Understanding the roles of glucose in the brain is important for people with metabolic disorders such as diabetes. Since the brain consumes large amounts of glucose, maintaining a constant source in the blood is crucial to insuring normal brain function. Thus, monitoring and managing fluctuations in blood glucose levels are central focuses of diabetic care.
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What is Glucose?
Glucose is chemically classified as a carbohydrate. Usually called a sugar, glucose is the primary source of energy for every cell in the body. Glucose is largely converted from other carbohydrates in the foods we eat. The body breaks down the carbohydrates in the intestines using enzymes and other chemicals resulting in glucose as a final product. The glucose is then absorbed through the intestines and enters the bloodstream for use in the brain and other tissues.
The Brain’s Energy
The brain is the most complex and energy demanding organ in the body, requiring almost twice as much energy as any other organ. This is because the brain is rich in neurons, or nerve cells. These cells expend energy to create specialized enzymes and proteins in order to function. A primary function of all neurons is to generate electrical signals for communication with other neurons in the brain. Generating and transmitting these electrical signals uses nearly 10 percent of the body’s total energy supply.
The key role of glucose in the body is fuel for energy, and the brain depends completely on glucose to operate normally. Brain functions such as thinking, learning and memory are closely tied to glucose levels and how effectively the brain utilizes glucose. If glucose is lacking, neurotransmitters are not synthesized and communication between neurons breaks down. Age also plays a role in glucose utilization since an older brain uses more glucose than a younger one to perform the same learning and memory tasks. Glucose is so crucial that memory function can be improved in elderly people with relatively poor memories after only one hour of eating a carbohydrate rich meal.
Brain and Blood Sugar
The term blood sugar refers to the amount of glucose circulating in the blood. The blood sugar of a normal person is below 120 milligrams per deciliter one or two hours after eating a meal. When blood sugar levels are too low or too high, it is referred to as hypoglycemia or hyperglycemia, respectively. Hypoglycemia can lead to loss of energy for brain function. This is why low sugar levels are linked to poor attention and cognitive function. Hyperglycemia can be a result of diabetes, where blood sugar is too high but the sugar is not getting to the brain. Thus, the brain is starved of energy and functions less efficiently, as if the body were hypoglycemic.