Deborah A. (2001). "Magnesium, Its Alloys and Compounds." U.S. Geological Survey Open-File Report 01-341. Also available from <http://pubs.usgs.gov/of/of01-341/>.
Raloff, J. (1998). "Magnesium: Another Metal to Bone up On." Science News. 154(9):134.