From the Guidelines
Inulin may not be the most effective option for constipation, as the current evidence suggests that its effectiveness is uncertain and limited compared to other fiber supplements like psyllium. The American Gastroenterological Association-American College of Gastroenterology clinical practice guideline recommends the use of fiber supplementation, but notes that only psyllium appears to be effective, with very limited and uncertain data on bran and inulin 1. Two studies assessed the effect of inulin for the treatment of chronic idiopathic constipation, but the results are not conclusive 1.
Key Considerations
- Inulin works as a prebiotic, feeding beneficial gut bacteria, which can improve bowel function and stool consistency.
- Typical dosages range from 5-10 grams daily, but starting with a lower dose (2-3 grams) and gradually increasing is recommended to minimize potential gas and bloating.
- Inulin should be taken with plenty of water (at least 8 ounces per dose) to help the fiber work properly.
- Results may take several days to a week to become noticeable as the gut microbiome adjusts.
- Inulin is available in powder form that can be mixed with beverages or food, or in supplement capsules.
Important Notes
- The evidence for inulin's effectiveness in treating constipation is limited and uncertain, and it may not be the best option for individuals with chronic idiopathic constipation.
- Psyllium is currently the most effective fiber supplement for constipation, according to the American Gastroenterological Association-American College of Gastroenterology clinical practice guideline 1.
- Individuals with irritable bowel syndrome or FODMAP sensitivities should introduce inulin cautiously, as it may initially worsen symptoms in some individuals.
- Adequate hydration should be encouraged with the use of fiber supplements, and flatulence is a commonly observed side effect 1.
From the Research
Effectiveness of Inulin for Constipation
- Inulin has been shown to have a positive effect on bowel function in patients with chronic constipation, improving stool frequency, consistency, and transit time 2.
- A meta-analysis of randomized controlled clinical trials found that inulin intake significantly improved stool frequency, consistency, and transit time, but did not improve pain and bloating 2.
- Another study found that the combination of inulin, choline, and silymarin with a specific constipation diet had beneficial effects on bowel movement, abdominal pain, and bloating in patients with irritable bowel syndrome with constipation (IBS-C) 3.
Mechanism of Action
- Inulin is a prebiotic that can improve bowel function by positively influencing intestinal biota, increasing the production of short-chain fatty acids, and promoting the growth of beneficial bacteria such as Bifidobacterium 2, 4.
- The increase in Bifidobacterium and other beneficial bacteria can lead to improvements in stool frequency, consistency, and transit time 4.
Comparison with Other Treatments
- A systematic review of over-the-counter therapies for chronic constipation found that there was insufficient evidence to support the use of inulin, but good evidence to recommend polyethylene glycol or senna as first-line laxatives 5.
- Another review found that prucalopride, a highly selective serotonin receptor subtype 4 agonist, was effective and safe in the management of patients with chronic constipation, but did not mention inulin as a treatment option 6.
Gut Microbiome Composition
- Inulin supplementation has been shown to increase the relative abundance of Bifidobacterium, Anaerostipes, Faecalibacterium, and Lactobacillus, and decrease the relative abundance of Bacteroides in the gut microbiome 4.
- However, the taxonomic alterations were not associated with an increase in short-chain fatty acids levels, suggesting that the mechanisms of action of inulin may be more complex than previously thought 4.