There are five main kinds of nutrients in food. A balanced diet means eating a variety of different foods to get the right mix of nutrients. Exactly what mixture you need changes during your life. A football-mad, growing teenager, for example, needs a lot more nutrients for energy and growth than a 70-year-old who likes fishing! Knowing what your body needs and where to get it will help you get the balance right. Your body also needs loads of water. In fact, you're over 70% water! You lose water all the time through breathing, sweating and going to the loo and you need to replace it by drinking - you should try to drink 2 litres of fluids such as water, juice or milk a day.