Which of the following is considered a primary source of energy for the body?

Glucose is considered a primary source of energy for the body because it is a simple sugar and the main form of carbohydrate that circulates in the bloodstream. When consumed, carbohydrates are broken down into glucose, which then can be used immediately for energy or stored in the liver and muscles as glycogen for later use. Glucose is especially critical for high-intensity activities, as it provides a quick and easily accessible energy source through glycolysis.

While fats and proteins can also provide energy, they are not primary energy sources in the same way that glucose is. Fats are a more concentrated form of energy and are utilized primarily during prolonged, lower-intensity activities. Proteins serve primarily as building blocks for tissues and are not typically utilized as an energy source unless necessary, especially in states of caloric deprivation.

Vitamins, on the other hand, do not provide energy themselves; they play vital roles as cofactors in various metabolic processes that can help the body utilize energy derived from carbohydrates, fats, and proteins. Thus, while other nutrients contribute to overall energy metabolism, glucose is the most immediate and accessible source of energy the body uses.