You need air, so you breath. You need food, so you get hungry and want to eat. But when you need water, your body may not send you a clear signal. People don't feel thirsty until they are already somewhat dehydrated. That's why it's important for athletes in particular to make a habit of drinking up.
Water is an essential nutrient, so it's very important.
But very often, athletes are not well hydrated. She teaches in the Nutritional Sciences Program based in the School of Public Health and Community Medicine. Steen has written books about sports nutrition, and counsels Husky athletes about their diets. The body needs water to keep cool. That can lead to a breakdown of the body's cooling system, which can lead to muscle cramping, heat illness, heat stroke and even death.