Roughage is the parts of plant foods that your body can't digest, also called fiber. When you eat an apple, carrot, or piece of whole wheat bread, your body breaks down most of it for energy and nutrients. But roughage passes through your digestive system mostly unchanged, like a gentle scrub brush cleaning as it goes.

Even though your body doesn't digest roughage, it's incredibly important for staying healthy. Roughage helps food move smoothly through your intestines and keeps your digestive system working well. Without enough roughage, digestion can become sluggish and uncomfortable.

You find roughage in vegetables, fruits, whole grains, beans, and nuts. The chewy skin on an apple contains roughage. So does the brown coating on brown rice (white rice has had this coating removed). Popcorn, oatmeal, and whole wheat pasta all contain roughage.

Your great-grandparents probably called it roughage, while doctors and nutritionists today usually say fiber, but they mean the same thing.