Magnesium Is Best Obtained From Dietary Sources, Not Supplements

Magnesium is critical for human health. The current Western diet — in which approximately 70% of energy comes from dairy products, refined cereals and vegetable oils — is a poor source of magnesium.[1] Therefore, it comes as no surprise that about half of Americans of all ages do not consume enough magnesium from their diets.[2] Older adults and adolescents are most likely to have inadequate magnesium intake from their diets.

It is estimated that more than a quarter of adult Americans take a magnesium supplement.[3] However, preference should be given to relying on dietary sources of magnesium whenever possible to avoid adverse effects.

Basic facts about magnesium

Magnesium is the fourth most abundant mineral in the human body.[4] The average healthy adult body contains about 25 grams of magnesium, up to 60% of which is found in the bones and the remainder in soft tissues and body fluids.[5]

Magnesium is involved in the function of more than 300 enzymes that regulate several body functions, including blood-pressure and blood-sugar control, muscle contraction and conduction of electrical impulses between nerve and muscle cells.[6] Moreover, magnesium plays a vital role in bone development and energy production as well as active transport of calcium and potassium across cell membranes.

The kidneys play a key role in controlling the body’s magnesium balance by controlling the amount of the magnesium excreted in the urine. In healthy individuals, the kidneys reduce the amount of magnesium lost in the urine when its levels in the body are low. Therefore, temporary deficiency of magnesium is usually not troublesome. However, prolonged magnesium deficiency has been linked to increased risk of hypertension and other cardiovascular diseases, osteoporosis and type 2 diabetes mellitus.

Conditions that can increase the risk of magnesium deficiency, leading to lower magnesium levels in the blood (hypomagnesemia), include alcoholism, diseases that cause intestinal malabsorption (including Crohn’s disease and celiac disease) and uncontrolled diabetes.

Moreover, certain drugs can cause hypomagnesemia.[7] These drugs include certain immunosuppressant and organ-transplant drugs (such as cyclosporine [GENGRAF, NEORAL, SANDIMMUNE]) and stomach-acid–blocking proton pump inhibitors (such as omeprazole [PRILOSEC]) as well as loop diuretics (such as furosemide [LASIX]) and thiazide diuretics (such as hydrochlorothiazide [MICROZIDE]).

Adequate magnesium intake and dietary sources

The recommended daily intake of magnesium varies by age and certain conditions. For adult men, the recommended daily intake is 400 milligrams (mg) per day until age 30 and 420 mg per day for age 31 and older.[8] For nonpregnant women, including those who are breastfeeding, the recommended daily intake of magnesium is 310 mg per day until age 30 and 320 mg per day for age 31 and older. Pregnant women should consume an additional 40 mg daily.

The recommended daily intakes of magnesium can be met by consuming a varied diet, including multiple servings each day from foods such as dark leafy vegetables, legumes, nuts and whole grains (see Table below for examples of these foods along with their magnesium content). Foods that provide 20% or more of the recommended daily intake of magnesium are considered high sources of this nutrient, but other foods with lower amounts contribute to a healthful diet. Generally, foods that are high in dietary fiber are good sources of magnesium.

Examples of Healthful Food Sources of Magnesium and Their Magnesium Content[9],[10]

Magnesium also is sometimes added to breakfast cereals and other fortified foods. However, some types of food processing (including refining grains by removing their nutrient-rich germ and bran) reduce their magnesium content. Notably, the Food and Drug Administration does not require food labels to indicate magnesium content, unless magnesium has been added to the food.

In addition, water can be a source of magnesium.[11] Whereas filtered bottled water contains less magnesium than tap water, mineral and spring waters are often good sources of magnesium depending on their brands.

Importantly, no adverse effects have been associated with magnesium that is naturally present in foods and beverages in healthy individuals.[12] Therefore, people should prioritize getting their magnesium intake from these sources.

Magnesium-containing medicines and supplements

Magnesium is a main ingredient in some laxatives for relieving constipation as well as certain antacids for heartburn and indigestion. It also is often included in multivitamin–mineral supplements.

Magnesium supplements often are used in adults whose diets or medical histories put them at risk of magnesium deficiency. These products are sometimes marketed as “super products” that can alleviate certain conditions, such as depression, hypertension, cancer and Alzheimer’s disease.[13] However, there is no evidence to support these claims.

Magnesium salts are available in several forms (including magnesium aspartate, chloride, citrate, gluconate, lactate, oxide and sulfate) and are sold in various formulations (including capsules, powders and tablets).[14] The amount of magnesium in these products usually is declared on the product label.

The absorption of magnesium from supplements varies. Forms that dissolve well in liquid are more completely absorbed in the intestines than less soluble forms. A few small studies show that magnesium in the magnesium oxide and sulfate salts is less completely absorbed than other types of magnesium salts.

Adverse effects occur with excessive use of high doses of various types of magnesium-containing drugs and supplements.[15] Of note, impaired kidney function increases the risk of adverse effects with use of these products. In fact, even moderate doses of magnesium-containing laxatives or antacids can lead to magnesium toxicity in individuals with impaired kidney function.

The initial symptom of excess magnesium supplementation is diarrhea. Moreover, elevated serum concentrations of magnesium (hypermagnesemia) can cause nausea, vomiting, abdominal cramping, facial flushing and retention of urine as well as low blood pressure (which can result in confusion, lethargy and heart-rhythm disturbances). Severe hypermagnesemia can cause muscle weakness, difficulty breathing and cardiac arrest.

What You Can Do

Unless you have kidney disease, try to consume adequate amounts of dietary magnesium from unprocessed, nutrient-dense and high-fiber dietary sources such as those mentioned in this article. This should be done in conjunction with other healthy eating and lifestyle habits.

If you are concerned about magnesium deficiency, ask your doctor about whether you should have a blood test to check your magnesium level. Do not take magnesium supplements without consulting your doctor, especially if you routinely use magnesium-containing antacids or laxatives. If you need a magnesium supplement, you should use an oral product. Do not use magnesium products applied to the skin to treat magnesium deficiency because magnesium is not efficiently absorbed into the body through the skin.[16]
 

References

[1] Tarleton EK. Factors influencing magnesium consumption among adults in the United States. Nutr Rev. 2018;76(7):526-538.

[2] National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact sheet for health professionals. August 11, 2021. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/. Accessed December 6, 2021.

[3] Kantor ED, Rehm CD, Du M, et al. Trends in dietary supplement use among US adults from 1999-2012. JAMA. 2016;316(14):1464-1474.

[4] Gröber U, Schmidt J, Kisters K. Magnesium in prevention and therapy. Nutrients. 2015;7(9):8199-8226.

[5] Tarleton EK. Factors influencing magnesium consumption among adults in the United States. Nutr Rev. 2018;76(7):526-538.

[6] National Institutes of Health, Office of Dietary Supplements. Magnesium; Fact sheet for health professionals. August 11, 2021. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/. Accessed December 6, 2021.

[7] Gröber U. Magnesium and drugs. Int J Mol Sci. 2019;20(9):2094.

[8] National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact sheet for health professionals. August 11, 2021. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/. Accessed December 6, 2021.

[9] National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact sheet for health professionals. August 11, 2021. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/. Accessed December 6, 2021.

[10] Oregon State University, Linus Pauling Institute. Magnesium. Updated November 2018. https://lpi.oregonstate.edu/mic/minerals/magnesium. Accessed December 6, 2021.

[11] Tarleton EK. Factors influencing magnesium consumption among adults in the United States. Nutr Rev. 2018;76(7):526-538.

[12] National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact sheet for health professionals. August 11, 2021. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/. Accessed December 6, 2021.

[13] Food and Drug Administration. Letter to Better Supplement Solutions Inc. dba XanFree. March 29, 2021. https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/better-supplement-solutions-inc-dba-xanfree. Accessed December 6, 2021.

[14] National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact sheet for health professionals. August 11, 2021. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/. Accessed December 6, 2021.

[15] Oregon State University, Linus Pauling Institute. Magnesium. Updated November 2018. https://lpi.oregonstate.edu/mic/minerals/magnesium. Accessed December 6, 2021.

[16] Gröber U, Werner T, Vormann J, Kisters K. Myth or reality—transdermal magnesium? Nutrients. 2017;9(8):813.