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Digestion and absorption of nutrients

Fragkos, K; Forbes, A; (2011) Digestion and absorption of nutrients. In: Sobotka, L and Allison, S and Forbes, A and Ljungqvist, O and Pertkiewicz, M and Meier, R and Soeters, PB, (eds.) Basics in Clinical Nutrition. (pp. 83-96). Galen: Prague.

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Abstract

The digestion and absorption of macronutrients (carbohydrates, lipids, proteins) and micronutrients (vitamins and minerals), essential for the requirements of the human body, take place mostly in the small intestine. In most cases digestion occurs both in the gastrointestinal lumen and at the mucosal surface, continuing in some cases within the enterocytes themselves. Substrate-specific enzyme processes exist for polysaccharide carbohydrates and polypeptides, linked with digest-specific active co-transporters to aid absorption at the cellular level. The hydrophobicity of fats makes lipid handling more complex, requiring the creation of intraluminal emulsions and micelles which present lipid degradation products to the enterocytes. The intestine (small bowel and colon) has additional mechanisms for absorption and re-absorption of water and key electrolytes. In most cases micro-nutrients are liberated from dietary macromolecules by non-specific digestion and then absorbed passively (or as other lipid-soluble moieties in the case of the fat-soluble vitamins) but some specific transporters are also involved as in the case of vitamin B12. Quantitatively minor but important digestion and nutrient absorption also occur in the colon.

Type: Book chapter
Title: Digestion and absorption of nutrients
ISBN-13: 9788072628216
Publisher version: http://www.espenbluebook.org/index.php
Keywords: digestion, absorption, amino acids, lipids, carbohydrates, minerals
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Medicine
URI: http://discovery.ucl.ac.uk/id/eprint/84861
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