What Causes Constipation? Why am I Always Constipated?

Dr. Jaudy discusses the roots and causes of constipation.

In this article, I will discuss some of the many causes of constipation with a focus on the nervous system (brain) neurological connections to the gastrointestinal tract (the gut). I will also discuss functional gastrointestinal disorders in some detail, as these are often the cause of chronic constipation.

There are numerous causes to constipation, but most of the causes are due to decreased electrochemical neural signaling to the intestines, and more specifically, the colon. Let’s take a look at the most prevalent causes of constipation, then I’ll tell you more about what I mean by decreased electrochemical neural signaling to the intestines.

The most common causes of constipation are:

  • Dehydration/Inadequate water intake 1
  • Inadequate or decreased fiber in the diet 2 3
  • Sedentary lifestyle 2
  • Numerous medications and vitamin supplements including 2 3:
    • Narcotics/Pain killers
    • Antacids
    • Anticholinergics
    • Anticonvulsants
    • Antispasmodics
    • Calcium channel blockers
    • Diuretics
    • Iron supplements
    • Antidepressants
  • Excess amount of dairy consumption 3 4
  • Laxative overuse 3 5
  • Pregnancy and childbirth 2 3
  • Stress 6
  • Travel 3
  • Loss of body salts 3
  • Ignoring the urge to defecate 3

And numerous medical conditions, including (but not limited to):

  • Irritable bowel syndrome (IBS) 2 3
  • Inflammatory bowel disease 2
  • Fissures and hemorrhoids 3
  • Spinal cord or brain injury (including stroke) 2 3 8
  • Disorders affecting the brain and spine, including Parkinson’s disease 2 3
  • Colonic Motility Disorders 3 (including colonic inertia 3 8 and Pelvic floor dysfunction 3 9)
  • Colon cancer or tumors in the GI tract 2
  • Diabetes 2
  • Hypothyroidism and hormonal disorders 2 3
  • Depression 10
  • Lupus 3
  • Multiple Sclerosis 3
  • Scleroderma 3
  • Intestinal pseudo-obstruction 11
  • Hirschsprung's disease 12
  • Chaga’s disease 13
  • Megacolon 13
  • Anismus (a type of dystonia where the anal sphincter fails to relax) 14
  • And many others

Okay, now that we have a general idea of the causes constipation, let’s take a more detailed look at this symptom.

The Brain-Gut/Gut-Brain Axes and Constipation

The GI tract is controlled by the brain through neurological pathways that make up what is called the brain-gut axis and the gut-brain axis. 15 – 20 Fecal matter passes through the colon and ultimately leaves the body due to peristaltic movements of intestinal wall musculature initiated by the brain.

Now, in the absence of some type of obstruction (such as a tumor or diverticula), or another explanation for constipation (such as medications or diet low in fiber), the inability to move fecal matter through the colon and out of the body (constipation) is often due to decreased signaling along the brain-gut axis. Let’s take a look at some of the conditions listed above, so you can get a better understanding of what I mean by this.

When we talk about constipation as it relates to damage to the brain or spinal cord or diseases that affect the brain or spinal cord, such as Parkinson’s disease, stroke, multiple sclerosis, etc., the reason that these conditions can cause constipation is that the brain regions and neural pathways that control intestinal motility become damaged. When these neural pathways or neurons are damaged, signals sent between the brain and the gut become disrupted. This disruption causes decreased motility, which can cause constipation.

Now, with this in mind, we now will look at what are called ‘functional GI disorders’. Functional GI disorders include conditions such as irritable bowel syndrome (IBS), colonic inertia, and pelvic floor dysfunction. In these conditions, there are no visible lesions in the nervous system, yet we see a similar type of motility dysfunction. The reason for this, and you can learn more by reading my article on irritable bowel syndrome, is that although there are no visible lesions (hard lesions), many times there are functional lesions (soft lesions) in the nervous system, which cannot be seen through advanced imaging, but can be detected through comprehensive neurological examination.

What happens is that signals sent to and from the gut become disrupted and the organs, specifically the colon, are unable to properly function.

Physiologically, the functions of the colon, including enzyme production and movements, are orchestrated by the brain via two main nerve networks called the myenteric (Auerbach’s) plexus and the submucosal (Meissner’s) plexus. These nerve networks communicate bi-directionally with the brain through the enteric nervous system.

Functional GI Disorders

Functional GI disorders, as the name implies, are problems in the function of the gastrointestinal tract. As I’ve mentioned, the GI tract’s functions are directed by the brain, specifically the brainstem (autonomic nervous system). It seems only logical that the neurological firing between the brain and the gut becomes aberrant in many patients diagnosed with functional GI disorders. If proper communication cannot occur, this leads to organs and tissues going haywire.

The viscera (organs) are connected to the brainstem via the vagal pathways. 21 - 26 What happens in many patients with functional GI disorders is that there is a shift from the parasympathetic to the sympathetic. When the sympathetic nervous system is initiated we get decreased peristaltic movement, which can lead to less frequent bowel movements, clumpy stools, constipation, abdominal bloating, and feeling like the bowel movement is incomplete. When the internal environment of the colon and intestines becomes altered, the normal processing becomes altered, which can lead to constipation.

Imagine that Cell A is not able to talk to Cell B, and Cells A and B can’t talk to Cell C, and Cells A, B, and C can’t talk to Cell D… it’s a domino effect. That’s why functional GI disorders can lead to bloating, gas, constipation, diarrhea, pain, spasm, swelling, bleeding, etc. Patients say, “I feel like I can’t keep my gut quiet, no matter what I do. It’s like a war going on inside of me, and it hurts.” If you could imagine, when the orchestration of the gut cells with the neurons of the gut and with the chemistry processing receptors, they become irritated due to decreased orchestration, and then you can develop any of the above mentioned symptoms. Also, these symptoms can lead to gradual failure and irritability in adjacent organs, such as those listed above.

If we look at some of the other causes listed, such as dehydration, medications, hormonal disorders, laxative abuse, etc. we can also apply problems in neural signaling. For example, medications and dehydration alter normal communication between brain regions and the gut.

Dangers of Chronic Constipation

Constipation due to dehydration, pregnancy, diet, medications, stress, travel, and other non-disease conditions is often transient, meaning that the symptom goes away once the cause is dealt with. However, when constipation is constant, it is considered chronic and can be the precursor or indicator of a more severe condition.

Everything is connected. Every organ, tissue, gland, and cell communicates with one another and they each affect the function of one another. Furthermore, the communication between the brain and the gut indicates that a problem in the gut can lead to problems in the brain and vice versa. This is why chronic constipation can be a dangerous symptom. In fact, chronic constipation is often a precursor to Parkinson’s disease. 27

If you ignore this symptom, or if your doctor ignores this symptom, or if you simply treat it by managing the symptom through medications, such as laxatives, then the underlying problem that caused the constipation is not addressed and can worsen over time. This can lead to functional GI disorders, or more severe conditions, such as Parkinson’s disease.


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Additional Resources

  1. Epidemiology of Chronic Constipation In North America. "An evidence-based approach to the management of chronic constipation in North America." American Journal of Gastroenterology 100.S1 (2005).
  2. Talley NJ, et al. Risk factors for chronic constipation based on a general practice sample. The American journal of gastroenterology 98.5 (2003): 1107-1111.

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