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Carbohydrates Overview - Nutrition (view source)
Revision as of 18:02, 29 March 2015
, 18:02, 29 March 2015→Roles in the Body
==Roles in the Body==
==Roles in the Body==
#'''Energy Production''': All cells in the body have a requirement for '''glucose''' and it must be obtained regularly either from the diet or synthesised through hepatic gluconeogenesis. Glucose absorbed from the diet can be used directly in intermediate metabolism (ATP production) or to synthesise glycogen and fatty acid.<ref name="Ebiner">Ebiner JR, ''et al.'' (1979)''' Comparison of carbohydrate utilization in man using indirect calorimetry and mass spectrometry after oral load of 100 g naturally-labelled (13C) glucose.''''' Br J Nutr'' 1979;41:419-429.</ref><ref name="Flatt">Flatt JP, ''et al''. (1985)'''Effects of dietary fat on postprandial substrate oxidation and on carbohydrate and fat balances.''''' J Clin Invest ''1985;76:1019-1024.</ref> In the absence of dietary starches or sugars, '''hepatic gluconeogenesis''' can support maintenance of normal blood glucose levels, gluconeogenic amino acids and glycerol in dogs<ref>Romsos DR,'' et al.'' (1976)''' Effects of dietary carbohydrate, fat and protein on growth, body composition, and blood metabolite levels in the dog. '''''J Nutr ''1976;106:1452-1456.</ref> and cats.<ref name="Morris">Morris JG, ''et al.'' (1977)''' Carbohydrate digestion in the domestic cat ''(Felis catus)'''. Br J Nutr'' 1977;37:365-373.</ref>
#'''Intestinal Health''': Non-absorbable carbohydrates (oligosaccharide and polysaccharide dietary fibres) are resistant to degradation by mammalian enzymes. These carbohydrates are more commonly referred to as '''dietary fibres''' and can be divided into two broader categories depending on whether they can be further metabolized (fermented) by intestinal bacteria or not.<ref name="NRC" />
#'''Fermentable, non-absorbable carbohydrates '''can be utilized as an energy substrate by bacteria in the [[Large Intestine Overview - Anatomy & Physiology|large intestine]]. By-products of bacterial fermentation include CO, H<sub>2</sub>, methane, and the short-chain fatty acids acetate, propionate and butyrate, which can support optimal colonocyte function and intestinal health. Diffusion of acetate and proprionate across the colonic mucosa facilitates water reabsorption. Butyrate is the preferred energy substrate of colonocytes.<ref>Herschel DA, ''et al.'' (1981)''' Absorption of volatile fatty acids and H<sub>2</sub>O by the colon of the dog. '''''AJVR ''1981;42:1118-1124.</ref><ref>Reinhart GA,'' et al.'' (1994)''' Source of dietary fiber and its effects on colonic microstructure, function and histopathology of the beagle dogs. '''''J Nutr ''1994;124:2701S-2703S.</ref><ref>Howard MD,'' et al.'' (1999)''' Blood flow and epithelial cell proliferation of the canine colon are altered by source of dietary fiber. '''''Vet Clin Nutr'' 1999;6:8-15.</ref>
#'''Non-fermentable, non-absorbable carbohydrates''' include structural components of plant cell walls such as cellulose, lignin and bran. These forms of carbohydrates resist degradation by animal or bacterial enzymes and pass through the intestinal tract intact.
====Cats and Carbohydrates:====
Cats are able to digest and absorb dietary sugars and starches well<ref name="Morris" /> but have low glucokinase activity in the liver<ref>Tanaka A, ''et al.'' (2005)''' Comparison of expression of glucokinase gene and activities of enzymes related to glucose metabolism in livers between dog and cat. '''''Vet Res Commun ''2005;29:477-485. </ref> and do not adapt carbohydrate metabolism to dietary intake.<ref>Buddington RK, ''et al.'' (1991) '''Dietary regulation of intestinal brush-border sugar and amino acid transport in carnivores.''''' Am J Physiol ''1991;261:R793–801.</ref> There has been controversy over the role of dietary carbohydrate in development of obesity and [[DM|diabetes mellitus]] in cats but carbohydrate intake has not been shown to be a risk factor in development of obesity,<ref> Backus RC, ''et al.'' (2007)''' Gonadectomy and high dietary fat but not high dietary carbohydrate induce gains in body weight and fat of domestic cats.''''' Br J Nutr ''2007;98:641-650.</ref> hyperglycaemia<ref>Hoenig M, ''et al.'' (2012)''' Evaluation of long-term glucose homeostasis in lean and obese cats using continuous glucose monitoring.''''' AJVR'' 2012:73:1100-1106.</ref> or diabetes mellitus<ref>Verbrugghe A,'' et al.'' (2012)''' Nutritional modulation of insulin resistance in the true carnivorous cat: a review. '''''Crit Rev Food Sci Nutr'' 2012;52:172–182.</ref> in otherwise healthy adult cats.
==Consequences of Deficiency==
==Consequences of Deficiency==