SIBO, IBS, and Constipation: Unrecognized Thiamine Deficiency?

 by Elliot Overton, DipCNM CFMP

In many of my clients, chronic upper constipation and gastroesophageal reflux disease (GERD) are misdiagnosed as bacterial overgrowth. Unfortunately, they are often non-responsive to antimicrobial treatments. Yet, sometimes the issues are fixed within a few days of vitamin B1 repletion. This has shown me that often times, the small intestinal bacterial overgrowth (SIBO) is simply a symptom of an underlying vitamin B1 or thiamine deficiency.

GI Motility and Thiamine

The gastrointestinal (GI) tract is one of the main systems affected by a deficiency of thiamine. Clinically, a severe deficiency in this nutrient can produce a condition called “Gastrointestinal Beriberi”, which in my experience is massively underdiagnosed and often mistaken for SIBO or irritable bowel syndrome with constipation (IBS-C). The symptoms may include GERD, gastroparesis, slow or paralysed GI motility, inability to digest foods, extreme abdominal pain, bloating and gas. People with this condition often experience negligible benefits from gut-focused protocols, probiotics or antimicrobial treatments. They also have a reliance on betaine HCL, digestive enzymes, and prokinetics or laxatives.

To understand how thiamine impacts gut function we have to understand the GI tract. The GI tract possesses its own individual enteric nervous system (ENS), often referred to as the second brain. Although the ENS can perform its job somewhat autonomously, inputs from both the sympathetic and parasympathetic branches of the autonomic nervous system serve to modulate gastrointestinal functions. The upper digestive organs are mainly innervated by the vagus nerve, which exerts a stimulatory effect on digestive secretions, motility, and other functions. Vagal innervation is necessary for dampening inflammatory responses in the gut and maintaining gut barrier integrity.

The lower regions of the brain responsible for coordinating the autonomic nervous system are particularly vulnerable to a deficiency of thiamine. Consequently, the metabolic derangement in these brain regions caused by deficiency produces dysfunctional autonomic outputs and misfiring, which goes on to exert detrimental effects on every bodily system – including the gastrointestinal organs.

However, the severe gut dysfunction in this context is not only caused by faulty central mechanisms in the brain, but also by tissue specific changes which occur when cells lack thiamine. The primary neurotransmitter utilized by the vagus nerve is acetylcholine. Enteric neurons also use acetylcholine to initiate peristaltic contractions necessary for proper gut motility. Thiamine is necessary for the synthesis of acetylcholine and low levels produce an acetylcholine deficit, which leads to reduced vagal tone and impaired motility in the stomach and small intestine.

In the stomach, thiamine deficiency inhibits the release of hydrochloric acid from gastric cells and leads to hypochlorydria (low stomach acid). The rate of gastric motility and emptying also grinds down to a halt, producing delayed emptying, upper GI bloating, GERD/reflux and nausea. This also reduces one’s ability to digest proteins. Due to its low pH, gastric acid is also a potent antimicrobial agent against acid-sensitive microorganisms. Hypochlorydria is considered a key risk factor for the development of bacterial overgrowth.

The pancreas is one of the richest stores of thiamine in the human body, and the metabolic derangement induced by thiamine deficiency causes a major decrease in digestive enzyme secretion. This is one of the reasons why those affected often see undigested food in stools. Another reason likely due to a lack of brush border enzymes located on the intestinal wall, which are responsible for further breaking down food pre-absorption. These enzymes include sucrase, lactase, maltase, leucine aminopeptidase and alkaline phosphatase. Thiamine deficiency was shown to reduce the activity of each of these enzymes by 42-66%.

Understand that intestinal alkaline phosphatase enzymes are responsible for cleaving phosphate from the active forms of vitamins found in foods, which is a necessary step in absorption. Without these enzymes, certain forms of vitamins including B6 (PLP), B2 (R5P), and B1 (TPP) CANNOT be absorbed and will remain in the gut. Another component of the intestinal brush border are microvilli proteins, also necessary for nutrient absorption, were reduced by 20% in the same study. Gallbladder dyskinesia, a motility disorder of the gallbladder which reduces the rate of bile flow, has also been found in thiamine deficiency.

Read more: https://www.hormonesmatter.com/sibo-ibs-constipation-thiamine-deficiency/