Fibre consists of thread like strands of cellulose or cell products that are not normally digested by humans. Fibre is a part of most vegetables, cereals, nuts and fruit, and the insoluble parts that cannot be broken down by intestinal bacteria and digested, is passed out in the faeces. Cut an orange in halves and you will see the white fibre.
Fibre food does not cause indigestion because it cannot be digested, and does not always look stringy. For example, peas and beans are high in fibre, cucumber is very low, and celery is in between. The average person should eat 40g of fibre a day.
A high-fibre diet is one way of overcoming obesity, since it makes the stomach feel full so one feel less hungry, but there are fewer kilojoules to be absorbed from the food into the body. Furthermore, the fibre residue in the bowel increases the size and wetness of the stools, and so eases defecation and prevents constipation. The down side may be an increase in flatulence (wind).
Diseases that benefit from a high-fibre diet include diverticulitis (small outpocketings of the large bowel), diabetes, gallstones, arteriosclerosis (hardening of the arteries), irritable bowel syndrome, cancer of the bowel, varicose veins, piles and hernias. The incidence of these diseases is significantly less in populations who eat high-fibre diets. Moderation, however, is important. A diet made up entirely of fibre-based foods would lack essential nutrients, fats, carbohydrates and vitamins.
Fibre comes in many different forms including:-
Cellulose is a polysaccharide that forms the wall of plant cells and maintains their structural integrity. It forms the major part of the fibre in a human diet and is completely insoluble and indigestible, having no nutritional value, but along with other fibres being essential for the function of the gut. High levels of cellulose are found in beans, celery, bran, bananas and apples.
Frangula is a fibre that is commonly used as a laxative in powder or granule form to ease constipation. It is safe in pregnancy, but not advised for use in breastfeeding and children under 12 years, and should not be used for a long period of time.
Do not take frangula supplements if on a salt, potassium or sugar restricted diet; suffering from severe constipation with impacted faeces; suffering from belly pain, nausea or vomiting, or suffering from ulcerative colitis or acute diverticulitis. It interacts with thiazide diuretics, steroids, liquorice and high sugar content sweets. Patients should ensure that they consume adequate amounts of water when taking frangula.
Ispaghula is a widely used form of fibre that may be taken as granules with water to ease constipation. It must be used with caution if on a salt restricted diet. Do not use it if suffering from phenylketonuria, mega-colon or gut obstruction. Belly discomfort and passing excess wind are the only side effects, and usually only occur if insufficient water drunk.
Methylcellulose is a dietary fibre supplement used to treat constipation, excessive appetite and diverticulitis. Two to five tablets are taken three times a day with water before meals. It is not recommended in children. Ensure an adequate fluid intake while using methylcellulose, but do not use it if suffering from a bowel blockage. Loose bulky motions are the only side effect. The absorption of a wide range of medications may be affected when methylcellulose is used, although it is totally inactive in body, and merely acts to add bulk to faeces.
is a gelatinous bulking agent found in plants and used as a setting agent in jellies and stabiliser in many foods. In medicine it is used as a tablet or suspension to manage mild diarrhoea. It is safe in children, but ensure an adequate fluid intake. Side effects are effectively non-existent, but it may affect the absorption of some drugs (eg: digoxin).
Psyllium is a fibre obtained from the seeds of a plant called Plantago psyllium. It is widely used as a laxative to ease constipation when taken with water two or three times a day. Do not take it if on a salt, potassium or sugar restricted diet, suffering from severe constipation with impacted faeces, or suffering from belly pain, nausea or vomiting. The side effects are usually minimal but may include diarrhoea, belly discomfort and bloating. It can affect the absorption of other drugs for up to two hours after use.
Senna (one of the sennosides) is a natural fibre used as a laxative to treat constipation. It is available as tablets, granules and even chocolate squares. It is safe in children over six years, but do not use it long term without medical advice. Do not take senna if suffering from stomach pain or gut obstruction, nausea, vomiting or diarrhoea. The side effects are minimal but it may cause belly discomfort. It is very safe and widely used.
Sterculia is a widely used natural fibre supplement. In medicine it is used in granule or powder form as a laxative to aid constipation. One or two heaped teaspoons are taken with water twice a day at least two hours before bedtime.
It is safe in children over six years. Do not take it if about to go to bed or suffering from ulcerative colitis, and ensure an adequate fluid intake. Side effects are minimal but may include diarrhoea and belly discomfort.