Digestion is largely taken for granted by just about everybody. You may assume that what you put into your mouth is going to be digested. But, digestion doesn't just happen: it is a complicated process that is extremely important and should not be overlooked as a root cause for many health problems. When digestion does not occur the way it should, symptoms such as gas, bloating, and pain may result.
Digestion, or hydrolysis, is the process of breaking up food "into simpler chemical compounds by means of hydrolyzing enzymes or chemical action…." 4 In other words, digestion breaks up food into small units so the body can use the nutrients for energy or growth and repair. More to the point, hydrochloric acid does not digest food; enzymes do. 5 If hydrochloric acid cannot be adequately produced, as may be the case with older adults, 6 enzymes do not activate.
The normal digestive process begins in the mouth. While you chew food, your salivary glands secrete digestive enzymes that begin to work immediately. You can demonstrate this enzyme action for yourself by thoroughly chewing a piece of bread. After a short time, the bread will begin to taste sweet as the sugar-digesting enzymes in the saliva liberate the sugar in the bread. If raw food is eaten, the naturally occurring enzymes in that food will also participate. If the food enzymes have been denatured or destroyed through a food processing method, only the enzymes in the saliva are available to begin digestion. Even after being chewed, some food pieces are still too large to pass through the wall of the stomach and intestines. They must be broken down into much smaller pieces.
Contrary to the popular conception of a bubbling cauldron of acid, your stomach is nearly empty when you first begin to eat. When you swallow food, the stomach begins to produce the acid and enzymes needed for digestion. This window of time, while the body gathers hydrochloric acid in the stomach, can last for up to one hour. In the meantime, the salivary enzymes and food enzymes are continuing to work at breaking down the ingested food.
As hydrochloric acid gathers in the stomach, it becomes an acidic environment. This acidity is ideal for the activation of the protein-digesting enzyme, pepsinogen, which upon activation becomes pepsin. These protein-digesting enzymes begin working while the food and salivary enzymes are deactivated, since this environment is not optimal for certain enzymes to work. Moreover, these enzymes—supplemental and naturally occurring—are not destroyed. 7 Based on the amount and type of food you have eaten, the body produces the exact amount of enzymes needed to continue digesting the food. 8
After the food leaves the stomach, it enters the upper part of the small intestine, called the duodenum. It is here that the liver (and gallbladder, if you still have yours) adds bile to the mix, making the intestinal environment alkaline. Bile does not contain enzymes and does no digestive work. However, it is responsible for degreasing food. In other words, bile acts as a detergent and breaks down any fats or oils that are coating the food. This step is necessary so that the enzymes from the pancreas can reach the food and finish digestion.
The enzymes that work in an alkaline environment are activated, such as supplemental pancreatic enzymes (derived from animals). The body has done most of the work by this time; therefore, supplemental pancreatic enzymes do not necessarily help with digestion before this point. The digested food particles now pass through the intestinal wall to be assimilated by the body. The indigestible portions of the food, such as insoluble fiber, are pushed into the colon for elimination. When one step of the process does not happen, the subsequent digestive actions are affected. For instance, if you take antacids, you are reducing your body's ability to produce hydrochloric acid and, therefore, your ability to digest protein, which now has no way of being thoroughly broken down. Protein digestion must begin in the acidic environment of the stomach.
» Enzyme Activity
- Stedman's Medical Dictionary.
- Guyton, pp. 833-844.
- Sharp and Fister; Sandstrom and Abrahamsson; and Krasinski, Russell, and Samloff. See the clinical studies references.
- Ambrus, Lassman, and DeMarchi; Rothman, Liebow, and Isenman. See the clinical studies references.
- Boivin et al. See the clinical studies references.