Sources of 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 magnesium¹ Refined grains are generally low in magnesium.² ³

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.

Eating a wide variety of legumes, nuts, whole grains, and vegetables will help you meet your daily dietary need for magnesium. Selected food sources of magnesium are listed in Table 1.

Table 1: Selected food sources of magnesium [5]

FOOD	Milligrams (mg)	%DV*
Halibut, cooked, 3 ounces	90	20
Almonds, dry roasted, 1 ounce	80	20
Cashews, dry roasted, 1 ounce	75	20
Soybeans, mature, cooked, ½ cup	75	20
Spinach, frozen, cooked, ½ cup	75	20
Nuts, mixed, dry roasted, 1 ounce	65	15
Cereal, shredded wheat, 2 rectangular biscuits	55	15
Oatmeal, instant, fortified, prepared w/ water, 1 cup	55	15
Potato, baked w/ skin, 1 medium	50	15
Peanuts, dry roasted, 1 ounce	50	15
Peanut butter, smooth, 2 Tablespoons	50	15
Wheat Bran, crude, 2 Tablespoons	45	10
Blackeyed Peas, cooked, ½ cup	45	10
Yogurt, plain, skim milk, 8 fluid ounces	45	10
Bran Flakes, ½ cup	40	10
Vegetarian Baked Beans, ½ cup	40	10
Rice, brown, long-grained, cooked, ½ cup	40	10
Lentils, mature seeds, cooked, ½ cup	35	8
Avocado, California, ½ cup pureed	35	8
Kidney Beans, canned, ½ cup	35	8
Pinto Beans, cooked, ½ cup	35	8
Wheat Germ, crude, 2 Tablespoons	35	8
Chocolate milk, 1 cup	33	8
Banana, raw, 1 medium	30	8
Milk Chocolate candy bar, 1.5 ounce bar	28	8
Milk, reduced fat (2%) or fat free, 1 cup	27	8
Bread, whole wheat, commercially prepared, 1 slice	25	6
Raisins, seedless, ½ cup packed	25	6
Whole Milk, 1 cup	24	6
Chocolate Pudding, 4 ounce ready-to-eat portion	24	6

*DV = Daily Value. DVs are reference numbers developed by the Food and Drug Administration (FDA) to help consumers determine if a food contains a lot or a little of a specific nutrient. The DV for magnesium is 400 milligrams (mg). Most food labels do not list a food's magnesium content. The percent DV (%DV) listed on the table above indicates the percentage of the DV provided in one serving. A food providing 5% of the DV or less per serving is a low source while a food that provides 10-19% of the DV is a good source. A food that provides 20% or more of the DV is high in that nutrient. It is important to remember that foods that provide lower percentages of the DV also contribute to a healthful diet. For foods not listed in this table, please refer to the U.S. Department of Agriculture's Nutrient Database Web site: http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl.

Eating a variety of whole grains, legumes, and vegetables (especially dark-green, leafy vegetables) every day will help provide recommended intakes of magnesium and maintain normal storage levels of this mineral. Increasing dietary intake of magnesium can often restore mildly depleted magnesium levels. However, increasing dietary intake of magnesium may not be enough to restore very low magnesium levels to normal.

When blood levels of magnesium are very low, intravenous (i.e. by IV) magnesium replacement is usually recommended. Magnesium tablets also may be prescribed, although some forms can cause diarrhea.⁴ It is important to have the cause, severity, and consequences of low blood levels of magnesium evaluated by a physician, who can recommend the best way to restore magnesium levels to normal. Because people with kidney disease may not be able to excrete excess amounts of magnesium, they should not take magnesium supplements unless prescribed by a physician.

Oral magnesium supplements combine magnesium with another substance such as a salt. Examples of magnesium supplements include magnesium oxide, magnesium sulfate, and magnesium carbonate. Elemental magnesium refers to the amount of magnesium in each compound. Figure 1 compares the amount of elemental magnesium in different types of magnesium supplements.⁵ The amount of elemental magnesium in a compound and its bioavailability influence the effectiveness of the magnesium supplement. Bioavailability refers to the amount of magnesium in food, medications, and supplements that is absorbed in the intestines and ultimately available for biological activity in your cells and tissues. Enteric coating (the outer layer of a tablet or capsule that allows it to pass through the stomach and be dissolved in the small intestine) of a magnesium compound can decrease bioavailability.⁶ In a study that compared four forms of magnesium preparations, results suggested lower bioavailability of magnesium oxide, with significantly higher and equal absorption and bioavailability of magnesium chloride and magnesium lactate.⁷ This supports the belief that both the magnesium content of a dietary supplement and its bioavailability contribute to its ability to restore deficient levels of magnesium.
Percent Magnesium content of oral supplements
The information in Figure 1 is provided to demonstrate the variable amount of magnesium in magnesium supplements.

Disclaimer
Reasonable care has been taken in preparing this document and the information provided herein is believed to be accurate. However, this information is not intended to constitute an "authoritative statement" under Food and Drug Administration rules and regulations.

About Source: ODS

The mission of the Office of Dietary Supplements (ODS) is to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, stimulating and supporting research, disseminating research results, and educating the public to foster an enhanced quality of life and health for the U.S. population.

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Health professionals and consumers need credible information to make thoughtful decisions about eating a healthful diet and using vitamin and mineral supplements. These Fact Sheets provide responsible information about the role of vitamins and minerals in health and disease. Each Fact Sheet in this series received extensive review by recognized experts from the academic and research communities.

The information is not intended to be a substitute for professional medical advice. It is important to seek the advice of a physician about any medical condition or symptom. It is also important to seek the advice of a physician, registered dietitian, pharmacist, or other qualified health professional about the appropriateness of taking dietary supplements and their potential interactions with medications.

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Footnotes

U.S. Department of Agriculture, Agricultural Research Service. 2003. USDA National Nutrient Database for Standard Reference, Release 16. Nutrient Data Laboratory Home Page, http://www.nal.usda.gov/fnic/foodcomp. [↩]
Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride. National Academy Press. Washington, DC, 1999. [↩]
U.S. Department of Agriculture, Agricultural Research Service. 2003. USDA National Nutrient Database for Standard Reference, Release 16. Nutrient Data Laboratory Home Page, http://www.nal.usda.gov/fnic/foodcomp. [↩]
DePalma J. Magnesium Replacement Therapy. Am Fam Phys 1990;42:173-6. [↩]
Klasco RK (Ed): USP DI® Drug Information for the Healthcare Professional. Thomson MICROMEDEX, Greenwood Village, Colorado 2003. [↩]
Fine KD, Santa Ana CA, Porter JL, Fordtran JS. Intestinal absorption of magnesium from food and supplements. J Clin Invest 1991;88:296-402. [↩]
Firoz M and Graber M. Bioavailaility of US commercial magnesium preparation. Magnes Res 2001;14:257-62. [↩]

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