Constipation: Why Does It Happen?

A Definition

Constipation means different things to different people. Some people experience strain when they try to go to the bathroom, while others have what they term ‘bloating’. Some patients complain that their bowel movements are pebble-like, marble-like, or flat and ribbon-shaped, which doctors call scybalus. In the medical community, the generally accepted definition of constipation is: less than three bowel movements a week. Another way the problem is defined is straining, hard stool, or incomplete evacuation more than 25% of the time.

What Does It Mean To Be Constipated?

Constipation is a very common problem in the United States, and has numerous causes. In order to understand them, we need to learn a little more about how our bodies function. You may not know it, but there is an extensive nervous system in your intestines. There are actually more neurons in the intestinal or enteric nervous system, than in the central nervous system, which includes the brain and spinal cord. Certain chemicals in your brain, like serotonin, also play a role in coordinating movement in the intestines. Usually, the intestines have a normal wave-like movement (peristalsis). When this normal movement is interrupted, the bowel can't empty and there may be bloating, pain, spasm or constipation.

Keeping the colon hydrated
One of the main purposes of the colon (section of intestine before the rectum, also know as the large intestine) is to reabsorb water. In order to prevent the stool from becoming too dry (dehydrated) and inhibiting motility, you need to drink a lot of water—approximately 50 ounces (about 6 normal glasses, or 1.5 liters) a day. Take a look at a one liter size bottle of soda for a general idea. If you are exercising, pregnant, or if the weather is very hot, you may need to drink even more. Other beverages, like decaffeinated tea, also work to rehydrate the body, but beverages like alcohol and coffee do not. In fact, they actively dehydrate the body instead of replenishing necessary fluids.

Be conscious that in certain medical conditions—like congestive heart failure, liver disease or kidney disease—too much water can be harmful, so if you suffer from any serious medical problems you should ask your doctor before greatly increasing your water intake.


We don't really understand exactly what bloating is, but we do know that often when people are constipated, they become bloated. When the constipation resolves, the bloating often goes away. It may be that the abdominal wall muscles relax and the bowel loops are more clearly present. Remember that there are at least six feet of intestine wrapped up in every adult body cavity. When that whole length is expanded, it is very uncomfortable. Another cause of bloating could be that the tone of the bowel is decreased causing it to ‘spread out’, and increase in diameter. In addition, gas trapped in the bowel can distend it and can cause discomfort.

Some Common Causes of Constipation

There are some common medical illnesses that cause constipation such as thyroid problems, diabetes, or a hyperactive parathyroid gland (the 4 glands in the neck that control the calcium level in your blood). A high level of calcium in the blood can cause constipation as well. Intestinal viral infections called viral gastroenteritis can also temporarily paralyze the stomach (gastroparesis) and lead to vomiting and constipation.

There are also many medicines that can cause constipation. They include:

  • Vitamins
  • Calcium supplements
  • Iron supplements
  • Codeine
  • Morphine
  • Anticholinergics
  • Blood pressure medicines
  • Low-fiber diet
  • Change in diet

You should ask your doctor if your constipation could be due to your medications.

Calcium supplements
If you are a woman, then you have probably been instructed to consume at least 1200 mg of calcium a day. Since one glass of milk only has about 200 mg of Calcium, and many people avoid cheese because of its fat content, it is almost impossible to consume a sufficient amount of calcium strictly through diet.

Certain calcium supplements and vitamin pills that are essential can cause bloating and constipation. The best calcium supplements are those that can dissolve in the pH of vinegar (also called acetic acid). These easily digested calcium supplements include TUMS, Calcitrate, and Oscal. Patients who suffer from acid reflux (heartburn) usually benefit from TUMS, since it not only supplies 200 mg of Calcium per tablet, but also helps with heartburn and bloating. Five or six a day, in addition to a well-balanced diet, provide an excellent source of calcium. Be careful to avoid antacids that contain aluminum, which is very constipating.

For my patients who struggle with constipation, gas, and bloating, I recommend they take prenatal vitamins. These vitamins, which are specially designed for pregnant women, are the most bioavailable. This means that they are well absorbed from the large intestine and will therefore cause less nausea and bloating. Prenatal vitamins also have the extra iron, folate and B vitamins that are good for women who are exercising, working, or nursing. Taking them at night will cause less nausea and bloating.

Remember that iron tablets can be very constipating as well. If you need to take iron supplements, it might help to take a stool softener like docusate with the iron, or to try a slow release formula of iron like Feosol.

Relieving and Preventing Constipation

There are a number of ways you can prevent the onset of constipation, and if you find that you are constipated, there are a number of ways you can relieve it.

Find the time
First, to prevent constipation, you must allow for a regular time to go to the bathroom.

Physical activity is helpful—even walking is great.

To relax the pelvic floor as you pass a stool, you can use a short foot stool, 7 inch high, to place your feet on while you go to the bathroom.

Stay hydrated
As we learned, you must avoid dehydration. Cold fluids or ice chips, alternating with warm fluids, stimulate and tone the bowel and help pass gas.

Eat Fiber
It is now widely accepted that fiber may help to prevent certain cancers and possibly some forms of the blood vessel disease atherosclerosis. Fiber also helps some people with constipation. The recommended daily allowance of fiber is 25g a day, which can be difficult to obtain in an American diet. Excellent sources of fiber are:

  • Split plea soup
  • Navy beans
  • Lentils or any other dried beans

(Here’s a hint: When the ‘legumes’ are soaked, cooked, and stewed they cause less gas.)

The best diet for your bowels, your heart and your brain should include vitamins A, C, E, calcium, and low fat, high fiber foods.

Take prepared fiber
Prepared fibers like Metamucil, Konsyl (Psyllium), Citrucel, and Fibercon (Carbophil) help some people with constipation. They are thought to bind water and therefore prevent excessive dehydration of the stool, as well as excess liquidity. These fibers are perhaps even more helpful for patients with diarrhea or diarrhea-predominant irritable bowel syndrome, not constipation. This is because constipated patients tend to get bloated easily.

Use a stool softener
If a stool softener is needed, it is good to use docusate or, if you need to avoid sodium, something called ‘surfak’. Stool softeners work as a surfactant to decrease the wall tension between the stool and the colon. They are not habit forming, and act mainly to keep the stool soft for easy, natural passage. They come in 100 mg capsules and are well tolerated. You may take 1-5 capsules 2 hours before bedtime, as needed.

Some Things to Avoid

Products that contain something called senna, although it is advertised as natural, can cause cramping and secretion of electrolytes and water from the colon, which can be harmful and lead to dehydration. Senna is also habit forming to the bowel and should therefore be avoided.

Prune juice is not recommend since the active ingredient is phenolphthalein, which can cause a secretory diarrhea as well as bowel dependence, (dependence on prune juice for regular bowel movements). Also, phenolphthalein is a cathartic (causes diarrhea) that passes through the liver and can cause a severe rash.

Another thing to avoid is liquid paraffin (used to treat constipation), which can cause aspiration. Aspiration means that a small quantity of oil stays in the esophagus and when you lie flat it travels up the esophagus, into the trachea and then into the bronchial tubes of the lung, resulting in breathing difficulty.

It is also wise to avoid sugars that are not absorbed by the intestine. Lactulose and Sorbitol are examples of sugars that cannot be absorbed. They pull water into the gut lumen (inside of the intestines) and cause loose stools, though sometimes they may cause diarrhea. Sorbitol causes less nausea than Lactulose. In general, I stopped using this approach with my patients because these sugars seem to cause bloating, gas and burping. Of note, Sorbitol is also present in diet candy and in sugar-free liquid medicines.

Constipation to Be Concerned About

Of course, if you have any significant constipation or abdominal discomfort you should consult with your doctor. There is a chance it may be the result of a serious medical condition, such as a thyroid problem (hypothyroidism).

Another condition associated with constipation is diverticulosis. Diverticulosis involves the herniation of the lining of the colon through the muscular coat. It often does not cause any symptoms. The condition becomes increasingly more common with age and may be a result of decreased fiber intake. Diverticulosis is treated with a high fiber diet, at least 30g per day. This increases the bulk of the stool and decreases pressure in the colon.

Blood in the stool
If you see blood in the stool or in the toilet, you must consult with your doctor right away. There are several things that can cause bleeding in the colon—polyps, hemorrhoids and diverticulosis. If you are experiencing cramping and bleeding, it may be ulcerative colitis, a condition caused by inflammation of the colon. Or, it could be caused by the growth of a colon cancer or tumor.

If there is a sign of bleeding in your stool, your gastroenterologist may perform a colonoscopy. A colonoscopy is a procedure in which a long, flexible tube with a small fiberoptic camera at the end is inserted through the rectum and into the colon. The tube is advanced to the end of the colon (the ileocecal valve) after which it is removed slowly. This procedure allows your doctor to look at the inside of your colon for any signs of change. A single colonoscopy has a great impact on colon cancer deaths. By catching cancers early and starting the appropriate treatment, there is a 68% reduction in colon cancer deaths with this one test.

The most important thing to remember is that the sooner cancer is detected, the more likely it is that it can be cured. Therefore, you should consult with your doctor at the onset of any troublesome symptom—including bleeding, abdominal pain, constipation or weight loss.


There are a number of different causes of constipation. For many people, drinking 8 glasses of water a day, eating a high fiber, low fat diet, and getting regular exercise can solve their problems with constipation. There are times, however, when constipation symptoms indicate more significant problems. When you are concerned about symptoms you might be experiencing, it is always wise to see your doctor.

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