Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome (IBS) is a group of symptoms which can be caused by a number of factors.   The symptoms of IBS include abdominal pain, bloating, with alterations in intestinal motility resulting in periodic diarrhea, constipation or both.  Mild cases may not involve motility, and only present as abdominal pain and bloating.

Most cases have multiple causes rather than a single cause.  The essence of effective treatment is the proper identification of each causative factor and a coordinated treatment program addressing all of them.

Many of the same factors that contribute to the development of functional dyspepsia can also cause IBS.  The digestive tract is a lot like an assembly line.  Digestion involves a series of functions that must occur sequentially.  If there is inadequate stomach digestion, the contents are going to pass to the small intestine inadequately broken down for the intestinal enzymes to finish the process efficiently.  If gallbladder function is inadequate, fats are poorly digested in the small intestine and will result in symptoms.

The common factors that can cause IBS include:

•Inadequate stomach phase digestion

•Insufficient pancreatic enzyme production

•Poor gallbladder function

•Imbalanced autonomic nervous system function (sympatheic dominance) 



Inadequate stomach phase digestion or functional dyspepsia causes the incomplete breakdown of foods in the stomach particularly proteins and complex carbohydrates.  The inadequately broken down food components are resistant to digestion by the enzymes in the small intestine.  They will often produce excessive fermentation by intestinal bacteria producing bloating and discomfort.  Treatment may involve attention to stomach digestion and supplementation with digestive enzymes.

Insufficient intestinal enzyme production can be caused by age, autonomic nervous system imbalance, diet and other factors.  Each must be assessed and treated.  Enzyme production occurs in the pancreas and their release into the small intestine is stimulated by the adequacy of the preceding stomach digestion and stimulus from the parasympathetic nervous system (PANs).  The PANs is inhibited by stress, anxiety, inflammation and other factors that cause imbalance in the autonomic nervous system as discussed below.

Poor gallbladder function may lead to inadequate fat digestion which will cause the typical symptoms of IBS.  This will typically alter intestinal motility causing constipation or diarrhea.  This is particularly true following a meal with higher fat content or more difficult fats to digest such as those in fried foods.  It is a common cause of vague nausea.  Poor gallbladder function also contributes to poor liver detoxification which can cause broad symptoms such as fatigue, non-specific aching and skin conditions.  Longstanding poor gallbladder function may lead to the development of gallstones.

Imbalanced autonomic nervous system function is a very common trigger of IBS.  It can be the sole trigger or can co-contribute with other triggers discussed here.   It is also perhaps the most under-appreciated contributing factor in IBS and needs to be both evaluated and managed for good resolution.

Stress, anxiety and other factors imbalance the autonomic nervous system to prioritize energy usage to the heart, muscles and brain.  This, however, impairs activation of other systems such as the digestive tract.  Stress, anxiety and inflammation all cause this prioritization by activating the sympathetic autonomic nervous system (SAN) and inhibiting the parasympathetic autonomic nervous system (PAN).  This imbalance is called sympathetic dominance.  Techniques aimed at restoring autonomic nervous system balance are often needed to resolve IBS.  These typically target activating the main parasympathetic nerve to the digestive tract, the vagus nerve.  These techniques may include transcutaneous vagus nerve stimulation, heart rate variability training and neurofeedback.  The choice of which techniques is unique to the cause and degree of each person’s imbalance.

Clustering of multiple functional digestive complaints in the same person such as reflux and IBS is particularly suggestive of autonomic nervous system imbalance.  The following components of digestion are inhibited by sympathetic dominance:


Stomach acid secretion                      Intestinal motility

Stomach motility                                 Maintenance of intestinal barrier function – “leaky gut”

Pancreatic enzymes secretion

Gallbladder function



Dysbiosis is an alteration or imbalance in the normal bacterial population in the digestive tract.  Ideally, about 1 trillion bacteria reside in the digestive tract.  These bacteria play several important roles including aiding in digestion, synthesizing several nutrients such as biotin and vitamin K, and in regulating immunity and inflammation.  The bacterial population is easily altered by antibiotic use, antibiotic pass-through from food, the use of several drugs including PPIs, diet content and many other factors.  When the bacterial population becomes unfavorably altered, all of the above functions become compromised and gut inflammation often results.

A variant of dysbiosis is small intestinal bacterial overgrowth or SIBO.  SIBO involves excessive small intestinal population of bacteria particularly with less preferred bacteria called opportunistic bacteria.  These are bacteria that cause no symptoms in small amounts but they can cause them if they overgrow and become the dominant population.  SIBO can be caused by many factors including kill-off of the more preferred bacterial population by antibiotics, poor diet quality, the use of stomach acid inhibiting drugs, poor intestinal motility and others.

Treatment of SIBO involves reduction in the opportunistic bacteria with herbs such as goldenseal, re-population of the preferred bacteria, dietary change and adequate treatment of other contributing factors such as reflux/dyspepsia.


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