Magnesium Oxide - Little Element, Big Impact


Magnesium, a common element in the body, is generally absorbed in sufficient quantities from a balanced diet in most individuals. Magnesium can be found in foods such as nuts, peas, beans, and green leafy vegetables. In the body, magnesium is important for the proper function of over 300 different enzymes performing critical functions such as reducing cholesterol in the blood, maintaining electrolyte balance in the blood, and keeping the heart in rhythm. For this reason, magnesium oxide is needed as a dietary supplement for individuals who do not receive enough magnesium from their diets. Magnesium oxide can also be found in several over-the-counter products like laxatives and products to relieve indigestion.  It has a laxative effect at high doses, and its anecdotal efficacy in relieving indigestion.

Magnesium supplementation is generally considered safe; however, it is not usually required in healthy individuals without a deficiency in the diet. Individuals at the highest risk for developing a magnesium deficiency include people with GI diseases (Crohn’s diseases, celiac disease, etc.), type 2 diabetics, people with an alcohol dependence, and older adults. Early symptoms of magnesium deficiency include loss of appetite, nausea, vomiting, fatigue, and weakness which may develop into more severe symptoms with worsening deficiencies.

The usual doses of magnesium oxide are 400 mg daily (deficiency) or 400 mg twice daily (indigestion/constipation), with the recommended daily allowances of elemental magnesium listed in Table 1, below. Each product contains a different amount of elemental magnesium so be sure to check this quantity before beginning supplementation. The only common side effect of magnesium oxide is diarrhea, due to the laxative effect.

Patients with conditions such as heart disease or chronic kidney disease may be negatively impacted by magnesium supplementation. Magnesium oxide can also interfere with the absorption of many different drugs including, but not limited to, tetracycline antibiotics, mycophenolate (Cellcept), azole antifungals, phenytoin, and digoxin, decreasing the drugs’ efficacy. Additionally, supplementation is generally not recommended in women who are pregnant or breast feeding. For these reasons, you should consult with your doctor before beginning a magnesium supplementation regimen.


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Nothing herein constitutes medical advice, diagnosis or treatment, or is a substitute for professional advice.  You should always seek the advice of your physician or other medical professional if you have questions or concerns about a medical condition.



©Collin Morrison, PharmD Candidate 2019




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