What is the main source of energy for the brain?

The brain primarily relies on glucose as its main source of energy. Glucose is a simple sugar that is easily transported and utilized by brain cells, allowing for efficient energy production through cellular respiration. The brain consumes a significant portion of the body's glucose despite making up only a small percentage of total body weight.

While other substances like fatty acids can be used for energy by other parts of the body, the brain has a high requirement for glucose due to its continuous activity and dependence on aerobic metabolism. Fructose and lactose, though they serve as carbohydrates, are not the principal energy sources for the brain. Fructose is metabolized differently and may not be as readily available to the brain. Lactose, which is found in milk, must be broken down into glucose and galactose prior to being utilized, making it less efficient for immediate brain energy needs. Therefore, glucose stands out as the most efficient and direct source of energy for brain function.