Changes

==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>

'''''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.1

'''''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. By-products of bacterial fermentation include CO, H2, 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 facility water reabsorption and butyrate is the preferred energy substrate of colonocytes.6-8

*'''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, H₂, 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 H₂O 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.

*'''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 well5 but have low glucokinase activity in the liver9 and do not adapt carbohydrate metabolism to dietary intake.10 There has been controversy over the role of dietary carbohydrate in development of obesity and diabetes mellitus in cats but carbohydrate intake has not been shown to be a risk factor in development of obesity,11 hyperglycaemia12 or diabetes mellitus13 in otherwise healthy adult cats.

 

Consequences of Deficiency

'''''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.

Dogs: Puppies, especially small and toy breeds, may be unable to maintain blood glucose concentrations from hepatic gluconeogenesis alone and can become hypoglycaemic with low intake of dietary carbohydrates.14 Hepatic gluconeogenesis may also be inadequate to meet glucose demands during late gestation and lactation unless increased intake of gluconeogenic amino acids are provided in the diet.15 There are no clinical signs of feeding a carbohydrate-free diet in otherwise healthy adult dogs, though some dogs with recurrent idiopathic colitis may benefit from feeding higher fibre diets.16

 

Cats: There are no reports of clinical signs relating to feeding carbohydrate-free diet to cats at any life-stage. Adult cats and growing kittens are able to maintain blood glucose concentrations via hepatic gluconeogenesis.5

==Consequences of Deficiency==

Toxicity

'''Dogs''': Puppies, especially '''small and toy breeds''', may be unable to maintain blood glucose concentrations from hepatic gluconeogenesis alone and can become hypoglycaemic with low intake of dietary carbohydrates.<ref>Vroom MW and Slappendel RJ. (1987) '''Transient juvenile hypoglycaemia in a Yorkshire terrier and in a Chihuahua.''''' Vet Q'' 1987;9:172-176.</ref> Hepatic gluconeogenesis may also be inadequate to meet glucose demands during '''late gestation and lactation''' unless increased intake of gluconeogenic amino acids are provided in the diet.<ref>Romsos DR, ''et al.'' (1981)''' Influence of low carbohydrate diet on performance of pregnant and lactating dogs.''''' J Nutr ''1981;111:678-689.</ref> There are no clinical signs of feeding a carbohydrate-free diet in otherwise healthy adult dogs, though some dogs with recurrent idiopathic colitis may benefit from feeding higher fibre diets.<ref>Leib MS. (2000) '''Treatment of chronic idiopathic large-bowel diarrhea in dogs with a highly digestible diet and soluble fiber: a retrospective review of 37 cases. '''''JVIM ''2000;14:27-32.</ref>

 

'''Cats''': There are no reports of clinical signs relating to feeding carbohydrate-free diet to cats at any life-stage. Adult cats and growing kittens are able to maintain blood glucose concentrations via hepatic gluconeogenesis.<ref name="Morris" />

 

==Toxicity==

The sugar-alcohol, xylitol (used as a low glycaemic index sweetener in many human foods) is toxic to dogs and cats and ingestion can lead to severe hypoglycaemia, liver failure and death.17 No toxicity has been associated with high intake of other carbohydrates in otherwise healthy dogs and cats, though in animals with pre-existing diabetes mellitus increased intake of sugars and starches can contribute to post-prandial hyperglycaemia and increase insulin requirements.18,19  

The sugar-alcohol, xylitol (used as a low glycaemic index sweetener in many human foods) is toxic to dogs and cats and ingestion can lead to severe hypoglycaemia, liver failure and death.17 No toxicity has been associated with high intake of other carbohydrates in otherwise healthy dogs and cats, though in animals with pre-existing diabetes mellitus increased intake of sugars and starches can contribute to post-prandial hyperglycaemia and increase insulin requirements.18,19  

Excessive intake of non-absorbable carbohydrates (both fermentable and non-fermentable dietary fibres) can increase stool bulk and slow gastrointestinal transit time.20,21 This may potentially result in constipation in healthy dogs and cats or worsening dysmotility in animals with underlying intestinal disease.  

Excessive intake of non-absorbable carbohydrates (both fermentable and non-fermentable dietary fibres) can increase stool bulk and slow gastrointestinal transit time.20,21 This may potentially result in constipation in healthy dogs and cats or worsening dysmotility in animals with underlying intestinal disease.  

Animals consuming inadequate dietary fibre may exhibit signs of colitis (e.g., tenesmus, hematochezia, mucousy loose stool, increased frequency of defecation), that resolves with addition of fibre to the diet.

Animals consuming inadequate dietary fibre may exhibit signs of colitis (e.g., tenesmus, hematochezia, mucousy loose stool, increased frequency of defecation), that resolves with addition of fibre to the diet.

References

==References==