Magnesium is important to carbohydrate metabolism. It may influence the release and activity of insulin, the hormone that helps control blood glucose levels. Elevated blood glucose levels, which are seen in poorly controlled diabetes, causes increased losses of magnesium in the urine, which in turn lowers blood levels of magnesium.
Evidence suggests that magnesium may play an important role in regulating blood pressure. Diets that provide plenty of fruits and vegetables, which are good sources of magnesium and potassium, are consistently associated with lower blood pressure. The Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure recommends maintaining an adequate magnesium intake, as well as potassium and calcium, as a positive lifestyle modification for preventing and managing high blood pressure.
Magnesium is a part of chlorophyll, the green pigment found in plants, so good sources include green leafy vegetables, potatoes, nuts (especially almonds and cashews), seeds, legumes, and whole-grain cereals. Seafood is also a good source. Meat and dairy products supply small amounts. Absorption is only 30 to 40 percent.
The magnesium content of refined foods is usually low. Whole-wheat bread, for example, has twice as much magnesium as white bread because the magnesium-rich germ and bran are removed when white flour is processed.
Although magnesium is present in many foods, it usually occurs in small amounts. As with most nutrients, daily needs for magnesium cannot be met from a single food. Eating a wide variety of foods, including five servings of fruits and vegetables daily and plenty of whole grains, helps to ensure an adequate intake of magnesium.
Even though dietary surveys suggest that many American do not consume magnesium in recommended amounts, deficiency is rarely seen in the United States in adults. When magnesium deficiency does occur, it is usually due to excessive loss of magnesium in urine, gastrointestinal disorders that cause a loss of magnesium or limit magnesium absorption, or a chronically low intake of magnesium. Treatment with diuretics (water pills), some antibiotics, and some medicines used to treat cancer can increase the loss of magnesium in urine. Poorly controlled diabetes and a high alcohol intake also increase excretion of magnesium. Signs of magnesium deficiency include confusion, disorientation, loss of appetite, depression, muscle contractions and cramps, tingling, numbness, abnormal heart rhythms, coronary spasm, and seizures.
Very high doses of magnesium supplements can cause diarrhea. Especially in the elderly, it can also cause problems with the kidneys because the kidneys are trying to remove excess magnesium. The elderly are at risk of magnesium toxicity because kidney function declines with age and they are more likely to take magnesium-containing laxatives and antacids. When excess magnesium impacts the kidneys, symptoms include nausea, diarrhea, appetite loss, muscle weakness, difficulty breathing, and irregular heartbeat.
Food Sources of Magnesium
Foods
|
Milligrams
|
% Daily Value
|
|---|---|---|
Avocado, Florida, 1/2 medium
|
103
|
26
|
Wheat germ, toasted, 1 oz.
|
90
|
22
|
Almonds, dry-roasted, 1 oz.
|
86
|
21
|
Cereal, shredded wheat, 2 rectangular biscuits
|
80
|
20
|
Cashews, dry-roasted, 1 oz.
|
73
|
18
|
Nuts, mixed, dry-roasted, 1 oz.
|
66
|
17
|
Spinach, cooked, 1/2 cup
|
65
|
16
|
Bran flakes, 1/2 cup
|
60
|
15
|
Cereal, oats, instant/fortified, 1 cup
|
56
|
14
|
Potato, baked with skin, 1 medium
|
55
|
14
|
Soybeans, cooked, 1/2 cup
|
54
|
14
|
Peanuts, dry-roasted, 1 oz.
|
50
|
13
|
Peanut butter, 2 tablespoons
|
50
|
13
|
Chocolate bar, 1.45 oz
|
45
|
11
|
100 percent bran, 2 tablespoons
|
44
|
11
|
Vegetarian baked beans, 1/2 cup
|
40
|
10
|
Potato, baked without skin, 1 medium
|
40
|
10
|
Avocado, California, 1/2 medium
|
35
|
9
|
Lentils, cooked, 1/2 cup
|
35
|
9
|
Banana, raw, 1 medium
|
34
|
9
|
Shrimp, mixed species, raw, 12 large, 3 oz.
|
29
|
7
|
Tahini, 2 tablespoons
|
28
|
7
|
Raisins, golden seedless, 1/2 cup
|
28
|
7
|
Cocoa powder, unsweetened, 1 tablespoon
|
27
|
7
|
Bread, whole-wheat, 1 slice
|
24
|
6
|
Spinach, raw, 1 cup
|
24
|
6
|
Kiwi fruit, raw, 1 medium
|
23
|
6
|
Hummus, 2 tablespoons
|
20
|
5
|
Broccoli, chopped, boiled, 1/2 cup
|
19
|
5
|
Source: Facts About Dietary Supplements. Office of Dietary Supplements, National Institutes of Health, 2001.
| ||
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