Constipation: the gut-brain axis and role of nutrition

Constipation is one of the most common problems we have, with some studies suggesting that as many as 1 in 5 people (20%) of both adults and children suffer from constipation at any given time [1]. It can significantly affect quality of life and can also influence the effectiveness of nutrient and medication absorption.

Emerging research shows that communication along the gut-brain axis – the bidirectional pathway between the intestinal microbiota, enteric nervous system and the brain – plays a key role in regulating bowel motility and sensitivity. Disruption of this axis, whether through microbial imbalance, inflammation or stress-related changes in neural signalling, can slow intestinal transit and contribute directly to constipation.

Two types of constipation

Typically, there are two main types of constipation:

• Slow-transit constipation – where stool moves too slowly through the colon.
• Defecatory dysfunction – where your stool consistency may be normal, but coordination of the pelvic floor muscles prevents proper elimination.

Managing slow-transit constipation

The foundation of management includes:

• Hydration – drinking sufficient water to support bowel function.
• Dietary fibre – from whole grains, legumes, fruits and vegetables and fibre as it helps create bulk and stimulates movement.
• Physical activity – movement encourages gut motility. 

Managing defecatory dysfunction

This form of constipation requires a different approach, and physical positioning during bowel movements can make a notable difference. A simple, practical tip is to elevate your legs into a crouching position, using a stool, which helps ease bowel movements.

The mediterranean diet and constipation

Diet plays a pivotal role in both constipation management, and the Mediterranean diet is particularly valuable [2].

This dietary pattern is, broadly speaking:

• high is fibre-rich foods such as legumes, fruits, vegetables and whole grains
• rich in fish, olive oil, nuts and seeds, providing healthy fats and antioxidants
• low in red and processed meats, with moderate intake of poultry and dairy

One of the best ways to work out if you are following a Mediterranean-style diet is to keep a food diary (3-7 days) and to ask a Nutritional Therapist for a Dietary Evaluation. 

Benefits of the mediterranean diet

Evidence suggests that the Mediterranean diet has several benefits for people with constipation:

• Improves constipation through fibre fermentation into short-chain fatty acids, which have anti-inflammatory properties.
• Reduced risk of other diseases, such as heart disease and neurological conditions, in those who adopt the diet, even when aged over 65 [3].

The gut microbiome and gut-brain axis

Science tells us so far that targeted, strain-specific probiotics may provide some benefit for constipation. However, a healthy, diverse diet remains more effective for microbiome health than probiotics alone. Probiotics may help with constipation in some individuals, but they are not a replacement for dietary changes and physical activity.

Other dietary and lifestyle considerations

Long-term stress, however, is known to reduce microbiome diversity and increase inflammation. Stress management strategies such as meditation or relaxation techniques may therefore be beneficial. A diet high in refined sugar and low in fibre harms microbiome diversity and promotes inflammation. Thus, reducing processed foods and added sugars is advised.

Antibiotics can also impact microbiome health. However, while antibiotics may temporarily disrupt gut bacteria, they are sometimes necessary for conditions such as an infection. However, there are certain probiotics that can be taken alongside antibiotics that might reduce some of the negative side effects.

Comprehensive stool testing, constipation and the gut-brain axis

Advanced stool testing can provide valuable insights for those struggling with constipation. Beyond identifying pathogens or inflammation, these tests assess how well digestion and absorption are functioning and whether microbial imbalances might be slowing gut motility.

For constipation, this is particularly important, as an altered microbiome can reduce short-chain fatty acid production, weaken the intestinal barrier, and contribute to systemic inflammation. The link to the brain is equally relevant. Research shows that changes in the microbiome can influence the gut-brain axis, affecting not only bowel function but also mood and cognition. 

By using advanced microbiome testing methods such as metagenomics, microbiome analysts can detect species-level imbalances and identify function disruptions that may underlie chronic constipation. This helps to create more personalised strategies – addressing both digestive health and the wider neurological effects that constipation can have.

References

1. Barberio B, Judge C, Savarino EV, Ford AC. Global prevalence of functional constipation according to the Rome criteria: a systematic review and meta-analysis. Lancet Gastroenterol Hepatol. 2021 Aug;6(8):638-648. doi: 10.1016/S2468-1253(21)00111-4. Epub 2021 Jun 4. PMID: 34090581.
2. Xu C, Lin YH, Yu XC, Huang GB, Hu JY, Shen H, Li CC. Association of Mediterranean Diet Adherence With Chronic Constipation and Chronic Diarrhea: Findings From NHANES. Food Sci Nutr. 2025 Aug 13;13(8):e70809. doi: 10.1002/fsn3.70809. PMID: 40822527; PMCID: PMC12351127.
3. Furbatto M, Lelli D, Antonelli Incalzi R, Pedone C. Mediterranean Diet in Older Adults: Cardiovascular Outcomes and Mortality from Observational and Interventional Studies-A Systematic Review and Meta-Analysis. Nutrients. 2024 Nov 19;16(22):3947. doi: 10.3390/nu16223947. PMID: 39599734; PMCID: PMC11597443.