Key Difference – Dietary Fiber vs Crude Fiber
Dietary fiber is an indigestible portion of food derived from plants. It is the sum of both soluble and non-soluble fiber groups. Crude fiber is part of insoluble fiber found in the edible portion of the plant cell wall. This is the key difference between dietary fiber and crude fiber. Further differences are described in this article.
What is Dietary Fiber?
Dietary fiber, also known an as bulk or roughage, is found in the edible portion of the plant cell wall (found in fruits, vegetable, whole grains, and legumes) and cannot be digested by the human body. It is the sum of polysaccharides and lignin. Major components are cellulose, hemicelluloses, non-cellulose polysaccharides, pectin, lignin and hydrocolloids (gums, mucilages, and algal polysaccharides). The average portion of cellulose, hemicelluloses (non-cellulose polysaccharides ) and lignin are 20%, 70%, and 10% respectively.
Definition of Dietary Fiber – Suggested by Trowell et al.,(1985)
“Dietary fiber consists of remnants of plant cells resistant to hydrolysis (digestion) by the alimentary enzymes of man whose components are hemicelluloses, cellulose, lignin, oligosaccharides, pectins, gums, and waxes.”
Dietary fiber can be classified into two groups based on its solubility in water as follows.
| Features | Fibre component | Description | Main food sources |
| Water insoluble/Less fermented | Cellulose | Main structural component of plant cell wall. Insoluble in concentrated alkali, soluble in concentrated acid. | Plants (vegetables, sugar beet, various brans) |
| Hemicellulose | Cell wall polysaccharides, which contain a backbone of β-1,4 glucosidic linkages. Soluble in dilute alkali. | Cereal grains | |
| Lignin | Non-carbohydrate cell wall component. Complex cross-linked phenyl propane polymer. Resists bacterial degradation. | Woody plants | |
| Water soluble/Well fermented | Pectin | Components of the primary cell wall with D-galacturonic acid as principal components. Generally, water soluble and gel forming | Fruits, vegetables, legumes, sugar beet, potato |
| Gums | Secreted at the site of plant injury by specialized secretary cells. Food and pharmaceutical use | Leguminous seed plants (guar, locust bean), seaweed extracts (carrageenan, alginates), microbial gums (xanthan, gellan) | |
| Mucilages | Synthesized by the plant, prevent desiccation of seed endosperm. Food industry use, hydrophilic, stabilizer. | Plant extracts (gum acacia, gum karaya, gum tragacanth) |
Benefits of a Dietary Fiber
- Normalize the bowel movement
They increase the weight and size of the stools and soften them to facilitate the easy passage. They also reduce the chance of constipation and solidify the watery stool and avoid loose motion.
- Promote bowel health
Dietary fiber reduces the risk of developing hemorrhoids and diverticular disease.
- Lower the cholesterol level
Beans, oats, flaxseed and oat bran may reduce Low-Density Lipoprotein (LDL) in total cholesterol.
- Control blood sugar level
Soluble fiber reduces the absorption of sugar and keeps the blood sugar level normal. Insoluble fiber also helps to reduce type11 diabetes.
- Support to maintain healthy weight
Dietary fiber provides less energy dense by facilitating few calories from the same volume of foods. They tend to be filling than low fiber foods.
What is Crude Fiber?
Crude fiber is a part of insoluble fiber found in the edible portion of the plant cell wall. It is basically cellulose material obtained as a residue of the chemical analysis of vegetable substances.
Crude fiber is analyzed in the laboratory by oven drying of the specimen after subjected to a series of sulfuric acid and sodium hydroxide solution treatment. What is remaining as crude fiber has no nutritional value.
The main health benefit of crude fiber is that it facilitates regular bowel movement. Leafy greens, whole grains, and beans (black beans) are some common examples of crude fiber.
What is the difference between Dietary Fiber and Crude Fiber?
Characteristics of Dietary Fiber and Crude Fiber:
Origin:
Dietary fiber: Dietary fiber is the sum of both soluble and non-soluble fiber groups.
Crude fibers: Crude fiber is a part of insoluble fiber found in the edible portion of the plant cell wall.
Solubility:
Dietary fiber: Dietary fiber is either soluble or non-soluble in water.
Crude fibers: Crude fiber is not soluble in water.
Fermentation:
Dietary fiber: Some dietary fibers are subjected to fermentation inside the digestive system.
Crude fibers: Crude fibers are not fermented inside the digestive tract.
Nature inside the digestive tract:
Dietary fiber: Dietary fiber might be relatively intact when it passes through the digestive tract, but this is based on the type of dietary fiber.
Crude fibers: Crude fiber is relative intact through a period of passage.
Composition:
Dietary fiber: Dietary fiber contains pectins,gums, and mucilages.
Crude fibers: Crude fibers do not contain pectins,gums, and mucilages.
References:
Dietary fiber [Online]. Available: https://en.wikipedia.org/wiki/Dietary_fiber [Accessed June 30 2016].
Crude Fiber [Online]. Available: http://www.foodscience-avenue.com/2008/04/crude-fiber.html [Accessed June 30 2016].
DHINGRA, D., MICHAEL, M., RAJPUT, H. & PATIL, R. T. 2012. Dietary fibre in foods: a review. J Food Sci Technol, 49, 255-66.
GARDNER, A. 2015. Soluble and Insoluble Fiber: What’s the Difference? [Online]. Available: http://www.webmd.com/diet/insoluble-soluble-fiber [Accessed June 30 2016].
MAYO ET AL. Nutrition and healthy eating [Online]. Available: http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/fiber/art-20043983 [Accessed June 30 2016]
Image Courtesy:
“Foods (cropped)” By Keith Weller, USDA ARS (Agricultural Research Service, the research agency of the United States Department of Agriculture), ID K3839-3 (Public Domain) via Commons Wikimedia
“Black beans” By Paul Goyette from Chicago, USA – black beans (CC BY-SA 2.0) via Commons Wikimedia