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Magnesium by Karen Schroeder Kassel, MS, RD, MEd

Image for magnesium Magnesium is an essential mineral that has a hand in many vital body functions, for example releasing energy, regulating body temperature, building protein, and stabilizing bone. It is also one of several nutrients that helps keep blood pressure within a healthy range. And since magnesium is plentiful in vegetables, legumes, and whole grains, it is easy to consume enough if you are eating healthy food.

Functions

Magnesium's functions include:

Activating more than 300 enzymes (Enzymes are chemicals that regulate a variety of body functions, including making body proteins and causing muscle contractions.)
Aiding in the metabolism of fat and carbohydrate to produce energy
Binding with ATP to form "active ATP," which provides energy for almost all metabolic reactions and processes
Ensuring proper nerve and muscle function and keeping heart rhythm steady
Helping synthesize nucleic acids (DNA and RNA) and proteins, which are the building blocks of body tissue
Giving structure to cell membranes
Helping keep bones healthy
Decreasing the risk of tooth decay by binding calcium to tooth enamel

Recommended Intake

Age Group	Recommended Dietary Allowance (mg/d)
Age Group	Male	Female
0-6 months	Adequate intake (AI) = 30	AI = 30
7-12 months	AI = 75	AI = 75
1-3 years	80	80
4-8 years	130	130
9-13 years	240	240
14-18 years	410	360
19-30 years	400	310
31-50 years	420	320
50-70 years	420	320
>70 years	420	320
Pregnancy (18 years or younger)	n/a	400
Pregnancy 19-30 years	n/a	350
Pregnancy 31-50 years	n/a	360
Lactation (18 years or younger)	n/a	360
Lactation 19-30 years	n/a	310
Lactation 31-50 years	n/a	320

Magnesium Deficiency

Magnesium deficiency is rare because most people have large stores of this mineral in their body. However, it can be caused by diseases or medicines that interfere with the body's ability to absorb magnesium. Symptoms of a magnesium deficiency include: irregular heartbeat, nausea, confusion, depression, tingling, weakness, loss of appetite, and muscle contractions and cramps.

Conditions and medicines that may lead to a magnesium deficiency include:

Gastrointestinal disorders, such as:
- Severe diarrhea
- Chronic or severe vomiting
- Surgical removal of part of the intestine
- Intestinal inflammation
Malabsorption disorders , including:
- Crohn’s disease
- Cystic fibrosis
- Celiac disease
- Diseases of the pancreas, liver, or gallbladder
Thiazide diuretics (can increase loss of magnesium in the urine)
Cisplatin (a drug used to treat cancer)
Certain antibiotics, including gentamicin , amphotericin, and cyclosporin
Poorly controlled diabetes (can increase the loss of magnesium through urine)
Alcoholism—Alcohol increases urinary excretion of magnesium. People who drink heavily typically have poor diets that are lacking in many essential nutrients, including magnesium.
Kidney disease—The kidneys are important for reabsorption and excretion of magnesium.

Tolerable Upper Intake

It's also possible to get too much magnesium. The Office of Dietary Supplements publishes tolerable upper intake levels for magnesium.

Age Group	Tolerable Upper Intake Levels (mg/d)
Age Group	Male	Female
1-3 years	65	65
4-8 years	110	110
9-18 years	350	350
19+ years	350	350
Pregnancy (18 years or younger)	n/a	350
Pregnancy 19+	n/a	350

Magnesium Toxicity

Magnesium toxicity through food intake is not a concern for most healthy people. However, people with kidney disease may develop toxicity because the kidneys are responsible for regulating the level of magnesium in the blood. Also it is possible to take too much magnesium in supplements. Symptoms of magnesium toxicity include:

Diarrhea
Abdominal cramping
Nausea and diarrhea
muscle weakness
irregular heartbeat

Major Food Sources

Magnesium is found in a variety of foods. The best sources are legumes, nuts, whole grains, and certain vegetables. "Hard" water (which is high in dissolved minerals, specifically calcium and magnesium) is also a source of magnesium.

Foods that provide high levels of magnesium include:

Wheat bran
Almonds
Spinach
Raisin brain cereal
Cashews, dry roasted
Soybeans
Wheat germ
Nuts
Bran flakes cereal
Shredded wheat cereal
Oatmeal

Health Implications

Blood Pressure

Greater magnesium intake is associated with a lower incidence of high blood pressure . This is the finding of a few large clinical studies. One of these, the DASH (Dietary Approaches to Stop Hypertension) study found that a diet high in magnesium, potassium, and calcium and low in sodium and fat can significantly lower blood pressure. You can get these nutrients by eating a diet rich in fresh fruits and vegetables, legumes, whole grains, and low-fat dairy foods. Another group of researchers studied 30,000 US male health professionals over several years. The study found a greater magnesium intake was significantly associated with a lower risk of hypertension.

Based on the growing number of studies showing a positive role for magnesium in managing blood pressure, the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure recommends maintaining an adequate magnesium intake to prevent and manage high blood pressure.

Heart Disease

Several studies have found links between magnesium status and heart health. Many of these suggest that an adequate intake of magnesium is protective of the heart. However, further study needs to be done to clarify magnesium's role.

Osteoporosis

Since a significant amount of magnesium is stored in the bones and one of magnesium's roles is to help keep bones healthy, it would make sense that magnesium would help protect bones from the thinning of osteoporosis . Several studies have suggested just that—magnesium supplementation may improve bone mineral density. However it is still not clear, and more study needs to be done.

Tips For Increasing Your Magnesium Intake

It is easy to meet your magnesium needs through foods. To increase your intake, try some of the following:

Sprinkle wheat germ over your morning bowl of cereal or oatmeal and on top of casseroles or in baked goods.
Throw a handful of nuts into a spinach salad to add a little crunch and some extra nutrition.
Wrap beans, rice, sauteed vegetables, and a little bit of cheese in a warm tortilla for lunch.
Add beans to dishes like chili, soup, salad, pasta, or rice.
Have a bowl of whole grain cereal for breakfast or to snack on; if you are not used to the taste, mix it with your usual cereal.
Bake a potato and top it with sauteed spinach, black beans, and salsa.
Spread peanut butter on your toast or bagel instead of butter, margarine, or cream cheese.

RESOURCES:

Academy of Nutrition and Dietetics http://www.eatright.org/
International Food Information Council http://www.foodinsight.org/

CANADIAN RESOURCES:

Canada's Food Guide http://www.hc-sc.gc.ca/fn-an/food-guide-aliment/index_e.html
Dietitians of Canada http://www.dietitians.ca/

References:

Appel L, Moore T, et al. A clinical trial of the effects of dietary patterns on blood pressure. N Engl J Med. 1997;336:1117-1124.
Larson Duyff R, American Dietetic Association. The American Dietetic Association's Complete Food & Nutrition Guide . Minneapolis, MN; Chronimed Publishing; 1998.
Magnesium. Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/. Accessed July 29, 2012.
Osteoporosis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated May 25, 2012. Accessed July 29, 2012.
The seventh report of the Joint National Committee on Prevention, Detection, and Treatment of High Blood Pressure. Hypertension.2003;42:1206. National Heart Lung and Blood Institute website. Available at: http://www.nhlbi.nih.gov/guidelines/hypertension/. Published December 2003. Accessed July 29, 2012.
Wardlaw G, Insel PM. Perspectives in Nutrition . 2nd ed. St. Louis, MO: Mosby; 1993.

Last reviewed July 2012 by Brian Randall, MD

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