Dietary Supplement Fact Sheet - Magnesium
Dietary Supplement Fact Sheet - Magnesium
Document Last Updated: 12/5/2005 12:36 PM
The Clinical Nutrition Service and the ODS thank the expert scientific reviewers for their role in ensuring the scientific accuracy of the information discussed in these fact sheets, along with the Nutrition Education Subcommittee of the NIH, the U.S. Department of Agriculture Dietary Guidance Working Group, and the Department of Health and Human Services Nutrition Policy Board Committee on Dietary Guidance. Reviewers:
Susan Percival, Ph.D., University of Florida
Robert Rude, Ph.D., University of Southern California
Connie Weaver, Ph.D., Purdue University
Elizabeth Whelan, D.Sc, MPH, American Council on Science and Health, New York, New York
Office of Dietary Supplements

Table of Contents
Magnesium: What is it?
What foods provide magnesium?
What are the Dietary Reference Intakes for magnesium?
When can magnesium deficiency occur?
Who may need extra magnesium?
What is the best way to get extra magnesium?
What are some current issues and controversies about magnesium?
What is the health risk of too much magnesium?
Selecting a healthful diet

Magnesium: What is it?
Magnesium is the fourth most abundant mineral in the body and is essential to good health. Approximately 50% of total body magnesium is found in bone. The other half is found predominantly inside cells of body tissues and organs. Only 1% of magnesium is found in blood, but the body works very hard to keep blood levels of magnesium constant [1].

Magnesium is needed for more than 300 biochemical reactions in the body. It helps maintain normal muscle and nerve function, keeps heart rhythm steady, supports a healthy immune system, and keeps bones strong. Magnesium also helps regulate blood sugar levels, promotes normal blood pressure, and is known to be involved in energy metabolism and protein synthesis [2-3]. There is an increased interest in the role of magnesium in preventing and managing disorders such as hypertension, cardiovascular disease, and diabetes. Dietary magnesium is absorbed in the small intestines. Magnesium is excreted through the kidneys [1-3,4].

What foods provide magnesium?
Green vegetables such as spinach are good sources of magnesium because the center of the chlorophyll molecule (which gives green vegetables their color) contains magnesium. Some legumes (beans and peas), nuts and seeds, and whole, unrefined grains are also good sources of magnesium [5]. Refined grains are generally low in magnesium [4-5]. When white flour is refined and processed, the magnesium-rich germ and bran are removed. Bread made from whole grain wheat flour provides more magnesium than bread made from white refined flour. Tap water can be a source of magnesium, but the amount varies according to the water supply. Water that naturally contains more minerals is described as "hard". "Hard" water contains more magnesium than "soft" water.

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