What is the main source of energy for the brain?

The main source of energy for the brain is glucose. The brain relies heavily on glucose because it is a quick and efficient source of energy. Neurons primarily metabolize glucose through glycolysis and oxidative phosphorylation to meet their energy demands.

Unlike other organs in the body, the brain has a limited capacity to use fatty acids as an energy source, as they cannot cross the blood-brain barrier effectively under normal circumstances. While certain conditions, such as prolonged fasting or a ketogenic diet, allow the brain to utilize ketone bodies derived from fatty acids, glucose remains the preferred and primary fuel under normal circumstances. Proteins and amino acids are not primary energy sources; they are primarily utilized for growth, repair, and synthesis of neurotransmitters rather than as direct sources of energy for brain function. Thus, glucose's pivotal role underscores its importance in brain metabolism and function.