Which nutrient is primarily used by the brain as an energy source?

The brain primarily uses carbohydrates as its main energy source. When carbohydrates are consumed, they are broken down into glucose, which is a form of sugar that the brain can directly utilize for energy. Glucose is crucial for proper brain function, as it provides the necessary fuel for neurons to operate effectively. Additionally, the brain requires a continuous supply of glucose; it cannot store significant amounts, making a regular intake of carbohydrates essential for cognitive functions.

Fats, while an important energy source for the body, are not the primary fuel for the brain in the same way that carbohydrates are. Proteins serve various functions in the body, such as building and repairing tissues, but they are not used directly as an energy source unless carbohydrates are lacking. Water, though vital for overall health and bodily functions, does not provide calories or serve as an energy source.