Fibre: Soluble and Insoluble

Fibre is plant constituent that is generally resistant to human digestion. The word fibre originates from the Latin word fibra, meaning fibre, thread, string, filament, entrails. Fibre is also known as roughage. It is the indigestible part of plant foods that pushes through our digestive system, absorbing water along the way and easing bowel movements.

insoluble fiber foods:

Plant material in the diet that is resistant to enzymatic action in the digestive system is called as dietary fibre. Fibre provides structural support to plant cell walls and plant in general. The diets which contain a good amount of insoluble fiber foods have been reported to have a positive effect on health.

Fibre is made of non-starch polysaccharides such as

1. cellulose
2. hemicellulose
3. gums
4. mucilages
5. pectin
6. oligosaccharides
7. lignin etc

Fibre is again classified as

1. soluble fiber foods
2. insoluble fiber foods

Typically, plants contain a mixture of both. Usually, when a food is said to contain soluble or insoluble fiber foods it means the majority of the fibre in it is soluble or insoluble. Food sources of dietary fibre are often divided according to whether they provide largely soluble or insoluble fiber foods. Both are important for health, digestion, and preventing diseases.

Soluble fibres are water soluble or gel-forming viscous fibres. Soluble fibre holds water and turns to gel during digestion. The effects of soluble fibres are because of viscosity. The constituents of soluble fibre are pectins, gums and mucilages. Soluble fibres used as food ingredients include inulin, fructo-oligosaccharides, guar gum and xanthan gum

Soluble fibre sources include

1. psyllium husk
2. oats
3. barley
4. legumes
5. fruits
6. vegetables                                                                                         

Insoluble fibres are hydrophobic. They are not digested in the small intestine, they increase the transit time through the gut, delay gastric emptying and slow glucose absorption. They can be degraded in the small intestine.

Insoluble fibres such as cellulose and lignin decrease gut transit time and increase fecal bulk. Being insoluble they are poorly fermented and mostly un-metabolised. About 60-75 % of the dietary fibre in a typical mixed food diet are insoluble. Insoluble fibre supports the growth of intestinal microflora (especially probiotic species) due to its fermentation in the large intestine

insoluble fiber foods include

1. whole grain cereal
2. wheat bran
3. flax and other seeds
4. fruits
5. vegetables

Why fibre is a must in our diets?

Because of the following health benefits that dietary fibre offers

1. Adds bulk to the diet, making us feel full faster (Helps maintaining weight)
2. Holds water increases stool weight (Prevents constipation)
3. Helps manage glucose and LDL cholesterol levels in blood (Aids in management of diabetes and reduces risk of heart diseases)
4. Helps regulate blood pressure
5. Balances intestinal pH and stimulates intestinal fermentation production of short-chain fatty acids
6. May reduce risk of colorectal cancers

Dietary guidelines recommend inclusion of about 30 gm soluble and insoluble fiber foods per day (50 % from grains, 30 % from vegetables and 20 % from fruits) or 10-13 gm dietary fibre per 1000 kcal. Management of weight, prevention and management of diabetes and the metabolic syndrome can all be linked to fibre content in the diet. Many products such as breakfast cereals, bread, cookies, cakes, beverages and meat products are being fortified with fibre to avail these health benefits.