Glucose is a simple sugar that provides the body with its primary source of energy. This type of sugar comes from digesting carbohydrates into a chemical that the body can easily convert to energy. When glucose levels in the bloodstream aren't properly regulated, a person can develop a serious condition, such as diabetes.
People get most of their glucose from digesting the sugar and starch in carbohydrates. Foods such as rice, pasta, grain, potatoes and processed sweets contain carbohydrates that can be converted into glucose. The body's digestive system, using bile and enzymes, breaks down the starch and sugar in these foods into glucose. This functional form of energy then gets absorbed through the small intestine into the bloodstream. It is then carried throughout the body, providing energy for the person to perform all types of activities, such as simple movements, demanding physical exercises or even thinking.
Foods can be rated according to the glycemic index, which indicates how quickly the carbohydrates are broken down by the body and the glucose is released into the bloodstream. White bread and most breakfast cereals have a high glycemic index, which means that the carbohydrates are broken down and the body's blood-sugar levels raised more quickly. Most fruits, vegetables and nuts have low glycemic indexes. Whole-wheat products and some types of potatoes have glycemic indexes in the middle.
Glucose it is such a vital source of energy, and it interacts with both the digestive and endocrine system in the body, so keeping its levels — also called blood-sugar levels — in the bloodstream within a normal range is extremely important to a person's health. The human body has adapted to maintain this ideal level by storing extra glucose in the liver and muscles as glycogen, so that it can be reabsorbed into the bloodstream when the body's blood-sugar levels drop. Insulin, a hormone that is released by the pancreas, regulates the body's blood-sugar levels.
Excessively high blood-sugar levels, a condition called hyperglycemia, might be caused by too much sugar or too little insulin in the blood. In a person who has Type 1 diabetes, for example, the pancreas does not produce insulin, so he or she typically must receive regular insulin injections. Extremely low blood-sugar levels might result from eating too little food or having too much insulin in one's bloodstream.