Macronutrients in our diet:
Fiber
Fiber is present in fruits, vegetables, grains, and legumes. Fiber is not digestible and has no nutrients or calories. Its value lies in its ability to speed foods through the digestive tract and (possibly) bind them.
Fiber is thought to help remove toxins so they do not harm the intestine. Some types of fiber also help control blood glucose and cholesterol levels.
Fiber is also useful because it helps the stomach feel full, and has semi-laxative properties making bowel movements easier. It is thought to help ward off colon cancer.