Insoluble fibres are a type of dietary fibres (also called roughage) which is the indigestible part of the plant. Because of this property of indigestibility, dietary fibres are included as a part of our food for the normal functioning of our digestive system.These comprise indigestible carbohydrate polymers and lignin. Humans cannot digest these fibres as we do not have the enzymes to digest them. Based on solubility, these dietary fibres are classified as soluble fibres and insoluble fibres. As the name suggests insoluble fibres are insoluble in water and are poorly fermentable or non-fermentable fibres.
Dietary fibres are extensively studied as they help in regulation of physiological functions such as lowering of blood cholesterol, improvements in gastrointestinal mobility, stimulation of bacterial metabolic activity, and can do a lot to support gut health.These fibres improve growth and activity of beneﬁcial bacteria in the human digestive tract by acting as food for intestinal microflora, an activity termed as prebiotic.
The sources of dietary fibres are cereals, legumes, fruits, and vegetables. Both fibres are present in different concentration in various foods. In general, Insoluble fibresare more abundant in foods as compared to soluble fibre. They generally constitute one-third or two-thirds of total dietary fibre. Insoluble fibres are mainly present in the outer shell of seeds, grains, fruits, and vegetables.
How are insoluble fibres different from soluble fibres –
Both types, soluble and insoluble have different actions and influence on normal gut activity. Apart from the difference in solubility there are many others which are classified in the following table –
- They are easily fermented by microfloraof the large intestine
- Upon dissolution in water they may or may not form a viscous gel
- They help in slower glucose absorption – by increasing intestinal transit time
- They are poorly fermented or cannot be fermented in the large intestine
- They do not form gel due to their water insolubility
- They generally increase faecal bulk and excretion of bile acids by decreasing intestinal transit time
Consumption of insoluble fibres in India –
The consumption of fibres in India is low compared to other parts of the world. The basic tendency of humans has always been to consume natural foods. However, urbanisation has increased the demand and consumption of processed and packaged foods. Different processing methods like milling of grain to yield refined flour, canning of fruits and vegetables reduce supply of fibre in diets.India’s traditional dietsincorporate all nutrients including fibre in proper proportion; however,changing lifestyles have reduced fibre intake and increased risk of various diseases.Therefore, many processed food manufacturers have introduced fibrerich products using wheat bran, oat bran and other ingredients.
Insoluble fibresare extracted from wheat, oat, pea, corn, cellulose, soy, apple, etc. However in India the production of these insoluble fibres is very low. Most insoluble fibres are imported and incorporated into various food products such as nutrition bars, beverages, supplements etc. In India, there is production of wheat bran which is considered a rich source of insolublefibre, soy fibre, cellulose, and insoluble citrus fibre; all the other insoluble fibres are imported. Food grade corn fibre is not produced in India; however, feed grade corn fibre manufacturers are available.
The recommended Daily Allowance (RDA) of dietary fibreis 35-40 gm per day for an adult.There is no dietary reference intake for insoluble fibre. Fibre intake in India varies from 15-41 gm per day depending on the type of food consumed.People who consume unrefined cereals and plant foods can achieve RDA of fibre, but the increasing trend towards replacing traditionally cooked foods with readily available processed foods has decreased fibre intake amongst Indians.More than 80% of the insoluble fibre consumption is contributed by cereals. The remaining is contributed by processed foods which contains extracted insoluble fibres.
Challenges and opportunities –
Fibre has now become the third most sought-after health information in supermarkets in India. Market drivers for insoluble fibres vary by region, sector, and consumer awareness about the ingredient. In India, in the functional food market, soluble fibres are favoured over insoluble fibres because soluble fibres have the ability to form gels and provide viscosity.Whereas insoluble fibres are favoured in the meat analogs sector, where they are used to improve the texture of the foods.
The major challenge faced by insoluble fibres is their low availability in India; there is lower production and usage of ingredient in different products. Importing insoluble fibres increases the overall product price, hence end-use sectors do not depend much on insoluble fibres.
People have forgotten the importance of traditional foods and moved towards processed food. This results in insufficient intake of insoluble fibres and supplementation of nutrients for the human body. Awareness levels of the Indian population about insoluble fibre and their nutritional properties possessedis low, resulting in lower demand of products with insoluble fibres. But slowly the demand for fibre rich products is increasing.
A survey on Digestive healthrevealed that nearly 56% of Indian families report digestive health issues and this can be managed by changing eating habits and including insoluble fibres in diet. Including insoluble fibres as a part of daily diet can help overcome the risk of digestive health issues.Creating awareness about the importance of digestive health can help overcome related diseases such as obesity, CVD, type 2 diabetes, and others.
Covid-19 has increased the demand of health supplement products rich in proteins, fibresetc, as people have become more health conscious. The use of insoluble fibres in supplement products like weight management products, dietary supplements, functional beverages can fulfil the demand of fibres.
Insoluble fibres have their own unique properties which can help maintain healthy gut health. Increased consumption of processed and packaged foods has led to reduction in fibre intake and has increased chronic disease prevalence. Consumption of insoluble fibres can help reduce the risk and maintain a healthy digestive system.
Overall the Indian demand for insoluble fibres is still nascent but is showing fastest growth compared to other regions of the world. Since India is a developing country, the demand for healthy products is increasing rapidly, people’s awareness is also growing which is why insoluble fibres have a great potential. Currently,insoluble wheat fibre and insoluble oat fibre are majorly used and contribute to more than 45% of total insoluble fibre usage.These two fibres are majorly used in the bakery sector to increase the fibre content of products and to improve texture. Oat fibre is also used in the meat analog sector to improve product texture.Pea fibre, Apple fibre and cellulose fibre have limited applications and very few products in India make use of these fibres. Although pea fibre has high potential to be used in the rapidly growing meat analog sector in India.
Increase in demand of insoluble fibres by creating consumer awareness can encourage local producers to produce insoluble fibreslocally. Currently end-use sectors are readily including insoluble fibres into various products. Given that lifestyle changes have increased processed food demand and lowered intake of insoluble fibrein India, it becomes imperative to include insoluble fibres in diet through other possible means, including through the consumptionofproducts that contain extracted insoluble fibres.
- MohiniNitturkar is a Research Analyst at F1rst. She has completed her B.Tech in Food Technology from Shivaji University, Kolhapur.