Irritable Bowel Syndrome (IBS) is a chronic functional gastrointestinal disorder characterized by abdominal pain that occurs alongside changes in bowel habits [1]. It affects an estimated 5% to 15% of the Western population, which a high prevalence among women under 50 years old [1]. However, IBS can develop at any age. Despite its prevalence, IBS does not present with detectable organic or biochemical abnormalities, making diagnosis and management complex.

Common symptoms include diarrhea, constipation, a combination of these two, bloating, and abdominal pain [2]. These persistent symptoms can negatively impact an individual’s quality of life, affecting daily activities and work productivity. While the exact cause of IBS remains unclear, researchers have identified several contributing factors, including alterations in gut motility, visceral hypersensitivity, bacterial imbalances, environmental influences like diet, and disruptions in the gut microbiota, also known as dysbiosis [1].

IBS is classified based on the predominant stool pattern, following the Rome IV criteria and the Bristol Stool Chart. The subtypes include [3]:

IBS-D (Diarrhea-predominant): More than 25% loose stools and less than 25% hard stools. This is the most common subtype, affecting approximately 40% of IBS patients.
IBS-C (Constipation-predominant): More than 25% hard stools and less than 25% loose stools.
IBS-M (Mixed-type): More than 25% hard stools and more than 25% loose stools.
IBS-U (Unclassified): Less than 25% hard stools and less than 25% loose stools.

For this article, we will focus on the most predominant IBS-D (Irritable Bowel Syndrome with Diarrhea), exploring its causes, symptoms, and management strategies to help individuals better understand and cope with this condition.

Understanding IBS-D

IBS-D is characterized by loose or watery stools, urgency, and episodes of abdominal pain that are often relieved after bowel movements. These symptoms can lead to dehydration, nutrient malabsorption, and social anxiety due to the unpredictability of bowel movements.

What Causes IBS-D?

The exact cause of IBS-D remains uncertain, but researchers suggest that most cases can be due to three primary mechanisms [4]:

Food Intolerances (30-40%): certain foods, particularly those high in fermentable carbohydrates (FODMAPs), artificial sweeteners, and lactose, can trigger IBS-D symptoms by affecting gut motility and sensitivity.
Bile Acid Diarrhea (20-30%): excess bile acids in the colon can increase water secretion in the intestines, leading to chronic diarrhea. Some IBS-D patients have impaired bile acid absorption, which may contribute to the symptoms.
Disturbed Microbial Flora (15-20%): alterations in the gut microbiota, including dysbiosis and small intestinal bacterial overgrowth (SIBO), can lead to increased gut permeability, gas production, and inflammation.

Managing IBS-D: Effective Approaches

Managing IBS-D involves can be divided into nonpharmacological/natural treatment and pharmacological treatment strategies tailored to an individual’s symptoms and triggers [5].

Nonpharmacological Interventions
- Dietary Modifications: adjusting diet is one of the first line approaches to managing IBS-D symptoms:
  - Low FODMAP Diet: avoiding fermentable carbohydrates can help reduce bloating diarrhea, and abdominal pain.
  - Bile Acid Reduction: since bile acid malabsorption play a role in IBS-D, reducing dietary fat intake may help control symptoms.
  - Soluble fiber: unlike insoluble fiber, soluble fiber is able to improve stool consistency without worsening diarrhea.
- Lifestyle Changes
  - Regular Physical Activity: exercise helps regulate gut motility and reduce stress, which can exacerbate IBS-D symptoms.
  - Stress Management: mindfulness, yoga, and cognitive-behavioural therapy (CBT) have been shown to improve gut-brain interactions and symptom severity.
- Prebiotics, Probiotics, and Postbiotics
  - Prebiotics: prebiotics are food for our gut microbiota, they can modulate the composition and activity of intestinal microbiota. However, the intake dosage should be carefully monitored to avoid worsening diarrhea.
  - Probiotics: probiotics are living microorganisms which, when administered in adequate amounts, have a positive effect on the host’s health. However, as these are live bacteria, there are still possible harmful effects like infections and transfer of antibiotic resistance genes from probiotics to other microorganisms in the gut.
  - Postbiotics: emerging research suggests that inactivated bacterial strains and their metabolites may support gut barrier function and reduce inflammation. These effects may help to reduce the frequency of loose stools.
Pharmacological Interventions

Antibiotics: rifaximin is a non-absorbable antibiotic that targets gut bacteria and has been shown to reduce bloating and diarrhea in IBS-D patients.
Peripheral Opioid Agonists: loperamide, is an over the counter (OTC) antidiarrheal that slows intestinal transit and improves stool consistency.
Bile Acid Sequestrants: cholestyramine, colestipol, and colesevelam are medications that bind excess bile acids in the gut, reducing water secretion and controlling diarrhea.
Serotonin 5-HT3 Receptor Antagonists: alosetron, ondansetron, ramosetron are medications that help regulate gut motility and sensitivity by blocking serotonin receptors, reducing diarrhea and abdominal discomfort.

The Bottom Line

IBS-D is a common yet challenging gastrointestinal disorder that significantly impact daily life. It is characterized by frequent loose stools, abdominal pain, and urgency, often leading to discomfort, dehydration, and social anxiety. While the exact cause remains unclear, research suggests that food intolerances, bile acid diarrhea, and gut microbial imbalances play a major role in symptom development.

Managing IBS-D requires a personalized approach with either nonpharmacological or pharmacological interventions. Dietary modifications, such as the low FODMAP diet and bile acid reduction, along with stress management and gut microbiota support through prebiotics, probiotics, and postbiotics, can help alleviate symptoms naturally. For those with persistent or severe IBS-D, medications like antibiotics, bile acid sequestrants, and serotonin receptor antagonists offer additional therapeutic options.

Since IBS varies from person to person, there is no one-size-fits-all solution. Identifying triggers, making lifestyle adjustments, and working with your doctor, can help individuals regain control over their symptoms and improve their overall well-being.

Read more about Gut Health and Its Role in Diarrhea here: https://advagen.com/prebio/gut-health-and-its-role-in-diarrhea/

Read more about the 5R Protocol to restore gut health here: https://advagen.com/prebio/restore-gut-health-using-the-5r-protocol/

References

Altomare, Annamaria et al. “Diarrhea Predominant-Irritable Bowel Syndrome (IBS-D): Effects of Different Nutritional Patterns on Intestinal Dysbiosis and Symptoms.” Nutrients vol. 13,5 1506. 29 Apr. 2021. https://pubmed.ncbi.nlm.nih.gov/33946961/
Altomare, Annamaria et al. “Diarrhea Predominant-Irritable Bowel Syndrome (IBS-D): Effects of Different Nutritional Patterns on Intestinal Dysbiosis and Symptoms.” Nutrients vol. 13,5 1506. 29 Apr. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8146452/
Satish Kumar, Lakshmi et al. “Probiotics in Irritable Bowel Syndrome: A Review of Their Therapeutic Role.” Cureus vol. 14,4 e24240. 18 Apr. 2022. https://pubmed.ncbi.nlm.nih.gov/35602835/
Bonetto, Silvia et al. “Recent advances in the treatment of irritable bowel syndrome.” Polish archives of internal medicine vol. 131,7-8 (2021): 709-715. https://pubmed.ncbi.nlm.nih.gov/34463082/
Frissora, Christine L, and Lawrence R Schiller. “Getting the BS out of Irritable Bowel Syndrome with Diarrhea (IBS-D): Let’s Make a Diagnosis.” Current gastroenterology reports vol. 26,1 (2024): 20-29. https://link.springer.com/article/10.1007/s11894-023-00909-1

Understanding and Managing IBS-D: Causes, Symptoms, and Treatment Approaches

The Bottom Line

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References