The digestion time varies from food to food, but overall most people can digest food completely in about 4 hours. In the process of food digestion fruits require the shortest digestion time, about half an hour to an hour; while the digestion time of vegetables is mostly forty minutes to two hours, with root vegetables such as sweet potatoes, taro and potatoes taking a relatively long time to digest. Cereals take from one and a half to three hours to digest, with the shortest and highest digestibility of fluid or semi-fluid; while proteins and fats take the longest, about four hours. This shows that consuming too much fatty food can increase the gastrointestinal burden; and patients with chronic gastrointestinal disease can be aggravated by eating fried foods. To sum up, different foods take different lengths of time to digest, and the digestion time varies from person to person. But as long as the amount of food suitable for their own, generally about four hours will be completely digested.