The human brain is about 73% water. Even mild dehydration, as little as a 1–2% loss in body weight due to fluid deficit, can impair mental performance. Children, in particular, are more vulnerable to the effects of dehydration because they have higher water needs relative to their body weight and are often less aware of thirst cues than adults. A study published in the Journal of the American College of Nutrition (2007) found that mild dehydration negatively affected mood, memory, and attention in both young and older adults. For children, whose brains are still developing, the stakes are even higher: water isn’t just a refreshment; it’s a fuel for learning.
