METABOLISM AND ELIMINATION
All carbohydrates are changed to the simple sugar glucose before metabolism can take place in the cells. After glucose has been carried by the blood to the cells, it can be oxidized. Frequently, the volume of glucose that reaches the cells exceeds the amount the cells can use. In these cases, glucose is converted to gly-cogen and is stored in the liver and muscles. (Glycogen is subsequently broken down only from the liver and released as glucose when needed for energy.) When more glucose is ingested than the body can either use immediately or store in the form of glycogen, it is converted to fat and stored as adipose (fatty) tissue.
The process of glucose metabolism is controlled mainly by the hormone insulin, which is secreted by the islets of Langerhans in the pancreas andwhich maintains normal blood glucose at 70–110 mg/dl. When the secretion of insulin is impaired or absent, the glucose level in the blood becomes excessively high.
This condition is called hyperglycemia (blood glucose more than 126 mg/dl) and is usually a symptom of diabetes mellitus. If control by diet is ineffective, an oral hypoglycemic or insulin injections must be used to control blood sugar. When insulin is given, the diabetic client’s intake of carbohydrates must be care-fully controlled to balance the prescribed dosage of insulin. When blood glucose levels are unusually low, the condition is called hypoglycemia (blood glucose less than 70 mg/dl). A mild form of hypoglycemia may occur if one waits too long between meals or if the pancreas secretes too much insulin. Symp-toms include fatigue, shaking, sweating, and headache.
Oxidation of glucose results in energy. With the exception of cellulose, the only waste products of carbohydrate metabolism are carbon dioxide and water. It is a very efficient nutrient.