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Introduction to Diabetes

Jessica Evert, MD, edited by Benjamin McDonald, MD

a chocolate glazed donut with sprinkles

Diabetes Mellitus ("diabetes" for short) is a serious disease that occurs when your body has difficulty properly regulating the amount of dissolved sugar (glucose) in your blood stream. It is unrelated to a similarly named disorder "Diabetes Insipidus" which involves kidney-related fluid retention problems.

In order to understand diabetes, it is necessary to first understand the role glucose plays with regard to the body, and what can happen when regulation of glucose fails and blood sugar levels become dangerously low or high.

The tissues and cells that make up the human body are living things, and require food to stay alive. The food cells eat is a type of sugar called glucose. Fixed in place as they are, the body's cells are completely dependent on the blood stream in which they are bathed to bring glucose to them. Without access to adequate glucose, the body's cells have nothing to fuel themselves with and soon die.

Human beings eat food, not glucose. Human foods get converted into glucose and other macronutrients as a part of the normal digestion process. Once converted, glucose enters the blood stream, causing the level of dissolved glucose inside the blood to rise. The blood stream then carries the dissolved glucose to the various tissues and cells of the body.

Though glucose may be available in the blood, nearby cells are not able to access that glucose without the aid of a chemical hormone called insulin. Insulin acts as a key to open the cells, allowing them to receive and utilize available glucose. Cells absorb glucose from the blood in the presence of insulin, and blood sugar levels drop as sugar leaves the blood and enters the cells. Insulin can be thought of as a bridge for glucose between the blood stream and cells. It is important to understand when levels of insulin increase, levels of sugar in the blood decrease (because the sugar goes into the cells to be used for energy).

The body is designed to regulate and buffer the amount of glucose dissolved in the blood to maintain a steady supply to meet cell needs. The pancreas, one of your body's many organs, produces, stores and releases insulin into the blood stream to bring glucose levels back down.

The concentration of glucose available in the blood stream at any given moment is dependent on the amount and type of foods that people eat. Refined carbohydrates, candy and sweets are easy to break down into glucose. Correspondingly, blood glucose levels rise rapidly after such foods have been eaten. In contrast, blood sugar rises gradually after eating more complex, unrefined carbohydrates (oatmeal, apples, baked potatoes, etc.) which require more digestive steps take place before glucose can be yielded. Faced with rapidly rising blood glucose concentrations, the body must react quickly by releasing large amounts of insulin all at once or risk a dangerous condition called Hyperglycemia (high blood sugar) which will be described below. The influx of insulin enables cells to utilize glucose, and glucose concentrations drop. While glucose levels can rise and fall rapidly, insulin levels change much more slowly.  When a large amount of simple sugar is eaten the bloodstream quickly becomes flooded with glucose.  Insulin is released by the pancreas in response to the increased sugar.  The glucose rapidly enters the cells but the high levels of insulin remain in the bloodstream for a period of time.  This can result in an overabundance of insulin in the blood, which can trigger feelings of hunger and even Hypoglycemia (low blood sugar), another serious condition. When blood glucose concentrations rise more gradually, there is less need for dramatic compensation. Insulin can be released in a more controlled and safer manner which requires the body experience less strain. This more gradual process will leave you feeling "full" or content for a longer period of time. For these reasons, it is best for overall health to limit the amount and frequency of sweets and refined sugars in your diet. Instead eat more complex sugars such as raw fruit, whole wheat bread and pasta, and beans. The difference between simple and complex sugars (carbohydrates) is exemplified by the difference between white (simple) and whole wheat (more complex) bread.

Insulin is the critical key to the cell's ability to use glucose. Problems with insulin production or with how insulin is recognized by the cells can easily cause the body's carefully balanced glucose metabolism system to get out of control. When either of these problems occur, Diabetes develops, blood sugar levels surge and crash and the body risks becoming damaged.