The Digestive System
Before we discuss the effects of stress on the formation of ulcers, we will take a brief look at the mechanical processes involved in digestion. Recall from our discussion on the digestive system from previous article, that it takes a huge amount of energy in terms of muscular movement to digest a stomach full of lunch. The food in the stomach is broken down mechanically and chemically. The stomach muscles contract violently on one side and the food is flung against the far sidewall of the stomach.
This movement is called peristalsis. The small intestine is next in line and it goes through a series of directional contractions to push the food from one end to the other. After that the bowels do the same and the remainder is excreted. Circular muscles called sphincters are located at the end of the organs to make sure that things don’t move to the next stage till the first stage is completed.
The whole process relies on the ready availability of water to keep everything in solution. At the end of the cycle, in the large intestine, the water has to be absorbed again so that we are not dehydrated due to inadvertent excretion of the fluids. As you can imagine this entire process requires tremendous amount of energy. To put some numbers on it, adults expend about 20 per cent of their daily energy on digestion!
Stress Response
We will now take a look at the digestive system’s response to stress. In the face of an acute physical stressor, it makes sense for the body to turn off all activities that consume a lot of energy and do not provide any immediate benefits. Digestion may be good in the long term by providing essential nutrients but it is useless in dealing with the immediate emergencies. The first step in the process is to stop the production of saliva as a result of which the mouth becomes dry.
The stomach grinds to a halt; enzyme and acid secretion and contractions are stopped. The small intestine stops its movement and absorption does not take place. The blood flow to the digestive system is reduced and the blood delivers the oxygen and glucose to the exercising muscles where it is required. It all shows a superbly adapted system responding as expected to a stressor. So where is the problem?
Before we look at how repeated stressors can cause prob-lems in the digestive system, it will help to know about one more process involved in digestion. Earlier, we saw how the muscular movement broke down food mechanically. The body uses another trick to break down food—the use of hydrochloric acid. This is a powerful acid and it breaks down virtually anything we eat—meats, vegetables, fats, refined foods, etc. The contractions help but the main weapon in the degradation is the hydrochloric acid.
Even before this explanation is over, the alert reader would have noted something amiss. How come the acid does not degrade our own stomach? The answer is that the stomach has built layers and layers of protective mucous. The stomach has to expend a huge amount of effort to make sure that the acid does not afTect its walls. This seems like a wonderful solution and di-gestion can proceed. Just to give an idea of the high level of protection, we see that there are at least six layers that protect the stomach from the acid.
Back to our original point on how stress causes problems with the digestive system. During a prolonged period of stress, digestion is frequendy inhibited. To conserve energy, the stomach starts to economize and slows down the process of building the mucous walls. At the end of the stressor, when digestion resumes, the acid attacks the stomach walls—ulcer!1 An interesting point to note here is that theactual damage does not occur during the stressor but in the phase of recovering from the stressor. The obvious non-workable solution to avoid ulcers is to continue in the stressed condition! A more practical conclusion is that several periods of transient stress are worse than one prolonged period of stress from the point of view of ulcer formation.
Most experts agree that massive stressors like trauma, infections, accidents or burns can lead to the formation of stress ulcers just as described above. The difficulty is in explaining the ulcers that form over a period of time (emerging ulcers). There is an interesting story behind the discovery of the causes of emerging ulcers.