Rosalee Brown, Contributor

In response to last week's article 'Out goes the washout in comes fibre' a reader writes that the article 'was not very helpful as most of the terms used could not be understood by the average reader including myself. In regards to the portion which deals with increasing faecal bulk, you mentioned that wheat and rice bran can achieve this, however, which other foods can be eaten to give similar results."

Here is my response to that email. I spoke of insoluble fibre in the last article. This indigestible plant material has great water-binding capacity and because they cannot be broken down by the human digestive system, travel through, increasing the size and moisture content of the stool and so prevent constipation.

When the diet has a higher than normal amount of insoluble fibre, the passage time of stool is faster than normal, giving a cleansing effect. Cellulose makes up the largest percentage of the insoluble fibre and is present in most unrefined plant foods, its high in bran, peas, beans, root vegetables, vegetable of the cabbage family, and the outer covering of seeds. In terms of water-binding capacity, wheat and rice bran (especially coarsely ground) are most effective.

Hemicellulose is also found in the plant cell walls, but contains types of sugars in its makeup, which influence fermentation in the large bowel. Some of these sugars influence flatulence.

Pectin

Pectin is a water-soluble gel-forming substance found in the plant and also contains special sugars. Unlike cellulose, pectin can almost be completely broken down by bacteria in the colon. Foods high in pectin are citrus fruits and apples.

About soluble fibre

Soluble fibres are soluble in hot water and are found in hemicelluloses, pectin and gums. In general, vegetables, wheat and most grain products contain more insoluble fibre than soluble fibre.

The soluble fibre absorbs water, becomes gel like and delays the movement of the stomach contents to the small intestine, causing a sense of fullness for longer. This causes a slower movement through the intestine and slow absorption of nutrients such as glucose.

It can also affect the activity of enzymes that digest fat, by absorbing some of the fatty acids, cholesterol and other components of fat digestion, resulting in its reduced digestion. It also absorbs bile acids, making it unavailable and therefore causing more cholesterol to be broken down to make the necessary bile acid, leading to lowering of cholesterol.

The presence of soluble and insoluble fibre in the colon can lower the risk of colon cancer by various mechanisms, including the provision of substances for bacteria to ferment in the large intestines. This can help in reducing the development of cancer-forming cells. We should therefore aim to eat more plant foods which are unprocessed.

Rosalee M. Brown is a registered dietitian/nutritionist who operates Integrated Nutrition and Health Services; email: yourhealth@gleanerjm.com.