Diabetes (medically known as diabetes mellitus) is a chronic metabolic disorder characterized by elevated levels of blood glucose, or sugar. It occurs when your body produces little or no insulin or when your cells don’t respond appropriately to the insulin that is produced. Diabetes usually can’t be cured; left untreated — or poorly managed — it can lead to serious long-term complications, including kidney failure, amputation, and blindness. Moreover, having diabetes increases your risk for cardiovascular disease, including heart attack and stroke.
How sugar is metabolized
Many of the cells in your body need sugar as a source of energy. When you eat carbohydrates, such as a bowl of pasta or some vegetables, your digestive system breaks the carbohydrates down into simple sugars (generally glucose), which are ferried into and through your bloodstream to nourish and energize cells.
A key player in the metabolism of sugar is the pancreas, an elongated gland behind your stomach and liver. The pancreas fills two roles. First, it produces enzymes that flow into the small intestine to help your body digest proteins, carbohydrates, and fats. Second, it makes hormones that regulate the disposal of nutrients, including sugars. The islets of Langerhans, tiny clusters of cells found throughout the pancreas, are responsible for producing these hormones. They are composed of alpha cells, which produce the hormone glucagon, and beta cells, which secrete insulin. These hormones generally have opposite actions, but both are important in regulating your body’s use of sugar, fat, and protein.
Much like traffic cops dispatched at rush hour to ease congestion, insulin is released by beta cells in response to the rise in blood sugar levels after you’ve eaten. By directing sugar into liver and muscle cells, it promotes the storage of nutrients and prevents blood sugar levels from rising excessively. It also increases the uptake of amino acids (the building blocks of proteins) and fatty acids (the building blocks of fats) into protein and fat stores, respectively. Insulin thus serves as one of the principal gatekeepers of metabolism, promoting energy storage and growth.
The liver turns glucose that is, not needed immediately for energy into glycogen. When blood glucose levels goes low, your pancreas releases the hormone glucagon, which prompts your liver to reconvert stored glycogen in glucose and release it to bloodstream. Usually insulin and glucagon levels fluctuate in a coordinated fashion to keep your blood glucose levels within a rather narrow range.
In healthy people, insulin prevents a large rise in blood sugar after eating. The normal blood sugar level before breakfast usually hovers between 70 and 110 milligrams per deciliter (mg/dL). Normal levels of sugar in the blood rarely exceed 180 mg/dL, even after having eaten a meal. This is important because certain organs, such as the brain and kidneys, depend on a consistent, steady supply of glucose. A normally functioning pancreas assures your body of a stable supply of nutrients.