Tracing nutrient digestion of a turkey sandwich meal from ingestion to absorption

Diabetes

Digestion and diabetes: Overview of the process

The digestive process begins even before food is consumed. Looking at or anticipating food causes salivation. Saliva aids digestion, along with chewing. For example, when Jane Doe looks at a plate consisting of a whole wheat turkey sandwich (garnished by vegetables and mayonnaise), potato chips, and apple juice, her body will begin to anticipate eating by secreting digestive juices. The first major involuntary muscular movement for Jane Doe will not occur until she consciously decides to swallow the food in front of her. "Although you are able to start swallowing by choice, once the swallow begins, it becomes involuntary and proceeds under the control of the nerves" (Your digestive system, 2010, NIH). The swallowed food is pushed into the esophagus, the organ that connects the teeth, mouth, and tongue through the throat to the stomach. "At the junction of the esophagus and stomach, there is a ring-like muscle, called the lower esophageal sphincter, closing the passage between the two organs. As food approaches the closed sphincter, the sphincter relaxes and allows the food to pass through to the stomach" (Your digestive system, 2010, NIH).

The stomach holds the swallowed food and liquid, and mixes the foods, liquids, and digestive juices and then empties the contents slowly into small intestine. To break down the food, the stomach produces stomach acid "and an enzyme that digests protein. A thick mucus layer coats the mucosa and helps keep the acidic digestive juice from dissolving the tissue of the stomach itself. In most people, the stomach mucosa is able to resist the juice, although food and other tissues of the body cannot" (Your digestive system, 2010, NIH). Once the food leaves the stomach, the pancreas, "produces a juice that contains a wide array of enzymes to break down the carbohydrate, fat, and protein in food" (Your digestive system, 2010, NIH).

However, if Jane is a type 1 diabetic, her pancreas may not be functioning properly. Type 1 diabetes is an autoimmune condition in which "the pancreas produces little or no insulin, a hormone needed to allow sugar (glucose) to enter cells to produce energy" (Type 1 diabetes, 2010, Mayo Clinic). The second organ involved in digestion is the liver, which produces bile to dissolve fat, such as the mayonnaise of the spread on the bread of the sandwich, and the oil in the potato chips. "After fat is dissolved, it is digested by enzymes from the pancreas and the lining of the intestine" (Your digestive system, 2010, NIH).

Thus not all nutrients are digested in the same fashion. Carbohydrates, such as the bread, potato chips, and apple juice, stay in the stomach the least amount of time. That is why athletes often use high carbohydrate foods as a quick energy source. And not even all carbohydrates are created equal. Simple sugars like juice are digested in one step: "An enzyme in the lining of the small intestine digests sucrose, also known as table sugar, into glucose and fructose, which are absorbed through the intestine into the blood" (Your digestive system, 2010, NIH). With starches such as the wheat of the bread, "an enzyme in the saliva and pancreatic juice breaks the starch into molecules called maltose," which is then converted to glucose in the small intestine "Glucose is carried through the bloodstream to the liver, where it is stored or used to provide energy for the work of the body" (Your digestive system, 2010, NIH). This is why whole wheat is a superior source of sustained energy, versus the simple sugars in juice. The need for sustained energy that does not cause quick spikes in blood sugar also makes high fiber, complex whole grain carbohydrates a superior source of nutrition for diabetics such as Jane.

If the whole wheat bread Jane eats is high in fiber, the digestion process is further slowed down. "Fiber is indigestible and moves through the digestive tract without being broken down by enzymes…Soluble fiber dissolves easily in water and takes on a soft, gel-like texture in the intestines. Insoluble fiber, on the other hand, passes essentially unchanged through the intestines" (Your digestive system, 2010, NIH). Fruits and vegetables, such as the tomato and lettuce on the bread are high in fiber as well as whole grains. Eating low-sugar fruits and vegetables like lettuce and tomato is important because these substances are high in essential vitamins. Dark green lettuces, such as spinach, are especially nutritious and tomatoes contain the vital nutrient of vitamin C Water-soluble vitamins like vitamin C and the B. vitamins "are not easily stored and excess amounts are flushed out in the urine," which is why it is so important to eat them every day (Your digestive system, 2010, NIH). Although juices are not optimal sources of nutrition because of their sugar content, vitamin C-containing fruits or vegetables such as apples and oranges could and indeed should be consumed on a daily basis. If Jane is worried about her sugar content, however, broccoli and some other green vegetables can be used as extremely low-sugar, non-fruit sources of vitamin C