Fibre is an essential part of our diet. It is important for the purposes of keeping bowel movement regular and there is very good evidence that it has important health benefits such as lowering cholesterol levels and reducing the risk of colon cancer. It is otherwise known as roughage and is the indigestible portion of food derived from plants.
There are two main components. Firstly, soluble fibre which as the as the name suggests dissolves in water and is readily fermented in the colon into gases and physiologically active by-products. Also, it delays gastric emptying and this in itself results in a feeling of satiety which is helpful in weight loss.
The other type is insoluble fibre which does not dissolve in water. This is metabolically inert and provides bulking. It absorbs water in the process of moving through the gut and, within the colon, it results in easing of defaecation.
Fibre can act by changing the nature of the content of the gut and by changing how other nutrients are absorbed.
Food sources of dietary fibre are often divided according to whether they provide soluble or insoluble fibre. Plant foods contain both types in varying quantities. The health advantages of fibre largely are through the production of healthy compounds during the fermentation of soluble fibre and also through insoluble fibres ability to increase bulk and to soften stool thereby shortening transit time in the gut.
Because of the gas produced in the colon, as a side effect of the action of bacteria on fibre, it tends to cause bloating which can be problematic particularly in patients who suffer from irritable bowel syndrome.
Soluble fibre is found in varying quantities in all plant foods but sources that are particularly high include legumes such as peas, soy beans and other beans, together with oats, rye, chia and barley. It is also found in fruits including figs, avocados, prunes and ripe bananas. It is found in vegetables such as broccoli and carrots, in psyllium husks and flax seeds. Nuts are also an important source of soluble fibre with almonds being the highest.
Sources of insoluble fibre include legumes once again together with nuts and seeds but also wholegrain foods such as wheat and corn. It is also found in vegetables such as green beans and cauliflower and celery.
As far as the amount of fibre that is desirable on a daily basis, there is no real minimum and importantly you can never take too much fibre in. However, it is important to bear in mind that some foods that are high in fibre are also high in carbohydrates and this is an important consideration if you’re also trying to lose weight. Minimising carbohydrate allows the body to utilise its stored adipose tissue as an alternative energy source hence promoting weight loss.