Fibre – why’s it so good for us?

by Ali on June 5, 2008


(This is the fourth post in the Dieting Basics series.)

What is fibre?

Fibre is actually a type of complex carbohydrate, but unlike other carbohydrates (and protein and fat), fibre can’t be digested by the body so is not turned into energy. It’s sometimes referred to as “dietary fibre” (to distinguish it from other fibres, such as the sort found in wood and in fibre optics). The scientific term for dietary fibre is “non-starch polysaccharides” or NSP.

Fibre is an essential part of the diet because it keeps things running smoothly, lowers cholesterol, controls blood-sugar and is calorie-free (whilst fibre does contain some calories, they aren’t used by the body). A particular bonus for dieters is that it helps create a “full” feeling.

Soluble and insoluble fibre


There are two types of fibre: soluble and insoluble: both are important as they have different benefits.

Insoluble fibre keeps your stools soft and bulky, helping your bowel to pass them easily and preventing constipation. This is often what people think of when “fibre” is mentioned – the “roughage” found in bran and most vegetables. It speeds the transit of food through the digestive system (including the stomach, intestine and colon).

Soluble fibre is used by bacteria in the colon to produce fatty acids. These are thought to lower cholesterol levels – reducing the risk of heart and arterial disease – and control blood sugar by delaying the absorption of glucose into the blood stream. This sort of fibre slows the digestion of food in the stomach, helping you to feel full.

Most soluble fibre is also highly fermentable (types of fibres which ferment in the colon are sometimes called “fermentable fibre”) and thought to help prevent colon cancer.

How much fibre should I eat?

The daily recommended minimum consumption of fibre is 18 grams – but most adults in the UK and US only eat 12 grams a day. The ideal level is thought to be between 25 grams and 40 grams per day.

If you currently don’t each much fibre, increase the levels of fibre in your diet gradually; for example, if you’re averaging 10 grams a day, increase to 15 grams a day for a week, then to 20 grams a day for the second week, then 25 grams a day. Suddenly eating a lot more fibre than usual can overburden your digestive system, and lead to stomach cramps, diarrhoea or wind (not very pleasant for your office mates…!) Make sure you drink plenty of water, too; fibre absorbs water (which is why it helps keep your stools soft.)

What foods are good sources of fibre?

Try adding in some of the following foods to your diet, or having more of them if you already eat them regularly. Don’t worry too much about getting a balance of soluble and insoluble fibre, as many foods contain both.

Soluble fibre

  • Fruits (especially apples)
  • Vegetables (especially peas)
  • Oats
  • Beans and lentils
  • Soya milk

Insoluble fibre

  • Bran
  • Vegetables (especially the skins of root vegetables)
  • Wholegrains (wholemeal bread, wholemeal pasta)
  • Seeds and nuts

If you’re eating your five-a-day for fruit and veg, and eating wholegrain breads, cereals and pastas, you’ll be easily meeting that 25 gram target!

If you missed part three of the Dieting Basics series, find it here: Protein: essential, but how much do you need?… and make sure you get the rest of the series in your feed reader.

(Image above by Cool Librarian)

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