Irritable Bowel Syndrome: Is Your Gut Microbiota to Blame?

1. What is Irritable bowel syndrome?

IBS is a chronic gastrointestinal disorder with multifactorial origins, including genetic, physiological, psychosocial, and environmental factors. It affects nearly 11% of the global population. Symptoms include recurrent abdominal pain, changes in stool frequency, and consistency. Interestingly, its prevalence varies across regions, with higher rates in affluent Asian cities, suggesting environmental factors like diet might play a role.

2. IBS & the Gut Microbiota Connection

The human gastrointestinal tract is home to trillions of microbes, collectively known as the gut microbiota. These microbes play a crucial role in our health, from developing our immune system to maintaining normal GI physiology. Recent studies have shown a connection between alterations in gut microbiota and IBS. For instance:

• Postinfectious IBS: Nearly 10% of IBS cases start after a gastroenteritis episode, leading to a type of IBS whose microbial signature resembles that of diarrhea-predominant IBS patients.

• Microbial Diversity: Some studies have shown decreased microbial diversity in IBS patients compared to healthy individuals. This decrease has also been observed in other conditions like obesity and type 2 diabetes.

3. Factors Influencing Gut Microbiota

Our gut microbiota is not static; it's influenced by various factors, which can potentially predispose individuals to IBS:

• Host Genetics: Familial patterns in IBS suggest a genetic component. Research involving monozygotic twins found greater similarity in gut microbiota profiles among twins than unrelated individuals. Another study found that the heritability contribution to IBS ranged between 0 and 57%.

• Stress: Chronic psychological stress can influence IBS onset and severity. Studies have found correlations between anxiety, depression, and IBS severity. In rodents, chronic stress models have shown significant alterations in gut microbiota composition.

• Diet: Dietary intolerance is common in IBS patients. Dietary patterns shape the gut microbial composition. For instance, protein and animal fat intake is associated with an increase in Bacteroides, while carbohydrate intake is linked to an increase in Prevotella spp. Short-term dietary changes, like the low FODMAP diet, have also been associated with improvements in IBS symptoms and changes in gut microbiota composition.

• Antibiotics: Antibiotic consumption can lead to both short-term and long-term changes in gut microbiota diversity. A study showed that intravenous injection of β-lactam antibiotics in a patient for 14 days led to significant short-term fluctuations in microbial diversity and long-term changes in microbial composition.

• Early Childhood Experiences: Events such as mode of delivery (C-section or natural) and feeding (formula or breast feeding) can influence microbiota assembly in infants. Infants delivered via C-section have a different microbiota composition than those born vaginally.

While the exact cause of IBS remains elusive, the role of gut microbiota is becoming increasingly clear. Understanding this connection can pave the way for new treatments and preventive measures.

Sources:

Bhattarai Y, Muniz Pedrogo DA, Kashyap PC. (2017). Irritable bowel syndrome: a gut microbiota-related disorder? Am J Physiol Gastrointest Liver Physiol.