Family, Internal Medicine, General Medical Questions/Help for constipation - Mg to the rescue



Which type of magnesium is better at relieving constipation? Magnesium citrate or magnesium oxide?

Thank you.


Elemental magnesium is an important element for our bodies.  Mg when used as a laxative or to relieve constipation can be taken in several forms.  Citrate, Aspartate and Oxide and many others bound to amino acids as chelates.  There are some advantages to each.  Aspartate is better absorbed by the gut for Mg deficiencies.  Magnesium citrate helps to increase the amount of water in the intestines, which can help with bowel movements by adding additional water to soften and bulk up the stool. It may be used as a laxative due to these properties (Milk of Magnesia), or as a supplement for magnesium deficiency.  Magnesium oxide may be used to treat heartburn or acid indigestion, acting as an antacid it does a better job for this function, so if one has heartburn and constipation Oxide is the way to go.  It also likely has the highest amount of elemental magnesium pound for pound.

One 500 mg capsule of magnesium oxide contains 300 mg of elemental magnesium. But little of that amount is available to the body because it is not absorbed and therefore not biologically available.  One recent study reported 4 percent absorption rate of magnesium oxide. This means 12 mg of 500 mg capsule are absorbed and 288 may stay in the intestines, acting like a laxative. Not too good for deficiencies but excellent for constipation. (*1)

If Mg deficiency is the problem: (From Time for Wellness) (*2):

Here are the bioavailability studies to date:

Lindberg et al (1990) demonstrated greater bioavailability from a single dose of magnesium citrate versus magnesium oxide (3).

Muhlbauer et al (1991) found magnesium aspartate superior to oxide (3).

Schuette et al (1993 & 1994) did not find a difference between magnesium glycinate and magnesium oxide (5,6).

Firoz & Graber (2001) revealed a relatively poor bioavailability of magnesium oxide when compared to magnesium chloride, lactate, and aspartate (7).

And Walker et al (2003) found magnesium citrate to be superior to a glycinate and oxide (8).
Interestingly, although magnesium oxide has generally been found to have poorer absorption a recent study by Schecter et al (2012) discovered that magnesium oxide was superior to magnesium citrate both in terms of bioavailability and health benefits (9). This well conducted and more recent study challenges the assumption that magnesium oxide is inferior.

So, as the current science stands there is not sufficient evidence to suggest one form of magnesium is superior to another in terms of bioavailability, in fact clinical intervention studies have generally found a variety of forms (in particular carbonate, chloride, citrate, orotate and oxide) able to correct deficiency and to be clinically effective for a wide range of illness (10).




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Yusuf (JP) Saleeby, MD


Will ONLY answer questions pertaining to Hypothyroidism, Hashimoto's disease and thyroid disorders. I will forward all other questions to the question pool. This forum does not allow for the diagnosis and treatment of illness, so please don't ask questions in that regard.


Medical School: Medical College of Georgia (Augusta, GA class of 1991) Post Graduate Training: ECU school of Medicine (Greenville, NC) 20 years in Emergency Medicine, Urgent Care and Occupational Medicine (retired 2012). *** Licensed in states of GA, NC, SC and VA. *** Medical Director of Priority Health of SC ( *** Former Medical Director and Founder of the Saleeby Longevity Institute a clinical practice and research center in integrative (CAM,Allopathic Medicine (1999 to 2004). *** Founder of Vita Sanus, Inc. Manufacturer & Distributer of Vita Sanus Nutraceuticals and Skin Care products ( Sold in 2006. *** Adjunct Professor in Graduate School of Nursing Georgia Southern University (2002-2006). *** Author of "Wonder Herbs: A Guide to Three Adaptogens" available for sale at or signed copies at *** Former Medical Director of the Emergency Department at Marlboro Park Hospital, Bennettsville, SC (2006-2010) *** Appointed to Medical Advisory Board for Aerobic & Fitness Association of America (AFAA) 2007-present & Contributing Editor AFAA (American Fitness magazine) 2013-present. *** Appointed to Medical Advisory Board for Beach Body (Product Partners) 2008-present *** Founder and regional director of an alternative to high priced lab testing sites (DAT). *** Life Extension 5th Edition Book on Prevention and Disease Treatment (contributor on Chapter on Adrenal Fatigue and Stress Management) 2013 5th edition. *** Worked as chief formulator for supplement companies: Vita Sanus Nutraceuticals (Longevity Pack & entire line), SSN's PreGame Formulas for Golf and Tennis, AdapTx Labs' CardioFactor & PreFight, BeachBody's Shakeology consultant, Parhelion Labs' Oviun BioPharma sub-fertility formula ''Fertility Regimen''.

South Carolina Urban Search & Rescue Task Force-1 (USAR), former Medical Director/Control. 2010-2012. Founder and developer of Current medical practice: Former member of American Telemedicine Association Former member of A4M and ACAM. Attend regular meetings of AMMG Member in good standing ILADS (

American Fitness magazine (multiple) Cortlandt Forum Medical Economics (blog) JIVE magazine (out of print) Tea Digest Experience (out of print) Authored Books on Adaptogen Herbs (Wonder Herbs: A guide to three adaptogens) 2006 Authored chapter on Stress Management for LEF text book on Prevention of Diseases and Treatments (2013) Authored Chapter 3 in "Stop the Thyroid Madness, II" (2014)

Health & Wellness Blogger, Medical Writer. Author of book on Adaptogens. Pioneer in Telehealth, member of ATA. Contributing Editor for American Fitness magazine. Authored Books on Adaptogen Herbs (Wonder Herbs: A guide to three adaptogens) 2006 Authored chapter on Stress Management for Life Extension Foundation LEF text book on Prevention of Diseases and Treatments (2013) Authored Chapter 3 in "Stop the Thyroid Madness, II" (2014)

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*** co-Author of "Stop the Thyroid Madness, II" (Laughing Grape, 2014) Chapter on NDT/Thyroid. *** Authored chapter in "Life Extension Foundation, 5th Edition book on Prevention and Disease Treatment" Chapter on Stress Management/ Adrenal Fatigue.

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