Under normal circumstances the human brain consumes approximately 120ΓÇô130g of glucose per day., which constitutes its main, if not sole, source of energy. During prolonged fasting or starvation the brain can metabolise ketones, such as aceto-acetate and b-hydroxybutyrate, as its main fuel (Fig. 20.5). In children, the switch from glucose to ketones as the main source of cerebral energy may occur as little as twenty-four hours after the withdrawal of food.
