Magnesium is a mineral that is essential for the human body to function properly. Magnesium’s primary role in the body is to act as a cofactor that enables the activation of important biological enzymes. More than 300 enzymes require magnesium to function, including the biological pathways responsible for energy production, synthesis of DNA and RNA, blood sugar control, nerve and muscle cell function, immunity, hormone production, and many other important processes.^{[3, 5, 6]}

Although severe magnesium deficiency is rare, most Americans are not getting their recommended daily dose of magnesium. Magnesium deficiency is particularly prevalent among those with diabetes, heart disease, kidney disease, hyperthyroidism, gastrointestinal illness, pancreatitis, osteoporosis, migraines, and hypertension. Conversely, magnesium deficiency can also be a risk factor contributing to those illnesses.^{[6, 7]}

Magnesium deficiency is a fairly modern phenomenon, largely caused by industrial farming and food processing techniques that have depleted both soil and crops of their former magnesium content. The typical American diet provides only half of the recommended daily allowance (RDA) of magnesium; consequently, the majority of Americans are, to some extent, deficient in magnesium.^[7] Older adults tend to be more deficient in magnesium because their intestines absorb less magnesium and their kidneys excrete more of it, compared to younger adults.^[3]

Magnesium deficiency often goes undetected because the vast majority of magnesium is stored within your bones and soft tissues, rather than in your blood. Doctor-administered blood serum magnesium tests actually only test 0.3% of the magnesium in your body, which means that only very severe magnesium deficiencies will be detected and diagnosed. This can have the dangerous consequence of leading people to believe that they are not deficient in magnesium due to their blood test results, when in fact they actually are deficient.^[7, 8]

The recommended daily allowance of magnesium is dependent on an individual’s weight, age, and gender, and thus can vary significantly from person to person. As a general guideline for adults, the RDA is 6 milligrams of magnesium/kg per day, as a total from all sources (ie. food and supplements). This means that a male who weighs 70 kg (174 lb) male should intake 420 mg of magnesium per day, while a 90 kg (198 lb) male should intake 540 mg of magnesium per day. A 55 kg (121 lb) female should intake 330 mg of magnesium per day.^{[6, 9]}

When supplementing, research shows that that body absorbs magnesium best when taken in doses of 100 to 125 mg at a time. If more is taken, the body is much less efficient at absorbing it due to intestinal permeability limits and it just passes through the body. Avoid taking a magnesium supplement at the same time as a zinc supplement as the zinc will extensively limit the body’s absorption of magnesium. Also, the body needs an adequate level of vitamin B6 to process magnesium correctly.^[8]

Supplements are not effectively regulated^[10] and it can be hard to tease out quality brands of supplements from those that use the wrong form or cut corners. We took a scientific approach to evaluating supplement options and here present our top choices after rigorous analysis and application of our methodology.

When buying a magnesium supplement, it is very important to get a highly-absorbable form from a good manufacturer. Magnesium glycinate is the current best form to take due to high absorption and no digestive side effects. Magnesium citrate is also very well absorbed by the body but some people experience diarrhea when taking it. Others, welcome it as a relief for constipation. Avoid taking magnesium oxide as it is not well absorbed by the body; research shows it is no different than taking a placebo.^[11, 12]

Over 300 biological pathways require magnesium, which acts a cofactor in the activation of many important enzymes. Here are some of the key biological pathways that need magnesium:

● Adenosine triphosphate (ATP) is the primary energy molecule in the human body; it is a coenzyme that transports chemical energy within cells and is responsible for proper metabolism. Magnesium is required to bond with the phosphates in order to protect ATP molecules from degrading in high pH levels. Thus, a magnesium deficiency can lead to muscle weakness, poor athletic performance, and fatigue.^[5]

● Magnesium is crucial for protein synthesis, as it serves as a marker for ribozymes to cleave mRNA. Without it, ribozymes are unable to locate the proper location and cannot synthesize new proteins. The proteins created by this process control the activities and growth of cells. Magnesium is also needed for the production of DNA and RNA molecules.^[7]

● As a positively charged ion, magnesium plays a major role in maintaining homeostasis in the body and helps to balance electrolyte levels in cells.

● Magnesium helps to regulate other nutrient levels in the body. It is especially crucial for regulating the movement of calcium into skeletal and smooth muscle cells, nerve cells, heart pacemaker cells, and other tissues. Although calcium is vital to the human body, too much of it can lead to ailments as diverse as anxiety, depression, insomnia, heart palpitations, asthma, cramps, muscle spasms, and chronic headaches. Thus, a magnesium deficiency means that cells throughout the human body will be detrimentally affected by excess calcium.

● Besides regulating calcium movement, magnesium is necessary for ensuring that vitamin D, copper, zinc, sodium and potassium are used properly in various biological processes.

● Magnesium is necessary for the healthy functioning of many other parts of the body and has a role in preventing kidney stones, fibromyalgia, depression, deafness, diabetes, insulin resistance, osteoporosis, migraines, preeclampsia and eclampsia, premenstrual syndrome, restless leg syndrome, colorectal cancer, and blood clots.^[5] It also helps to regulate cholesterol levels and has laxative properties.^[4]

Magnesium is a positively charged ion, otherwise known as a “cation.” Therefore, it has to be bonded with another compound before it can be consumed in either supplement or dietary form. When taken as a supplement, magnesium is typically bonded with compounds such as oxide, citrate, or chloride to help deliver it to the intestines. Once processed in the intestines, magnesium and the compound to which it is bonded will dissociate, leaving the magnesium free to perform its many roles in the body. The kidneys play a crucial role in conserving and excreting magnesium, depending on the level in the body.^[5]

About 50% to 60% of all magnesium in the human body is stored in bone. The rest is found in the soft tissues of the body, while less than 1% of magnesium is found in blood and blood serum.^[4]

Magnesium deficiency can be difficult to detect because it does not present as one single symptom, but rather as a wide variety of vague symptoms such as fatigue, irritability, and muscle weakness that are likely to be ascribed to other causes and thus misdiagnosed.^[7] Loss of appetite, nausea, vomiting, irregular heartbeat, insomnia, muscle spasms, seizures, confusion, and even restless leg syndrome can also be symptoms of magnesium deficiency.^[5] Magnesium deficiency is particularly common in people suffering from osteoporosis, heart disease, kidney disease, hypertension, and diabetes mellitus. Emerging research is tying severe depression to magnesium deficiency as well.^[13]

There are many risk factors to having low levels of magnesium in the body. Heavy menstrual periods can contribute to magnesium deficiency. Individuals taking diuretics are at higher risk for magnesium deficiency, as they can cause magnesium to be excreted in urine rather than absorbed. Certain antibiotics, steroids, and chemotherapy drugs can also lower magnesium levels.^[5] People who are active and sweat a lot, those who are stressed, and those who don’t get enough sleep tend to need more magnesium. Drinking alcohol, coffee or tea, and consuming high amounts of sugar or salt can exacerbate magnesium deficiency.^[6]

25% – 39% of diabetics, type I and type II, develop a magnesium deficiency.^[1] Obesity is also a risk factor as 35% of pre-bariatric surgery patients were found to be deficient.^[14]

Magnesium deficiency is notoriously hard to test for, however. The body maintains a constant blood concentration, at the expense of other body needs of magnesium so blood serum magnesium tests will not reveal a deficiency until it is very dire. Urine excretion tests after giving a large magnesium dose are much more accurate at diagnosing a magnesium deficiency but are invasive and often require a hospital stay.

It is estimated that women need about 320 mg of magnesium per day and men need about 420 mg, although depending on an individual’s weight and other factors, this may vary.^[6]

The latest large-sample studies show that nearly 50% of individuals in the United States have inadequate intake levels of magnesium. Moreover, over two-thirds of teens and adults over 71 consume insufficient amounts of magnesium.^[15] On average, Americans consume about 212 mg of magnesium from food each day, which is only about 50% of the level required for optimal health.

Dark, leafy vegetables such as spinach, Swiss chard, and kale are the best dietary sources of magnesium, followed by nuts and seeds. Certain fruits, peas, beans, soy products, and whole grains contain magnesium, as do wheat bran, oatmeal, chocolate, meat, seafood, and milk.^[7, 8]

Sources ^[17]

However, only about 30% to 40% of the dietary magnesium consumed is actually absorbed by the body.^[5] Certain foods that contain magnesium actually bind with the mineral, preventing it from being absorbed by the body, and nearly all processed foods (especially white flour and white sugar) have been depleted of magnesium during the manufacturing process. Likewise, cooking, especially boiling, depletes food of most of its magnesium content.^[6]

Sources ^[17]

In the process of treating tap water to make it “soft,” most tap water has been de-mineralized and has had its magnesium content removed, while the fluoride in tap water binds to the magnesium ions and prevents their absorption by the body.^[5] Drinking mineral water is a good way to increase your magnesium intake, although different brands vary significantly in magnesium content. Some contain as little as 1 mg/liter while others contain up to 120 mg/liter.^[7]

Taking a daily magnesium supplement (usually between 100 and 300 mg) is a safe way to increase your intake of magnesium, along with eating magnesium-rich foods and drinking mineral water.

Because magnesium is an ion, it is commercially available as an oral supplement only when combined with a carrier, to which it binds and which carries it to the intestines, where it is broken down into elemental magnesium and used throughout the body. Different carriers break apart at different rates, which affects the bioavailability of elemental magnesium and how much can be absorbed by the body.

There are different recommendations for how much magnesium people should ingest each day, depending on age, gender, and other factors. The Food and Nutrition Board at the Institute of Medicine of the National Academies has set the Recommended Dietary of Allowance (RDA) of magnesium for adult men at 400-420 mg daily, while it is 310-320 mg daily for adult women.^[7]

The Mayo Clinic has similar, yet slightly lower, recommended guidelines — teenaged and adult men should ingest 270 to 400 milligrams (mg) of magnesium each day, while teenaged and adult women should ingest 280 to 300 mg each day. Pregnant women are advised to take 320 mg per day and breastfeeding women are advised to take 340 to 355 mg each day. The daily recommended amount of magnesium for children is significant less — 40 to 80 mg for children up to age 3, 120 mg for children aged 4- 6, and 170 mg for children aged 7 -12.^[16] You should not administer magnesium supplements to a child without a doctor’s express permission.^[8]

However, other healthcare professionals recommend a higher amount of magnesium for adults. Some nutritionists recommend ingesting as much as 600 to 800 mg of magnesium each day, as a combination of all sources — food, mineral water, and supplementation. In most cases, taking a daily 300 mg magnesium supplement and maintaining a nutritious diet will ensure that you are receiving a consistently healthy amount of magnesium. It is generally not recommended to take more than 350 mg of magnesium as a supplement each day, except under the advice of a doctor in order to correct a severe deficiency.^[7]

Magnesium supplements are most frequently sold in tablet, capsule, liquid, and powder form, containing between 100 mg and 250 mg of magnesium for daily intake (although some contain as much as 400 mg). In tablet and capsule form, they are frequently combined with zinc, vitamin D, or calcium. Magnesium supplements should always be taken with meals; taking some magnesium supplements on an empty stomach could cause diarrhea.^[16]

Although it is always a good idea to have a discussion with your doctor before beginning any kind of supplementation, it is especially important for people with certain health issues. For example, people with severe kidney disease and those on dialysis should not take magnesium without the express permission of a doctor. Diabetics, individuals with hypertension (high blood pressure), and those with heart disease should not take magnesium supplements without consulting a doctor. Because magnesium competes with calcium for absorption in the bone, those with a calcium deficiency should consult with a doctor before taking a magnesium supplement.^[16] As with all supplements, you should consult with your doctor if you are pregnant, breastfeeding, or have allergies.

Magnesium has been cited to interfere with more than 30 prescribed drugs.^[5] For optimal effectiveness, avoid combining a magnesium supplement with the following medications: aminoglycosides, antibiotics (ciprofloxacin, moxifloxacin, tetracycline, doxycycline, minocycline), blood pressure medications, calcium channel blockers (aamlodipine, diltiazem, felodipine, verapamil), diabetes medications, digoxin, diuretics, fluoroqinones, hormone replacement therapy, labetol, levomethadyl, levothyroxine, penicillamine, tiludronate and alendronate, amphotericin B, corticosteriods, antacids, and insulin. Seek advice from a healthcare professional before considering taking magnesium at the same time as any of these medications.^{[7, 16]}

It is difficult and very uncommon to overdose on magnesium because the kidneys excrete excess amounts of magnesium into the urine. However, there is a limit to how much the kidneys can do and once that limit is reached, there can be negative consequences. Diarrhea is the most common side effect of excessive magnesium intake and it can be accompanied by nausea and abdominal cramping as the body excretes excessive magnesium.^[7]

Severe magnesium overdose can result in additional problems such as kidney failure, severely lowered blood pressure, and heart problems. But in order to overdose, one must consume an exorbitantly large amount of magnesium.

Because magnesium is an ion, it must be taken as part of a compound. There are a wide variety of magnesium compounds on the market, all of which contain very different ingredients. The most common form, which is sold over-the-counter in all drugstores, is magnesium oxide. Although this product is widespread and cheap, it is also largely ineffective — magnesium oxide is absorbed very poorly by the human body. And while many multivitamins do contain magnesium, it is most often in the form of the poorly-absorbed magnesium oxide. Better-quality multivitamins sometimes contain magnesium citrate, which is preferable, but often not in a high enough dosage, as magnesium is often too physically bulky to fit into a pill with a host of other vitamins and minerals. Taking zinc at the same time, or in the same pill, will limit magnesium absorption in the intestine. Some healthcare professionals recommend a B-vitamin complex or a multivitamin containing vitamin B6 to help with magnesium absorption.^[8]

Although magnesium oxide has a poor absorption rate, it is essentially harmless. Magnesium sulfate, more commonly known as Epsom salt, is generally considered to be a poor dietary supplement but can be used in a bath to absorb magnesium through the skin.^[11]

There are various other compounds that are more effective than magnesium oxide yet are still reasonably priced, such as magnesium citrate, which is absorbed well by the body and is also useful in avoiding kidney stones and constipation.^[5] Other studies have shown that magnesium supplements that dissolve well in water are better able to be absorbed by the intestines and thus provide more bioavailable elemental magnesium. In these studies, magnesium citrate, magnesium lactate and magnesium chloride appeared to release more bioavailable elemental magnesium than the magnesium oxide form.^[9]

Some people prefer magnesium glycinate or magnesium gluconate because those forms are less likely to cause diarrhea than other magnesium compounds. Magnesium glycinate is a chelated form of magnesium that has been shown to be well absorbed. Certain magnesium compounds are recommended to combat specific symptoms of magnesium deficiency. In cases where magnesium deficiency is linked with heart arrhythmia or preeclampsia / eclampsia, doctors may recommend a magnesium injection. Always consult with your physician if you are trying to use supplements to fix a specific health symptom or concern.

While some magnesium supplement products are sold as liquid-filled capsules and tablets (and sometimes liquids, powders, and syrups), magnesium chloride is another option for those who prefer a topical preparation, which is applied to the skin in the form of magnesium “oil.” Most oral magnesium preparations, including the ones recommended here, can be purchased online, as well as being stocked at pharmacies, health food stores, and grocery stores. Avoid magnesium oxide and look out for combined forms which typically have a very high percentage of the first ingredient listed, and products that just list “magnesium” without stating its formulation – it’s likely to be magnesium oxide.

The recommended products below made our cut for high quality effective magnesium supplementation. All of these products are manufactured by companies that follow strict manufacturing guidelines, are certified by independent consumer protection agencies, and have bioavailable formulations. Read more about our methodology for selecting recommended products.

References:

¹ de Valk VH. Magnesium in diabetes mellitus. Neth J Med. 1999;54:139–146.

² Jacobs, R. A. et al. Improvements in exercise performance with high-intensity interval training coincide with an increase in skeletal muscle mitochondrial content and function. Journal of Applied Physiology, doi:10.1152/japplphysiol.00445.2013 (2013).

³ Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride.” Washington, DC: The National Academies Press, 1997, 190-240. Available at: http://www.nap.edu/read/5776/chapter/8.

⁴ “Magnesium.” Micronutrient Information Center. Linus Pauling Institute. Oregon State University. Accessed: http://lpi.oregonstate.edu/mic/minerals/magnesium

⁵ Jahnen-Dechent, W., Ketteler, M. “Magnesium Basics.” Clinical Kidney Journal 5, 3-14 (2012).

⁶ Riley, P. Thomas. “Magnesium.” University of Mary Washington Student Health Center. July 2011. http://students.umw.edu/healthcenter/files/2011/08/Magnesium2.pdf.

⁷ “Magnesium: Fact Sheet for Health Professionals.” National Institutes of Health, Office of Dietary Supplements. February 2016.

⁸ “Magnesium.” University of Maryland Medical Center. August 2015. https://umm.edu/health/medical/altmed/supplement/magnesium.

⁹ Seelig, Mildred S. “The Requirement of Magnesium by the Normal Adult.” The American Journal of Clinical Medicine. Vol. 14. 6 (June 1964). http://ajcn.nutrition.org/content/14/6/342.abstract.

¹⁰ “Information for Consumers on Using Dietary Supplements.” U.S. Food and Drug Administration. September 2015.

¹¹ Lindberg JS, Zobitz MM, Poindexter JR, Pak CY. “Magnesium bioavailability from magnesium citrate and magnesium oxide.” J Am Coll Nutr. 1990 Feb;9(1):48-55.

¹² Walker, Ann F.; Georgios Marakis; Samantha Christie; and Martyn Byng. “Mg citrate found more bioavailable than other Mg preparations in a randomized, double-blind study.” Magnesium Research. Vol. 16.3 (Sept. 2003):183-91. http://www.ncbi.nlm.nih.gov/pubmed/?term=14596323.

¹³ Eby GA 3rd, Eby KL. “Magnesium for treatment-resistant depression: a review and hypothesis.” Med Hypotheses. 2010 Apr;74(4):649-60. doi: 10.1016/j.mehy.2009.10.051.

¹⁴ Lefebvre P, Letois F, Sultan A, Nocca D, Mura T, Galtier F. “Nutrient deficiencies in patients with obesity considering bariatric surgery: a cross-sectional study.” Surg Obes Relat Dis. 2014 May-Jun;10(3):540-6. doi: 10.1016/j.soard.2013.10.003.

¹⁵ Moshfegh, Alanna; Joseph Goldman; Jaspreet Ahuja; Donna Rhodes; and Randy LaComb. “What We Eat in America, NHANES 2005-2006: Usual Nutrient Intakes from Food and Water Compared to 1997 Dietary Reference Intakes for Vitamin D, Calcium, Phosphorus, and Magnesium.” U.S. Department of Agriculture, Agricultural Research Service. July 2009. Available at: http://www.ars.usda.gov/SP2UserFiles/Place/80400530/pdf/0506/usual_nutrient_intake_vitD_ca_phos_mg_2005-06.pdf.

¹⁶ “Magnesium Supplement (Oral Route, Parenteral Route).” Mayo Clinic. January 2016.

¹⁷ U.S. Department of Agriculture, Agricultural Research Service. USDA National Nutrient Database for Standard Reference, Release 28. “Nutrients: Magnesium, Mg (mg)” 2015.