Answer: Dietary fibres (roughage) are not digested and give no energy, but they keep the digestive system healthy.
Fibres absorb water and add bulk to the food, so the movement of food through the intestine becomes easier. They prevent constipation and help in the smooth removal of waste. They also help to lower blood cholesterol and control blood sugar. Since the body cannot make them, they must be taken in the diet through fruits, vegetables and whole grains.