According to the World's Healthiest Foods, one apple contains 17 percent of the daily value of fiber. Fiber can be soluble or insoluble, with both types having health benefits.
Because insoluble fiber can't be digested by the body, it adds bulk to the stool and slows down its transit time through the intestines. Soluble fiber also adds weight to the food while it's in the stomach and contributes to the feeling of satiety.
Fiber also helps more kinds of beneficial flora enter the intestine and increases the production of short-chain fatty acids, pancreatic enzymes and soluble bile. This balances levels of blood sugar and insulin.