Answer:
The body uses sugars from carbohydrates which supply the brain with glucose as the brain uses it as a "fuel source".
Why is glucose so important for the brain?
Quick answer: It takes a lot of energy to receive, interpret, and send signals via your neurons. Glucose is the simples sugar that can be used to make energy.
Cells require energy to carry out their typical everyday tasks. The simplest sugar that our cells can utilize for energy is glucose. Since your neurons are specialized cells, many additional cells are also present to support or protect them. All of the senses you can experience utilizing incoming neurons (from the body to the brain) are transmitted to and interpreted by the brain, including touch, pain, vibration, temperature, smell, sight, hearing, taste, and others. Signal reception and interpretation need energy. Additionally, your brain instructs your body to "do" things, which uses energy. Additionally, you spend a significant portion of your waking hours "thinking," which consumes energy. This explains why 20% of the glucose in your body is used by our teeny, tiny, little brains.
Thank you,
Eddie