Why Do They Sell Magnesium Oxide? Exploring Its Many Uses

December 21, 2025 •

4 min read

According to industrial data, the refractory industry alone consumes over 50% of the world's magnesium oxide production. But why do they sell magnesium oxide to the general public, primarily for its medical and dietary applications, when so much is used for other purposes?

Quick Summary

Magnesium oxide is sold for a diverse range of applications, including over-the-counter medical treatments for constipation and acid reflux, dietary supplementation for magnesium deficiency, and critical industrial uses in metallurgy and manufacturing. Its low cost and high elemental magnesium content make it suitable for different needs.

Key Points

Diverse Utility: Magnesium oxide is sold for both common over-the-counter medical issues and large-scale industrial applications, utilizing its distinct properties for each use.
Low Bioavailability: While a high source of elemental magnesium, its low absorption rate makes it an inefficient supplement for correcting long-term deficiency, but an effective osmotic laxative.
Medical Uses: As a medication, it is primarily used as an antacid for heartburn and a laxative for constipation due to its ability to neutralize stomach acid and draw water into the intestines.
Industrial Importance: In industry, it is a crucial refractory material for lining high-temperature kilns and furnaces, and is used in agriculture for feed and fertilizer, and for environmental waste treatment.
Cost-Effectiveness: Its low cost and high elemental magnesium content make it a common and affordable choice for both medical and industrial manufacturers.
Formulation Matters: The specific form of magnesium dictates its best use; oxide is ideal for targeted effects like laxation, while organic forms like glycinate or citrate are better for increasing systemic magnesium levels.

The Dual-Purpose Compound: Medical and Industrial Applications

Magnesium oxide (MgO), a white, odorless powder, is a highly versatile inorganic compound derived from magnesium and oxygen. Its market presence is split between massive industrial-scale operations and consumer-facing health products. The reasons for selling magnesium oxide are as varied as its properties, ranging from its ability to neutralize stomach acid to its use as a heat-resistant material in steel production.

Medical and Health Applications

For consumers, magnesium oxide is primarily encountered in the health and wellness sector, available over-the-counter for several common ailments.

Antacid and Indigestion Relief: Magnesium oxide acts as a rapid-acting antacid, effectively neutralizing stomach acid to relieve heartburn and upset stomach. Its basic nature makes it a reliable remedy for occasional acid indigestion, offering short-term relief.
Laxative for Constipation: One of its most common uses is as an osmotic laxative. It draws water into the intestines, softening stool and stimulating bowel movements. This makes it effective for short-term relief from constipation, particularly for bowel preparation before certain medical procedures.
Dietary Supplement: As a supplement, magnesium oxide is sold to treat or prevent magnesium deficiency. Despite having lower bioavailability compared to other forms like magnesium citrate or glycinate, its high concentration of elemental magnesium makes it a cost-effective option for some manufacturers.
Migraine and Headache Relief: Some studies suggest that magnesium oxide can help reduce the frequency of migraine headaches. Adequate magnesium levels are necessary for proper nerve cell function, and deficiency has been linked to migraines.
Blood Pressure and Blood Sugar Regulation: Magnesium supplementation has shown potential in helping to manage blood pressure and blood sugar levels in certain populations, though more robust research is needed.

Industrial and Agricultural Applications

Beyond the pharmacy, magnesium oxide is a cornerstone of heavy industry, prized for its high thermal stability and chemical resilience.

Refractory Material: The single largest application is its use as a refractory material, capable of withstanding extremely high temperatures without physical or chemical breakdown. This makes it essential for lining furnaces, kilns, and crucibles used in the steel, glass, and cement industries.
Electrical Insulation: Due to its high dielectric strength and heat resistance, it is used as an electrical insulator in heating elements found in appliances like electric stoves.
Agricultural Feed and Fertilizer: In agriculture, magnesium oxide is added to animal feed, particularly for dairy cattle, to prevent magnesium deficiency (hypomagnesemia). It is also used as a fertilizer to correct magnesium-deficient and acidic soils, boosting crop yields.
Environmental Remediation: Its acid-neutralizing properties make it valuable for wastewater treatment and air pollution control. It is used to buffer acidic waste and stabilize heavy metals in contaminated soil and water.
Food Additive: As a food additive (E530), magnesium oxide functions as an anti-caking agent and pH regulator in products like milk powders, cocoa, and certain beverages.

Bioavailability and the Low Absorption Factor

While magnesium oxide is a common and cheap supplement, its poor bioavailability is a significant consideration. Studies have repeatedly shown that it is absorbed less effectively than organic magnesium salts like citrate, malate, or glycinate. A 2017 rat study highlighted its low absorption, with only about 15% absorbed and the majority excreted. This low absorption rate is precisely why it works so well as a laxative; most of it remains in the intestinal tract where it draws in water. For individuals needing to correct a systemic magnesium deficiency, a more bioavailable form is often recommended.

Comparison of Common Magnesium Supplements


Feature	Magnesium Oxide	Magnesium Citrate	Magnesium Glycinate	Purpose
Bioavailability	Low	High	High	How well the body absorbs and uses the magnesium.
Primary Use	Constipation, antacid, budget supplement	Digestive support, correcting deficiency	Relaxation, stress, sleep	The main application for which the form is best suited.
Cost	Low	Moderate	High	Relative cost compared to other forms.
Gastrointestinal Effect	Osmotic laxative effect; can cause diarrhea	Stimulates bowels; less harsh than oxide	Gentle on the stomach	The impact on the digestive system.
Elemental Magnesium	High percentage per dose	Lower percentage per dose	Lower percentage per dose	The total amount of pure magnesium in the compound.

Conclusion

Ultimately, they sell magnesium oxide because it is a highly versatile and cost-effective compound with a broad range of uses, from treating common medical complaints like constipation and acid reflux to serving as a critical component in heavy industry. For consumers, its low bioavailability makes it an effective short-term laxative and antacid, but less ideal for long-term correction of a magnesium deficiency compared to more absorbable forms. The reason for its sale, therefore, depends entirely on the intended application: high-concentration and low-cost for manufacturing, or targeted, short-term relief for health issues. Informed consumers should consider their specific needs before choosing a magnesium supplement, recognizing that 'magnesium' can refer to different formulations with distinct properties.

For more information, consult the National Institutes of Health https://www.ncbi.nlm.nih.gov/.

Frequently Asked Questions

Magnesium oxide acts as an osmotic laxative, which means it draws water into the intestines. This softens the stool and increases its volume, which stimulates bowel movements and relieves constipation.

Not usually. While it contains a high percentage of elemental magnesium, its bioavailability is low, meaning the body does not absorb it efficiently. More bioavailable forms like magnesium citrate or glycinate are generally better for correcting a systemic deficiency.

In industrial settings, it's used as a refractory material for lining furnaces and kilns due to its high heat resistance. It is also used in agriculture for animal feed and fertilizer, and for environmental waste treatment to neutralize acids.

Yes, magnesium oxide can be used as an antacid to relieve heartburn and acid indigestion by neutralizing stomach acid. It is typically used for short-term, occasional relief.

Common side effects, particularly at higher doses, include diarrhea, stomach cramps, and nausea. In rare cases with prolonged use or impaired kidney function, it can lead to dangerously high magnesium levels (hypermagnesemia).

Magnesium oxide is less bioavailable and generally cheaper, making it better for its laxative or antacid effects. Magnesium citrate is more easily absorbed, making it a better supplement for increasing overall magnesium levels in the body.

Yes, magnesium oxide is approved as a food additive (E530). It functions as an anti-caking agent and pH regulator in various products, including milk powders, cocoa products, and sports drinks.

Magnesium oxide is typically less expensive to produce than organic chelate forms like magnesium glycinate. This, combined with its high elemental magnesium content, makes it a cost-effective choice for many supplement manufacturers and industrial buyers.