fibre

Fibre is the indigestible part of plants. It includes cellulose, hemi-cellulose, lignin, pectin, and gums. It is sometimes called bulk or roughage. Fibres are grouped into two basic types: insoluble fibre and soluble fibre.

Insoluble fibre absorbs many times its own weight in water and swells up in the alimentary canal. People on high fibre diets tend not to suffer from obesity because they feel full and so consume less food. By increasing the bulk of faeces, fibre promotes efficient waste elimination from the colon and may help to prevent colon cancer. The bulk also provides a resistance against which the gut muscles can work. These muscles produce the peristaltic waves of contraction that push food along the gut. Efficient peristalsis reduces the risk of intestinal disorders such as constipation. Insoluble fibre is found in wholegrains and vegetables; it includes cellulose and lignin. Much of it is resistant to human digestive enzymes and therefore passes through the alimentary canal virtually unaltered.

Soluble fibre is found in many plant foods, but is especially rich in oat bran. Some types are broken down by micro-organisms in the large intestine into substances that can be absorbed through the gut wall and into the bloodstream. Fibre regulates the transit time of faeces and reduces the risk of constipation. It may prevent or reduce the absorption of cholesterol (high cholesterol levels are a risk factor of coronary heart disease). It may also delay the entry of glucose into the blood. This means that blood glucose levels do not fluctuate widely, reducing the risk of glucose overload or deficiency, and diabetes.

Most nutritional experts agree that Western diets are deficient in fibre. The National Institute of Cancer in the United States, recommends that 25-50 grams of fibre should be eaten per day. Although wholegrain cereals are an excellent source, the fibre should be provided from a variety of sources (for example, fruits, vegetables, beans, and whole baked potatoes). In addition to providing fibre, these foods provide valuable minerals and vitamins.

People on high fibre diets should drink plenty of water or the fibre may partially block the gut, inhibit digestion, and cause intestinal problems. They should also be aware that fibre can reduce protein absorption. This problem can be reduced by eating plenty of protein and by getting fibre from a variety of foods. Some types of dietary fibre, such as unprocessed bran, are not recommended as sources of fibre because they contain high levels of phytic acid which may interfere with the absorption of minerals. See also fibre supplements; F-plan diet; and non-starch polysaccharide.

1. The indigestible part of plants consisting of non-starch, structural polysaccharides including cellulose, hemicellulose, gums, pectin, and lignin. Nutritionists divide fibre into two main types: water-insoluble fibre (e.g. cellulose and lignin) and water-soluble fibre (e.g. guar and pectin). Foods high in fibre include cereals, fruit, and vegetables. Fibre is resistant to human digestion and therefore passes through the gut virtually unaltered, absorbing water, and helping to accelerate the elimination of faeces. A diet rich in fibre decreases the time taken for food to pass through the alimentary canal. It reduces the risk of constipation and some types of cancer. It may also help to reduce cholesterol levels, but a diet that has too much fibre may lead to diarrhoea, loss of body fluids, and dehydration. A balanced diet contains about 20-40 g of fibre (depending on age) per day with about three-quarters being water soluble.

2. A thread-like process such as a muscle fibre, collagen fibre, or nerve fibre.

The noun has 3 meanings:

Meaning #1: a slender and greatly elongated solid substance
  Synonym: fiber

Meaning #2: the inherent complex of attributes that determine a persons moral and ethical actions and reactions
  Synonyms: character, fiber

Meaning #3: a leatherlike material made by compressing layers of paper or cloth
  Synonyms: fiber, vulcanized fiber