Dr. Thomas Dwan - Is It Bad For You? Approved by Dr. Thomas Dwan

Is Magnesium Oxide Bad For You?

Also Known As: MgO



Short answer

Magnesium oxide is not optimal for correcting magnesium deficiencies due to its low bioavailability, with absorption rates around 4%. It's less effective for systemic nutritional benefits compared to other forms with higher absorption. However, for treating constipation, its laxative effect from poor absorption can be beneficial. Long-term overuse can lead to serious side effects like hypermagnesemia and imbalances in other minerals. It's advised to critically evaluate health goals and possibly consider other magnesium forms for better systemic use.



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Long answer

Magnesium Oxide: Absorption Efficiency and Bioavailability

When assessing whether a supplement like magnesium oxide is beneficial or potentially harmful, we must scrutinize its absorption efficiency and bioavailability. Bioavailability refers to the proportion of a nutrient that, once ingested, is absorbed and utilized in the body's systems. Not all forms of magnesium are created equal in this department, and contrary to popular belief, the compound's bioavailability can significantly influence its effectiveness.

Magnesium oxide, a common form of magnesium supplement found on shelves, is often marketed for its high magnesium content by weight. However, when it comes to how well our bodies can use it, the picture gets less rosy. Studies have shown that magnesium oxide has a relatively low bioavailability when compared to other forms of magnesium. For instance, a study in the Journal of the American College of Nutrition demonstrated that magnesium oxide's solubility in water is poor, which implies that it's less absorbable in the gut. Absorption rates have been reported to be as low as 4%, suggesting that most of what's ingested does not end up being utilized by the body effectively.

Why does this matter? When consumed, magnesium must dissolve in the stomach's acid to be absorbed in the small intestine. Magnesium oxide's poor solubility means it struggles to dissolve in the stomach acid, leading to suboptimal absorption. This calls into question the efficacy of magnesium oxide supplementation in correcting magnesium deficiencies or delivering the purported health benefits tied to magnesium. Symptoms of a deficiency might not be alleviated if the body can't effectively use the form provided.

However, it's not all doom and gloom. There are specific clinical applications where magnesium oxide's low bioavailability may not be a significant concern. For instance, its laxative effect, which derives from the body's poor absorption of the compound, is beneficial in treating constipation. The unabsorbed magnesium attracts water into the intestines, increasing stool liquidity and easing bowel movements.

But if we're talking about systemic nutritional benefits – such as supporting nerve function, muscle health, and energy production – it's essential to consider forms of magnesium with higher bioavailability. Studies suggest that magnesium citrate, lactate, and chloride are absorbed more effectively than magnesium oxide. The choice of supplement greatly matters if the goal is to increase magnesium levels efficiently within the body.

List of magnesium forms by bioavailability (from higher to lower):

  • Magnesium Citrate
  • Magnesium Lactate
  • Magnesium Chloride
  • Magnesium Glycinate
  • Magnesium Malate
  • Magnesium Taurate
  • Magnesium Oxide

In conclusion, when pondering whether magnesium oxide is a suitable supplement, consumers should critically evaluate their specific health needs in the context of magnesium oxide's low bioavailability. This knowledge empowers individuals to make informed decisions and possibly look towards alternatives that can be utilized by the body more efficiently.

Short-Term and Long-Term Use: Potential Side Effects

When deliberating the use of magnesium oxide, it's important to distinguish between short-term and long-term effects, as the body's response may vary over time. Magnesium is an essential mineral, pivotal for various bodily functions, including muscle and nerve function, blood glucose control, and blood pressure regulation. Its oxide form, magnesium oxide, is commonly used as an over-the-counter remedy for acid reflux and as a magnesium supplement.

Short-Term Side Effects

In the short term, magnesium oxide is generally considered safe when taken within the recommended dosage. However, even within this boundary, some individuals may encounter side effects, which primarily include:

  • Gastrointestinal disturbances, such as diarrhea or abdominal cramping
  • Nausea
  • Vomiting

These effects can often be attributed to the osmotic activity of magnesium in the intestine, which pulls water into the gut and can result in loose stools.

Long-Term Side Effects

For long-term use, the safety profile needs a more scrupulous examination. Overconsumption over extended periods can lead to more serious side effects, including:

  • Hypermagnesemia, a condition caused by excessive levels of magnesium in the blood, which can impede neuromuscular function and affect cardiovascular health.
  • Electrolyte imbalances, potentially disrupting the balance of other essential minerals like calcium and potassium.
  • Impaired kidney function, as excess magnesium must be filtered out by the kidneys, posing a risk to those with pre-existing kidney conditions.

A study published in the European Journal of Epidemiology highlighted the potential risk of excessive supplementation, reinforcing the importance of adhering to recommended doses (Kieboom et al., 2016).

Magnesium oxide's bioavailability is also a point of contention for its long-term efficacy. Research suggests that it may not be the most efficient form of magnesium for supplementation, given its comparatively lower absorption rate. Consequently, the consumed dosage may not accurately reflect the magnesium levels reaching the body's systems, leading to either unintended deficiency or surplus.

As with any supplement, medical advice is crucial before initiating a regimen, especially for those with existing health issues or those taking other medications. Health care providers can offer personalized guidance rooted in clinical expertise and awareness of potential drug-supplement interactions.

Magnesium Oxide vs. Other Magnesium Supplements

When it comes to magnesium supplements, not all forms are created equal. Let's cut through the marketing fog and look at the cold, hard science. Magnesium oxide is one of several types of magnesium supplements available on the market, and it's crucial to understand how it stacks up against its counterparts.

Magnesium oxide is often lauded for its high magnesium content by weight, which might seem like a bonus. However, the body's ability to absorb magnesium oxide is significantly less compared to other forms such as magnesium citrate, lactate, or chloride. Bioavailability—that is, the proportion of a nutrient that is actually absorbed into the bloodstream—is a critical factor to consider when choosing a magnesium supplement.

Studies suggest that the bioavailability of magnesium oxide is markedly lower than that of other forms. For instance, a key study shows that magnesium citrate has higher solubility and is more bioavailable than magnesium oxide (Coudray C et. al, 2001).

Gastrointestinal Effects:
Due to its poor absorption, magnesium oxide can also act as a laxative. While this may be beneficial for individuals suffering from constipation, it can lead to gastrointestinal discomfort or diarrhea for others, potentially leading to dehydration and an imbalance of electrolytes if taken in large doses.

Dosage and Efficiency:
Because of its reduced bioavailability, you may need a larger dose of magnesium oxide to achieve the same effect as a smaller dose of a more bioavailable form of magnesium. However, larger doses increase the risk of digestive issues, negating the perceived benefits of the supplement's higher magnesium content.

It's tempting to opt for magnesium oxide due to its lower price point, but this can be misleading. Since you may need higher doses to get the desired amount of elemental magnesium, the cost can quickly add up, making other forms of magnesium that are better absorbed more cost-effective in the long run.

Therapeutic Use:
Certain forms of magnesium are tailored for specific health issues. Magnesium oxide may be recommended for acid reflux or as a short-term laxative, while magnesium glycinate is often suggested for those seeking to improve sleep or reduce anxiety, thanks to its calming effect.

Ultimately, selecting the right magnesium supplement depends on individual health goals, tolerance to the supplement, and specific health concerns. Critical evaluation of scientific evidence combined with personal health needs should guide this decision. Always consult a healthcare provider to determine what form and dosage of magnesium is appropriate for you.

In summary, while magnesium oxide has its uses, consider other options if you're looking for a magnesium supplement that your body can absorb more efficiently and with fewer gastrointestinal side effects. Now let's break down the details and bust some myths about the superiority of one magnesium form over another.

Interaction with Medications and Absorption of Nutrients

Magnesium oxide, despite its widespread use as a supplement for countering magnesium deficiency, interacts with a variety of medications, potentially dampening their effectiveness or exacerbating side effects. Understanding the confluence of magnesium oxide with pharmacological agents is paramount for those seeking to maintain optimal health. Below are pivotal considerations regarding this interaction.

Influence on Medication Absorption: Magnesium oxide is known to affect the absorption of certain drugs by binding to them in the gastrointestinal tract, creating a complex that is not readily absorbed. For example, it can diminish the absorption of specific antibiotics like tetracyclines and fluoroquinolones. Patients on such medications should typically take magnesium oxide either 2 hours before or 4 to 6 hours after these drugs to circumvent interaction.

Interference with Bisphosphonates: Similarly, osteoporosis treatments such as bisphosphonates are less effective when taken close to the ingestion of magnesium oxide. The recommended strategy is to allow a gap to ensure the medication can be appropriately absorbed without interference.

  • Tetracyclines and Fluoroquinolones: Separate administration by 2-6 hours
  • Bisphosphonates: Allow extended gap time for absorption

Impact on Blood Pressure Medications: Individuals on blood pressure lowering drugs, particularly calcium channel blockers, may experience enhanced effects when combined with magnesium oxide, potentially leading to hypotension or muscle weakness. Monitoring by healthcare professionals is advised in such cases to avoid negative interactions.

Effect on Muscle Relaxants: The use of magnesium oxide can potentiate the action of muscle relaxants. Due to the role of magnesium in muscular function, additional intake through supplements might amplify the effect, necessitating dosage adjustments of the relaxant medications.

Reduction in Effectiveness of Levothyroxine: Those with thyroid issues who are taking levothyroxine should be particularly cautious, as magnesium oxide supplements can reduce the drug's absorption, compromising thyroid hormone replacement therapy. Adequate spacing between the supplement and medication intake is crucial here.

Moreover, magnesium oxide's propensity to bind with other minerals can interfere with the absorption of essential nutrients, such as:

  • Iron: Concurrent intake may decrease iron absorption; separate by at least 2 hours
  • Calcium: Excessive magnesium can compete with calcium, influencing bone health
  • Zinc: High levels of magnesium may hinder zinc absorption without adequate spacing

Such interactions underline the necessity for timing the intake of magnesium oxide supplements in relation to meals and other nutrient sources. Vigilance and consultation with healthcare professionals can mitigate the risks of unintended nutrient malabsorption and negative medicinal interferences.

It's not just about taking a supplement; it's about integrating it effectively into one's daily regimen, without compromising the intended benefits of both the supplement and the concurrent medications. As ever, individual factors such as dosage, overall health status, and specific medication types call for personalized guidance from certified medical practitioners. The aforementioned details paint a picture of the complex interaction landscape of magnesium oxide, advocating an approach fuelled by cognizance and precision.

Recommended Dosages and Risk of Overconsumption

Magnesium is a crucial mineral for numerous bodily functions, impacting everything from muscle health to sleep regulation. The recommended dietary allowances (RDAs) for magnesium vary based on age, sex, and life stage. For instance, adult men require about 400-420 mg per day, while adult women should aim for 310-320 mg daily. Pregnant and lactating women have increased demands and should consult healthcare providers for their specific needs.

When it comes to magnesium oxide, it's important to note that while it's inexpensive and widely available, it is not as readily absorbed by the body as other forms like magnesium citrate or magnesium chloride. This lower bioavailability means that a higher dose of magnesium oxide might be required to deliver the same amount of elemental magnesium as other forms. However, blindly increasing the dose without proper guidance can veer into dangerous territory.

Overconsumption of magnesium through supplements can lead to magnesium toxicity, which is rare but serious. Symptoms of excessive magnesium intake include:

  • Diarrhea
  • Nausea and vomiting
  • Lethargy
  • Muscle weakness
  • Irregular heartbeat
  • Low blood pressure
  • Urinary retention
  • Respiratory distress
  • Cardiac arrest in the most severe cases

The upper limit for supplemental magnesium for adults is 350 mg per day, beyond which the risk for adverse effects increases significantly. This doesn't apply to dietary magnesium, which is not harmful and difficult to overconsume through food alone.

Several populations are more vulnerable to the risks associated with magnesium supplementation. Individuals with kidney dysfunction are at a higher risk for magnesium accumulation because their kidneys cannot excrete excess magnesium efficiently. Also, people on certain medications should consult their doctors before taking magnesium oxide, as it can interact with drugs like bisphosphonates, antibiotics, diuretics, and proton pump inhibitors.

Deciphering the appropriate dosage for magnesium oxide supplementation calls for a personalized approach. Ideally, individuals should seek guidance from healthcare professionals who can consider potential interactions with other medications and the overall health status of the person. Self-prescribing high doses of magnesium oxide or any supplement can lead to unintended and potentially harmful consequences.

To establish an evidence-based dose recommendation, healthcare providers often refer to clinical studies and official guidelines. However, the absorption rates and individual body responses vary, so monitoring and adjusting dosages is crucial. For instance, a study published in the American Journal of Clinical Nutrition revealed that magnesium oxide has a bioavailability of just 4%, significantly lower than other forms, which influences how much one should take to meet their magnesium needs.

Essentially, the adage 'more is not always better' holds particularly true with magnesium oxide. Prudence and professional advice go hand-in-hand in preventing the risk associated with overconsumption.

Frequently asked questions

Dietary magnesium is found in foods like leafy greens, nuts, seeds, and whole grains and is not associated with the adverse effects of high-dose supplementation. For many people, a balanced diet may provide sufficient magnesium without the need for supplements.

Magnesium is known to support sleep due to its calming effect on the nervous system, but magnesium oxide specifically has low bioavailability, making it less efficient for sleep improvement. More readily absorbed forms, such as magnesium glycinate, are generally recommended for enhancing sleep quality.

Yes, magnesium oxide can interact with certain vitamins by affecting their absorption, such as vitamin D and B vitamins. It's advisable to space out the consumption of magnesium oxide and multivitamins or to consult with a healthcare professional for personalized advice.

Yes, magnesium supplements come in various forms, including chewable tablets, powders that dissolve in water, topical oils, and transdermal patches. These alternatives may provide a solution for individuals who struggle with swallowing pills.

Ask a question about Magnesium Oxide and our team will publish the answer as soon as possible.

Possible short-term side effects

  • gastrointestinal disturbances
  • nausea
  • vomiting

Possible long-term side effects

  • hypermagnesemia
  • electrolyte imbalances
  • impaired kidney function

Ingredients to be aware of


  • laxative effect for constipation
  • may treat magnesium deficiency

Healthier alternatives

Our Wellness Pick (what is this?)

High Absorption Magnesium

  • 100% Chelated Formula
  • Non-GMO
  • Vegan Friendly
  • Gluten & Soy Free
  • Supports Muscle Health
Learn More!

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Written by Joey Conners
Published on: 02-22-2024

Thank you for your feedback!

Written by Joey Conners
Published on: 02-22-2024

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