Like cancer, diabetes mellitus—diabetes for short—is a group of diseases with a common biochemical characteristic. In diabetes, the common feature is abnormal metabolism of carbo¬hydrates, particularly glucose.
This can lead, over many years, to kidney disease, atherosclerosis, heart attack, stroke, gan¬grene, and other complications including blindness. In fact, diabetes is the third leading cause of blindness in the United States.
All types of diabetes have something to do with insu¬lin, a hormone produced by special cells in the pancreas, called islets of Langerhans. Insulin is one of several compounds the body uses to control the levels of glucose in the blood. With¬out insulin, blood sugar levels rise dangerously high. The same thing can happen if the body loses its ability to respond to insulin.
There are two main types of diabetes. The most seri¬ous is called insulin-dependent diabetes. In this disorder, the insulin-producing cells of the islets of Langerhans are destroyed, depriving the body of insulin. In most cases, this destruction seems to occur by the body’s own hand—cells of the immune system, for some unknown reason, come to see the islets cells as being invaders, and therefore the immune system destroys the cells as it would any foreign object. Diet is not thought to be a cause of this disease.
Insulin-dependent diabetes usually appears well before the age of 40. The only treatment is regular injections of insulin. About 10 percent of all diabetics—about 1.1 million people in the United States—have insulin-dependent diabetes.
The more common form of diabetes is called noninsulin-dependent diabetes. It is closely linked to the resistance to the action of insulin that occurs in obesity. It accounts for about 90 percent of diabetes cases, or nearly 10 million people in the United States.
Noninsulin-dependent diabetes usually appears in middle or old age, particularly in people who are overweight. As many as 9 percent of people 65 and older may have this disease.
Genetic, environmental, and lifestyle fac¬tors can place a person at increased risk for developing noninsulin-dependent diabetes.
The most important risk factors are in¬creasing age, family history of diabetes, and obesity—especially fat carried in the abdomen.
Researchers have found that fast¬ing blood sugar levels tend to increase as body weight in¬creases, but exactly how these risk factors contribute to the development of noninsulin-dependent diabetes is still the subject of research.