Constipation is one of the most common gut complaints I see in clinic. Laxatives can help in the short term, but lasting relief comes from finding the underlying cause, which usually involves addressing the gut microbiome.

What is constipation?

Constipation occurs when stool is moving too slowly through the digestive tract, becoming dry and hard, or when the pelvic floor doesn’t coordinate properly to let stool out. Bowel motions can become infrequent, difficult to pass, or leave you feeling like you haven’t fully emptied.

Common symptoms include:

• Infrequent, hard or lumpy stools
• Straining or painful bowel motions
• A feeling of incomplete emptying
• Bloating, excess gas and distension

Many people also report fatigue and brain fog alongside their constipation.

How often should you go?

Healthy bowel movements should happen at least once a day and be well formed and easy to pass.

Frequency alone doesn’t tell the whole story. It’s common to go every day and still be constipated if your stools are hard, small, or you never feel fully empty.

Occasional constipation is normal. Chronic constipation, however, can significantly affect your quality of life, and it’s worth investigating rather than putting up with.

What causes constipation?

The most common causes are the everyday ones:

• Dehydration
• A low-fibre diet
• Lack of movement
• Stress
• Certain medications and supplements, such as iron, opioid pain relief and some antidepressants

Other contributors are often missed:

• Low thyroid function, including subclinical hypothyroidism
• Pelvic floor dysfunction
• SIBO (small intestinal bacterial overgrowth) or methane overgrowth
• Microbiome imbalance (dysbiosis)

For most people, improving fibre, hydration and movement is enough to get things moving. But what if it isn’t? That’s when it’s time to look deeper, and the gut microbiome is one of the first places I look.

How your gut microbiome affects your bowels

The trillions of microbes in your large intestine don’t just sit there, they actively help regulate how quickly things move through. Research suggests they influence motility in four key ways.

1. Short-chain fatty acids (SCFAs). When your gut bacteria ferment fibre, they produce SCFAs such as butyrate. These fuel the cells lining your colon and help stimulate the muscle contractions that move stool along. Lower numbers of SCFA-producing bacteria may be linked to slower transit.

2. Bile acids. Gut microbes transform the bile acids your liver releases. Some of these microbial bile acids help stimulate bowel movement and draw water into the colon. When this process is disrupted, transit can slow.

3. Serotonin. Around 90% of your body’s serotonin is made in the gut, and your microbes help regulate how much is produced. In the gut, serotonin is a key signal for peristalsis — the wave-like contractions that keep things moving.

4. Methane. Some gut microbes, called methanogenic archaea (mainly Methanobrevibacter smithii), produce methane gas. Methane is strongly associated with slower transit and constipation.

This is why two people eating the same diet can have very different bowel habits — and why more fibre and water alone doesn’t always solve the problem.

What I look for in clinic

When a client comes to me with constipation, these are the three things I consider first.

1. Are the basics in place? Enough fibre, water and movement. If not, these are the easiest and quickest things to fix.
2. What is their gut transit time? A simple at-home test using sweetcorn or beetroot shows how long food takes to travel from plate to toilet. Conventional ranges extend up to around 72 hours, but in practice I like to see transit closer to 14–24 hours. Slow transit is a common reason people go daily and still feel constipated.
3. Is there a methane or microbial imbalance? Methane-producing microbes can overgrow in the small or large intestine (called Intestinal methane overgrowth – IMO) and slow everything down. Hydrogen-dominant SIBO, on the other hand, more often shows up as bloating and looser stools.

Testing, not guessing

To find out what’s driving a client’s constipation, I use:

• Gut microbiome stool testing — this shows not just which microbes are present, but what they’re doing: levels of methane-producing archaea and the capacity of your SCFA-producing bacteria.
• SIBO breath testing — this measures hydrogen and methane gas to identify overgrowth and its type.

From there, I build an individual treatment protocol focused on food, probiotics, prebiotics and, where needed, herbal support.

My top tips for stubborn constipation

1. Eat 2 green kiwifruit a day. Green kiwifruit has the strongest research behind it for constipation, and gold kiwifruit can help too. Eating the skin adds extra fibre. Give it around four weeks to see the full effect.
2. Add prunes or mango. Prunes contain sorbitol, which draws water into the bowel, plus polyphenols that feed beneficial gut bacteria. Mango has also been shown to ease constipation. Note that both are high FODMAP, so if you have SIBO or IBS they may increase bloating.
3. Feed your fibre fermenters. Aim for a wide variety of plant foods across the week — vegetables, fruit, legumes, wholegrains, nuts and seeds. Polyphenol-rich foods such as berries, extra virgin olive oil, cacao and green tea help support SCFA-producing bacteria.
4. Consider magnesium. Magnesium citrate, around 400mg in the evening, draws water into the bowel. Check with your practitioner first, particularly if you have kidney issues or take other medications.
5. Fix your toilet posture. Use a footstool so your knees sit above your hips. A pelvic floor physiotherapist can make a big difference if emptying is difficult.
6. Don’t ignore the urge. Go as soon as you feel the need. Putting it off can teach the bowel to ignore its own signals. The 20–30 minutes after breakfast is often the most productive window.
7. Move every day. A 10–15 minute walk after meals helps stimulate gut motility.

Get help from a professional

If you’re struggling with constipation and want to understand what’s really driving it, book in for a discovery call with me. Together we can find the root cause and build a long-term plan.

This article is general information only and is not a substitute for individual medical or nutrition advice.

REFERENCES:

Bin Waqar et al. (2019). Methane and Constipation-predominant Irritable Bowel Syndrome: Entwining Pillars of Emerging Neurogastroenterology. Cureus, 11(5), e4764. https://doi.org/10.7759/cureus.4764

Chan et al. (2007). Increasing dietary fiber intake in terms of kiwifruit improves constipation in Chinese patients. World journal of gastroenterology, 13(35), 4771–4775. DOI: 10.3748/wjg.v13.i35.4771

Chey SW, Chey WD, Jackson K, Eswaran S. (2021). Exploratory comparative effectiveness trial of green kiwifruit, psyllium, or prunes in US patients with chronic constipation. American Journal of Gastroenterology, 116(6), 1304–1312.
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Gao et al. (2019). Exercise therapy in patients with constipation: a systematic review and meta analysis of randomized controlled trials. Scandinavian journal of gastroenterology, 54(2), 169–177.
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Soltanian et al. (2019). Effect of flaxseed or psyllium vs. placebo on management of constipation, weight, glycemia, and lipids: A randomized trial in constipated patients with type 2 diabetes. Clinical Nutrition ESPEN,  29, 41-48. https://doi.org/10.1016/j.clnesp.2018.11.002