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The Underlying Factors That May Cause IBS-D

Diarrhea is one of the symptoms that can occur along with IBS. Other symptoms that can occur include abdominal pain, intestinal gas, and nausea.

If you are living with diarrhea-predominant IBS, it is important to know that there may be an underlying cause. This article will explore some of the underlying factors that can contribute to IBS-D.

Diet for IBS

When you eat a meal, it stimulates a set of reactions that facilitate the processing and absorption of food through the gut. These processes are complex and coordinated through neurons (or the nervous system), hormones, and the immune system via communication between the gut and the brain.1

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The relationship between IBS and diet is not fully understood but can contribute to IBS-D in the following ways:1

  • Alterations in the gut microbiome (which is the ecosystem of bacteria and other organisms that live in our gut).
  • Inflammation which leads to intestinal permeability. This phenomenon is also called ‘leaky gut’ where bacteria and toxins leak through the small gaps of the intestinal wall.
  • Food sensitivities can contribute to microbiome imbalances and can also disrupt the communication between the gut and the brain.

Increased transit time

The gastrointestinal tract is partially controlled by the enteric nervous system, which uses chemicals such as serotonin to alter motility. Motility is the contraction of muscles that mix and move contents along the intestine, influencing absorption, immune function, and even blood flow.1

Alterations in serotonin signaling have been reported in people with IBS-D, which results in changes such as increased transit time through the intestine and increased contractions.1

Organ hypersensitivity

Visceral or organ hypersensitivity is another phenomenon that occurs in IBS-D patients.1 Visceral hypersensitivity is the term used to describe the sensation of pain from internal organs (known as viscera). And is a feature of IBS, however it should be noted that not all IBS patients experience it.

Visceral hypersensitivity can occur because of the sensitization of neurons and possibly also inflammation that occurs because of microbiome changes.1 Communication between the central nervous system and the enteric nervous system, which is the cross-talk that happens between the brain and the gut, may also be implicated in IBS-D.1

Gut bacteria (microbiome)

The microbiome is responsible for a range of functions in the gut. These functions range from the structure, metabolism, and immune health.1

Because of the array of functions the gut microbiome performs, when it’s disrupted or becomes imbalanced it causes problems in a number of areas such as; changes to the brain-gut cross-communication, immune health and contributes to symptoms of IBS-D.1

In fact, there is a good amount of evidence that supports the role of the gut microbiome in the development of IBS-D.1 Often people with IBS-D have altered microbiome composition and diversity compared to those without IBS-D.1

What else could it be?

It’s always best to see a doctor to rule out any serious underlying conditions such as inflammatory bowel disease, Clostridium difficile overgrowth, Celiac disease, or cancer.

If there is persistent diarrhea without any explanation, it could be bile acid malabsorption or small intestine bacterial overgrowth:

Bowel symptoms such as persistent diarrhea can occur when your intestines don’t absorb bile acids properly. Bile is a natural substance which your body makes in the liver. Bile is stored in the gallbladder and released when you eat. The acids in the bile help break down food so your body can absorb it. Diarrhea can happen if your bile acids aren’t being reabsorbed properly.

Small intestine bacterial overgrowth (SIBO) may also be the cause. SIBO occurs where there are too many bacteria in the small intestine which leads to malabsorption and diarrhea.

If you’re looking for answers, it’s best to work with a qualified health professional to find the root cause.

Yours in health,
Meredith

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