Chewing is an extremely important, yet oftentimes overlooked, part of healthy digestion. Most people put food in their mouth, chew a few times, and swallow. Yet, in reality it doesn't really take much time and effort to chew your food well. What you get in return is worth the effort in terms of better health and enjoyment of food.
While various health professionals advocate distinct numbers of times you should chew food, I recommend more personal guidelines. I feel that this approach will better help you get a sense of your own eating patterns and help you further develop your relationship with your food. My suggestion is that you chew your food completely until it is small enough and dissolved enough to be swallowed with ease. A good rule of thumb is as follows: if you can tell what kind of food you are eating from the texture of the food in your mouth (not the taste), then you haven't chewed it enough. For example, if you are chewing broccoli and you run your tongue over the stalk and can tell that it is still a stalk or over the floret and you can still tell that it is still a floret, don't swallow. You need to keep on chewing until you can't tell the stalk from the floret.
The action of chewing mechanically breaks down very large aggregates of food molecules into smaller particles. This results in the food having increased surface area, an important contributing factor to good digestion. In addition to the obvious benefit of reduced esophageal stress that accompanies swallowing smaller, rather than larger, pieces of food, there is another very important benefit to chewing your food well that comes with its ability to be exposed to saliva for a longer period of time.
Food's contact with saliva is important because it helps to lubricate the food, making it easier for foods (notably dry ones) to pass easier through the esophagus. It's also important because saliva contains enzymes that contribute to the chemical process of digestion. Carbohydrate digestion begins with salivary alpha-amylase secreted by glands positioned near the mouth. This alpha-amylase helps break down some of the chemical bonds that connect the simple sugars that comprise starches. Additionally, the first stage of fat digestion also occurs in the mouth with the secretion of the enzyme lingual lipase by glands located at the root of the tongue.
When food is not well chewed and the food fragments are too big to be properly broken down, incomplete digestion occurs. Not only do nutrients not get extracted from the food but undigested food also becomes fodder for bacteria in the colon; this can lead to bacterial overgrowth, flatulence, and other symptoms of indigestion.
Chewing is directly connected with the movement of food through your digestive tract, and, in particular, with the movement of food from your stomach to your small intestine. At the lower end of your stomach, there is a muscle called the pylorus. This muscle must relax in order for food to leave your stomach and pass into your small intestine. Sufficient saliva from optimal chewing helps relax the pylorus, and, in this way, helps your food move through your digestive tract in healthy fashion.
Yet, the contribution of chewing to good digestion does not even stop there. The process of chewing also activates signaling messages to the rest of the gastrointestinal system that trigger it to begin the entire digestive process. This is because when chewing is a well-paced, thorough process, it can actually be said to belong to the "cephalic stage of digestion," the phase in which you first see, smell, and taste your food. The length of time spent chewing the food is related to the length of the cephalic stage of digestion since with more extensive chewing, the longer the food gets to be seen, tasted, and smelled. Cephalic phase responses have been extensively analyzed in the research literature. The release of small messaging molecules that are critical for digestion—such as cholecystokinin, somatostatin, and neurotensin—have been found to increase by over 50% just by the mere sight and smell of food. Additionally, research has shown how chewing, as well as the activation of taste receptors in the mouth, can prompt the nervous system to relay information to the gastrointestinal system to optimize the process of digestion. For example, stimulation of the taste receptors can signal the stomach lining to produce hydrochloric acid that helps in the breakdown of protein. Additionally, chewing signals the pancreas to prepare to secrete enzymes and bicarbonate into the lumen of the small intestines.