Tuesday, April 21, 2009

Dietary Fibre - The Roughage Provider

Have you ever thought of the latest buzz of a multi national food brand's - 2 1/2 kgs weight loss programme? What are brown breads, digestive biscuits, white oats famous for? With a wide range of advertisements of food products flooding the market and claiming health benefits, it becomes extremely important for us, as consumers to be aware of the ingredients which make these products health friendly. Well, all these products are designed due to their fibre rich contents which imparts several health benefits.

With the advancement of food science and growing awareness of food items and their health related benefits, the term fibre has become a lay man’s term. Its origin comes from the textile industry because of its appearance. Hence, the thread like substance in food is referred to as ‘Dietary Fibre’.
It is popularly known as ‘Roughage’ and has been used for its beneficial effect since ancient times e.g. Isabgol used to relieve constipation is a well practiced grandma’s remedy, which does not need any doctor’s prescription. Likewise, fibre plays an important role in many health related issues.
Dietary fibre refers to that part of plant material which is resistant to enzymatic digestion by the human saliva because of the lack of the enzyme ‘Cellulase’, which is otherwise seen in ruminating animals like cows.

Categories of Dietary fibre
Cellulose found in bran, legumes, peas, root vegetables, cabbage family, outer covering of seeds, and apples
Hemicellulose found in bran and whole grains
Polyfructoses (inulin and Oligofructans)
Gums found in oatmeal, barley, and legumes.
Pectins, found in apples, strawberries, and citrus fruits
Lignin found in root vegetables, wheat, fruits with edible seeds (such as strawberries)
Resistant Starches found in ripe bananas, potatoes

Their function depends upon their soluble and insoluble properties.
e.g. Soluble fibre present in oat bran are known to reduce blood cholesterol levels by chelating to the dietary cholesterol and then eliminating them out of the body through faeces. On the other hand, insoluble fibre in bran maintains bowel regularity. But many plant sources contain both soluble and insoluble fibre.
Following are the functions of dietary fibre:-
Reduce cholesterol levels – Researches have proved that Fructo oligosaccharide present in tomatoes, chicory, onions, broccoli, when consumed upto 20 gms/ day and more help to get the deranged lipid profile within the normal range. This is by reducing the bad LDL cholesterol and increasing the good HDL levels.
Control blood sugar levels - Fibre in soluble forms in foods like oats cause a slow release of the carbohydrates present. Thus, help in controlling blood sugars.

Foods containing high fibre content such as whole wheat flour, beans, vegetables are known for their low Glycemic index (term relates to the rise in blood sugar level after consumption of a food item). Therefore, fibre imparts low glycemic index property to the foods in which they are present.
Promote weight loss – Fibrous foods like fruits with skin provide a greater and an early satiety than the ones without. It is because of this effect, salads or unstrained soups are prescribed as starters.
Maintain bowel regularity and thereby prevent colon cancer and haemorrhoids – Dietary fibres promote laxation (faecal bulking and softening, increased frequency), and regulate bowel movements. Insoluble fibre especially contributes to laxation and normal bowel function, but fermentable/soluble fibre promotes faecal bulking through fermentation and microbial growth.
Gut microbes ferment part of the fibre to short-chain fatty acids (SCFA) like propionic acid, butyric acid qnd acetoacetic acid. The concentration of SCFA produced varies depending on substrates, commensal microbes and site of fermentation. SCFA seems to be beneficial to gut health via several actions. Colonocytes absorb and metabolise SCFA, which are major respiratory fuels and trophic to the small bowel and colon. Short-chain fatty acids also lower pH in the intestines and are therefore believed to prevent the overgrowth of pH-sensitive pathogenic bacteria.
Thus, deficiency of fibre in the diet causes the relative health hazards.

Recommended Intake
Indians being majorly cereal eaters, there is less scope of fruits and vegetables in the Indian Diet. Therefore, an average Indian consumption ranges from 9 gms to 15 grams per day which is nearly half the recommended intake. Whereas WHO recommends, an average intake of 35 – 40 grams per day to maintain gut integrity and normal health.
Any consumption greater than 50g/day is supposed to be toxic and causes intestinal obstruction. In most individuals however, this amount will bring bowel health.
For Diabetics, 25 -50 gms/day is recommended to achieve a good glycemic control.
Dietary Fibre and Nutrient Interactions
Insoluble fibre that passes all through the intestine and remain unchanged may reduce the absorption and /or increase the excretion of several minerals including calcium and iron.
Food Sources
Whole grains, unsieved flour for kneading the chapatti dough, fruits like pomegranate, apples, papaya, guava, bananas, citrus fruits, vegetables like green leafy vegetables, salad vegetables like cucumber, cabbage, lettuce, broccoli etc. whole pulses, beans, legumes, nuts and oilseeds are all good sources of fibre.
Fruits like bananas, chickoos, grapes, custard apple, mangoes inspite of containing considerable amounts of fibre, should be judiciously consumed incase of diabetes because of their high fruit sugar content.
So next time you are stuck up with your high blood sugars, cholesterol, weight gain or constipation, think twice before popping up a pill !