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Guide Health: Keep your bowel moving

Thanks to your autonomic nervous system, which regulates evacuation from your bowel, you probably take your bowel habits for granted… except when you can’t.

At any one time, anywhere between two and 28 per cent of Canadians are affected by constipation, which can range from a single episode to chronic constipation. In fact, the real numbers are probably higher because you often purchase a non-prescription laxative, so the problem doesn’t get reported.

The defecation reflex along with two anal sphincters (the external and internal) are responsible for your bowel movements. When fecal material enters the rectum, stretching of the rectal walls sends signals to the parts of the colon causing peristalsis or contractions. When these contractions reach the internal sphincter, this sphincter relaxes, and if the external sphincter is also relaxed you have a bowel movement.

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You feel the relaxation of the two sphincters as the “urge to go,” but luckily for you the external sphincter is not controlled by the autonomic nervous system, but by the somatic nervous system which you consciously control. Otherwise you would have no control over your bowel habits.

You delay defecation until a socially acceptable time, then with a deep breath you contract the abdominal muscles and elicit the defecation reflex. People who routinely inhibit the defecation reflex for longer periods of time are more prone to constipation because their reflex becomes blunted, for example long haul truck drivers. As well, there is a natural urge to go to the bathroom after eating a meal, which makes sense.

Many people believe that you should have a bowel movement each day, but this is not so. “Normal” bowel habits are considered to be anywhere from three each day to one every three days. Your normal routine is unique to you!

Solid fecal material is made up of approximately one-third dead bacteria from your bowel, one-third fibre and undigested food materials, and one-third materials like cholesterol that are excreted from your body. Water is always present and the amount depends upon how much liquid you drink. In fact, whatever you drink or eat may appear in your stools, taking 24 to 72 hours for something you put in your mouth to come out of the other end.

Obviously, a diet low in fibre and fluids will contribute to constipation. Some drugs, most notably narcotic pain relievers, slow bowel motility and cause constipation. Bowel obstructions or bowel abnormalities and pregnancy are implicated in constipation because they physically make normal bowel passage more difficult.

Functional problems such as depression, confusion, immobility, and inaccessible bathrooms may mean that getting to the bathroom is difficult, so constipation occurs. Diseases that interfere with the nervous system control of defecation often have constipation as a potential complication, for example diabetes, and Parkinson’s disease. And, because nicotine increases bowel actions, quitting smoking can slow bowel functioning.

After ruling out any contributing factors to constipation, the recommended first steps are non-drug approaches. Common recommendations are regular bowel habits; a high fibre and fluid diet; consumption of prune, apple, or pear juice with their sorbitol (a natural laxative); and exercise. Being overweight can complicate constipation, so weight loss is also a good idea.

Laxatives are commonly used to treat constipation, and are safe for use from time to time. However, for chronic constipation, they should be used only after a medical recommendation.

There are four general groups of laxatives. Bulk-forming laxatives such as psyllium are like increased dietary fibre, but you need to remember to drink plenty of fluids with them. Osmotic laxatives, for example polyethylene glycol or PEG and lactulose, increase the water content in stools and are often used on a regular basis. They cause less gas and bloating than the bulk-forming laxatives. Senna and bisacodyl are stimulant laxatives which increase bowel contractions. Emollient or stool softeners like docusate do just exactly what their name suggests, making stools easier to pass. Laxatives are also available as enemas and suppositories for faster action.

Keep in mind that bowel cancer is the third most commonly diagnosed cancer in Canada, and that a change in bowel habits is one of the first symptoms. So, if you notice a change in your bowel habits, don’t just assume it’s constipation and self-treat with laxatives. Get your symptoms checked!

About the author


Marie Berry is a lawyer/pharmacist interested in health and education.



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