Water is a vital component of our diets, even though it's not considered a specific nutrient. Water makes up 50 to 70 percent of an adult's total body weight. Without regular top-ups, our body's survival time is limited to a matter of days. Water is essential for the body's growth and maintenance. For example, it helps get rid of waste and regulates temperature, and it provides a medium for biological reactions to occur in the body. Water is lost from the body through urine and sweat, and must be replaced through the diet. If you don't consume enough water, your kidneys suffer, causing symptoms such as headaches, tiredness and loss of concentration. Most healthy adults need between 0.5-3 litres a day, so aim to drink 6-8 medium glasses of fluid daily. Beverages such as tea, coffee and fruit juices count towards fluid intake, and may bring with them other nutrients or benefits.