You might think that with all the things adults do in a day, their brains would need a lot of fuel. Children on the other hand just play all day. Some go to preschool, but even then, they do fun activities like crafts, they play in the playground, and they play with their friends. Surely, that doesn’t require much brain energy, right? Well, as with most things in science, things can seem a certain way until someone decides to conduct a study on it.
Researchers found that children’s brains account for up to 87% of their resting metabolic rate, which is the rate at which their bodies burn energy when it is at complete rest. This energy is primarily in the form of glucose (more commonly, sugar). This is no surprise since young children have incredibly active brains, and have many more neurons than adults. Infants are born with a surplus of neurons, which are pruned and rewired over the years of childhood. During those years, their experiences largely dictate how neurons in their brains form connections, which pathways are strengthened, and which are weakened or removed. These processes are collectively known as synaptogenesis and synaptic pruning, but we’ll get into that next time. For now, just think of it as the brain’s way of increasing efficient information transfer.
A child’s brain can consume up to 150g of glucose per day between the ages of 4-9. Adult brains, on the other hand, consume on average 90g of glucose per day. Researchers speculate that one of the reasons a child is able to allocate so much energy to her brain is because her body is not going through many physical changes at that time (i.e. no major growth spurts). It is only during adolescence that the body begins to transform drastically. As with all humans, food is the main source of energy for a baby's brain. That's why early childhood nutrition is as important for brain development as it is for physical development. This is also a topic of interest that we will discuss next time. For now, we can just look at our children in awe, wondering what their busy brains might be thinking of.
Metabolic costs and evolutionary implications of human brain development
Author(s): Christopher W. Kuzawa, Harry T. Chugani, Lawrence I. Grossman, Leonard Lipovich, Otto Muzik, Patrick R. Hof, Derek E. Wildman, Chet C. Sherwood, William R. Leonard, and Nicholas Langel