Irritable Bowel Syndrome (IBS) and Small Intestinal Bacterial Overgrowth (SIBO) are two distinct yet often interconnected conditions that can significantly impact digestive health. Here’s how these conditions arise and why supporting vagus nerve function is central to treatment.

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What is IBS?

IBS is a functional gastrointestinal disorder characterized by symptoms such as abdominal pain, bloating, and irregular bowel habits (diarrhoea, constipation, or both). Unlike structural digestive diseases, IBS doesn’t damage the digestive tract directly but is largely related to dysregulated gut-brain signalling, in which the vagus nerve plays a significant role.

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What is SIBO?

SIBO involves an excessive growth of bacteria in the small intestine, which can lead to malabsorption, bloating, pain, and other digestive disturbances. The bacteria involved, such as Escherichia coli, Klebsiella, and Aeromonas, produce gases and other byproducts that exacerbate symptoms and create an environment of imbalance within the gut microbiome. These bacteria often proliferate in response to the need for toxin bioremediation, a process that the vagus nerve typically helps regulate through its role in maintaining motility and immune function.

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These bacteria—while associated with negative health symptoms like diarrhoea—are also known for their bioremediation abilities:

• Escherichia coli can help detoxify cadmium, chromium, copper, lead, and mercury.

• Klebsiella species assist in breaking down phthalates, NSAIDs, pesticides, PAHs, lead, arsenic, mercury, and sodium lauryl sulphate.

• Aeromonas species contribute to detoxifying copper, nickel, chromium, arsenic, and mercury.

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Interestingly, the gases commonly associated with SIBO, such as hydrogen and methane, may not be entirely detrimental. Hydrogen gas has shown protective effects on the intestinal lining through antioxidant mechanisms, while methane gas appears to protect human tissues in low-oxygen environments.

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The Vagus Nerve and Gut Health

The vagus nerve is responsible for numerous gut functions, including stimulating digestion, bile secretion, pancreatic enzyme release, and maintaining intestinal motility. When the vagus nerve is compromised—due to factors such as toxicity, physical compression, medication side effects, or surgeries impacting its pathways—the gut can suffer. Reduced vagal tone leads to decreased motility and weakened immune responses, creating a favourable environment for the development of IBS and SIBO symptoms.

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In cases of vagal dysfunction, toxins may accumulate in the small intestine, which can lead to damage in the intestinal lining and vagal receptor sites. This damage prompts bacterial species specializing in toxin bioremediation to proliferate as part of an attempted repair mechanism. However, this bacterial overgrowth further reduces motility due to the loss of sensory and motor neuron function, allowing toxins to accumulate and perpetuate epithelial damage.

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Treatment Through Vagus Nerve Support

Treating IBS and SIBO by supporting the vagus nerve can be highly effective, as it restores the nerve’s ability to modulate gut function, encourage motility, and support healthy microbial populations. Treatment focuses on enhancing vagal tone through detoxification practices, reducing physical compression on the nerve, and employing supportive therapies that stimulate vagal function.

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By prioritizing vagus nerve health, we can address the root dysfunctions contributing to IBS and SIBO, moving beyond symptom management to restore gut function and resilience in a natural and holistic manner.