A nutritious diet can help to catapult your training, but there are some foods that can negatively affect your running routine when they are eaten too soon before a run. To play it safe, two to four hours before you head out, you should avoid spicy foods as these can irritate the gastrointestinal tract. Capsaicin, the chemical that gives food its fiery kick, can play havoc with the lining of the small and large intestine so avoid ingredients like chilli and paprika.