Which foods are insoluble fiber sources?

• A. Oats, peas, beans, apples
• B. Barley, psyllium, citrus fruits
• C. Whole-wheat flour, wheat bran, nuts, beans and vegetables such as cauliflower, green beans, and potatoes.
• D. Chicken, fish, eggs

Answer: (C)

Insoluble fiber comes mainly from parts of plant foods that add bulk and resist digestion, such as bran, skins, and cell walls. Foods like whole-wheat flour and wheat bran provide a lot of insoluble fiber, and nuts, beans, and vegetables with edible skins (such as cauliflower, green beans, and potatoes) contribute insoluble fiber as well. By contrast, oats and barley are rich in soluble fiber (like beta-glucan), psyllium is mostly soluble, citrus fruits contain soluble pectin, and chicken, fish, and eggs have no fiber. So the set that best represents insoluble fiber sources is the one that emphasizes bran, whole grains, nuts, and skin-on vegetables.