Effects of Inulin and Why
- Octavian Belcea, MD
- Apr 12
- 3 min read
We’ve had a lot of patients asking about the effects of inulin—especially when starting gutloops™—which is why I’m putting this information into a blog. Many people are surprised to experience gas or even constipation at first, so let’s break down what’s actually happening in your gut and why it’s a sign of something good.
What Is Inulin?
Inulin is a soluble, fermentable fiber found naturally in chicory root, artichokes, and other plants. Your body can’t digest inulin—but your gut bacteria can. That’s what makes it a prebiotic: it feeds the beneficial microbes that support digestion, immunity, and long-term health. If you'd like more introduction to inulin check out my first blog: What Is Inulin? The Gut-Loving Prebiotic You’ve Probably Never Heard Of
Why Does Inulin Cause Gas?
Since inulin bypasses digestion in the small intestine, it arrives intact in the colon, where your gut microbes ferment it. This process creates short-chain fatty acids (SCFAs) that benefit your body—but also produces gas as a natural byproduct.
Gas | Produced By | Effect |
Hydrogen (H₂) | Common fermenters like Bifidobacteria | Bloating, flatulence |
Carbon Dioxide (CO₂) | General bacterial metabolism | Can contribute to distention |
Methane (CH₄) | Methanobrevibacter smithii | Slows digestion, may cause constipation |
Hydrogen Sulfide (H₂S) | Sulfate-reducing bacteria | Odor and possible irritation |
Most people will adapt within a week or two as their gut flora rebalances.
Can Inulin Cause Constipation?
Yes—although inulin is commonly used to relieve constipation, some people may experience the opposite when they first begin using it.
Why This Happens:
Methane production from M. smithii slows gut motility
Rapid dose increase causes excess gas and spasm
Low hydration makes stool dry and harder to pass
Unbalanced microbiome may ferment inefficiently and disrupt gut rhythm
If your gut lacks key fiber-fermenting species—like Bifidobacteria or Lactobacilli—inulin fermentation becomes sluggish or incomplete. This can lead to excess gas, irregular stool formation, or alternating constipation and bloating.
On the other hand, dominance of methane-producing archaea or sulfate-reducing bacteria may worsen motility and slow bowel transit further.
A disrupted or depleted microbiome (common after antibiotics, illness, or poor diet) may struggle to adapt to prebiotics, causing symptoms until balance is restored.
In most cases, these symptoms improve with hydration, slower dosing, and persistence.
The Role of Serotonin in Gut Motility
Most people think of serotonin as a “brain chemical,” but over 90% of your body’s serotonin is made in the gut—and it plays a crucial role in bowel movements.
Serotonin (5-HT) regulates peristalsis, the rhythmic contractions that move stool along the intestines.
Low serotonin levels or reduced signaling can slow transit, leading to constipation.
This can be caused by:
A disrupted microbiome (which influences serotonin production)
Nutrient deficiencies (e.g. B vitamins or tryptophan)
SSRI withdrawal or certain medications
Chronic stress or inflammation
Certain beneficial gut bacteria (e.g. spore-forming Clostridia) help stimulate serotonin production in the colon. By nourishing these microbes, inulin may indirectly support serotonin balance over time—but during the adjustment phase, low baseline serotonin could be part of why constipation occurs.
What Kind of Gut Reacts This Way?
Every microbiome is different. A few common patterns:
People with methane-dominant SIBO or IBS-C may feel more constipated at first
Those new to fiber may be more prone to gas
People low in Bifidobacteria may take longer to adapt
How to Minimize Side Effects
Start low: Begin with a small dose (e.g., one gutloop™).
Go slow: Increase gradually over 1–2 weeks.
Hydrate: Fiber needs water to work effectively.
Stay consistent: Your gut adjusts best with regular intake.
Move your body: Exercise helps motility and digestion.
Why It’s Still Worth It
Yes, there might be a little discomfort at first—but the benefits of inulin are significant. Fermentation creates SCFAs like butyrate, which:
Fuel your colon cells
Strengthen the gut lining
Reduce inflammation
Improve metabolic flexibility
So if gutloops™ makes you a little gassy or sluggish at first, don’t worry—it usually means your gut microbes are waking up and getting to work.
gutloops™: One simple ingredient. One powerful shift.
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