Recommendations for magnesium are provided in the Dietary Reference Intakes (DRIs) developed by the Institute of Medicine of the National Academy of Sciences.1 Dietary Reference Intakes is the general term for a set of reference values used for planning and assessing nutrient intake for healthy people. Three important types of reference values included in the DRIs are Recommended Dietary Allowances (RDA), Adequate Intakes (AI), and Tolerable Upper Intake Levels (UL). The RDA recommends the average daily intake that is sufficient to meet the nutrient requirements of nearly all (97%-98%) healthy people. An AI is set when there is insufficient scientific data available to establish a RDA for specific age/gender groups. AIs meet or exceed the amount needed to maintain a nutritional state of adequacy in nearly all members of a specific age and gender group. The UL, on the other hand, is the maximum daily intake unlikely to result in adverse health effects. Table 2 lists the RDAs for magnesium, in milligrams, for children and adults.2
Table 2: Recommended Dietary Allowances for magnesium for children and adults3
| Age (years) |
Male (mg/day) |
Female (mg/day) |
Pregnancy (mg/day) |
Lactation (mg/day) |
|---|---|---|---|---|
| 1-3 | 80 | 80 | N/A | N/A |
| 4-8 | 130 | 130 | N/A | N/A |
| 9-13 | 240 | 240 | N/A | N/A |
| 14-18 | 410 | 360 | 400 | 360 |
| 19-30 | 400 | 310 | 350 | 310 |
| 31+ | 420 | 320 | 360 | 320 |
There is insufficient information on magnesium to establish a RDA for infants. For infants 0 to 12 months, the DRI is in the form of an Adequate Intake (AI), which is the mean intake of magnesium in healthy, breastfed infants. Table 3 lists the AIs for infants in milligrams (mg).4
Table 3: Recommended Adequate Intake for magnesium for infants5
| Age (months) |
Males and Females (mg/day) |
|---|---|
| 0 to 6 | 30 |
| 7 to 12 | 75 |
Data from the 1999-2000 National Health and Nutrition Examination Survey suggest that substantial numbers of adults in the United States (US) fail to get recommended amounts of magnesium in their diets. Among adult men and women, the diets of Caucasians have significantly more magnesium than do those of African-Americans. Magnesium intake is lower among older adults in every racial and ethnic group. Among African-American men and Caucasian men and women who take dietary supplements, the intake of magnesium is significantly higher than in those who do not.6
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.7 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.8 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.9 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.10 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.
The information in Figure 1 is provided to demonstrate the variable amount of magnesium in magnesium supplements.
Related Links: What is magnesium? | What foods provide magnesium? | How much magnesium do I need? | What happens if I do not get enough magnesium? | Do I need extra magnesium? | Can magnesium be harmful? | What are some of the current issues and controversies about magnesium?
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.
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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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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
- Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride. National Academy Press. Washington, DC, 1999. [↩]
- Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride. National Academy Press. Washington, DC, 1999. [↩]
- Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride. National Academy Press. Washington, DC, 1999. [↩]
- Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride. National Academy Press. Washington, DC, 1999. [↩]
- Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride. National Academy Press. Washington, DC, 1999. [↩]
- Ford ES and Mokdad AH. Dietary magnesium intake in a national sample of U.S. adults. J Nutr. 2003;133:2879-82. [↩]
- 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. [↩]