Fibre. A basic outline of the importance of fibre in the diet.

dietary fibre

What is fibre?
Fibre or "roughage" as it is also known, is essentially a carbohydrate and is found solely in plants. It is found in the walls of the plant's cells and is the only part of the plant that cannot be digested by the human body.

What is the function of fibre?

The main function of fibre is to keep the digestive system healthy and functioning properly. Fibre aids and speeds up the excretion of waste and toxins from the body, preventing them from sitting in the intestine or bowel for too long, which could cause a build-up and lead to several diseases.

Insoluble fibre
Fibre passes through the body virtually unchanged along with other digested food until it arrives at the large intestine. What happens next depends on which type of fibre is present.

In the case of insoluble fibre, it promotes the growth of a certain friendly bacteria that ferments and makes the waste material soft and bulky, which in turn helps it to pass through the intestines quicker to the bowel and out of the body.

Insoluble fibre prevents constipation, which consists of small, hard and dry faeces that are hard to pass, by adding bulk and liquid to aid movement, and promote regular bowel movements. A larger and softer stool is able to pass through the intestines and bowel more easily and fluidly and is easier to evacuate.

As waste material passes through the body quickly and does not stay in the intestines or bowel for very long, toxins are not able to build up and accumulate. This is important in the prevention of distressing diseases such as bowel cancer or other cancers, constipation, irritable bowel syndrome, haemorrhoids and diverticulitis.

Sources of insoluble fibre
Insoluble fibre can be found in foods such as bran, wholemeal flour and breads, brown rice, whole grain cereals, vegetables, edible peels of fruit, nuts and seeds.

Soluble fibre
Soluble fibre absorbs water in the intestine, which softens the stool and helps the waste material move through the body more quickly.

It is thought that soluble fibre may help to reduce the level of cholesterol in the blood. This is due to the fact that soluble fibre binds the cholesterol from food or from bile acids, which are made up of cholesterol, preventing it from being absorbed into the bloodstream. This is then eliminated as waste, as the fibre cannot be digested.

Soluble fibre also slows down digestion and the sudden release of energy, especially from carbohydrates into the bloodstream. This means that blood sugar levels are more stable, which is good for people with diabetes, and energy or glucose is released slowly and steadily, preventing sudden feelings of tiredness, lack of energy or hunger pangs.

Sources of soluble fibre
Soluble fibre-rich foods include fruits, vegetables, lentils, peas, beans, oats, barley, oatmeal, potatoes, dried fruit, soya milk and soya products.

Foods that are low in fibre
Eating a diet that does not contain enough fibre can lead to bowel irregularities and stomach discomforts. Foods that do not contain any or contain very little fibre include refined cereals and white bread, meat and animal products, dairy produce and fast foods.

What is the recommended daily fibre intake?

An adequate intake of fibre is about 18g a day, however anything up to 30g - 35g is recommended.

If you are going to increase the amount of fibre in your diet, you should also drink higher levels of water to compensate the water that is absorbed by the fibre; otherwise this could also lead to constipation.

Is too much fibre bad for you?

Just as too little fibre in the diet is not good for the body, too much fibre can also have a negative impact.

Too much fibre can lead to a deficiency in important minerals such as zinc, calcium and iron.

These minerals sometimes bind to the fibre, which is then eliminated from the body without allowing the minerals to be absorbed into the bloodstream.

Fibre-rich foods should be increased gradually, starting off with adding more fruit, vegetables and cereals to the diet first.

This is because foods such as pulses and beans can lead to excessive flatulence and abdominal discomfort if the body is not used to them. This is not a long-term problem and should only last for a few days whilst the body has time to adjust.

Can eating fibre-rich foods help you lose weight?

Foods that are rich in fibre are generally low in fat and calories and do not make you put on weight.

In addition, fibre slows down digestion, making you feel satisfied and full up for longer. This will stop you from snacking on unhealthy foods, which do make you put on weight.

Fibre-rich foods are often bulky and fill you up quicker as well, which prevents you from overeating. This type of food also slows down the rate at which you eat, giving your brain time to register that your stomach is full with food.

How can I introduce more fibre into my diet?

Fibre should be introduced gradually into the diet and can be done in a number of ways including:
  • Start the day with porridge, high fibre cereals or wholemeal bread.
  • Eat more portions of fruit and dried fruit.
  • Eat potatoes with their skins intact.
  • Include chickpeas or lentils to salads, stews and curries.
  • Try to eat more raw fruit and vegetables.
  • Add seeds and nuts to salads or eat as a snack.
  • Switch to brown rice, brown bread and wholemeal pasta.
  • Buy foods containing whole grains.
  • Add barley to homemade soups.
  • Remember to also increase your water intake.

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