Carbohydrates form the basis of providing the energy need to carry out aerobic activity. Examples of carbohydrates are wholemeal pasta, porridge oats, bananas etc. Eat small portions and often and have something small about an hour before you run. Eating too much or too soon before running will make you ill or give you a stitch. You will eventually get to know your own metabolism and what works for you. After exercising a combination of protein and carbohydrates is best. Protein helps repairs the muscles and carbohydrates help restore energy levels. You should have something within an hour of exercising (banana, bagel etc.).  

Keep hydrated. The body requires on average two litres of water a day. When exercising you need even more. For activities of duration under 1.5 hours water is sufficient but when participating in events for longer then this, a sports drink should be used. This helps replace energy, electrolytes and salts. It is important to stress that drinking too much can be dangerous. This can cause swelling of the brain and there have been know fatalities in sporting events due to this. A rule of thumb is to consume about 250-300 mls of fluid every 20 minutes when running.