Consuming sufficient dietary fibre is essential to maintain a healthy digestive system. There are two main types of fibre – soluble and insoluble – and many different components of plants act as dietary fibres, including cellulose, lignin, beta-glucans and oligosaccharides.
Insoluble fibre passes straight through the digestive tract unchanged. Because it absorbs water on the way, it softens the stool and helps waste material pass through the intestines more quickly. Important sources include beans, lentils, whole grains and wheat bran.
Soluble fibre is not digested, but it does not pass through the body unaltered – it absorbs water to form a gel, and may be fermented by bacteria within the large intestine. Increasing the amount of soluble dietary fibre in the diet may increase the feeling of fullness, or satiety, and contribute to weight management. Sources include oats, peas, beans, lentils, fruits such as apples, oats, potatoes and some green vegetables.