Magnesium Oxide Benefits and Side Effects - Dr. Axe

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Magnesium Oxide: Effective Supplement or Poorly Absorbed?


Magnesium oxide benefits - Dr. Axe

Although a diet including foods high in magnesium usually provides adequate amounts of the mineral for your health, certain situations may cause your body to lose magnesium faster than you are able to replace it. For people with certain medical conditions that don’t allow for the proper absorption of this essential nutrient, magnesium supplements like magnesium oxide may help avoid a deficiency.

Magnesium oxide is a type of magnesium supplement that’s used to prevent deficiency and relieve health concerns like constipation, migraines, anxiety and muscle cramps. Its laxative and antispasmodic effects have been well-researched and proven effective.

However, magnesium oxide use doesn’t come without some warnings. It is known as the most poorly absorbed magnesium supplement, and although you technically get more magnesium by weight when using magnesium oxide, some researchers believe that magnesium citrate is a better option.

So does magnesium oxide benefit your health and prevent a deficiency, or should you stick with another option?

What Is Magnesium Oxide?

Magnesium oxide is a mineral supplement that’s used to increase blood magnesium levels. It’s a white solid that is commonly found in powder form. It contains more magnesium than other magnesium supplements and is often used to prevent or reverse magnesium deficiency. However, the issue of magnesium oxide absorption has been raised by researchers who don’t believe it to be as bioavailable and effective as other types of magnesium supplements.

Magnesium oxide is made by burning magnesium with pure oxygen. In some magnesium oxide supplements, oxygen is exposed to magnesium salts from underground deposits or salt beds. Products made this way tend to be less expensive than pure magnesium oxide, but the quality may not be equivalent, as it depends on the type of magnesium salt used in the process.

The molar mass of magnesium oxide is 40.3 grams per mol. The empirical formula for magnesium oxide is MgO, and it contains around 60 percent elemental magnesium, which is the highest percentage amount all types of magnesium supplements. MgO also interacts with hydrochloric acid (HCL) to form magnesium chloride salt and water.

Because magnesium is a molecule that can’t be by itself, it needs to be bound to something to be ingested in supplement form. Magnesium oxide is bonded to oxygen, while other supplements, like magnesium chelate, are bound to an amino acid.

The salts of magnesium oxide have antacid, laxative and muscle relaxant activities. Although the absorption of magnesium oxide is considered poor, this type of magnesium supplement provides more magnesium per tablet, so it is known to be an effective remedy for magnesium deficiency symptoms.


1. Prevents or Reverses Magnesium Deficiency

For people who are unable to maintain normal magnesium levels from food sources, taking a magnesium oxide supplement can help prevent or correct a deficiency. Magnesium deficiency can lead to major health issues, including insomnia, anxiety, muscle pain, type 2 diabetes, high blood pressure, migraines and leg cramps.

Research published in the journal Open Heart states that “certain individuals will need to supplement with magnesium in order to prevent suboptimal magnesium deficiency, especially if trying to obtain an optimal magnesium status to prevent chronic disease.”

2. Relieves Constipation

Magnesium oxide has a natural laxative effect because it helps osmotically mediate water retention. This is why magnesium oxide for constipation is one of the most common uses. It also relaxes the muscles in the digestive tract, which helps to move stool through the intestines and helps to control stomach acid that can lead to indigestion.

Research published in Annals of Clinical Research found that when elderly patients received magnesium oxide supplements, stool consistency was more normal, and the supplements were more efficient than bulk laxatives in treating constipation.

3. Helps Improve Depression and Anxiety

Because the mineral is vital for GABA (gamma-aminobutyric acid) function, which allows for the proper production of “happy hormones” like serotonin, it can indeed help calm anxiety and boost your mood. For people who don’t get enough magnesium through natural food sources, supplementing with magnesium oxide may help regulate hormones that are needed for calming the brain and promoting relaxation.

Magnesium oxide benefits depression as well, according to research published in PLOS One. Researchers found that when adults with symptoms of anxiety and depression used magnesium supplements for a six-week period, it caused improvements and was well-tolerated, without the need for close monitoring for toxicity.

4. Relieves Migraines

When it comes to using magnesium oxide for migraines, studies indicate that it can be helpful. The Journal of Headache and Pain published a trial that used a combination of magnesium, riboflavin and coenzyme Q10 to improve symptoms for adults with frequent migraine attacks. Researchers found that migraine symptoms and burden of disease were significantly reduced compared to placebo.

Beyond this study, research indicates that use of oral magnesium treatment is a simple, inexpensive, safe and well-tolerated option.

5. Promotes Regular Sleep

Studies show that magnesium supplements are able to increase melatonin levels, helping induce sleepiness and lower cortisol levels that are associated with stress. Using magnesium oxide for sleep may help relieve symptoms of insomnia and promote a normal circadian rhythm.

6. Relieves Muscle Cramps

Magnesium oxide plays a role in muscle contractions and helps relieve spasms that are associated with muscle cramps and issues like restless leg syndrome. Magnesium ions behave as calcium antagonists in our vascular smooth muscles. This means that magnesium helps balance calcium levels within the body so they don’t become too high and create problems with muscle control.

The studies conducted on magnesium oxide for cramps have mixed conclusions, with some showing that it isn’t more effective than placebo for night leg cramps. But research does suggest that magnesium benefits leg cramps during pregnancy.

7. Improves High Blood Pressure

Magnesium and calcium work together to support proper blood pressure levels and prevent hypertension. Taking magnesium oxide can help to prevent magnesium deficiency. This is good news considering magnesium deficiency has been shown to increase the risk of serious morbidity and mortality from cardiovascular disease.

According to research published in BMJ, “In industrial western countries, a low intake of magnesium often predisposes to a high prevalence of magnesium deficiency, increasing the risk of cardiovascular evens and cardiovascular death.”

8. Reduces Stomach Acid

When the salts of magnesium are combined with water, they form magnesium hydroxide, which reacts chemically to neutralize stomach acid. Magnesium can be used as an antacid and to manage gastrointestinal issues like indigestion.

One study conducted in France found that when patients with indigestion received a combination of magnesium oxide, activated charcoal and simethicone, an agent that’s used to relieve gas bubbles in the stomach, symptom intensity was significantly reduced compared to the placebo. Patients noticed improvements in abdominal bloating, post-meal fullness and pain in the upper abdomen area.

Risks and Side Effects

Is magnesium oxide safe to take daily? It may cause digestive issues, especially when taken in high doses. This is due to its laxative effects, which may lead to magnesium oxide side effects like diarrhea, abdominal cramping and sometimes nausea.

Magnesium side effects generally occur when someone takes doses of 600 milligrams or more. Taking too much magnesium produces osmotic activity in the intestines and colon, which overstimulates the bowels.

High doses of magnesium oxide may also cause issues like low blood pressure, irregular heartbeat, slowed breathing and confusion. In very serious but rare cases, coma and even death are possible. This is due to an imbalance of other nutrients and toxicity.

Although this is rare, for people allergic to magnesium oxide, they may experience symptoms like a rash, itching, swelling and dizziness. If these symptoms occur, discontinue use of magnesium oxide powder or tablets.

There may be magnesium oxide nursing implications, but more research is needed to fully understand if magnesium passes into breast milk. If you are struggling with magnesium deficiency symptoms and need a supplement, consult your doctor before using one if you are pregnant or breastfeeding.

Drug Interactions

Magnesium oxide does interact with some medications, so it’s important to check with your health care professional before using magnesium supplements when you take pharmaceutical drugs.

Some commonly prescribed drugs that interact with magnesium oxide include thyroid medications (like levothyroxine), quinolone-type antibiotics, tetracycline-type medications (used for bacterial infections) and bisphosphonate (for loss of bone density). These are not all of the possible magnesium oxide interactions, so be sure to consult with your health care professional.

If you use magnesium supplements, they may interact with certain medications and prevent their full absorption. Also, be aware that magnesium and calcium compete for absorption, so taking both at the same time hinders their absorption. It’s important to separate taking medications and magnesium oxide supplements by at least three hours, and talk to your doctor to make sure you’re cleared to take magnesium.

People on pharmaceutical medications should consult their health care professionals before adding magnesium oxide to their health regimes. Those with kidney disease should also consult a doctor before using magnesium supplements.

Magnesium Oxide Supplements

Magnesium oxide supplements are taken by mouth in tablet, powder and liquid forms. The recommended daily allowance of elemental magnesium for adult males over 30 is 420 milligrams per day and 320 milligrams per day for women.

When taking magnesium oxide supplements to prevent deficiency, the dosage is typically one to two tablets orally per day. For people using magnesium oxide for sleep or as an antacid, taking one tablet once daily is a common dosage.

Magnesium oxide dosage beyond one tablet per day depends on a person’s medical condition and should be determined by a health care professional. Magnesium oxide 400 mg tablets and 500 mg tablets are the most commonly offered forms that are widely available.

Although the supplements are available over-the-counter, your doctor can advise you on which magnesium supplement type and brand is best for your health needs. Read the product label carefully for directions, dosage and storage. Generally, magnesium oxide supplements are taken by mouth once daily with a full glass of water.

Does It Work?

Although many studies show the benefits of magnesium supplements, the bioavailability of magnesium oxide has proved to be limited, ranging from only 0 percent to 4 percent. In fact, using magnesium oxide in studies analyzing the efficacy of magnesium supplements is discouraged because researchers are concerned that it will damage the reputation of magnesium as an effective treatment for serious health concerns, like depression.

A notable distinction is magnesium oxide vs. magnesium citrate. The difference between magnesium oxide and magnesium citrate is that the latter is bonded to citric acid, which allows for a better absorption rate. However, citrate is a longer molecule than oxygen, which is used to make magnesium oxide, so there is less magnesium present in a standard supplement preparation.

While magnesium citrate is the best absorbed form of magnesium, magnesium oxide absorption is the poorest of all magnesium supplements. However, it has the highest amount of magnesium per weight, allowing you to get more of the mineral from the same dose as a citrate supplement.

Essentially, even though it’s the most poorly absorbed magnesium supplement, it can still serve as a great general purpose supplement because it contains the highest percentages of elemental magnesium compared to other options. Although you absorb less, it has more magnesium than citrate and other supplements.

Of course, eating magnesium-rich foods, including spinach, Swiss chard, pumpkin seeds, almonds, black beans, avocado, yogurt and dark chocolate, is the best way to avoid magnesium deficiency. For people who aren’t dealing with a magnesium absorption issue, getting the mineral in natural food sources is best.

Final Thoughts

  • What is magnesium oxide used for? It’s a magnesium supplement that’s used to prevent or reverse a deficiency.
  • The benefits of magnesium oxide include relieving constipation, muscle cramps, anxiety, high blood pressure and indigestion.
  • Which is better, magnesium oxide or citrate? While magnesium oxide isn’t absorbed by the body as well, it does contain the highest amount of magnesium per weight.

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