SIBO and Stress: Is it Beneficial or Harmful?

In the modern lifestyle, stress is being an omnipresent part of our life. Literally, stress denotes emotional or mental stress and physiological or physical stress. In a stressful event, our body likely responds with sympathetic nervous system, release of various hormones and helps us to act accordingly. Although, stress can be helpful to cope up with an unexpected event or perform better in certain situations, prolonged stress can likely cause or aggravate several medical conditions such as high blood pressure, lack of energy, anxiety, emotional and behavioral problems and Small Intestinal Bacterial Over growth (SIBO).

In this article, we would like to point out the irrefutable links between stress and SIBO.

What is SIBO?

If you get stressed, the non-essential body functions including digestive and immune system can slow down a bit to divert our body’s response on blood circulation, alertness, muscle use and rapid breathing. It is common for all to experience a stomach upset after a stressed event. You may have suffered lack of appetite in depressed situations. This is because our brains ‘chemically’ communicate or ‘talk’ with our gut in stress via gut-brain axis. These chemical reactions can affect the digestive health by altering the levels of certain good bacteria present in our gut.

For this we have to understand that our lining of the gut comprises of billions of bacteria that can be helpful as well as harmful. If there are good ones then they develop our immune system, regulate autoimmunity and prevent allergies. But if the bacteria are bad that it can cause inflammation, auto immune disease and lot more. Healthy people’s gut contains a variety of bacteria (microbiome) which remains the same for years. However, persistent stress can adversely affect gut bacterial composition and cause deleterious health effects including SIBO.

SIBO is a condition in which an individual have too much of normal gut bacteria or bad bacteria in the small intestine. Normally, a variety of bacteria are present in the large intestine, though SIBO is referred to bacterial overgrowth in the small intestine. Although, SIBO can be treated with antibiotics, the recurrence is not uncommon.

Stress and SIBO: Unraveling the links

Even with medical breakthroughs, stress cannot be measured or marked with a threshold level. Surprisingly, one man’s stress is another’s de-stressor. For example a teenager loves loud rap music at full bass but the same is very stressful for a kid, old people or any other teenager who has no taste for that sort of music. In such case, the kid may suffer emotional or mental stress.

In most of the cases of SIBO, stress is the likely cause. SIBO and stress goes hand in hand, in which, one feeds the other and the sufferer is likely get caught in a vicious cycle. Prolonged or untreated stress can likely make SIBO to come back even after it is treated. SIBO can also cause stress by gut-brain axis communication.

According to a study conducted on Russian astronauts revealed that the number of intestinal Lactobacillus bacteria gradually decreased as the launch day was coming close. This is a classical example of psychological stress and this alteration suggests that the physiological stress hampers the number of good bacteria in our gut. Also to be noted is that the good bacteria keeps the harmful bacteria numbers in check and when the good bacteria decreases it is natural that the opportunistic bad bacteria can occupy (colonize) the small intestine, multiply rapidly and cause infectious disease.

Another example to show the effect of physical stress on gut microbiome is – if we exercise or have a long-walk after a long sedentary stage, we will likely suffer with leg cramps and pain in the same day night or at least next day with delayed or missed bowel movement on the next day. Our body can get accustomed to these physical activities only if start and go gradually. This is the body’s natural response to a physical stress.

This is because the blood needed for proper assimilation of the food and the normal migrating motor complex (MMC) waves of the gut get affected by such abrupt activity which the body is not used to.

Our gut’s primary response to stress can vary; but mostly results in SIBO.

  • Stress can elicit certain inflammatory response (chronic achlorhydria) in the gut that reduces stomach acid levels and leads to SIBO. Low stomach acid can aid growth or colonization of disease-causing bacteria (bad bacteria) and cause SIBO
  • Stress can induce gut motility or leaky gut that contributes to gut microbiome alterations, bad bacteria proliferation and SIBO.
  • Stress can cause intestinal barrier dysfunction and enhance the uptake of bad bacteria from the intestinal lumen. These events can contribute to the development of SIBO.
  • Stress can weaken our immune system and cause infection, which is often treated with antibiotics. Antibiotics don’t differentiate good and bad bacteria. It kills both and paves a pathway for growth of bad bacteria (antibiotic-resistant bacteria) and cause SIBO.

After learning these facts, it is clear that gut and brain is a two-way communication. To cure SIBO, taking antibiotics, probiotics and diet modifications cannot cure the underlying problem, without recurrence. Stress management is the key.

Stress, Sympathetic Nervous System, MMC and SIBO

Medically speaking, our nervous system is classified into two types such as autonomous and parasympathetic nervous system. The former involves in regulation of involuntary actions while the latter’s function is to maintain optimal balance of body function (homeostasis) and stimulation of body’s fight or flight response in a stressed situation.

One of the vital functions of the parasympathetic nervous system is to facilitate the body’s ‘rest and digest’ function, which is inversely related to fight-or-flight response in stressed condition. Meaning, if the body’s fight or flight response gets activated, the ‘rest and digest’ function will be halted. Prolonged stress can cause persistent shift to this negative condition can potentially contribute to bacterial overgrowth in the small intestine which is commonly referred as SIBO.

We have concrete evidence to show you that stress can delay nervous system-dependent gastric emptying and colonic motility. These negative effects are often caused either by increased sympathetic pathways or reduced parasympathetic pathways.

Studies have shown that exposure to even loud noise has resulted in sound-induced stress and delayed gastric (phase III) MMC in the experimental animals. Phase III is regulated by vagus nerve and its activity is suppressed in sound-induced stress. These negative effects can be potentially modulated by butyric acid treatment.

MMC is generally characterized by presence of gastrointestinal contractions in the inter-digestive state. In our normal life, gastric MMC often acts as mechanical and chemical cleanser of the empty stomach that can help us to prepare for the next meal. Impaired gastric phase III activity can cause retention of fecal materials in our stomach and increase the risk of bacterial overgrowth. In addition to this, impaired gastric MMC can severely affect our intestinal health and cause acid secretion abnormalities after a meal. It is now clear that absence of inter-digestive MMC, acid secretion and delayed gastric emptying can contribute to bacterial overgrowth in the small intestine.

Ways to attenuate Stress Response

  1. Probiotics for stress – Are they really helpful?


We have convincing clinical evidences to show that probiotics are beneficial against certain gastrointestinal problems including inflammatory bowel syndrome which is a predisposing factor for SIBO.

Surprisingly, probiotics can offer supportive benefit (adjuvant) in reducing stress response and anxiety as well as mood improvement in chronic fatigue and IBS patients. Recently it has been shown that a combination of certain bacteria such as Lactobacillus helveticus and Bifidobacterium longum can reduce anxiety, stress and stress-related hormones such as cortisol. Although, the mechanism of action is not completely understood, probiotics did decrease oxidative stress, inflammatory biomarkers such as cytokines and BDNF, improve nutritional status and correct SIBO in major depressive disorder patients.

The above said probiotic bacteria are not the exhaustive list. In experimental studies,

Lactobacillus reuteri has been shown to have immunomodulatory benefits to fight infection including gut infection, reduce anxiety and stress-induced cortisone elevation.

A study published in psychoneuroendocrinology study has suggested that normal (good) intestinal bacteria play an important role in stress response mechanism. Reduced colonies of normal gut microbiome can promote colonization of bad bacteria such as Escherichia coli, which is a known activator of HPA and causative of stress. The same study suggests that probiotics treatment has blunted HPA response, lowered stress and normalized intestinal permeability/motility as well.

A study that looked into the effect of probiotic supplementation in stressed experimental animals has found that stress hormones appeared to cause inflammation of the gut lining with remarkable reduction of normal gut bacteria. These symptoms mimic the inflammatory bowel disease. Probiotic supplementation has reduced the inflammation and improved the clinical symptoms.

Based on the available evidence-based research study results, we can clearly understand that probiotics can influence microbiome-gut-brain axis and reduce stress. In future, the medical community would focus of gut and gut microbiome to treat stress and related medical problems.

  1. Soluble and insoluble fiber to combat oxidative stress

High Fiber Foods

Dietary fibers such as soluble and insoluble fiber are generally ‘gut-friendly’ substances that serve as an important food source for intestinal bacteria.

One bacterial species feeds on this fiber and converts it into certain chemical substances that serve as a food source for another bacterial species. Henceforth all the species of bacteria are inter-dependent on each other while having a beneficial effect on the host. One of the substances created when the bacteria feed on fiber is butyrate. Butyrate is known to attenuate stress response and inflammatory bowel disease and even fight certain cancer by repairing the damaged cells in the colon.

  1. Butyrate and oxidative stress

Butyrate is a modulator of inflammatory disease process that is associated with cancer development and progression. In most of the cases, oxidative (physiological) stress is the predominant cause of cancer development.

Oxidative stress is an essential part of normal life cycle but has a threshold level. Upon exposure to various noxious stress factors, oxidative stress can occur as a result of imbalance between the generation of reactive oxygen species (OCl, H2O2 etc) and antioxidant defense mechanisms that results in a cascade of biomolecular (lipids, proteins and DNA) breakdown and irreversible damage to cell structure. Biologically, DNA damage is considered to be the predominant causative of cancer development.

Although, the complete molecular mechanism is not completely understood, mounting evidences have shown that butyrate can attenuate oxidative stress by reducing H2O2-mediated DNA damage. Butyrate may also prevent oxidative stress by facilitating DNA repair system enzymes and increasing antioxidants levels inside the cell compartments.

Butyrate may also enhance the protection against oxidative stress-induced damage in mucosa by influencing DNA repair systems or by increasing the activity of antioxidant enzymes and intracellular antioxidants.

  1. Butyrate and colonic defense barrier

Besides anti-cancer property, butyrate also possesses beneficial chemicals that enhance the intestinal barrier protection against bad bacteria infection. Reduced intestinal mucous thickness can cause bacterial colonization and SIBO. Experimental studies has shown that butyrate increase mucous production and thickness and reduce the risk of colon infection.

Some of the chemical components of the colonic defence barrier that are involved in the maintenance of the colonic barrier, which may be influenced by butyrate are mucins, transglutaminase, antimicrobial peptides and heat shock proteins (HSPs).

Studies that employ human cancer cell models have shown that butyrate can rapidly repair mucosal damage and re-establish epithelial barrier. With this property, butyrate can prevent bacterial colonization and SIBO.

Taken together, butyrate can prevent inflammatory process in the intestine as well as bacterial infection.

Bottom line

SIBO is not just an intestinal disease but a brain-dependent disease. Physical and mental disorder can deleteriously affect the digestive health by increasing the risk of developing SIBO. Even if you treat SIBO it can likely return upon the exposure to stressors. If you still cannot avoid getting stressed due to nature of job or living environment, practice stress management techniques and take probiotics to reduce the risk of getting SIBO.

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