We’ve all heard “an apple a day can keep the doctor away.” But there is some hard science behind the age-old anecdote. Fiber, not only from apples, but also in a host of other fiber-rich foods, can add years to your life. Roughage, as our grandparents used to call it, goes a long way in fighting disease and building our bodies. Simply put, eating more fiber can save your life. Here are three ways eating more fiber can save your life.

What Is Fiber?

Fiber is the indigestible part of plants. It moves through the digestive system and in the process absorbs water. Foods like fruits and vegetables typically contain some level of fiber, some higher than others. And no, not all fiber is created equal.

Insoluble fiber is generally the kind of fiber that does not dissolve in water nor change form as it moves through the digestive tract. Some excellent sources of insoluble fiber are seeds and fruit peels. So rather than remove the skin of your favorite fruit, go ahead and eat it as well. Some other examples are whole-wheat bread and brown rice.

Soluble fiber, on the other hand, dissolves in water and typically transforms into a gelatinous form as bacteria in the stomach ferment it.

Fiber Fights Cancer

Insoluble fiber is an excellent weapon in the fight against cancer. Imagine insoluble fiber as the fit friend in your entourage. She’s the one who looks like a billboard poster. No jiggly fat. No independently moving parts. Hard as nails. Insoluble fiber is essentially the kind of fiber that runs through the digestive system like a bulldozer.