The best advice when training is to stick a healthy, balanced diet. If you do this, you will be getting all the nutrients you need to exercise regularly, so you won't need to take vitamins or other supplements to improve your running.
On training days, have a meal about three to four hours before you run if you can. This should be low in fat and fibre and high in carbohydrate, and include some protein. Then have a snack half an hour to an hour before your training.
Try to eat some starchy food within two hours of finishing long training runs and after the race - your muscles can replace energy (glycogen) twice as quickly during this time.
The week before your run
It's very important in the days before your race and during it that you stick to food and drink that you have tried before. Don't start trying lots of new foods as it may affect your digestion.
Sports dieticians recommend that in the three days leading up to the race more than the normal 60% of your food intake should be carbohydrates. This is important for maximising your muscles' energy stores.
The morning of your run
On the day of the race, have a meal that is high in carbohydrate and low in protein, fibre and fat, for example porridge with a banana or toast with honey. This will top up the level of energy in your muscles - particularly important if your race is first thing in the morning after eating nothing overnight.
Eat this meal between one and four hours before the start of the race so your stomach has time to empty.
After the race
Have something to drink and eat as soon as you can after crossing the finish line. Eating something salty will help you to rehydrate more quickly.