Fiber and roughage are often used interchangeably, and to a certain extent, that's OK. Roughage is fiber, the part of plant foods that travels through your digestive system unchanged, promoting regularity and keeping your digestive system healthy. However, there are two kinds of fiber, soluble and insoluble, and roughage specifically refers to insoluble fiber.

Soluble fiber comes primarily from oat bran, beans, peas, lentils, seeds, nuts and some types of fruits and veggies. During digestion, soluble fiber binds with water to form a gel-like substance. Roughage, however, remains mostly intact during digestion, adding bulk to stool to help speed its passage. You can find roughage in vegetables, whole grains and wheat bran.

Roughage is largely responsible for maintaining regularity and bowel health. Its bulkiness helps clean out the colon and prevent waste from getting trapped and causing inflammation of the intestine, called diverticular disease. It also prevents constipation. The gel-like soluble fiber, on the other hand, is best known for its role in controlling bad cholesterol levels by interfering with the absorption of cholesterol during digestion.