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The causes and types of diabetes

November 24, 2010
By Mary Lou Williams, M. Ed.

The two types of diabetes

There are two types of diabetes, Type 1, formerly called juvenile diabetes, and Type 2, formerly called adult-onset diabetes. Type 1 diabetes is the less common of the two and accounts for five to 10 percent of all cases of diabetes. It is due to little or no insulin production by the pancreas. Type 1 diabetes most often occurs in children and young adults. Most people who have Type 1 diabetes develop the disease before the age of 30. Type 2 diabetes accounts for 90 to 95 percent of all people with diabetes. It usually begins in adults older than 40 years and is most common in people older than 55. It becomes progressively more common with age.

Approximately 25 percent of Americans over age 60 have diabetes. (However, it is becoming increasingly common in people under 30, including children and adolescents, for reasons we will explain shortly.) The excess sugar in the blood of Type 2 diabetics is due not to a lack of insulin but to a lack of response to the insulin that is present. The bodies of Type 2 diabetics develop resistance to the effects of insulin. In this way, Type 2 diabetes differs from Type 1 diabetes. In Type 2 diabetes the pancreas continues to produce insulin. In fact, early in the course of the illness, many Type 2 diabetics have high levels of circulating insulin as the pancreas attempts to compensate for the insulin resistance. Over the years, this causes the pancreas to "burn out," and the insulin level then falls below normal.

The causes of Type 1 diabetes

Type 1 is believed to be caused by infection; type 2 is believed to involve genetic predisposition. This is a simplification, but it gives the basic difference between the causes of the two types of diabetes. The inability of the pancreas to produce insulin is thought to be an auto-immune disorder in which the immune system destroys the insulin-producing cells of the pancreas. Why the immune system starts attacking and destroying these cells is unknown, but scientists have a number of theories. Possibly a viral infection such as mumps, measles, whooping cough, or the flu might trigger the immune response. Incidence of Type 1 diabetes increases after major influenza epidemics. Perhaps an allergic reaction to foods introduced early in life may play a role. One study done in 1992 implicated the drinking of cow's milk in infancy as a cause of Type 1 diabetes. Breast-fed infants have a significantly lower risk for developing Type 1 diabetes than bottle fed infants. Pediatricians now advise new mothers not to feed their infants cow's milk during the first year of life.

The causes of Type 2 diabetes

Type 2 diabetes is thought to be due to a combination of heredity and environmental influences such as diet. A person is more likely to develop diabetes if family members have it. However, the genetic predisposition will not manifest itself unless there is an environmental trigger or triggers. Those environmental triggers are diet and lack of exercise. Evidence supporting environmental influences such as diet in the cause of Type 2 diabetes includes the fact that obesity is the chief risk factor for developing Type 2 diabetes: 80 to 90 percent of people with this disease are obese. Obesity is directly related to diet. But what about the 10 to 20 percent of Type 2 diabetics who are not obese? This paradox will be addressed in next week's column. Next week's article will also address the way to prevent or reverse Type 2 diabetes without the use of drugs.

Mary Lou Williams, M. Ed., is a writer and lecturer in the field of nutrition. She welcomes inquiries. She can be reached at 267-6480.



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