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Some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts, such as Trichonympha. In human nutrition, cellulose is a non-digestible constituent of insoluble dietary fiber, acting as a hydrophilic bulking agent for feces and potentially aiding in defecation.
The structural components of plants are formed primarily from cellulose. Wood is largely cellulose and lignin, while paper and cotton are nearly pure cellulose. Cellulose is a polymer made with repeated glucose units bonded together by beta-linkages. Humans and many animals lack an enzyme to break the beta-linkages, so they do not digest cellulose.
However, their ability to extract energy from cellulose digestion is less efficient than in ruminants. [2] Herbivores digest cellulose by microbial fermentation. Monogastric herbivores which can digest cellulose nearly as well as ruminants are called hindgut fermenters, while ruminants are called foregut fermenters. [3]
Digestion is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream .
Human nutrition deals with the provision of essential nutrients in food that are necessary to support human life and good health. [1] Poor nutrition is a chronic problem often linked to poverty, food security , or a poor understanding of nutritional requirements. [ 2 ]
Another polymer of glucose is cellulose, which is a linear chain composed of several hundred or thousand glucose units. It is used by plants as a structural component in their cell walls. Humans can digest cellulose only to a very limited extent, though ruminants can do so with the help of symbiotic bacteria in their gut. [67]
The cellulose used as a food additive is usually made from wood pulp or cotton lint, according to the Center for Science in the Public Interest, an independent food and health watchdog group.
Dietary fiber is defined to be plant components that are not broken down by human digestive enzymes. [1] In the late 20th century, only lignin and some polysaccharides were known to satisfy this definition, but in the early 21st century, resistant starch and oligosaccharides were included as dietary fiber components.