Magnesium & Constipation
Magnesium supplementation is effective for the management of chronic idiopathic constipation. The American College of Gastroenterology, in its 2023 guideline, states magnesium increases the number of complete and spontaneous bowel movements per week, improves stool consistency, and enhances quality of life compared to placebo, with a favorable safety profile in individuals with normal kidney function. The typical studied dose is 1.5 g/day but elemental magnesium content varies by formulation. The evidence is based on randomized controlled trials, but the overall certainty is rated as low to moderate due to small sample sizes and limited geographic diversity of studies. [1][2]
Magnesium citrate is an osmotic laxative that is effective for acute bowel evacuation (e.g., bowel preparation before colonoscopy). Its efficacy is comparable to polyethylene glycol (PEG)-based regimens, with some studies showing higher patient tolerability and willingness to repeat the regimen. [3][4]
For chronic constipation, only magnesium oxide has been studied in RCTs and is guideline-recommended. Magnesium citrate, while effective as an acute osmotic laxative for bowel prep, has not been studied in the same way magnesium oxide has, for chronic constipation in the outpatient setting [1]
Juice Doctor’s Summary of the evidence:
Magnesium can be used for: 1) Management of chronic constipation, and 2) To clean out the bowels (in preparation for colonoscopy, for example).
Certain forms of magnesium have been studied more than others, for specific indications.
When it comes to chronic constipation, supplementation with Magnesium Oxide has been more thoroughly studied.
When it comes to cleaning out the bowel, Magnesium Citrate has been studied to a greater extent than Magnesium Oxide.
We know Magnesium Citrate is effective at cleaning out the bowels – it is a key ingredient in the most commonly prescribed bowel preparation in North America!
Given the extensive literature on magnesium Oxide for chronic constipation, it is unlikely researchers will look to replicate those studies in Magnesium Citrate. That’s NOT because it doesn’t work - but because the cost to do so would be prohibitive, and the result would be unlikely to change clinical practice in any meaningful way.
What is most likely, is that both Magnesium Citrate and Magnesium Oxide could be used interchangeably for the above indications. Having said that, you will likely never see Oxide replacing Magnesium Citrate for bowel Preparation – because Citrate has been shown to be effective, and is prescribed every day for patients awaiting colonoscopy.
We hope this helps with your understanding on Magnesium and Constipation. If you are interested in more Articles like this, come learn with us at Juicedoctor.co
References
1. American Gastroenterological Association-American College of Gastroenterology Clinical Practice Guideline: Pharmacological Management of Chronic Idiopathic Constipation. Chang L, Chey WD, Imdad A, et al. Gastroenterology. 2023;164(7):1086-1106. doi:10.1053/j.gastro.2023.03.214.
2. The Effect of Food, Vitamin, or Mineral Supplements on Chronic Constipation in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. van der Schoot A, Creedon A, Whelan K, Dimidi E. Neurogastroenterology and Motility. 2023;35(11):e14613. doi:10.1111/nmo.14613.
3. Optimizing Bowel Preparation Quality for Colonoscopy: Consensus Recommendations by the US Multi-Society Task Force on Colorectal Cancer. Jacobson BC, Anderson JC, Burke CA, et al. Gastroenterology. 2025;168(4):798-829. doi:10.1053/j.gastro.2025.02.002.
4. Optimizing Bowel Preparation Quality for Colonoscopy: Consensus Recommendations by the US Multi-Society Task Force on Colorectal Cancer. Jacobson BC, Anderson JC, Burke CA, et al. Gastrointestinal Endoscopy. 2025;101(4):702-732. doi:10.1016/j.gie.2025.02.010.