The 3 Most Common Types of Magnesium and What They Do

You’ve seen magnesium on the periodic table of the elements, populating the supplement section of health food stores, and as an ingredient in everything from smoothies to antacid tablets. The mineral is also abundant in our own bodies, where it benefits heart, muscle, brain, bone, and nerve health. But for something so omnipresent, data shows that most Americans aren’t getting enough of it. That’s where things get tricky: With several forms of magnesium at our disposal, finding the right magnesium product for our needs requires more than a simple search and “add to cart.” 

With the help of Vanessa King, M.S., RDN, CNSC, NBC-HWC, a registered dietitian nutritionist based in Hawaii and a spokesperson for the Academy of Nutrition and Dietetics, we're delving into the differences between magnesium glycinate, magnesium oxide, and magnesium citrate — which are significant and can mean the difference between reaching for a dietary supplement or a laxative.

What Is Magnesium’s Function in the Body?

Magnesium is a workhorse micronutrient that is naturally abundant in our bodies (with only calcium, potassium and sodium occurring more prevalently). It's typically stored in the bones, muscles, and soft tissue. As far as minerals go, it wields quite the CV: Studies show that the micronutrient activates more than 600 enzymes and influences extracellular calcium levels, is an important part of activating an array of transporters and enzymes, and is essential for stable cell function, maintaining cells’ antioxidant status, RNA and DNA synthesis, and cell repair, among other functions. For example, research has shown vitamin D can’t be metabolized without sufficient magnesium levels. In short, “every cell needs this mineral to work,” King says.

How Much Magnesium Does the Body Need?

Given that it's essential to many cellular functions, it’s no wonder our bodies are stocked with ample supply of the stuff to keep operations humming — or they should be, at least. Though King notes that the best way to boost our coffers of magnesium is to do so nutritionally by consuming a wide variety of foods (including beans, nuts, seeds, unrefined grains, leafy green vegetables, hard water, and dark chocolate), data from USDA Beltsville Human Nutrition Research Center show that only 45% of Americans, on average, obtain adequate intakes of magnesium (based on average requirement for magnesium from food sources). According to the Food and Nutrition Board (FNB) at the Institute of Medicine of the National Academies, the recommended dietary allowance of magnesium for nonpregnant women over the age of 30 is 320 milligrams per day.

Who Is at Risk for Magnesium Deficiency?

Imbalanced nutrition isn’t the only cause of magnesium deficiency in the body; King notes that medical conditions can also cause the body’s magnesium levels to drop. Such conditions include impaired kidneys, diabetes, gastrointestinal diseases, Crohn's disease, alcohol dependency Gitelman syndrome, and Bartter syndrome type 3. “Other risk factors for magnesium deficiency include low estrogen levels in women, acute pancreatitis, aging, chronic alcoholism, and obesity,” King adds.

What Are the Effects of Magnesium Deficiency?

Because magnesium is a factor in so many cellular functions, its absence can materialize in a variety of ways. Research shows that those low in magnesium may initially experience weakness, loss of appetite, fatigue, nausea, and vomiting; as the deficiency worsens with time, the body is more susceptible to muscle contractions and cramps, numbness, tingling, personality changes, coronary spasms, abnormal heart rhythms, and seizures. Severe magnesium deficiency can result in hypocalcemia or hypokalemia. What’s more, in studies, magnesium deficiency over a long period of time has been linked to an increased risk of hypertension and cardiovascular disease, type 2 diabetes, osteoporosis, and migraine headaches.

But here’s the rub: According to King, many magnesium deficient Americans might not even know they’re lacking in the micronutrient. For one, the kidneys excel at retaining magnesium when needed. “The signs and symptoms of magnesium deficiency can also go undetected because they are masked by other electrolyte imbalance,” she says. “Magnesium levels are not routinely monitored in clinical settings, which may also contribute to underreporting of deficiency. However, the body adapts and will retain magnesium if necessary, rather than letting in be excreted in urine.”

Magnesium Glycinate, Citrate, and Oxide: What’s the Difference?

In addition to maintaining a magnesium-rich diet (something King says can be done easily and deliciously, as the micronutrient is found in a wide variety of foods), you canboost the body’s magnesium levels through supplementation. Before winging it with supplements, talk to your medical provider about which might be best for your needs, because there is a variety of magnesium supplements to choose from, most notably magnesium glycinate, magnesium citrate, and magnesium oxide — and each is used for widely different needs. What’s more, King notes that the U.S. Food and Drug Administration (FDA) does not test supplements before they go to market, and she recommends people “always look for third-party certification [such as NSF] to ensure they’re buying what’s intended.”

What Are the Benefits of Magnesium Glycinate?

Magnesium glycinate supplements pair magnesium with glycinate, an amino acid with antioxidant properties found in foods such as meat and beans. “This form of magnesium supplement could be helpful in treating depression, anxiety, and improving sleep,” King says. “Unlike other forms of magnesium, magnesium glycinate tends to have less of a laxative effect.” The supplement can also help those with magnesium deficiency who have been unable to adequately boost their levels of the mineral with diet alone. King notes that the use of this and any supplement, “should be discussed with a doctor before being taken, as medication and other nutrient interactions can impact absorption of magnesium.”

What Are the Benefits of Magnesium Oxide?

Most commonly used as a mild laxative, magnesium oxide has been shown to help relieve constipation by triggering a process that increases water content of the stool for a softening effect. Magnesium oxide is also commonly used as an antacid to neutralize stomach acids. 

What’s more, it may help those suffering from migraines. “The American Academy of Neurology and American Headache Society has acknowledged the potential benefits of magnesium for migraines,” King says. However, since the recommended dose is above the daily upper limit for magnesium, 350 milligrams a day, the organization recommends only using under the supervision of a health care provider via things like magnesium IV support. 

What Are the Benefits of Magnesium Citrate?

A type of saline laxative, magnesium citrate is commonly used as a short-term treatment for infrequent constipation. The supplement works to assist in bowel movement by softening the stool. King says consuming a diet rich in magnesium is the best way to ingest magnesium citrate. “I recommend treating the underlying cause of constipation first,” she says. “A food-first approach works to meet regular magnesium needs. Magnesium-rich foods will also provide other important nutrients, including fiber, which promote bowel regularity and prevent constipation.” But those who aren’t able to do so or those who notice side effects of a deficit may want to check with their health care provider about supplementing with magnesium citrate tablets and powders.