Micronutrients: Magnesium

Food containing magnesium and potassium.
Photo: Thinkstock/samael334

Magnesium is the fourth most abundant mineral in the body, with the majority found in the skeleton and the rest in muscle, soft tissue and blood. The 2015-2020 Dietary Guidelines for Americans list magnesium as an under-consumed nutrient.

Roles in Health

Magnesium is needed in biochemical reactions, including energy production, nutrient metabolism, fatty acid and protein synthesis, transmission of nerve and muscle impulses, glucose control, blood pressure regulation and transport of calcium and potassium ions. Higher levels of serum magnesium have been associated with reduced risk of cardiovascular disease. Evidence supports an inverse relationship between dietary intake of magnesium and risk of Type 2 diabetes. One large cohort study showed magnesium intake may aid in preventing pancreatic cancer.

Research continues for magnesium therapy in risk reduction and management of heart disease, hypertension, Type 2 diabetes, pregnancy complications, asthma and migraine headaches. However, the Academy of Nutrition and Dietetics and the American Diabetes Association do not recommend magnesium supplementation to manage diabetes.

Current Recommendations

Daily requirements begin at 80 milligrams for children age 1 to 3 and advance to 410 milligrams for adolescent males and 360 milligrams for adolescent females. Adult males require 400 to 420 milligrams, while the RDA for adult females is 310 to 320 milligrams. Pregnant and lactating women require up to 400 milligrams and 360 milligrams, respectively, depending on age. Without sufficient data to establish an RDA, infants younger than 1 have an Adequate Intake based on consumption from breast-feeding and solid foods, or about 30 milligrams per day for infants 0 to 6 months, and 75 milligrams per day for infants 7 to 12 months.

Tolerable Upper Intake Levels for supplements are 65 milligrams per day for children 1 to 3 years old, 110 milligrams per day for ages 4 to 8 and 350 milligrams per day for ages 9 and older.

Sources of Magnesium

Magnesium is widely available in plant and animal foods and often is included in fortified foods and enriched grains. Soil health can impact the amount of magnesium in foods. Tap and bottled waters are potential sources; levels range from 1 to more than 120 milligrams per liter.

Magnesium supplements come in a variety of forms with varying bioavailability. Research shows aspartate, citrate, lactate and chloride forms may be absorbed better than oxide and sulfates. If supplements are used, they should be taken with meals to avoid the risk of diarrhea.

Food Sources Rating
1 ounce dry roasted almonds 80mg Excellent
? cup boiled spinach 78mg Excellent
? cup oil roasted peanuts 63mg Good
1 cup soymilk 61mg Good
2 slices whole-wheat bread 46mg Good
1 cup cubed avocado 44mg Good
? cup cooked brown rice 42mg Good
1 cup low-fat plain yogurt 42mg Good
Fortified breakfast cereals 40mg Good

Signs of Deficiency

Chronic low levels of magnesium can negatively affect body functions that may be associated with chronic diseases, such as hypertension, cardiovascular disease, Type 2 diabetes, osteoporosis, Alzheimer’s disease and conditions including attention deficit disorder and migraines. Magnesium deficiency is rare, primarily because it is abundant in food and the kidneys limit urinary excretion when dietary intake is low. However, chronic low intakes of magnesium or conditions such as alcoholism can promote magnesium deficiency, which has been associated with an increased risk of cardiovascular disease, Type 2 diabetes and osteoporosis. Preliminary signs of deficiency include loss of appetite, nausea, vomiting and fatigue, which can progress to more serious symptoms such as abnormal heart rhythm, seizures and coronary spasms.

Populations at Risk

Older adults and individuals with gastrointestinal diseases, Type 2 diabetes, renal disorders or alcoholism are more susceptible to magnesium deficiency, since they are likely to underconsume or experience reduced absorption or increased losses of magnesium. Large doses of magnesium supplements, magnesium-based antacids or laxatives can interfere with magnesium absorption (especially for people who have impaired kidney function) and can cause diarrhea, nausea and cramping. Cases of fatal hypermagnesemia have occurred with medications exceeding 5,000 milligrams per day of magnesium.

Bottom Line

Studies continue to discover magnesium’s benefits in health promotion and disease prevention, but more research is needed. Well-balanced eating plans provide adequate amounts of magnesium. If deficiency is confirmed, dietary supplements may be required under the care of a physician.

Kathleen Zelman
Kathleen Zelman, MPH, RDN, is the nutrition director of WebMD.