Introduction

Dietary fiber also called roughage or bulk is a form of fiber that is not digestible by the enzymes present in our bodies. Dietary fibers are obtained from cereals, beans, dried peas, nuts, lentils, whole grain products, and grains

Examples of dietary fibers include resistant starch, cellulose, lignins, inulins, non-starch polysaccharides, oligosaccharides, etc.

Dietary fibers function by altering the composition of gastrointestinal tract contents, and by modifying the absorption of other nutrients and chemicals. These effects have several benefits and help in treating and preventing many diseases.

 

Components of Dietary Fiber

The dietary fibers are divided into two groups, on the basis of solubility.

 

 

 

Recommended Daily Allowance

Following is the recommended daily allowance (RDA) of dietary fibers according to USDA.

 

 

The average intake of dietary fibers by Americans despite the USDA guidelines is 10-15 g per day, but we recommend 60-100 g / day for achieving benefits.

 

Dietary fibers have multiple health benefits which include decreased risk of death from coronary artery disease (CAD) and prevention of CAD, lower rates of colon cancer, and development of type 2 diabetes. Today we have articulated this article to review the beneficial effects of adding an adequate amount of fiber to our diets.

 

Effects of Dietary Fibers on Health

The following are a few benefits of a diet high in fiber content.

 

Gut Microbiome and Fiber

The bacteria that reside in the gut are not all bad or evil. The normal flora of the gut is necessary to maintain healthy bowel function and fight off infections. Prebiotic foods are dietary fibers that assist the gut microbiome to produce nutrients that nourish the colon cells. They fight off infectious pathogens and have anti-inflammatory properties as well. (1) Garlic, chicory root, onions, asparagus, etc. contain several prebiotic fibers.

A double-blind randomized control was conducted in 2006, to study the effects of Jerusalem artichoke inulin (JA) or chicory inulin (CH) that contain high inulin content in snack bars on the composition of fecal microbiota and gastrointestinal symptoms. Results showed a dose-related increase in gut microbiota and suggested that fiber-containing ingredients in bakery items play a role in suppression of potentially pathogenic bacteria. (2)

 

Maintains Gut Motility

Different dietary fibers have distinct effects on gut motility and bowel movements. In general, fiber is observed to improve the frequency of bowel movements and can be of great use in the treatment of constipation, a widespread condition of childhood. (3)

A clinical trial was conducted in 2006 on children (3-10 years) with idiopathic constipation who were treated with cocoa husk to study its effects on colonic transit time. The result showed that cocoa husk improved colonic idiopathic constipation and reduced colonic transit time along with improving stool consistency, with no serious adverse effects. (4)

 

Protection Against Cardiovascular Diseases (CVDs)

A meta-analysis of 15 studies indicated that a high fiber diet may prove to be effective in reducing the risk of death due to cardiovascular diseases and almost all cancers. The results supported the recommendation of a high fiber diet. (5)

Although soluble, gel-forming fiber has beneficially affected CVD risk factors, the most reliable association with a lower occurrence of CVD are food sources with mostly insoluble fibers, predominantly contributed by cereal products. In conclusion, a diet with mixed types of fibers would prove to have greater benefits. (6) 

 

Lowers Cholesterol Levels

Soluble dietary fibers have been associated with lower serum total and low-density lipoprotein levels and improvement in insulin resistance. (6)

Soluble fibers can lower bad cholesterol by approximately 18%. This is beneficial for heart health when paired with exercises. (7) They prevent the absorption of cholesterol from the small intestine and promote excretion via feces. (8)

 

Controls Blood Sugar Levels

An umbrella review covered 16 meta-analyses of researches from 1980-2017 to study the effects of fibers on blood sugar levels. Most benefits were mainly obtained from cereal fibers. The following results were reported:

• A high fiber diet reduces the incidence of type 2 diabetes.

• It is effective in reducing fasting blood glucose levels.

• It causes a small decrease in glycosylated hemoglobin percentages in individuals with established type 2 diabetes. (9)

 

Reduces Risk of Colon Cancer

Several intervention studies have reported that adding dietary fibers to the diet, especially wheat bran can reduce the levels of tumor promoters in the colon and inhibit colon carcinogenesis. (10)

The risk of colon cancer is also reduced in individuals who switch from a high-fat diet to a whole-grain food diet with high fiber content. (10) 

 

Helps in Weight Loss

Soluble dietary fibers produce a sense of fulfillment and may cause early satiety and result in a reduction of food intake and lower body weight. (11) Decreased food intake can help in weight loss and also reduce cholesterol levels. For effective weight loss and treatment of obesity dietary alterations along with exercise may prove to be a more powerful approach.

 

Reduces Inflammation

Increased systemic inflammation has been observed to be associated with low dietary fiber intake. Fiber metabolites produced by gut bacteria are believed to have an anti-inflammatory role in the human body. More clinical trials are required to make it a plausible treatment option. (12)

It has been suggested that dietary fibers may prove to be a potential agent in the management of asthma and may even assist in its prevention. (12)

 

Conclusion

Adding fiber-containing foods is not that difficult since many naturally occurring food options contain fibers that also taste good and many processed foods are fortified with fibers. The benefits are indispensable and one should maintain a healthy and balanced diet, by adding sufficient amounts of fiber along with water to allow optimum advantage. 

Excessive intake may cause abdominal bloating, intestinal gas, cramping, and pain. Always use caution and immediately visit your healthcare provider if you develop side effects.

 

 

References

1. Macfarlane GT, Steed H, Macfarlane S. Bacterial metabolism and health-related effects of galacto-oligosaccharides and other prebiotics. J Appl Microbiol. 2008;104(2):305‐344.

2. Kleessen B, Schwarz S, Boehm A, et al. Jerusalem artichoke and chicory inulin in bakery products affect fecal microbiota of healthy volunteers. Br J Nutr. 2007;98(3):540‐549.

3. Hillemeier C. An overview of the effects of dietary fiber on gastrointestinal transit. Pediatrics. 1995;96(5 Pt 2):997‐999.

4. Castillejo G, Bulló M, Anguera A, Escribano J, Salas-Salvadó J. A controlled, randomized, double-blind trial to evaluate the effect of a supplement of cocoa husk that is rich in dietary fiber on colonic transit in constipated pediatric patients. Pediatrics. 2006;118(3):e641‐e648.

5. Young Kim, Youjin Je. Dietary fiber intake and mortality from cardiovascular disease and all cancers: A meta-analysis of prospective cohort studies, Archives of Cardiovascular Diseases, Volume 109, Issue 1, 2016, Pages 39-54.

6. Erkkilä AT, Lichtenstein AH. Fiber and cardiovascular disease risk: how strong is the evidence?. J Cardiovasc Nurs. 2006;21(1):3‐8.

7. Zhou Q, Wu J, Tang J, Wang JJ, Lu CH, Wang PX. Beneficial effect of higher dietary fiber intake on plasma HDL-C and TC/HDL-C ratio among Chinese rural-to-urban migrant workers. Int J Environ Res Public Health. 2015;12(5):4726–4738.

8. Cleveland Clinic. Heart healthy eating to help lower cholesterol levels. Reviewed February 2018.

9. McRae MP. Dietary Fiber Intake and Type 2 Diabetes Mellitus: An Umbrella Review of Meta-analyses. J Chiropr Med. 2018;17(1):44‐53.

10. Reddy BS. Role of dietary fiber in colon cancer: an overview. Am J Med. 1999;106(1A):16S‐51S.

11. Clark MJ, Slavin JL. The effect of fiber on satiety and food intake: a systematic review. J Am Coll Nutr. 2013;32(3):200‐211.

12. Williams, L., Scott, H., and Wood, L., 2020. Soluble Fibre As A Treatment For Inflammation In Asthma.

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