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magnesium

What can high-magnesium foods do for you?

  • Relax your nerves and muscles
  • Build and strengthen bones
  • Keep your blood circulating smoothly

What events can indicate a need for more high-magnesium foods?

  • Muscle weakness, tremor, or spasm
  • Heart arrhythmia, irregular contraction, or increased heart rate
  • Softening and weakening of bone
  • Imbalanced blood sugar levels
  • Headaches
  • Elevated blood pressure

Excellent sources of magnesium include Swiss chard and spinach. Avoid overcooking to minimize loss of magnesium.

Description

What is magnesium?

Magnesium is usually referred to as a "macromineral," which means that our food must provide us with hundreds of milligrams of magnesium every day. (The other macrominerals that all humans must get from food are calcium, phosphorus, sodium:nutrient, potassium, and chloride).

Inside our bodies, magnesium is found mostly in our bones (60-65%), but also in our muscles (25%), and in other cell types and body fluids. Like all minerals, magnesium cannot be made in our body and must therefore be plentiful in our diet in order for us to remain healthy.

Magnesium is sometimes regarded as a "smoothie" mineral, since it has the ability to relax our muscles. Our nerves also depend upon magnesium to avoid becoming overexcited. The use of magnesium as a muscle relaxer is familiar to many individuals who have taken liquid magnesium (for example, through the product Milk of Magnesia™) as a laxative. This product can help relieve constipation by relaxing the muscles around the intestine.

How it Functions

What is the function of magnesium?

Bone Formation

About two thirds of all magnesium in our body is found in our bones. Researchers have discovered, however, that bone magnesium has two very different roles to play in our health. Some of the magnesium in our bones helps give them their physical structure. This magnesium is part of the bone's crystal lattice and is found in this "bone scaffolding" together with the minerals phosphorus and calcium.

Other amounts of magnesium, however, are found on the surface of the bone. This surface magnesium does not appear to be involved in the bone's structure, but instead acts as a storage site for magnesium which the body can draw upon in times of poor dietary supply.

Nerve and Muscle Relaxation

Magnesium and its fellow macronutrient, calcium, act together to help regulate the body's nerve and muscle tone. In many nerve cells, magnesium serves as a chemical gate blocker - as long as there is enough magnesium around, calcium can't rush into the nerve cell and activate the nerve. This gate blocking by magnesium helps keep the nerve relaxed. If our diet provides us with too little magnesium, this gate blocking can fail and the nerve cell can become overactivated. When some nerve cells are overactivated, they can send too many messages to the muscles and cause the muscles to overcontract. This chain of events helps explain how magnesium deficiency can trigger muscle tension, muscle soreness, muscle spasms, muscle cramps, and muscle fatigue.

Other functions of magnesium

Many chemical reactions in the body involve the presence of an enzyme. Enzymes are special proteins that help trigger chemical reactions. Over 300 different enzymes in the body require magnesium in order to function. For this reason, the functions of this mineral are especially diverse. Magnesium is involved in the metabolism of proteins, carbohydrates, and fats. It helps genes function properly. Some fuels cannot be stored in our muscle cells unless adequate supplies of magnesium are available.

The metabolic role of magnesium is so diverse that it is difficult to find a body system that is not affected by magnesium deficiency. Our cardiovascular system, digestive system, nervous system, muscles, kidneys, liver, hormone-secreting glands, and brain all rely on magnesium for their metabolic function.

Deficiency Symptoms

What are deficiency symptoms for magnesium?

Because magnesium plays such a wide variety of roles in the body, the symptoms of magnesium deficiency can also vary widely. Many symptoms involve changes in nerve and muscle function. These changes include muscle weakness, tremor, and spasm. In the heart muscle, magnesium deficiency can result in arrhythmia, irregular contraction, and increased heart rate.

Because of its role in bone structure, the softening and weakening of bone can also be a symptom of magnesium deficiency. Other symptoms can include: imbalanced blood sugar levels; headaches; elevated blood pressure; elevated fats in the bloodstream; depression; seizures; nausea; vomiting; and lack of appetite.

Toxicity Symptoms

What are toxicity symptoms for magnesium?

The most common toxicity symptom associated with high levels of magnesium intake is diarrhea. This symptom is most commonly seen in situations where magnesium is taken as a dietary supplement. In research studies, the doses of magnesium associated with diarrhea usually range from 1-5 grams (1,000-5,000 milligrams), but diarrhea can occur at lower supplemental doses. Magnesium toxicity can also be associated with very generalized symptoms like increased drowsiness or sense of weakness.

In 1997, the National Academy of Sciences set a tolerable upper limit (UL) on intake of magnesium at 350 milligrams per day for individuals 9 years and older. This limit was restricted, however, to magnesium obtained from dietary supplements, and no upper limit was set on intake of magnesium from food sources.

Impact of Cooking, Storage and Processing

How do cooking, storage, or processing affect magnesium?

The impact of cooking and processing on magnesium can vary greatly from food to food, since magnesium is found in different forms in different types of food. In some foods, where a greater percent of magnesium is found in water-soluble form, blanching (boiling or steaming for 1-4 minutes), steaming, or boiling of these foods can result in a substantial loss of magnesium. For example, about one third of the magnesium in spinach is lost after blanching. Similarly, when navy beans are cooked, they lose 65% of their magnesium.

In other foods that serve as good sources of magnesium, like almonds or peanuts, there is very little loss of magnesium either from roasting or from processing into almond or peanut butter (as long as the whole almond or peanut is used).

Factors that Affect Function

What factors might contribute to a deficiency of magnesium?

In addition to poor dietary intake, problems in the digestive tract are the most common cause of magnesium deficiency. These digestive tract problems include malabsorption, diarrhea, and ulcerative colitis. Many kinds of physical stresses can contribute to magnesium deficiency, including cold stress, physical trauma, and surgery. Kidney disease and alcoholism can also contribute to a deficiency of this mineral.

Drug-Nutrient Interactions

What medications affect magnesium?

A particularly long list of prescription medications have been shown to reduce the body's supply of magnesium. Several types of diuretics used to lower blood pressure, including thiazide diuretics like Diuril ™ or Enduron,™ and loop diuretics like furosemide, have been shown to compromise magnesium status.

Antibiotics can also lower magnesium availability. Included on the antibiotic list are neomycin, tetracycline, erythromycin, sulfamethoxazole, and sulfonamides. Other medications that reduce the body's supply of magnesium include the anticoagulant drug warfarin; corticosteroids; oral contraceptives (birth control pills); and the immunosuppressant drug cyclosporine.

Nutrient Interactions

How do other nutrients interact with magnesium?

The relationship between magnesium and calcium is one of the most actively researched, and yet not fully understood mineral-to-mineral relationships. On one hand, magnesium is required in order for calcium to maintain a balanced role in the body's metabolism. On the other hand, magnesium can compete with calcium and prevent calcium from trigger certain events, like the relay of a nerve message or the contraction of a muscle.

Because of the complex relationship between calcium and magnesium, healthy diets almost always need to contain foods rich in both minerals. Magnesium also has an important relationship with potassium, and helps regulate the movement of potassium in and out of our cells. Finally, because magnesium can be attached to certain building blocks of protein (called amino acids), increased intake of protein can sometimes help improve the body's magnesium status.

Health Conditions

What health conditions require special emphasis on magnesium?

Magnesium may play a role in the prevention and/or treatment of the following health conditions:
  • Alcoholism
  • Angina pectoris
  • Arrhythmia
  • Asthma
  • Autism
  • Chronic fatigue
  • Congenital heart disease
  • Congestive heart failure
  • Coronary artery disease
  • Diabetes
  • Eclampsia
  • Epilepsy
  • Glaucoma
  • Heart attack
  • HIV/AIDS
  • Hypertension
  • Hypertriglyceridemia
  • Inflammatory bowel disease
  • Migraine
  • Multiple sclerosis
  • Osteoporosis
  • Peptic ulcers
  • PMS
  • Pre-eclampsia
  • Raynaud's syndrome
  • Systemic lupus erythematosus

Form in Dietary Supplements

What forms of magnesium are found in dietary supplements?

Magnesium can be purchased as a dietary supplement in one of two basic forms: chelated or non-chelated. "Chelated" means connected with another molecule. In the case of magnesium, the most common chelates fall into the category of amino acid chelates. In these supplements, magnesium is attached to a building block of protein (called an amino acid). The most widely-available amino acid chelates are magnesium glycinate, magnesium aspartate, and magnesium taurate.

Magnesium can also be attached to an organic acid (like citrate) or to a fatty acid (like stearate). The non-chelated forms of magnesium include magnesium oxide, magnesium sulfate, and magnesium carbonate. There is some research evidence that the chelated forms of magnesium (like magnesium citrate) are better absorbed than the non-chelated forms (like magnesium oxide).

Food Sources

Introduction to Nutrient Rating System Chart

The following chart shows the foods which are either excellent, very good or good sources of this nutrient. Next to each food name you will find the following information: the serving size of the food; the number of calories in one serving; DV% (percent daily value) of the nutrient contained in one serving (similar to other information presented in the website, this DV is calculated for 25-50 year old healthy woman); the nutrient density rating; and the food's World's Healthiest Foods Rating. Underneath the chart is a table that summarizes how the ratings were devised. Read detailed information on our Nutrient Rating System.

Foods Ranked as quality sources of:
magnesium
Food Serving
Size
Cals Amount
(mg)
DV
(%)
Nutrient
Density
World's
Healthiest
Foods Rating
Chard, Boiled 1 cup 35.0 150.50 37.6 19.4 excellent
Spinach (boiled, with salt) 1 cup 41.4 156.60 39.1 17.0 excellent
Kelp 0.25 cup 8.6 24.20 6.0 12.7 very good
Basil, Ground 2 tsp 7.5 12.68 3.2 7.6 good
Parsley, Fresh 1 oz-wt 10.2 14.18 3.5 6.2 good
Squash, Summer, All Varieties 1 cup 36.0 43.20 10.8 5.4 very good
Peppermint Leaves, Fresh 1 oz-wt 19.9 22.68 5.7 5.1 very good
Coriander, Seeds 2 tsp 9.9 11.00 2.8 5.0 good
Greens, Turnip, Cooked 1 cup 28.8 31.68 7.9 4.9 very good
Greens, Mustard, Boiled 1 cup 21.0 21.00 5.3 4.5 very good
Pumpkin Seeds, Dried 0.25 cup 186.7 184.58 46.1 4.5 very good
Blackstrap Cane Molasses 2 tsp 32.1 29.38 7.3 4.1 very good
Broccoli (pieces, steamed) 1 cup 43.7 39.00 9.8 4.0 very good
Cucumber, Raw 1 cup 13.5 11.44 2.9 3.8 good
Dill Seed 2 tsp 13.4 11.26 2.8 3.8 good
Cloves, Ground 2 tsp 14.2 11.60 2.9 3.7 good
Halibut, Baked/Broiled 4 oz-wt 158.8 121.34 30.3 3.4 very good
Flax Seeds 2 tbs 95.3 70.14 17.5 3.3 good
Green Snap/String Beans, Boiled 1 cup 43.8 31.25 7.8 3.2 good
Celery, Raw 1 cup 19.2 13.20 3.3 3.1 good
Collard Greens, Boiled, Drained 1 cup 49.4 32.30 8.1 2.9 good
Kale, Fresh, Boiled 1 cup 36.4 23.40 5.8 2.9 good
Seeds, Mustard 2 tsp 35.0 22.28 5.6 2.9 good
Ginger Root 1 oz-wt 19.6 12.19 3.0 2.8 good
Sunflower Seeds, Dried 0.25 cup 205.2 127.44 31.9 2.8 good
Seeds, Sesame 0.25 cup 206.3 126.36 31.6 2.8 good
Quinoa, Dry 0.25 cup 158.9 89.25 22.3 2.5 good
Buckwheat Groats, Cooked 1 cup 154.6 85.68 21.4 2.5 good
Fennel Bulb, Sliced, Raw 1 cup 27.0 14.80 3.7 2.5 good
Beans, Black, Boiled 1 cup 227.0 120.40 30.1 2.4 good
Chinook Salmon Fillet-Baked/Broiled 4 oz-wt 261.9 138.35 34.6 2.4 good
Tomato, Red, Raw, Ripe 1 cup 37.8 19.80 5.0 2.4 good
Beets, Boiled 1 cup 74.8 39.10 9.8 2.4 good
Brussels Sprouts, Boiled 1 cup 60.8 31.20 7.8 2.3 good
Scallops, Baked, Broiled 4 oz-wt 151.7 77.12 19.3 2.3 good
Soybeans, Cooked 1 cup 297.6 147.92 37.0 2.2 good
Kiwifruit 1 each 46.4 22.80 5.7 2.2 good
Green Peas-Boiled 1 cup 134.4 62.40 15.6 2.1 good
Eggplant, Boiled 1 cup 27.7 12.87 3.2 2.1 good
Tuna, Yellowfin, Baked/Broiled 4 oz-wt 157.6 72.58 18.1 2.1 good
Nuts, Cashews, Raw 0.25 cup 196.6 89.05 22.3 2.0 good
Asparagus, Boiled 1 cup 43.2 18.00 4.5 1.9 good
Beans, Navy, Cooked 1 cup 258.4 107.38 26.8 1.9 good
Mushrooms, Crimini, Raw 5 oz-wt 31.2 12.76 3.2 1.8 good
Beans, Pinto, Cooked 1 cup 234.3 94.05 23.5 1.8 good
Tofu, Raw 4 oz-wt 86.2 34.02 8.5 1.8 good
Tempeh, Cooked 4 oz-wt 223.4 87.55 21.9 1.8 good
Cauliflower (boiled, drained) 1 cup 28.5 11.16 2.8 1.8 good
Rice, Long Grain Brown, Cooked 1 cup 216.4 83.85 21.0 1.7 good
Oats, Whole Grain 1 cup 145.1 56.16 14.0 1.7 good
Wheat, Bulgur, Cooked 1 cup 151.1 58.24 14.6 1.7 good
Beans, Lima, Cooked 1 cup 216.2 80.84 20.2 1.7 good
Millet, Cooked 1 cup 285.6 105.60 26.4 1.7 good
Raspberries, Fresh 1 cup 60.3 22.14 5.5 1.7 good
Cabbage (shredded, boiled) 1 cup 33.0 12.00 3.0 1.6 good
Rye, Whole Grain (1 cup cooked) 0.33 cup 188.7 68.16 17.0 1.6 good
Beans, Kidney, Cooked 1 cup 224.8 79.65 19.9 1.6 good
Carrots, Raw 1 cup 52.5 18.30 4.6 1.6 good
Watermelon 1 cup 48.6 16.72 4.2 1.5 good
Shrimp, MixedSpecies, Steamed, Boiled 4 oz-wt 112.3 38.56 9.6 1.5 good
Strawberries, Fresh 1 cup 43.2 14.40 3.6 1.5 good
World's Healthiest
Foods Rating
Rule
excellent DV>=75% OR Density>=7.6 AND DV>=10%
very good DV>=50% OR Density>=3.4 AND DV>=5%
good DV>=25% OR Density>=1.5 AND DV>=2.5%

Public Health Recommendations

What are current public health recommendations for magnesium?

The Adequate Intake (AI)levels for magnesium, set in 1997 by the Institute of Medicine at the National Academy of Sciences, are as follows:

  • males and females, 0-6 months: 30 milligrams
  • males and females, 6-12 months: 75 milligrams

The Recommended Dietary Allowances for magnesium, set in 1997 by the Institute of Medicine at the National Academy of Sciences, are as follows:

  • males and females, 1-3 years: 80 milligrams
  • males and females, 4-8 years: 130 milligrams
  • males and females, 9-13 years: 240 milligrams
  • males, 14-18 years: 410 milligrams
  • males, 19-30 years: 400 milligrams
  • males, 31 years and older: 420 milligrams
  • females, 14-18 years: 360 milligrams
  • females, 19-30 years: 310 milligrams
  • females, 31 years and older: 320 milligrams
  • pregnant women, 18 years or younger: 400 milligrams
  • pregnant women, 19-30 years: 350 milligrams
  • pregnant women, 31-50 years: 360 milligrams
  • lactating women, 18 years or younger: 360 milligrams
  • lactating women, 19-30 years: 310 milligrams
  • lactating women, 31-50 years: 320 milligrams

References

  • Abbott LG, Rude RK. Clinical manifestations of magnesium deficiency. Miner Electrolyte Metab 1993;19:314-322.
  • Bengtsson BL. Effect of blanching on mineral and oxalate content of spinach. J Food Technol 1969;4:141-145.
  • Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995.
  • Iseri LK, French JH. Magnesium: Nature's physiologic calcium blocker. Am Heart J 1984;108:188-193.
  • Lindberg JS, Zobitz MM, Poindexter JR, et al. Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr 1990;9:48-55.
  • Meiners CR, Derise NL, Lau HC, et al. (1976). The content of nine mineral elements in raw and cooked mature dry legumes. J Arg Food Chem 1976;24:1126-1130.
  • National Research Council. Recommended dietary allowances. 9th edition. National Academy of Sciences Press, Washington, DC, 1980;134-136.
  • Pearson HA, Campbell V, Berrow N, et al. Modulation of voltage-dependent calcium channels in cultured neurons. Ann N Y Acad Sci 1994;747:325-335.
  • Shils ME. Magnesium. In: Shils ME, Olson JA, and Shike M. Modern nutrition in health and disease. 8th Edition. Lea and Febiger, Philadelphia, 1994;164-184.
  • Touyz RM. Role of magnesium in the pathogenesis of hypertension. Mol Aspects Med 2003 Feb 6;24(1-3):107-36.
  • Wester PO. Magnesium. Am J Clin Nutr 1987;45(suppl):1305-1312.

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