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Magnesium
What is the health risk of too much magnesium?
Dietary magnesium does not pose a health risk, however very high doses of magnesium supplements, which may be added to laxatives, can promote adverse effects such as diarrhea. Magnesium toxicity is more often associated with kidney failure, when the kidney loses the ability to remove excess magnesium. Very large doses of laxatives also have been associated with magnesium toxicity, even with normal kidney function (38). 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.
Signs of excess magnesium can be similar to magnesium deficiency and include mental status changes, nausea, diarrhea, appetite loss, muscle weakness, difficulty breathing, extremely low blood pressure, and irregular heartbeat (4, 39-41).
The Institute of Medicine of the National Academy of Sciences has established a tolerable upper intake level (UL) for supplementary magnesium for adolescents and adults at 350 mg daily. As intake increases above the UL, the risk of adverse effects increases (4).
Table of Food Sources of Magnesium (3)
| Food | Milligrams |
%DV* |
| 100 percent Bran, 2 Tbs | 44 |
11 |
| Avocado, Florida, 1/2 med | 103 |
26 |
| Wheat germ, toasted, 1 oz | 90 |
22 |
| Almonds, dry roasted, 1 oz | 86 |
21 |
| Cereal, shredded wheat, 2 rectangular biscuits | 80 |
20 |
| Seeds, pumpkin, 1/2 oz | 75 |
19 |
| Cashews, dry roasted, 1 oz | 73 |
18 |
| Nuts, mixed, dry roasted, 1 oz | 66 |
17 |
| Spinach, cooked, 1/2 c | 65 |
16 |
| Bran flakes, 1/2 c | 60 |
15 |
| Cereal, oats, instant/fortified, cooked w/ water, 1 c | 56 |
14 |
| Potato, baked w/ skin, 1 med | 55 |
14 |
| Soybeans, cooked, 1/2 c | 54 |
14 |
| Peanuts, dry roasted, 1 oz | 50 |
13 |
| Peanut butter, 2 Tbs. | 50 |
13 |
| Chocolate bar, 1.45 oz | 45 |
11 |
| Vegetarian baked beans, 1/2 c | 40 |
10 |
| Potato, baked w/out skin, 1 med | 40 |
10 |
| Avocado, California, 1/2 med | 35 |
9 |
| Lentils, cooked, 1/2 c | 35 |
9 |
| Banana, raw, 1 medium | 34 |
9 |
| Shrimp, mixed species, raw, 3 oz (12 large) | 29 |
7 |
| Tahini, 2 Tbs | 28 |
7 |
| Raisins, golden seedless, 1/2 c packed | 28 |
7 |
| Cocoa powder, unsweetened, 1 Tbs | 27 |
7 |
| Bread, whole wheat, 1 slice | 24 |
6 |
| Spinach, raw, 1 c | 24 |
6 |
| Kiwi fruit, raw, 1 med | 23 |
6 |
| Hummus, 2 Tbs | 20 |
5 |
| Broccoli, chopped, boiled, 1/2 c | 19 |
5 |
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*DV = Daily Value. DVs are reference numbers based on the Recommended Dietary Allowance (RDA). They were developed to help consumers determine if a food contains very much of a specific nutrient. The DV for magnesium is 400 milligrams (mg). The percent DV (%DV) listed on the nutrition facts panel of food labels tells adults what percentage of the DV is provided by one serving. Even foods that provide lower percentages of the DV will contribute to a healthful diet. |
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What is the Recommended Dietary Allowance for magnesium for adults?
