Introduction

Do you ever feel like your stomach's always acting up, causing pain and discomfort and making your bathroom routine unpredictable? If so, you might be experiencing Irritable Bowel Syndrome (IBS), where these symptoms become part of your daily life. IBS stands as one of the most frequently diagnosed gastrointestinal conditions, impacting approximately 9% to 23% of the global population.^1,3 In the United Kingdom (UK), a formal diagnosis of IBS accounts for 4.8%, while 7.8% remain undiagnosed. Collectively, these figures represent 12% of the UK population affected by the condition.²

IBS is a common digestive system condition, often chronic, capable of significantly impacting one’s daily life. You may experience cramps, bloating, diarrhoea, and constipation, all of which can be quite uncomfortable.⁴ This article will explore what causes IBS and what symptoms to look out for. 

Causes of irritable bowel syndrome 

The exact cause of IBS is not known - IBS is a complex condition with multiple potential contributing factors.

Infection³

• 10% of individuals with IBS suspect their IBS began after an infection. 
• Intestinal infections (3-36%) can lead to ongoing new IBS symptoms. 
• Viral gastroenteritis typically leads to temporary symptoms. Bacterial gastroenteritis, protozoan, and helminth infections result in extended periods of post-infectious IBS. 
• Following an infection, the gut may have persistent inflammation, altered immune responses, and disrupted balance of bacteria in the gut, potentially leading to symptoms of IBS. Risk factors include how severe the initial illness was, the type of bacteria involved, smoking, the female gender, and experiencing depression or stressful events.

Abnormal gastrointestinal motility⁵

• Individuals with IBS experience elevated irregular movement or passage through the colon. 
• IBS may stem from disruption in brain-gut interaction, impacting bodily functions and leading to symptoms like altered bowel movements and increased sensitivity to normal gut content. Problems with this interaction can cause food to move through your digestive system too fast or too slow while also triggering pain sensations in response to levels of gas or stool in the gut.
• Serotonin levels are vital in regulating gut movement, sensation and secretion. Fluctuation in serotonin levels can lead to symptoms like constipation and diarrhoea. 

Intestinal inflammation^3,6

• Inflammation and immune system issues might contribute to IBS.
• Increased activity of immune system cells (i.e. mast cells) in the gut could be linked to gut sensitivity. 
• Infections like gastroenteritis may cause inflammation throughout the body and change gut bacteria, sustaining inflammation. 
• In addition, nerves in the gut might also become inflamed, affecting hormone and gene functioning. 
• These factors may lead to more inflammation throughout the body, an imbalance in hormones, and disruptions in serotonin function, which could worsen IBS symptoms. 

Microbial imbalance in the gut^7,8

• Gut host-microbial interaction, the way the gut interacts with the bacteria inside it may be a key factor in causing IBS. 
• The gut microbiota helps with digestion, maintaining gut health and protection against harmful germs. Imbalances in the gut microbiota, known as dysbiosis, can occur for various reasons such as the overgrowth of certain organisms. This imbalance in gut bacteria can result in inflammation and heightened gut permeability. This can have a particularly significant impact on individuals with IBS.

Psychological distress^1,3 

• Psychological distress, such as stress, anxiety and depression, may significantly contribute to the development of IBS.
• This psychological distress has the potential to worsen gastrointestinal symptoms, amplifying the severity of issues like diarrhoea and abdominal discomfort. 
• Furthermore, it can trigger an immune response in individuals with IBS, which could be important in developing the condition. 

Food sensitivities or intolerances³

• Given the complexity of IBS symptoms, it’s challenging to draw definitive conclusions from studies. However, it’s worth noting fat intake and certain carbohydrates, like FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides and polyols), can contribute to worsening gastrointestinal symptoms. 
• Additionally, certain individuals may find that particular foods can worsen their symptoms. 

Poor dietary habits⁹

• Studies have found that people with IBS tend to have more irregular eating habits compared to those without the condition. These studies suggest that irregular eating habits may influence colonic motility (i.e. how the gut moves food along the gut),  potentially contributing to the manifestation of IBS symptoms. 
• Research found that women who binge eat, regardless of their weight, have a 2-4 times higher risk of experiencing IBS symptoms. This suggests that eating large meals could worsen and trigger gastrointestinal issues in people with IBS.

Excessive intake of certain foods (e.g., caffeine, alcohol)

• Caffeinated coffee has been shown to increase gastric acid secretion and colonic motor activity. Consumption of coffee has been associated with worsened symptoms in some people with IBS.⁹ Though there is conflicting evidence, with some studies suggesting that drinking coffee may decrease the risk of developing IBS, other research indicates that consuming coffee and caffeine is associated with a higher likelihood of having IBS. This association appears particularly pronounced among women and individuals with higher body mass index.^10,11
• Alcohol impacts gut function by altering movement (i.e. how things move inside the gut), nutrient absorption, and barrier permeability (i.e. how easily substances pass through its walls). This affects your gut’s overall function.⁹ The impact of different alcohol consumption patterns on gastrointestinal symptoms, especially in individuals with IBS, is still uncertain. However, it is suggested that excessive alcohol consumption, rather than light to moderate intake, seems to influence gastrointestinal symptoms in women with IBS.¹²

Other factors

IBS could also arise from a combination of genetic, environmental and dietary factors.¹³

Symptoms of irritable bowel syndrome^1,3,5,14

You may encounter the symptoms listed in the table below, and the frequency or alteration in your bowel movement can vary based on the type of IBS you’re diagnosed with. 

Summary

• IBS can arise from various factors such as infections, disruptions in brain-gut communication and dietary habits. 
• Symptoms often include abdominal pain, changes in bowel habits, bloating and pain. 
• Understanding these factors can aid in identifying triggers and managing symptoms effectively. 
• Seeking medical advice is essential for individuals experiencing symptoms of IBS, as proper diagnosis is crucial for effective management.
• Healthcare professionals can provide personalised treatment plans, dietary advice, and lifestyle modifications tailored to each individual's needs, improving their quality of life and symptom control.
• Despite the challenges IBS poses, ongoing research offers hope for a better understanding and management of the condition in the future.

FAQs

What is the main cause of IBS?

The exact reason why IBS develops isn't fully understood. Still, it's thought to be linked to several factors like infections, how the brain and gut communicate, certain chemicals in the body, inflammation in the intestines, immune system reactions, imbalances in the gut's bacteria, sensitivity to certain foods, and unhealthy eating habits. It's likely a combination of genetics, environment, and diet.

What are the symptoms of IBS flare-ups?

During an IBS flare, you may experience the following symptoms: cramping, abdominal discomfort or pain, bloating, diarrhoea or constipation.