Fiber and monogastric health Flashcards
Role of dietary fibre
**Too little or too much= negative effects
-fibre impacts gut health, immune system, systemic health
-maintenance of health
-disease prevention
-therapeutic applications in treatment of certain disease
Fibres impact on gut microbiota
-fiber is a energy source for microbe populations (can cause shifts)
-used to produce essential nutrients for host (eg. Vit K)
-produce substances that act locally/systemically via immune or nervous system and other organs
Effects of fibre
Clinical applications
-brushing teeth
-dilute calorie intake
-promote satiety
-hairball control
-modulate post-prandial glycemic response
-alter fat or cholesterol absorption+metabolism
-affect gut motility
-promote laxation
-normalize fecal quality
-treat bile-salt induced diarrhea
-increase resistance to pathogenic bacteria
Define dietary fibre
Indigestible plant and non plant materials can act at dietary fibre
*naturally derived, extracted or synthetic forms
*from plants, fungi or animals
What is the sole thing that makes something dietary fibre?
Anything unified by resistance to animals’ digestive enzymes
-incapable of hydrolyzing some chemical bonds (beta-bonds found in indigestible polysaccharides)
Fibre sources
- plant derived carbohydrates (simple sugars and complex carbohydrates)
-some complex carbohydrates (resistant starch and non digestible carbohydrates) are dietary fiber - Non carbohydrate or non plant sourced fibre
-are not digested in small intestine
-includes polyphenol lignin, flavonoids, fungi, animal sources like chitin, and synthetic forms
What happens if an animal cannot digest a fibre?
- interacts with GIT and digesta (physical, chemical, mechanical)
- some forms (eg.cellulose) pass through GIT unchanged and are excreted in feces
OR
some forms used by gut microbes and disappear and the appearance of metabolites of fermentation
Fermentation
Metabolic process by which microbes extract energy from food by creating new substances
**success depends on presence of specific microbes with correct substrate in favourable environment
What does fibre fermentation result in?
-metabolites from fermentation increases
-fibre disappears then fecal bulk increases
-microbiome may maintain or shift
-microbial mass might increase
Where does fermentation occur in monogastrics?
Occurs in lower GIT
-determined by microbiome and types of fibre
Potential by products of fermentation
-amino acids
-vitamins (B vit, Vit K)
-gases (methane)
-short chain fatty acids (volatile fatty acids)
**what is made depends on bacterial species in the biome
Healthy microbiota
-diverse population
-adequate proportion of good bacteria
-production of ideal amounts of healthy fermentation products (post biotics)
Dysbiosis
-decreased diversity
-unbalanced ratios of microbes
-fermentation products unbalanced (too little or too much)
Short chain fatty acids
-acetate
-proprionate
-butyrate
**make up 90-95% of SCFAs in animals
Functions of SCFAs
-source of energy
-act as signalling molecules
-influence immune system
-maintain or alter intestinal environment
(help maintain anaerobic environment, increase tight junction proteins and mucin, and acidify pH in lumen of GIT to inhibit growth of pathogenic microbes and to assist in ammonia trapping to ensure excretion in feces)
SCFAs as energy source in herbivores
Major daily contributor for energy (calories)
SCFAs as energy source in carnivores and omnivores
-negilgible contribution to daily maintenance
*1-2% but this is vital for enterocytes and colonocytes
Which is the SCFA that is most important for enterocytes and colonocytes?
Butyrate
What does insufficient fermentation fibre lead to?
-decreased microbial diversity
-impaired intestinal health
-increased risk of colitis and obesity
What does over abundant fermentable fibre cause?
-abdominal distention/discomfort
-increased flatulence
-altered frequency of defecation
-decreased fecal quality
Pre-biotic fibre
eg. inulin, FOS
-selectively supports metabolism/growth of good bacteria to support or improve host animals health
What are the 4 main descriptors for dietary fibre?
- viscosity
- fermentability
- solubility
- molecular weight
What descriptors are physiologically significant?
-viscosity
-fermentability
*difficult to measure in a lab
Viscosity
-ability to form mucilages and gels
-alters flow; slows gastric emptying and small intestinal transit
-can influence diffusion, digestion, absorption
What does viscosity depend on?
-concentration fibre dependent
-conditions in GIT
-presence of other fibres
-overall food matrix
Viscosity effect in upper GIT
-enhance satiety and decrease food intake
-modulates post-prandial glycemic response
Viscosity effect in lower GIT
Depends on fermentability
-if high= used by gut microbes
-if low= persists through transit of colon= normalize fecal consistency (water holding/gelling)
Fermentability
variable; determined by:
-individual fibre
-animals GIT and microbiome
What are the easily measurable descriptors of dietary fibre?
-solubility
-molecular weight/chain length
Solubility
-easy to measure in water
Insoluble dietary fibres
-does not disssolve in water
-high molecular weight
-non viscous
-very low fermentability in non herbivores
-bulking fibre= laxation, dilute calories, alter digestibility
eg. cellulose, hemicellulose, lignin
Soluble dietary fibre
-dissolves in water
-high molecular weight
>adds some volume to food
>absorbs water
>may or may not alter viscosity depending on amount and type
-variable fermentability
eg. pectins and gums
Viscous fibres solubility
All viscous fibres are soluble but not all soluble fibres are viscous
Oligosaccharides
-dissolve in water therefore soluble
-low molecular weight
-often fermentable or prebiotic
-not included in most fiber quantifications
ex. inulin, FOS, dextrins
Resistant starches
Resistant to digestion
-many are moderately to highly fermentable in lower GIT
-most resistant starches are not included in tradtitional mesures/quantification of fibre
Molecular weight/chain length
-natural fibres= mixed MW/length
-if less than 10 units= low molecular weight (eg. non digestible oligosaccharides)
Monogastric categorization
Hind gut fermenters= monogastric herbivores; large intestines large
-rabbits, horses
Monogastrics
-large intestines are small
-pigs, dogs, cats
GIT evolution and complexity
Simple to complex: Dog, humans, then horses
*display increasing time to pass digesta, ability to utilize plant fibres, and reliance on microbial fermentation
Monogastric herbivores/ hind gut fermentators
-relatively small stomach
-large ceca and colon
>ferments more fibres completely
>significant source of energy and vitamins to herbivores
What is the importance of foraging and grazing for hind gut fermenters?
Cecotrophs
-produced by lagomorphs, some herbivore rodents (guinea pigs), some marsupials (possums)
-cecal microbiota synthesizes essential nutrients not in typical forage, put them into cecotrophs to be re ingested and absorbed in small intestine (b vita, Vit K, protein)
*typically reingested directly from anus
Mixing fibers
-most foods contain a mix of fibres
-overall effect depends on the other foods/fibres present, microbiota variability, and fibre type and function
Benefits of mixing fibres
-interact to create overall effect
-moderate fermentaion (accessibility or preference)
Common fibres in pet foods
- cellulose
-non viscous, poorly fermentable - beet pulp
-80:20 IDF:SDF - psyllium husk
4.oligosaccharides and blends - ‘hidden’ in whole food ingredients
