In a normal healthy person, the bowel movement or the emptying of the bowels is supposed to happen swiftly and with ease. If you have had difficulty ever since you were a child, you may have come to realize that some amount of straining at emptying of the bowels is normal.
It is not.
It is supposed to happen with complete ease with no straining whatsoever. However it doesn't mean that if you have to strain a little, once in a while, it is wrong. Occasionally if you have to strain a bit, it is not a big deal. But for the most of the time, the movement is supposed to happen kind of automatically.
Formally constipation is defined as a condition in which there is difficulty in emptying the bowels. Bowel movement becomes infrequent. The difficulty is present in very much all bowel movement. Also in constipation feces becomes hard. According to National Institute of Health (NIH) a bowel movement of less than three times a week qualifies as constipation.
Intestinal muscles and intestinal walls are made to handle soft feces. If it hardens too much, the intestinal muscular movement cannot empty the bowel with ease.
Lets understand a bit more of what goes on in our intestine to get a better idea about constipation.
When partially digested food is in the small intestine, it is pretty much in a liquid form. When the food enters the large intestine from the small intestine, it is in complete liquid form.
Within the large intestine, the water is absorbed from the liquified partially digested food. This makes the food semi solid (still very soft) and gives it a shape. This transformation of liquid to a semi solid shape is taking place when food is travelling through the large intestine.
As the bulk forms in the large intestine, the walls of the large intestine detect the presence of the partially digested food. If food remains shapeless liquid in the colon, the presence of the food is not recognized by the intestinal wall.
If the presence of food is detected by the intestinal wall in the large intestine, it triggers the muscular movement in the large intestine. This pushes the content of the large intestine forward towards the rectum.
An important characteristic of the colon is that as soon as the partially digested food enters the colon, the walls of colon start absorbing water from the food. The colon wall will keep absorbing the water as long as the contents are present in the colon and as long as there is water.
The implication is that as soon as liquified food enters the colon, it starts losing water. By the time it has lost all the water, if it cannot form enough bulk, it will be trigger enough muscular movement in the colon to propel the contents forward.
You can see that the food content needs to have bulking agent to trigger the proper muscular movement in the colon. Only if there is proper muscular movement in the colon, the contents will progress towards the rectum and the proper elimination will happen.
Also the food content needs to have enough water. If there isn't enough water entering into the colon, the feces will become hard fast. Hard feces cannot travel easily through the colon. It slows down and causes difficulty.
With typical western food habits, what happens is that by the time all the water is absorbed in the colon wall, there isn't enough bulk formed in the remaining semi-solid mass. And the colon walls don't contract enough as they don't detect enough mass.
This causes the content of the colon get stuck and not move in the colon. This leads to even more water loss if there is any water left. What you get is constipation.
As you can see that lack of bulking agent or lack of water could cause constipation.
You may wonder what is this bulking agent? Yes it is the dietary fiber. But it is a very specific type of fiber. It is insoluble fiber. The soluble fiber doesn't usually bulk up. But the insoluble fiber is the one that bulks up.
As the name suggests insoluble fiber doesn't get dissolved in water. But it actually absorbs water and swells in the size. It can increase in volume by up to 20 times its original size! This property of insoluble fiber to swell up or bulk up is crucial in helping the colon detect the presence of the contents and get the muscle movement going. Hence it is critical that you have enough of insoluble fiber in your diet.
Usually any food that has dietary fiber, has both soluble fiber and insoluble fiber. But their proportions vary and they may have more or less of insoluble fiber. Some common examples of foods high in insoluble fiber are legumes, cereal bran and certain vegetables like okra.
Another cause of constipation is ignoring the urge. When you ignore the urge, the stool will stay longer in the colon. As mentioned earlier, as long as the stool is in the colon, it will keep losing water. The stool will become drier, which will lead to constipation.
Unfortunately in our day-to-day lives, we often have all three causes of constipation present altogether. Our diets are low in fiber, we don't hydrate enough and we frequently resist the urge. No wonder, constipation is so widespread.
Sedentary lifestyle also contributes to constipation. It turns out that physical activity stimulates the large intestinal muscles. Physical activity plays a key role in maintaining a healthy transit time through the colon. Although the actual mechanism is not known but it seems to have mechanical origins. It is not difficult to imagine that moving legs would stimulate the digestive organs.
Stress is also a major reason that contributes to the constipation. When we are in stress, our body deploys fight or flight response. It shuts down parts of the body which are not essential at that moment and diverts the blood flow and the neural activity towards the other parts of the body where it thinks it is more needed.
Unfortunately during the stress response, the digestive system get low priority. Blood flow is diverted away and neural activity directed towards the intestines is at least subdued. Digestive hormone activity slows down and intestinal movement slows down. This leads to both indigestion and constipation as digestion pretty much comes to a halt temporarily.
More frequent stressful episodes leads to the frequent shutdown of digestion and more constipation.
Human large intestine holds hundreds of different types of bacteria. Most of them are beneficial ones which have a symbiotic relation with the host. Some of them are not so friendly. But usually there is a balance between two types of bacteria.
There is growing evidence that the imbalance of bacterial flora is responsible for many digestive disorders including constipation. We inherit gut flora at birth. The use of antibiotics, probiotics and prebiotics can change gut flora.
Gut flora is a huge topic that we will discuss at length in later articles, but there is growing suspicion that antibiotic use can cause constipation through gut flora imbalance.
Normal intestinal muscles propel stool for elimination. This muscular movement towards the end is called defecation reflex. If one loses defecation reflex, the stool gets stuck and due to extra water loss, one gets constipated.
Stimulant laxative stimulates the colon wall to cause the defecation reflex. Overuse of such laxative could cause the colon wall to become insensitive. Which may cause one to lose the defecation reflex and associated constipation.
Muscle relaxant can interfere with normal intestinal muscular movement and could cause the stool to get stuck.
Aging can also cause muscles to become weak. This would mean less strong defecation reflex and associated constipation.
Long term diabetes can cause nerve damage to the nerves responsible for proper intestinal muscular movement. This may lead to improper colon muscle movements and loss of defecation reflex and associated constipation.
Surgery can cause temporary paralysis of the intestine and could cause stool to get stuck and later constipation.
Having learned about causes of constipation, it is obvious that you would expect to know more about the cure and prevention of the constipation.
I have listed major causes of constipation like lack of dietary fiber, proper hydration and the stress. One can address those issues to try to prevent constipation. There are other remedies which can help with constipation.
We will discuss the prevention and cure of constipation at length in future articles.
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