The Beginners Guide to Magnesium


What is Magnesium?

In human health, magnesium is a trace mineral required for hundreds of different biochemical processes that ultimately allow us to function properly. Inside our cells, magnesium is required for the synthesis of DNA, RNA, protein, and an antioxidant called glutathione. It also plays a role in the cellular pathway that makes energy in the form of ATP (adenosine triphosphate).

While magnesium is fairly ubiquitous in our bodies, it’s typically associated with our nervous system, muscles, and metabolic pathways. Magnesium actively moves calcium and potassium ions across cell membranes, creating electrochemical gradients for nerve impulse conduction, muscle contraction, and normal heart rhythms. Magnesium has some effects on calcium storage in our bones as well. In people with magnesium deficiency, a cell that breaks down bone becomes more active. Insulin regulation and blood glucose control also depend on adequate levels of circulating magnesium.

In newer areas of research, magnesium has been found to affect neurotransmitters and brain pathways that regulate mood and pain signaling. Magnesium levels may also have some effect on acid levels in our stomachs, which can subsequently affect gut motility. In research on magnesium and cardiovascular disease, studies have shown that magnesium can also affect how blood vessels in our brains and bodies constrict or dilate, a possible reason that abnormal magnesium levels can cause headaches and flushed skin.

How Much Do We Need?

An adult body contains about 25 grams of magnesium. About half is stored in bones, while the other half is dispersed in soft tissues. The National Academy of Sciences cites the following Recommended Dietary Allowances (RDA) for specific age ranges to prevent overt magnesium deficiency:

  • 1-3 years: 80 mg
  • 4-8 years: 130 mg
  • 9-13 years: 240 mg
  • 14-18 years: 410 mg (male), 360 mg (female), 400 mg (pregnant), 360 mg (lactating)
  • 19-30 years: 400 mg (male), 310 mg (female), 350 mg (pregnant), 310 mg (lactating)
  • 31 years and older: 420 mg (male), 320 mg (female), 360 mg (pregnant), 320 mg (lactating)

Signs of Magnesium Deficiency

Early signs of magnesium deficiency include a loss of appetite, nausea, vomiting, fatigue, and weakness. Inside our bodies, as magnesium levels decrease, so do calcium and potassium levels. Each of these ions is heavily involved in nerve, muscle, and heart functioning, so when their levels drop, these organs also stop working correctly. With abnormal nerve signal conduction comes numbness, tingling, and possible seizures. You may even pick up changes to your personality or mental functioning. ADHD (attention deficit-hyperactivity disorder), for example, is associated with low magnesium levels. Your muscles begin to oddly contract and cramp. And your heart can start to beat in abnormal rhythms while blood vessels feeding oxygen to your heart may spasm, which can lead to heart tissue damage. As calcium levels drop, the risk for osteoporosis can also increase. Researchers are also looking into whether magnesium deficiency can lead to diabetes.

Signs of Magnesium Toxicity

In moderate excess, supplement-source magnesium can cause gastrointestinal symptoms like diarrhea, nausea, and abdominal cramping. Magnesium supplements, especially magnesium carbonate, chloride, gluconate, and oxide, draw water out from our intestines into our stool. Magnesium-based laxatives work based on this mechanism. Tolerable Upper Intake Levels (ULs) have been established to show when the risk for these adverse effects begins to appear for most people in these age ranges:

  • 1-3 years: 65 mg
  • 4-8 years: 110 mg
  • 9 years and older: 350 mg

Effects of extreme toxicity include tiredness, nausea and vomiting, urine retention, and depression. They can become so severe as to include difficulty breathing, a severe drop in blood pressure, heart rhythm irregularity, and cardiac arrest. Very large doses (more than 5000 mg/day) of magnesium supplements have, in fact, caused documented deaths in children and adults.

Note: According to the NIH, our kidneys eliminate food-source magnesium more readily than supplement-source magnesium, so unless kidney disease is present, excessive food-source magnesium does not pose a health risk.

Groups at High Risk for Deficiency

The National Institutes of Health (NIH) notes that US dietary surveys consistently show that most of us are not getting enough magnesium. In 2010, the US Food and Drug Administration (USDA) estimated that 57% of the US population 2 years old and older was falling short of daily magnesium requirements. Surveys show that adult men 71 years of age and older and adolescent females tend to fair the worst in magnesium status.

People with impaired nutrient absorption or increased nutrient excretion are often low in magnesium. Impaired nutrient absorption occurs in people with gastrointestinal diseases like Crohn’s or celiac disease and those who have undergone bypasses. People who take diuretics or people with Type 2 diabetes have increased rates of urine output, which tend to drain the body of nutrients like magnesium too.

Older adults often have lower magnesium levels because they have lower intakes of dietary magnesium. On top of that, intestinal magnesium absorption decreases and urinary excretion of magnesium increases with age. Certain chronic medications like diuretics and proton-pump inhibitors for GERD commonly used by older adults can also interfere with magnesium levels and lead to greater risks for deficiency.

Like older adults, people with chronic alcoholism are at higher risk for magnesium deficiency due to poor overall nutrition and higher rates of gastrointestinal and renal problems. Alcohol-related liver and pancreatic diseases also contribute to decreased magnesium status.

Uses for Magnesium

Outside of preventing deficiencies, people take magnesium supplements for many reasons even though research shows that it may only be helpful in a select number of cases. The greatest evidence for magnesium efficacy is in treating constipation and acid reflux. Some research points to these other possible uses:

Metabolic Syndrome

Research shows that magnesium supplements may benefit metabolic syndrome and its related conditions of hypertension, high cholesterol, diabetes, and stroke. In one study, people with metabolic syndrome were about 7 times more likely to have low magnesium levels. In studies featuring healthy young adults, higher magnesium intake from diet and supplements lowered the risk for metabolic syndrome by 31%.

In studies on Type 2 diabetes, the research is conflicting, but some studies show that magnesium supplements given to people who were magnesium-deficient reduced the risk for diabetes and even slowed the progression of disease, especially in the kidneys. Similarly, although findings have been conflicting, some studies show that magnesium supplements have helped to decrease mortality up to 34% in adult populations at high risk for cardiovascular disease.


At least two studies on magnesium supplementation in fibromyalgia patients have shown promise in magnesium’s ability to decrease fibromyalgia-related pain, tenderness, and depression.


Initial research seems to show that magnesium supplements, especially in combination with calcium and estrogen, can reduce bone loss and bone turnover in postmenopausal osteoporosis.

Premenstrual Syndrome (PMS)

In women who are magnesium-deficient, taking magnesium supplements has been shown in research to mitigate premenstrual symptoms like nervous tension, mood swings, irritability, anxiety, migraines, and fluid retention. Combining 200 mg of magnesium with 50 mg of vitamin B6 daily was found in one study to be helpful for anxiety-related symptoms.

Migraine Headaches

The American Academy of Neurology has stated that magnesium supplements are probably effective for stand-alone migraines, particularly for people who have low magnesium levels. However, magnesium doses for migraine treatment are high enough that a licensed healthcare provider should supervise treatments.

Mental Disorders – Anxiety, Bipolar, Mania

Very early research is starting to show that oral magnesium may be useful as supplements to conventional treatments for anxiety, bipolar disorder, and mania. Daily magnesium doses of 300 mg have been used to treat mild to moderate anxiety disorders. In a study on rapid cycling bipolar affective disorder, magnesium-based treatments were as effective as lithium in 50% of patients. In treatments for mania, supplementing prescription medications with 375 mg of magnesium oxide has been shown to be more effect than taking medications alone.

Sources of Magnesium

The NIH states that green leafy vegetables, legumes, nuts, seeds, and whole grains (generally, foods with dietary fiber) are good magnesium sources. Sometimes, even tap, mineral, or bottled waters can provide magnesium, ranging from 1 mg/L to more than 120 mg/L. These are 5 of the NIH’s top-ranked sources:

  • Almonds, dry roasted (1 oz.): 80 mg
  • Spinach, boiled (0.5 cup): 78 mg
  • Cashews, dry roasted (1 oz.): 74 mg
  • Soymilk, plain or vanilla (1 cup): 61 mg
  • Black beans, cooked (0.5 cup): 60 mg

Some medications can also be significant sources of magnesium and should be counted towards daily intake quantities. Rolaids ® for heartburn and upset stomach, for example, contains 55 mg of magnesium, while Tums ® is magnesium-free.

Magnesium supplements are helpful if you’re not getting enough magnesium from foods, but supplement formulations greatly affect how much you absorb. Magnesium amino acid chelates like magnesium glycinate and organic salts like magnesium aspartate and citrate are better absorbed than inorganic salts like magnesium oxide.

In case you already take other supplements, you should also be aware that high doses of zinc supplements (142 mg/day) have been shown in research to interfere with magnesium absorption. Your best source of information about supplement and medication interactions, especially in the context of your individual health, is your personal healthcare provider.

Labdoor recently tested 36 popular magnesium supplements. You can find the rankings and full reports here.

  • Azoulay A, et al. (2001). Comparison of the mineral content of tap water and bottled waters. J Gen Intern Med. 16(3):168-75. [source link]
  • Barbagallo M, et al. (2009). Magnesium homeostasis and aging. Magnes Res. 22(4):235-46. [source link]
  • Chaudhary DP, et al. (2010). Implications of magnesium deficiency in type 2 diabetes: a review. Biol Trace Elem Res. 134(2):119-29. [source link]
  • Christiansen J, et al. (1975). Interaction of calcium and magnesium on gastric acid secretion and serum gastrin concentration in man. Gastroenterology. 65:1140-3. [source link]
  • Firoz M & Graber M. (2001). Bioavailability of US commercial magnesium preparations. Magnes Res. 14:257-62. [source link]
  • Guerrera MP, et al. (2009). Therapeutic uses of magnesium. Am Fam Physician. 80:157-62. [source link]
  • Institute of Medicine. (1997). Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride. [source link]
  • Lindberg JS, et al. (1990). Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr. 9(1):48-55. [source link]
  • McGuire JK, et al. (2000). Fatal hypermagnesemia in a child treated with megavitamin/megamineral therapy. Pediatrics. 105(2):E18. [source link]
  • Musso CG. (2009). Magnesium metabolism in health and disease. Int Urol Nephrol. 41(2):357-62. [source link]
  • National Institutes of Health. (2016). Magnesium Fact Sheet for Health Professionals. [source link]
  • Natural Medicines Comprehensive Database. (2013). Magnesium.
  • Onishi S & Yoshino S. (2006). Cathartic-induced fatal hypermagnesemia in the elderly. Intern Med. 45(4):207-10. [source link]
  • Ranade VV & Somberg JC. (2001). Bioavailability and pharmacokinetics of magnesium after administration of magnesium salts to humans. Am J Ther. 8(5):345-57. [source link]
  • Rivlin RS. (1994). Magnesium deficiency and alcohol intake: mechanisms, clinical significance and possible relation to cancer development (a review). J Am Coll Nutr. 13(5):416-23. [source link]
  • Sebastian RS, et al. (2007). Older adults who use vitamin/mineral supplements differ from nonusers in nutrient intake adequacy and dietary attitudes. J Am Diet Assoc. 107(8):1322-32. [source link]
  • Spencer H, et al. (1994). Inhibitory effects of zinc on magnesium balance and magnesium absorption in man. J Am Coll Nutr. 13(5):479-84. [source link]
  • Tosiello L. (1996). Hypomagnesemia and diabetes mellitus. A review of clinical implications. Arch Intern Med. 156(11):1143-8. [source link]
  • US Department of Agriculture. (2009). The Community Nutrition Mapping Project. [source link]