forbes 2014
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ESPEN Congress Geneva 2014
DISEASES ACROSS BORDERS: THE CASE OF IRRITABLE BOWEL
SYNDROME
Fibre in gastroenterology: is there anything new to say?
A. Forbes (UK)
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Alastair ForbesNorwich Medical School
Fibre in Gastroenterology
Is there anything new to say?
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Cocoa
Theobroma cacoa
Drink of Gods (Xocoatl)
theo = God
broma = drinkMexico (Maya, Incas, Aztecs)
Aphrodisiac
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Norwich
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Resistant carbohydrate Not digested by human enzymes
Poorly absorbed
Poorly metabolised
2 main groups
Fibre an introduction
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Polysaccharides with alpha (1,4)glycosidic bonds can be digested by the
small intestine
Polysaccharides with beta (1,4)
glycosidic bonds cannot
Fibre an introduction
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Predominantly non-starch polysaccharides Also oligosaccharides and lignin
(polyphenols)
Mostly have structural roles in plants
Fibre an introduction
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Cellulose beta (1,4) glucopyranoside
Hemicelluloses various sugar monomers Pectin galacturonate & some rhamnose
Mucilage plant gums
Lignin highly branched phenylpropanoid
units
Oligosaccharides various monomer units Inulin beta (2,1) linked fructose polymer
Resistant starch functional definition
Specific fibres some examples
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Fibre an introduction
Insoluble and soluble fibre
Physical and metabolic differences Water-holding capacity
Viscosity Solubility
Fermentability
Prebiotic capacity
Binding capacity
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Dietary fibre properties also affected by
Ripeness of food (eg fruit)
Preparation
raw vs cooked
whole vs grated
etc
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Fibre an introduction
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Determined by physicochemical
properties
Higher in non-soluble fibre
Effect on stool mass
Influenced also by effects on flora as
bacteria contribute to stool water content
Fibre water-holding
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Water-solubility affects proportion that
reaches colon in health Some fibres form gels (eg pectin, guar)
Viscous gels important in delayingabsorption
Lower the glycaemic and hyper-cholesterolaemic effects of foods
Fibre solubility/viscosity
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Property mainly of soluble fibre Essential for colonic health
Only source of essential short chain fattyacids
Fibre fementability
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Saccharolytic fermentation dominates
and especially so in proximal colon Proteolytic fermentation more distal
(when most fermentable substratesexhausted)
Putrefaction (anaerobic metabolism of
peptides) also occurs yielding SCFAs
and ammonia, thiols, indoles, etc
Fibre fermentability
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Saccharolytic fermentation mainly yields
SCFAs, lactate, H2 and CO2 Butyrate 15%
Propionate 25%
Acetate 60%
All are rapidly absorbed
Provide ~5% of energy needs in health
Fibre fermentability
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~5% of energy needs in health
Main energy source for colonocytes Promote absorption of salt and water
Stimulate mucosal proliferation Increase mucus production
mucosal blood flow & oxygen uptake
Maintain mucosal integrity
Fibre SCFAs
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Most important and most active SCFA
Increases MUC2 and mucus production Promotes cell differentiation
Decreases paracellular permeability Enhances ICAM-1, enteroglucagon
Direct anti-inflammatory effects TNF, IL6, IL8, IFN, COX-2, NFB
Butyrate
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RCT of whole grain fibre
End-point = urinary markers of proteincatabolism
Short-term study but impressive results Potential clinical value ?
Ross 2013
Fibre is anabolic ?
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Concept parallel to probiotic
Specific non-digestible carbohydrates
growth of bacteria with health benefits
Highest butyrate production is from
fructose oligosaccharide and inulin pathogenic G+ve and G-ve bacteria
Major effects on Clostridium, Lactobacilliand Bifidobacteria
Clinical data largely supportive
Prebiotic effects of fibre
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Absorptive and binding effects of fibre
Fibre is ion binding
Historically thought to pose risk of
inhibition of absorption of key minerals
Recent evidence suggests the opposite
Calcium uptake and BMD increased by
fibre in adolescents
Binding of bile salts and some bacteriamay be valuable
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Fibre and satiety/appetite control
Delays gastric emptying
Increases viscosity of gastric content Probable hormonal effects in small bowel
Fruit, fibre foods and supplements reduceappetite in the short-term
Visholm 2014
Meta-analysis confirms (minor) weight loss
Camilleri 2010
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Benefit from delayed gastric emptying
Slower small bowel transit Less glucose transport through unstirred
layer
Reduced access of amylase to dietary
starch
Lower postprandial glucose level (AUC)
Viscous fibre and glycaemia
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In combination reduce post-prandial
glucose and increase insulin sensitivity Especially guar, pectin, -glucan
Improve diabetic control
Probably non-fermentable fibre reduces
risk of diabetes
eg Fujii 2013, Yu 2014
Viscous fibre and glycaemia
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Lowers LDL (no effect on other lipids)
No effects from non-soluble fibre Attributed in part to effect on bile salts
Small effect Bigger overall influence on CVS morbidity
from insoluble fibre but mechanismsremain unclear
Viscous fibre and blood lipids
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Transit normalised if abnormal
Frequency increased by 1.4x per week if
constipation
Mainly bulk/water effect from insoluble fibre
Diarrhoea ameliorated and durationshortened (acute in children & antibiotic-
associated) Enteral tube feed-associated diarrhoea
improvedElia 2008
Fibre and the gut
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Dietary guidance & evaluation in IBS: n=46
Review at 3-6 months Advice was not just increased fibre
Patients increased dairy and vitaminintakes with decrease in FODMAPs
Overall symptom score and QoL improved
No correlation with any food group!
Mazzawi 2013
Fibre and IBS
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Systematic review and meta-analysis
Comparisons with placebo, control or
usual management; n = 906
Significant overall benefit: RR = 0.86
CI 0.80-0.94; NNT =10
Effect from soluble fibre: RR = 0.83
No significant effect from bran: RR = 0.9
Unclear if effect limited to IBS subgroups
Moayyedi 2014 Epub
Fibre and IBS
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Common and responsible for considerable
morbidity from complicaions Because of low fibre Western diet
Fibre and diverticula
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Common and responsible for considerable
morbidity from complications Not because of low fibre Western diet
No protection against diverticulosis
Association with diverticulitis also
questioned
Risk from seeds/nuts once diverticulosis
present also not supported by data
Peery 2013
Fibre and diverticula
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Relatively few reliable human data
Animal models show benefit in severalforms of colitis
Butyrate probably effective in human colitis Plantago ovata not helpful in preventing
relapse of ulcerative colitis
Hallert 2003, Vernia 2003, Fernandez-Banares 1994
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Fibre and inflammation
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New prospective study in IBD pathogenesis
Nurses Health Study n=170,776
269 incident CD, 338 UC compared to mean
Fibre and IBD
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New prospective study in IBD pathogenesis
Nurses Health Study n=170,776
269 incident CD, 338 UC compared to mean
Intake of highest quintile of fibre (24.3g/d)
associated with 40% reduction in risk of CD
HR 0.59: CI 0.39-0.90
Most of benefit from fruit fibre
Little influence of fibre on UC incidence
HR 0.82 (NS)Ananthakrishnan 2013
Fibre and IBD
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Not relevant after diagnosis
Evidence for protection from cereal fibre
still controversial .
No benefit from insoluble dietary fibre (FDA2000)
Clear benefit from all fibre (EPIC 2003)
Fibre and colon cancer
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Confusion perhaps because of typical
difficulties of interpreting diet in aetiology Or other factors?
Fibre and colon cancer
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Confusion perhaps because of typical
difficulties of interpreting diet in aetiology Or other factors?
Difference between dietary andsupplementary fibre
Host genome
Dietary co-factors
Fibre and colon cancer
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Type of fibre - EPIC database
Plasma alkyl resorcinol reflects wholegrainintake (wheat and rye)
Higher in North European populations thanMediterranean
Unclear how to interpret
Kyro 2014
Fibre and colon cancer
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Calcium also important thought to be
protective - but possibly a fibre effect
Case-control study of 1556 (703 vs 853)
incident cases using 148-item Food
Frequency Questionnaire
Higher consumption of calcium associated
with lower colon cancer risk OR
=
0.93 (CI: 0.89-0.98) for every extra
100 mg Ca/day Galas 2013
Fibre and colon cancer
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>1000 mg/day yielded ORof 0.54
CI: 0.35-0.83 Effect modified by dietary fibre
Cancer risk reduced with increasinglevels of dietary calcium and fibre
intake to more than additive extent
Galas 2013
Fibre and colon cancer
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Meta-analysis of almost 11000 patients
Summary relative risk of high vs low fibreintake = 0.72 (CI 0.63-0.83)
Stronger effect in case-control than incohort studies (RR 0.66 vs 0.92)
Effect strongest for cereal fibre and least
for vegetable fibreBen 2014
Fibre and colonic adenomas
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Interventional study of family members
Supplementary fibre
No apparent effect on cancer risk
Mathers 2012
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Fibre in HNPCC / Lynch
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Genome-wide diet-gene interactions
Diet and ~2.7m genetic variants studied in
>9000 cases and >9000 controls
Red and processed meat intake more
common in cases; fruit / vegetable / fibre less
Fibre and colon cancer
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Genome-wide diet-gene interactions
Diet and ~2.7m genetic variants studied in
>9000 cases and >9000 controls
Red and processed meat intake more
common in cases; fruit / vegetable / fibre less 2 specific polymorphisms of rs4143094 (on
10p) (TG and TT) plus dietary processedmeat yield OR of 1.3 and 1.4
But GG genotype has no link OR 1.03
Figueiredo 2014
Fibre and colon cancer
Fib l i li t d
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Meta-analysis of >580,000 cases
Highest vs lowest fibre intakes compared Retrospective and much heterogeneity
Overall protective effect OR 0.58 Different types of fibre not analysable
Equivalent to a 44% reduction in risk for a10g/d dietary supplementation
Zhang 2013
Fibre also implicated
in gastric cancer
Fib l i li t d
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Dietary analyses in case-control study of
326 vs 652 controls
4 dietary patterns identified
Those with the fibre and vitamin diet had
the lowest rate of pancreatic cancer
OR 0.55 (CI 0.36-0.86)
While the red meat diet doubles the risk
Bosetti 2013
Fibre also implicated
in pancreatic cancer
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Fibre in artificial feeding
Historically, commercially prepared feeds
were without fibre and the addition of fibrewas special
Increasingly fibre-containing feeds areconsidered the default typically 5-10g/L
Is this correct and safe?
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Fibre in artificial feeding
Indicated if constipation or diarrhoea Confirmation of value is stronger for
patients with diarrhoea than it is for
patients with constipationRabenek 1997
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Fibre in artificial feeding
Contra-indicated in some GI conditions
Intestinal strictures questionable
Abdominal compartment syndrome but
enteral feeding contra-indicated too
Acute pancreatitis ? (Besselink 2008)
Gastroparesis ?
Short bowel syndrome ? Poor appetite ??
No evidence against in most conditions
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Clear recommendations for boosting fibre
intake in the general population
Benefits of certain or probable extent
GI health, CVS, diabetes, cancer, etc
Soluble and insoluble fibres yield
complementary actions
No evidence for harm
Should be default for artificial feeding
Fibre what next?
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