Diabetes affects the manner in which the body handles digested carbohydrates. If neglected, diabetes can cause serious health complications, ranging from blindness to kidney failure.

Approximately 8% of the population in the United States has diabetes. This means that approximately 16 million people have been diagnosed with the disease, based only on national statistics. The American Diabetes Association estimates that diabetes accounts for 178,000 deaths, 54,000 amputees, and 12,000-24,000 cases of blindness annually. Blindness is 25 times more common among diabetic patients compared to nondiabetics. It is proposed that by the year 2010, diabetes will exceed both heart disease and cancer as the leading cause of death through its many complications.

Diabetics have a high level of blood glucose. The blood sugar level is regulated by insulin, a hormone produced by the pancreas, which releases it in response to food consumption. Insulin causes the cells of the body to take in glucose from the blood. The glucose is used as fuel for cellular functions.

Diagnostic standards for diabetes have been fasting plasma glucose levels greater than 140 mg/dL on two occasions and plasma glucose greater than 200 mg/dL following a 75-gram glucose load. More recently, the American Diabetes Association lowered the criteria for a diabetes diagnosis to fasting plasma glucose levels equal to or greater than 126 mg/dL. Fasting plasma levels outside the normal limit require additional tests, usually by repeating the fasting plasma glucose test and (if indicated) giving the patient an oral glucose tolerance test.

The symptoms of diabetes include excessive urination, excessive thirst and hunger, sudden weight loss, blurred vision, delay in healing of wounds, dry and itchy skin, repeated infections, fatigue and headache. These symptoms, while suggestive of diabetes, may be due to other reasons also.

There are two different types of diabetes.

Type I Diabetes (juvenile diabetes or insulin-dependent diabetes): The cause of type I diabetes is caused by pancreatic inability to produce insulin. It is responsible for 5-10% of cases of diabetes. The pancreatic Islet of Langerhans cells, which secrete the hormone, are destroyed by the body's own immune system, probably because it mistakes them for a virus. Viral infections are thought to be the trigger that sets off this auto-immune disease. It is more common in caucasians and runs in families.

If untreated, death occurs within a few months of the onset of juvenile diabetes, as the cells of the body starve because they no longer receive the hormonal prompt to take in glucose. While most Type I diabetics are young (hence the term Juvenile Diabetes), the condition can develop at any age. Autoimmune diabetes can be definitely diagnosed by a blood test which shows the presence of anti-insulin/anti-islet-cell antibodies.

Type II Diabetes (non insulin dependent diabetes or adult onset diabetes): This diabetes is a result of body tissues becoming resistant to insulin. It accounts for 90-95% of cases. Often the pancreas is producing more than average amounts of insulin, but the cells of the body have become unresponsive to its effect due to the chronically high level of the hormone. Eventually the pancreas may exhaust its over-active secretion of the hormone, and insulin levels fall to below normal.

A tendency towards Type II diabetes is hereditary, but it is unlikely to develop in normal-weight individuals eating a low- or moderate-carbohydrate diet. Obese, sedentary individuals who eat poor-quality diets based on refined starch, which constantly activates pancreatic insulin secretion, are prone to develop insulin resistance. Native peoples such as North American Indians whose traditional diets did not include refined starch until its recent introduction by Europeans have extremely high rates of diabetes, up to 5 times the rate of caucasians. Blacks and hispanics are also at higher risk. Though Type II diabetes is not fatal within a matter of months, it can lead to health complications over several years and cause severe disability and premature death. As with Type I diabetes, the condition is found primarily in one age group, in this case people over 40 (which is why it is often termed Adult Onset); however, with the rise in childhood and teenage obesity, it is appearing in children as well.

If neglected, diabetes can lead to life-threatening complications such as kidney damage (nephropathy), heart disease, nerve damage (neuropathy), retinal damage and blindness(retinopathy), and hypoglycemia (drastic reduction in glucose levels). Diabetes damages blood vessels, especially smaller end-arteries, leading to severe and premature atherosclerosis. Diabetics are prone to foot problems because neuropathy, which affects approximately 10% of patients, causes their feet to lose sensation. Foot injuries, common in day-to-day living, go unnoticed, and these injuries do not heal because of poor circulation through the small arteries in the foot. Gangrene and subsequent amputation of toes or feet is the consequence for many elderly patients with poorly-controlled diabetes. Usually these sequelae appear earlier in Type I than Type II diabetes, because Type II patients have some of their own insulin production left to buffer changes in blood sugar levels.

Type I diabetes is a serious disease and there is no permanent cure for it. However, the symptoms can be controlled by strict dietary monitering and insulin injections. Implanted pumps which release insulin immediately in response to changes in blood glucose are in the testing stages.

In theory, since it caused by diet, Type II diabetes should be preventable and manageable by dietary changes alone, but in practice many diabetics (and many obese people without diabetes) find it personally impossible to lose weight or adhere to a healthy diet. Therefore they are frequently treated with drugs which restore the body's response to insulin, and in some cases injections of insulin.