Irritable Bowel Syndrome: The Science Behind the Symptoms and Daily Life

 The information presented in this article is based on the comprehensive review “Recent developments in the pathophysiology of irritable bowel syndrome,” published in 2015 in the World Journal of Gastroenterology (Volume 21, Issue 25, Pages 7621–7636). The author of the publication is Professor Magdy El-Salhy, a consultant gastroenterologist at the Department of Gastroenterology, Stord Hospital, Norway, and a researcher at the University of Bergen. Professor El-Salhy is a leading expert in the field of functional gastrointestinal disorders and neuropeptide regulation of intestinal function, with numerous scientific publications on irritable bowel syndrome (IBS).

This material provides the most important, up-to-date, and evidence-based information on IBS, which can be useful for patients and their families. It answers frequently asked questions about diagnosis, subtypes, the impact on quality of life, risk factors, and dietary habits.

“IBS is not just an upset stomach—it’s a multifaceted disorder involving our genes, diet, and microbiome.”

Scientific Consensus on Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders, significantly affecting patients’ quality of life and placing a burden on the healthcare system. Despite a large volume of research, the exact cause of IBS remains unclear, and no definitive treatment currently exists. However, in recent years, several key interacting factors have emerged: genetic predisposition, dietary habits, gut microbiota composition, low-grade inflammation, and abnormalities in gastrointestinal endocrine cells.

Here, you'll find five expert insights and scientific findings to help patients and their loved ones navigate the latest scientific understanding of IBS. Each quote or scientific conclusion is accompanied by a clarifying question or heading.

1. What is the role of genetics and social learning in IBS?

“There is evidence that several factors play a central role in the pathophysiology of IBS, such as genetic/social learning factors, diet, the intestinal microbiota, low-grade chronic intestinal inflammation, and abnormal gastrointestinal endocrine cells.”

Explanation: Genetics and the family environment have a measurable influence—children of parents with IBS are at higher risk of developing the condition. Social learning—how close relatives respond to pain and illness—also plays a role.

2. What is the relationship between diet and IBS symptoms? Can certain diets help?

“There is no convincing evidence that IBS patients suffer from food allergy/intolerance, with the effect exerted by diet seemingly caused by intake of poorly absorbed carbohydrates and fiber. ... FODMAPs have been found to trigger gastrointestinal symptoms in IBS, and a low-FODMAPs diet reduces symptoms and improves the patient’s quality of life.”

Explanation: Despite popular beliefs about allergies, the real issue often lies in poorly absorbed sugars (FODMAPs) found in many foods. The low-FODMAP diet is one of the most recommended strategies by gastroenterologists.

3. What role does the gut microbiota play in IBS? Can changes in it affect symptoms?

“Differences in the microbiota between IBS patients and healthy controls have been reported, but the association between IBS symptoms and specific bacterial species is uncertain. ... However, contradictory results have been reported, decreased levels of lactobacilli and bifidobacteria, and increased levels of anaerobic bacteria such as streptococci and Escherichia coli, as well as increased ratios of Firmicutes, Bacteroidetes, and Clostridium species have been confirmed in several studies.”

Explanation: The gut microbiome in IBS patients is indeed different, but science has not yet clearly identified which changes matter most. Probiotics and personalized diets remain an active area of research.

4. Is there “inflammation” in IBS, and what does that mean?

“The research performed to date provides compelling evidence that low-grade inflammation occurs in a subset of IBS patients, namely those with PI-IBS, but not in those with non-PI-IBS. PI-IBS represents a considerable proportion of IBS patients, with an incidence of 7%-31% among IBS patients. Thus, low-grade inflammation plays a significant role in the pathophysiology in a subset of IBS patients.”

Explanation: In some people, IBS develops after a gastrointestinal infection. In these cases, low-grade chronic inflammation is found and may be responsible for the symptoms.

5. What are the abnormalities in gut endocrine cells in IBS, and why does that matter?

“There is compelling evidence that genetic factors, diet, the intestinal microbiota, and mucosal low-grade inflammation play a major role in the pathophysiology of IBS. These factors are known to affect the gastrointestinal endocrine cells, with the densities of intestinal endocrine cells being reduced in IBS patients. The abnormalities in the gastrointestinal endocrine cells can explain the visceral hypersensitivity, disturbed gastrointestinal motility, and abnormal gut secretion observed in IBS patients.”

Explanation: Endocrine cells in the gut produce hormones that regulate sensations, motility, and secretions in the GI tract. A reduced number of these cells is a hot topic in current research and is linked to many of the core symptoms of IBS.

Questions and Answers

1. Can IBS be diagnosed with a specific test or analysis?

Answer: Currently, there is no specific diagnostic test or lab analysis that can definitively confirm irritable bowel syndrome (IBS). The diagnosis is based on symptoms and by ruling out other diseases. That’s why IBS patients often go through more medical exams, testing, and medication use than individuals without this condition.

2. Are there different types of IBS, and how are they different?

Answer: Yes, IBS is divided into three main subtypes based on predominant symptoms:

• IBS with predominant diarrhea (IBS-D)

• IBS with predominant constipation (IBS-C)

• Mixed IBS (IBS-M), where diarrhea and constipation alternate

This classification helps doctors recommend more appropriate treatment based on the specific subtype.

3. How does IBS affect quality of life and daily functioning?

Answer: IBS significantly reduces quality of life—patients often suffer from abdominal pain, bloating, and irregular bowel movements. These symptoms lead to missed work, lower productivity, and a substantial economic burden on both patients and society. In addition to the physical discomfort, IBS has clear social and economic impacts.

4. Are there risk groups and hereditary factors for IBS?

Answer: Yes, there is a well-established hereditary component—about 33–37% of people with IBS have a family member with the condition. The likelihood of developing IBS is higher if a parent or close relative has it. Social and behavioral factors within the family also play a role—how pain and illness were handled during childhood can influence IBS development later in life.

5. Can weight and eating habits change with IBS?

Answer: People with IBS often avoid certain foods because they associate them with triggering symptoms. However, there's no evidence they consume fewer calories, proteins, or fats than the general population. Data on the relationship between IBS and body weight (BMI) are mixed—some patients are of normal weight, others are overweight, and some may be underweight. Nonetheless, malnutrition is not considered a common problem in IBS.

Conclusion

In conclusion, current scientific evidence presented by Prof. El-Salhy confirms that irritable bowel syndrome (IBS) is a complex condition with multifactorial causes and manifestations. Although there is still no specific lab test or universal treatment, understanding the IBS subtypes, the role of heredity, diet, and its impact on daily life enables patients to manage their condition more effectively. Ongoing scientific research offers hope for more precise diagnostic tools and personalized therapeutic approaches in the future.

Source: El-Salhy M. Recent developments in the pathophysiology of irritable bowel syndrome. World J Gastroenterol 2015; 21(25): 7621–7636. DOI: 10.3748/wjg.v21.i25.7621