Importance of Dietary Fibre

Whenever you read an article or hear an expert talk about nutrition and a balanced diet, you must have noticed that dietary fibre is always one of the key focusing areas. Have you ever wondered why? Reason being, that it holds varied potential health benefits. Let’s begin by understanding what is dietary fibre. It is a type of complex carbohydrate which doesn’t get digested by our body. This plant-based fibre passes our small intestine undigested but on reaching the large intestine, it gets partially or completely fermented by the gut bacteria.  

ABSTRACT

Dietary fibre is an essential requirement of our diet. The indigestible plant parts are broadly classified as insoluble and soluble fibres. They vary on the basis of their water absorption capacity, fermentability and physical properties. Studies have shown that fibres aid in improving gut health, adds bulk to stool, alleviates constipation, diarrhoea and enhances the absorption of nutrients. Health benefits of fibre are mostly associated with maintaining blood sugar and lipid levels, mitigating the chances of cancer, improving digestion. After careful analysis and assessment of dietary needs, health authorities across the world have recommended specific intake of dietary fibres so as to get the majority of their benefits. A diet rich in fruits, vegetables, whole wheat grains, dalia, oats, ragi, barley, nuts, etc. are usually recommended to get a blend of all fibres in our diet. Let’s throw some more light in understanding fibres in detail. 

HISTORY

With the passage of time the concept and understanding of dietary fibre has changed substantially. Earlier the only significant association was bran in pacifying constipation and colitis. Hipsley gave the term “Dietary fibre" in 1953. It was defined as a plant cell component of our diet. Later in the 1970s, scientists mentioned dietary fibre as plant cell components which remains undigested even after acted upon by our digestive enzymes. Further research studies in later years gave us terms like cellulose, hemicellulose, pectin, gums, etc. as a part of fibres with each carrying out his or her significant roles in our diet. Eventually, dietary fibre evolved as an essential nutrient of our diet and was designated with a specified recommended dietary allowance by all Nutrition Authorities. As per National Institute of Nutrition India, minimum intake 30-40 grams of dietary fibre is advisable per day.

TYPES OF DIETARY FIBRE

Types of Dietary Fibre

Fibres are broadly classified as Insoluble and Soluble Fibre.

  • Insoluble fibres are not soluble in water. Though they pass undigested through our small intestine but are very important for our intestinal health. Reason being they absorb water, add bulk to stool thereby ensuring its smooth passage through the large intestine. Insoluble fibres are less fermentable than soluble fibres. 
  • Soluble fibres on the other hand, are soluble in water. They act as feed for probiotics in our gut. These fibres remain undigested even after being acted upon by digestive enzymes. Soluble fibres have the property of forming gel-like structures on coming in contact with water. We all know that our colon has numerous good and bad bacterias in it, also there has to be a balance in order to evade any chances of infection. On reaching colon in the large intestine these benefitting bacterias ferment on these fibres resulting in their proliferation. This fermentation results in the production of short chain fatty acids (SFAs). SFAs produced are used as energy source by colon cells. It also results in nutrients that are more feasible for absorption, improves colon health, hence ensures a healthy gut. 

  COMPONENTS OF DIETARY FIBRE 

Main components of dietary fibre are cellulose, hemicellulose, pectins, guar gums, inulin, beta - glucan and lignin. We will now understand each of them in detail.

  • Cellulose - This is a polysaccharide which means multiple glucose units linked to each other in a linear structure. Cellulose is an insoluble dietary fibre and forms a primary wall of plant cells. Most animals are able to digest this fibre as they have the digesting enzyme - cellulase in their body but humans do not have this enzyme due to which it remains undigested. Even though cellulose is not digestible by us, still its water holding and roughage forming property adds bulk to stool and aids in defecation.  
  • Hemicellulose - This polysaccharide also contains glucose and other sugar structures but these units are slightly less in number as compared to cellulose, linked to each other in a branched structure. These insoluble fibres are slightly soluble in an alkaline medium and have the same function as that of cellulose in our body. 
  • Lignin - This is a non-carbohydrate polysaccharide found in plant cells between the gaps of cellulose and hemicellulose. Lignin is also an insoluble dietary fibre which is most resistant to digestion.
  • Beta Glucan - β glucan are soluble fibres fermented by our gut bacteria. They serve as prebiotic on which Probiotic caters and results in the production of short chain fatty acids. Primarily found in oats, barley, wheat and bran. This soluble fibre majorly accounts for maintaining blood sugar, lipid levels and boosting immunity.
  • Pectin - This soluble fibre is found in citrus fruits. Due to its property of forming a thick gel-like structure when heated together with sugar, pectins are primarily used in making jams and jellies.
  • Guar Gum - It is a mix of two sugars - galactose and mannose, which is categorised under soluble fibres. As the name says, it is derived from a legume named Guar. This fibre is also used by many food processing industries as a thickener due to its gel-forming ability in water.
  • Inulin - This fibre is typically derived from chicory roots. It acts as a prebiotic in our body, boosting immunity and maintaining gut health like other soluble fibres.

BENEFITS OF DIETARY FIBRE

Benefits of Dietary Fibre

1. Dietary Fibre and Colorectal Cancer 

Dietary fibre has been significantly associated with a decreased risk of colon cancer. Fermentation of dietary fibre results in an increased growth of probiotics in the colon which overpowers unhealthy bacterias. Also during fermentation, organisms produce a substance Butyrate, which has anti-cancerous properties. Bingham et al. (2003) conducted a study on individuals aged 25-70 years from 10 European countries. It was observed when the fibre intake was doubled through food, then the risk of colorectal cancer was reduced by 40%.

In another study conducted by Wakai et al. (2007), results showed a decrease in risk of colorectal cancer with increased intake of total dietary fibre. 

2. Dietary Fibre and Cardiovascular Disease

Decreased risk of cardiovascular diseases has also been associated with dietary fibre intake. Credit goes to their gel-forming property which prevents instant blood glucose and lipid spike. These soluble fibre gels slowly release energy after enzymatic action on them, which gives satiety for long, prevents untimely cravings and hence weight gain. Another contributing factor in lowering bad cholesterol levels is that on fermentation of soluble fibres, organisms produce short chain fatty acids (SFA). The production of SFA prevents hepatic cholesterol synthesis, thereby preventing synthesis of LDL (Low-Density Lipoprotein). Burley V.J. et al (2013) conducted a study in which findings revealed a strong association with between dietary fibre intake and low risk of heart diseases. 

3. Dietary Fibre and Diabetes

As already discussed above, dietary fibre forms gel-like substance preventing instant glucose release and provides sustained energy. This aspect makes it ideal for diabetics. Multiple studies have supported this claim. The InterAct Consortium (2015) undertook a study in which participants were given diets more based on cereal and vegetable fibre. Its findings revealed indications of dietary fibre with a reduced risk of type 2 diabetes.

4. Dietary Fibre and Gut Health

Since dietary fibre came into existence as an important part of our diet, it was believed by scientists that regular consumption of the same has a positive effect on our gut health. Bacterial fermentation of soluble fibre improves the body’s ability to absorb nutrition. This also minimises chances of infection and keeps our gut in favour of good health. A healthy gut also prevents the occurrence of gastrointestinal discomforts like acidity, bloating, indigestion, abdominal cramps, nausea, heartburn and gastric pain. A study led by Healey et al. (2018) also gave similar findings. It was concluded that people with high dietary fibre intake have a greater gut microbiota than those with low dietary fibre intake. 

5. Dietary Fibre and Constipation

Constipation is a common problem these days. Many people take laxatives regularly to relieve constipation but continuous usage of drugs might lead to side effects in the long run. This is when dietary fibre comes to rescue. Its water holding property aids in pacifying constipation as dietary fibre softens the stool and makes it easy to defecate. Along with faulty dietary patterns, irregular meals, stress, sedentary lifestyle, constipation can also be seen as a symptom in people suffering from Irritable Bowel Syndrome (IBS) and diverticulosis. Nutrition experts recommend such people to increase their dietary fibre intake because of its potential to ease the bowel movements. This ability of dietary fibre was supported by a study conducted by Cabre (2011). In this study, fibre intake was increased in the dietary management of all three conditions and evidence proved in favour of dietary fibre to treat IBS, constipation and diverticulosis.    

6. Dietary Fibre and Obesity

 Due to its potential to maintain blood sugar and lipid levels, dietary fibre also reduces body’s tendency of gaining weight. The slowly releasing glucose keeps us full for long, thus providing satiety and preventing untimely nibbling in between meals. People who are aiming to lose that extra weight should always focus more on dietary fibre in their diet. It helps in averting excess calorie intake which is the main root cause of gaining weight. A study was conducted in the Netherlands by Vijver, et al (2009). Based on results, it was interpreted that people with a high intake of whole grains had lower BMI and reduced risk of gaining weight than people with a low intake of whole grains. Intake of Dietary fibre from both the groups was carefully monitored based on which researchers favoured the consumption of a fibre rich diet.  

SOURCES OF DIETARY FIBRE

Source of dietry fibre

With so many potential benefits, you must be wondering how to incorporate dietary fibre in your daily diet. We are blessed with various food sources rich in both insoluble and soluble fibres. We can consume below-listed fibre rich foods so as to meet our daily needs.

  • Cereals like whole wheat chapati, wheat bran, dalia, oatmeal, multigrain bread, ragi, jowar, bajra, millets, quinoa and brown rice. 
  • Whole pulses, legumes, lentils, beans and sprouts.
  • Fruits like amla, apple, avocado, berries, pear, plum, melon, orange, guava, pomegranate, kiwi, apricot, mango, figs, dates and pineapple.
  • Vegetables like peas, ladyfinger, cauliflower, sweet potato, carrots, broccoli, French beans, beetroot, green leafy vegetables, cabbage,  cucumber, zucchini, celery, lettuce, radish, tomato, potatoes with skin and capsicum.
  • Nuts like almonds, walnuts, prunes, chestnuts, pine nuts, pistachios, hazelnuts, peanuts and dried coconut.
  • Seeds like chia seeds, flaxseeds, pumpkin seeds, sesame seeds, melon seeds, sunflower seeds and gingelly seeds.
  • Due to its necessity as a part of our diet, food companies have introduced some fibre fortified food products like breakfast cereals, muesli, fortified bread, etc. We can make use of them as well to increase the nutrition content.
  • A fibre supplement is also an interesting option. They are convenient, easy to carry and safe to use. 

WHICH IS BETTER?

Now what if I ask you which one is better—soluble or insoluble fibres. Some of you might say either one or some may opt for both. The correct answer is a blend of both soluble and insoluble fibre. Both of them have a significant role to play in our digestion, gut health and many other processes so one should always ensure that our diet includes sources of both soluble and insoluble fibre. 

Another impressive choice would be a blend of different sources of fibres for example if you are using a supplement, it can be a blend of wheat fibre with inulin or inulin with guar gum. This way our body would be able to extract the majority of their unique health benefits.

CONCLUSION

So the takeaway from this literature is that both soluble and insoluble fibres are of paramount importance. They should be a part of a balanced diet. They are complex carbohydrates, without any calorie content, and help provide strength to our gut. Soluble fibres form a gel-like substance which assists in maintaining blood lipid and glucose levels. They make us feel satiated and prevent hunger pangs. By acting as a food source to microbes, soluble fibre promotes colon health and maximal absorption of nutrients. If you suffer from frequent constipation or diarrhoea, then opt for more of soluble fibres. Insoluble fibre adds bulk to our stool and creates the urge to defecate. This regular movement is important for our bowel as not only it is a kind of exercise of bowel muscle but irregularities might increase the chance of infections, piles, haemorrhoids and cancer. As per our Indian guidelines, 25-30 grams of dietary fibre is recommended for females and 30-40 for males. Make sure to consume a well-balanced diet rich in other nutrients as well. Fluid intake is a must to keep our body hydrated. 

To conclude, we can say that both soluble and insoluble fibres deserve equal attention. 

REFERENCES 

  • Sarker,M., & Rahman, M.(2017).Dietary fiber and obesity management.Adv Obes Weight Manag Control.7(3):295‒297
  • Li, Y. O., & Komarek, A.R.(2017) Dietary fibre basics: Health, nutrition, analysis, and applications, Food Quality and Safety, 1(1)47–59
  • Dietary fibre intake and risk of cardiovascular disease: systematic review and meta-analysis.BMJ (2013).347:f6879.Retrieved from https://www.bmj.com/content/347/bmj.f6879
  • Bingham, S.A., Day,N.E., Luben,R., Slimani,N.,Norat, T., et al.(2003) Dietary fibre in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition.361(9368), P1496-1501
  • Wakai, K., Date, C., Fukui, M. et al.(2007).Dietary Fiber and Risk of Colorectal Cancer in the Japan Collaborative Cohort Study.Cancer Epidemiology, Biomarkers & Prevention.16(4)
  • Hara,H., Haga, S., Aoyama, Y., Kiriyama, S.(1999) Short-Chain Fatty Acids Suppress Cholesterol Synthesis in Rat Liver and Intestine, The Journal of Nutrition, 129(5), 942–948
  • Holscher, H.D. (2017) Dietary fiber and prebiotics and the gastrointestinal microbiota, Gut Microbes, 8:2, 172-184, Retrieved from 10.1080/19490976.2017.1290756
  • Healey, G., Murphy, R., Butts, C., Brough, L., Whelan, K., & Coad, J. (2018). Habitual dietary fibre intake influences gut microbiota response to an inulin-type fructan prebiotic: A randomised, double-blind, placebo-controlled, cross-over, human intervention study. British Journal of Nutrition, 119(2), 176-189. doi:10.1017/S0007114517003440
  • Vijver, L.P., Bosch, L.V., Brandt, P.A., & Goldbohm, R.A. (2009). Whole-grain consumption, dietary fibre intake and body mass index in the Netherlands cohort study. European Journal of Clinical Nutrition, 63, 31-38.
  • InterAct Consortium (2015). Dietary fibre and incidence of type 2 diabetes in eight European countries: the EPIC-InterAct Study and a meta-analysis of prospective studies. Diabetologia, 58(7), 1394-408.

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