Most food intolerances are found through trial and error to determine which food or foods cause symptoms. You may be asked to keep a food diary to record what you eat and when you get symptoms, and then look for common factors. Another way to identify problem foods is to go on an elimination diet. This involves completely eliminating any suspect foods from your diet until you are symptom-free. You then begin to reintroduce the foods, one at a time. This can help you pinpoint which foods cause symptoms. Seek the advice of your healthcare provider or a registered dietitian before beginning an elimination diet to be sure your diet provides adequate nutrition.