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Nutrition

A little bit about fibre

Fibre is essential to the digestive system. It swells the bulk of food left after the nutrients have been removed, giving it shape and a dough-like consistency. Without it, your daily poo will come out slimy – like a wet fish, and diets with insufficient fibre can result in irritable bowel syndrome, constipation, haemorrhoids and piles.

Western diets tend to be low in fibre because we eat so much processed and refined food. Fibre comes from vegetables, high fibre breads and fruit and is the part of food that is not digested. It stays in your gut and is passed in poo stools (faeces) adding bulk.

You should aim to have 18-25g a day. Even if you’re on the go, there are easy ways to increase your fibre intake, although too much fibre can lead to constipation if taken with insufficient fluid.

Why is fibre important?

Poo stools are usually soft and easy to pass if you eat enough fibre, and drink enough fluid. We should aim to eat at least 18 grams of fibre per day. (The average person in the UK eats only about 12 grams of fibre each day.) A diet with plenty of fibre:

  • Will help to prevent and treat constipation
  • Will help to prevent some bowel conditions such as diverticular disease, piles (haemorrhoids) and a painful condition of the back passaged (anus), which is called anal fissure
  • May help you to lose or control weight. Fibre is filling but it has no calories and is not digested
  • May reduce the risk of developing bowel cancer
  • May help to lower your blood lipid (cholesterol) level
  • May reduce the risk of developing diabetes and help to control your blood sugar levels

Types of fibre

There are two types of fibre in the diet – insoluble fibre and soluble fibre. They work differently in the body. A combination of both types of fibre should form part of a healthy balanced diet in order to keep your gut healthy. Many foods containing fibre will naturally contain both types.

Insoluble fibre

This type of fibre is found in skin, pith and pips of fruit and vegetables, wheat and bran, corn (maize), nuts and whole grains
This type of fibre cannot be dissolved in water. It passes through the digestive system mostly unchanged. It acts like a sponge and absorbs water, adds bulk to stools (faeces), and allows waste to be passed through bowels more quickly. This helps to prevent constipation and other conditions such as piles (haemorrhoids) and diverticular disease.

Soluble fibre

This type of fibre is found in oats, barley, psyllium and ispaghula, nuts and seeds, fruit and vegetables, and beans and pulses.
This type of fibre does dissolve in water and can be broken down by the natural germs (bacteria) in the bowels. It softens stools and makes them larger, so that they are easier to pass. It also forms a gel in the stomach when mixed with water. The gel binds with excess cholesterol so it does not get absorbed, which helps to reduce the risk of heart disease. Also, soluble fibre helps to slow down the digestion of food; therefore, sugar (glucose – our main source of energy) is released and absorbed slowly. This keeps our blood sugar levels steady.

Fluid

Fibre needs fluid to work, so have lots to drink when you eat a high-fibre diet or fibre supplements. Drink at least two litres (about 8-10 cups) per day. This is to prevent a blockage of the gut, which is a rare complication of eating a lot of fibre without adequate fluid. This might include water, sugar-free squashes, herbal/fruit teas, tea and coffee.

Increasing fibre in the diet

You may find that if you eat more fibre or fibre supplements, you may have some bloating and wind at first. This is often temporary. As your gut becomes used to extra fibre, the bloating or wind tends to settle over a few weeks.

If fibre intake is suddenly increased, this can cause symptoms of wind and bloating. Introduce high-fibre foods gradually to allow the gut to become used to the extra fibre. Introduce one new food over a 2- to 3-day period. For example, have porridge for breakfast on the first day; then add beans or extra vegetables to a casserole two days later; then maybe have an extra piece of fruit 2 to 3 days later.

Some people report that a high-fibre diet causes some persistent mild symptoms such as mild pains and bloating. In particular, some people with irritable bowel syndrome find that an increase in fibre makes symptoms worse. But, this may be related to the type of fibre you take. It is probably soluble fibre rather than insoluble fibre that is most helpful, especially when aiming to ease symptoms of irritable bowel syndrome. Bran and other insoluble-based fibre may actually make symptoms worse in some people.

Tips for increasing fibre

  • Swap white bread for wholemeal bread
  • Swap refined cereals such as Rice Krispies® or Cornflakes® to wholegrain versions such as porridge or Bran Flakes®/ Weetabix®/ Shredded Wheat®
  • Swap white rice and pasta to brown/ whole wheat varieties
  • Add extra vegetables to mince, casseroles, soups, stews, curries or chillies
  • Add beans and pulses to mince, casseroles, soups, stews, curries or chillies
  • Snack on a piece of fruit or vegetable sticks
  • Sprinkle seeds (eg, pumpkin seeds, golden linseeds, sunflower seeds) over soups, salads or yoghurt
  • Choose foods labelled with ‘high-fibre’
  • Keep the skins on fruit and vegetables when possible
  • Add nuts or dried fruit to breakfast cereals
  • Serve at least one portion of fruit or vegetables at each mealtime

  Why is fibre important? | NHS Choices
  Dietary fibre | British Nutrition Foundation
  Dietary fibre | Wikipedia

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