Your Gut

Constipation & Diarrhea Opposite Symptoms. Often the Same Story.

From the moment you swallow, your digestive system gets to work. Food moves through, nutrients are absorbed and waste is eventually eliminated.

Too slow, and things back up. Too fast, and things get loose. But the processes behind both, movement, nerves, muscles and gut microbes, are often the same.

Medically reviewed by Dr. Ken Brown, Gastroenterologist · Updated October 2026 · Sources

Constipation Diarrhea Motility Gut Microbes
Line drawing of the brain and digestive tract connected by two-way signals
How Does Digestion Work?

One System. Many Jobs.

Your digestive system is a coordinated network of organs.

Stomach
Stomach

Mixes food with digestive juices and gradually releases its contents into the small intestine.

Small Intestine
Small Intestine

Where much of the digestion and absorption of nutrients occurs.

Large Intestine
Large Intestine

Absorbs water, processes remaining material and houses a dense community of microorganisms.

Each part has a different job, but they work together.

Line drawing of the intestines

Your Gut Is Always on the Move.

Your digestive tract uses coordinated muscle contractions to move food and waste through the intestines.

Changes in that movement can influence bowel habits.1

What Slows Things Down?

Several factors may contribute.1,2

Fibre and Fluids
Fibre and Fluids
Physical Activity
Physical Activity
Medications
Medications
Changes in Intestinal Movement
Changes in Intestinal Movement
Certain Medical Conditions
Certain Medical Conditions
Gut-Brain Communication
Gut-Brain Communication
The Other Direction

When Things Move Too Quickly.

Diarrhea involves loose or watery stools.

It may be associated with infections, medications, food intolerances and various digestive conditions.

Changes in intestinal movement, fluid secretion and absorption can all contribute.

Not all diarrhea is caused by unusually fast transit.

Opposite Symptoms. Often the Same Story.

How Microbes Can Slow Things Down, or Speed Them Up.

Illustration of intestinal transit and microbes

Constipation and diarrhea sound like opposites. But they can share a starting point: gut microbes fermenting food and producing gas.

Elevated intestinal methane, produced by microorganisms called archaea, has been associated with slower intestinal transit and constipation in some people.

Excess bacteria in the small intestine, which tend to produce hydrogen, have more often been linked with bloating and diarrhea.

It's one reason two people can share a diagnosis like IBS while experiencing opposite symptoms. Microbial activity is one part of a much larger system.

Explore Your Gut Microbiome Understanding IBS
Two-Way Traffic

The Gut-Brain Connection.

Illustration of intestinal transit and microbes

Your digestive tract has an extensive nervous system that helps coordinate movement, secretion and sensation.

It communicates with the central nervous system through multiple pathways, and much of that signalling travels from the gut to the brain.

This communication helps regulate digestive function and may influence how symptoms are experienced.

Researchers continue to investigate the relationship between gut-brain signalling, digestive sensitivity and conditions such as IBS.

When Should You Seek Advice?

Persistent constipation, significant changes in bowel habits or concerning symptoms should be discussed with a healthcare professional.2

When Should You Seek Advice?

Don't ignore these.

Talk to your healthcare provider promptly if constipation comes with:2

Blood in your stool
Unexplained weight loss
A sudden change in bowel habits
Symptoms that keep getting worse
Atrantil Canada, 90 capsules, NPN 80083205
Digestive Support

Meet Atrantil.

GI Doctor-Formulated. Polyphenol-Powered.

Atrantil is a GI doctor-formulated supplement containing Quebracho Colorado, Horse Chestnut and Peppermint Leaf.

In Canada, Atrantil is licensed to help relieve symptoms of IBS-C, such as bloating and constipation.

NPN 80083205
Discover Atrantil
Keep Learning
Understanding IBS Bloating & Gas

Common Questions About Bowel Habits

Yes. Some people alternate between the two. In IBS, this pattern is called IBS-M (mixed).

Short-term changes are common with travel, diet, stress or illness. Persistent or significant changes should be discussed with your healthcare provider.

Soluble fibre, such as psyllium, is often recommended. Increase it gradually and drink enough fluids.

Seek prompt care for diarrhea with blood, fever, severe pain, signs of dehydration, or diarrhea that lasts more than a few days.

References

This page is for education and isn't a substitute for advice from your healthcare provider.

1

Lacy BE, Mearin F, Chang L, et al. Bowel disorders (Rome IV). Gastroenterology. 2016;150(6):1393–1407. PubMed ↗

2

Moayyedi P, Andrews CN, MacQueen G, et al. Canadian Association of Gastroenterology clinical practice guideline for the management of irritable bowel syndrome (IBS). J Can Assoc Gastroenterol. 2019;2(1):6–29. Free full text (PMC) ↗

3

Pimentel M, Lin HC, Enayati P, et al. Methane, a gas produced by enteric bacteria, slows intestinal transit and augments small intestinal contractile activity. Am J Physiol Gastrointest Liver Physiol. 2006;290(6):G1089–G1095. DOI ↗

4

Triantafyllou K, Chang C, Pimentel M. Methanogens, methane and gastrointestinal motility. J Neurogastroenterol Motil. 2014;20(1):31–40. Free full text ↗

5

Pimentel M, Saad RJ, Long MD, Rao SSC. ACG clinical guideline: small intestinal bacterial overgrowth. Am J Gastroenterol. 2020;115(2):165–178. PubMed ↗