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The American Journal of GASTROENTEROLOGY VOLUME 108 | MAY 2013 www.amjgastro.com
ROME FOUNDATION WORKING GROUP nature publishing group
718
ROLE OF FOOD IN FUNCTIONAL GASTROINTESTINAL DISORDERS
see related editorial on page x
INTRODUCTION
Fiber has long been used for the treatment of various gastroin-
testinal and non-gastrointestinal conditions including constipa-
tion ( 1 – 4 ), diarrhea ( 5 – 12 ), ulcerative colitis ( 13 – 15 ), obesity in
children and adolescents ( 16,17 ), hypercholesterolemia ( 18 – 23 ),
and diabetes mellitus ( 22,24,25 ). e National Academy of
Sciences Institute of Medicine recommends that adults consume
20 – 35 g of dietary ber per day, but the average American ’ s daily
intake of dietary ber is only 12 – 18 g ( 26 ). Although a univer-
sally accepted de nition for dietary ber does not exist, it is gen-
erally agreed that this term includes carbohydrates that are not
hydrolyzed or absorbed in the upper part of the gastrointestinal
tract. For the purpose of communicating nutrition information
to the consumer, the term dietary ber is of great value because it
clearly distinguishes between this non-digestible class of carbohy-
drates and digestible, glycemic carbohydrates such as sugars and
starches. Despite the confusing terminology surrounding the dif-
ferent ber types, the term dietary ber has been useful in nutri-
tion education and product development. In nutritional labeling,
ber is typically listed as a single category and not broken down
into soluble or insoluble subtypes.
Fiber metabolism
Dietary ber has a major role in the gastrointestinal tract
( Figure 1 ). Any undigested carbohydrate that reaches the colon
will be fermented (partly or totally) by the gut bacteria to produce
short-chain fatty acids (SCFAs) and a number of gases, including
carbon dioxide, hydrogen, and methane ( 27,28 ). SCFAs (mainly
acetate, propionate, and butyrate) in turn create an osmotic load,
are absorbed, and are further metabolized by colonocytes, hepato-
cytes, or the peripheral tissues ( 29 – 31 ). e fermentation of ber
also in uences fecal bulking in an indirect manner as fermentation
by colonic micro ora stimulates growth and results in increased
microbial biomass ( 32 ). us, the type of ber consumed leads to
adaptation of, and changes to, the microbiome. Dietary ber can
also in uence bulking directly via water retention ( 3,33,34 ). e
unwanted side-e ect of ber ingestion and subsequent fermenta-
tion, however, is the production of gas. is gas is o en malodor-
ous and may in turn cause undesirable discomfort, bloating, and
atus in many individuals. is characteristic of many ber types
may be particularly relevant for those with functional gastrointes-
tinal disorders.
Types of fi ber
e fermentability and solubility of di erent “ ber ” types relates
closely to their chemical composition (e.g., presence of cellu-
lose, hemicellulose, gums, resistant starch, lignins, pectins).
For the purpose of this review, ber will be broadly divided
into short chain- and long- chain carbohydrates or ber-types,
based on their solubility and fermentation characteristics
( Tab l e 1 ( 35 – 38 )). Short chain carbohydrates or ber includes
the oligosaccharides: fructo-oligosaccharides and galacto-
oligosaccharides (e.g., ra nose and stachyose). Owing to their
size and solubility, both fructo-oligosaccharides and galacto-
oligosaccharide bers are highly fermentable. e long-chain
carbohydrates include four major groups: (1) soluble, highly
fermentable non-starch polysaccharide ber (e.g., resistant
starch, pectin, inulin, guar gum); (2) intermediate soluble and
fermentable ber (psyllium / ispaghula) and oats; (3) insoluble,
slowly fermentable ber (wheat bran, lignin ( ax), and fruits
and vegetables); and nally (4) insoluble, non-fermentable ber
(cellulose, sterculia, and methycelullose).
Fiber and Functional Gastrointestinal Disorders
Shanti Eswaran , MD
1 , Jane Muir , PhD
2 and William D. Chey , MD, AGAF, FACG, FACP
1
Despite years of advising patients to alter their dietary and supplementary fi ber intake, the evidence surrounding the
use of fi ber for functional bowel disease is limited. This paper outlines the organization of fi ber types and highlights
the importance of assessing the fermentation characteristics of each fi ber type when choosing a suitable strategy for
patients. Fiber undergoes partial or total fermentation in the distal small bowel and colon leading to the production of
short-chain fatty acids and gas, thereby affecting gastrointestinal function and sensation. When fi ber is recommended
for functional bowel disease, use of a soluble supplement such as ispaghula / psyllium is best supported by the
available evidence. Even when used judiciously, fi ber can exacerbate abdominal distension, fl atulence, constipation,
and diarrhea.
Am J Gastroenterol 2013; 108:718–727; doi: 10.1038/ajg.2013.63; published online 2 April 2013
1 Division of Gastroenterology, University of Michigan Health System , Ann Arbor , Michigan , USA ;
2 Monash University , Melbourne , Victoria , Australia .
Correspondence: William D. Chey, MD, AGAF, FACG, FACP , Division of Gastroenterology, University of Michigan Health System , 3912 Taubman Center,
SPC 5362, Ann Arbor , Michigan 48109-5362 , USA . E-mail: wchey@umich.edu
Received 17 December 2012; accepted 11 February 2013
© 2013 by the American College of Gastroenterology The American Journal of GASTROENTEROLOGY
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ROLE OF FOOD IN FUNCTIONAL GASTROINTESTINAL DISORDERS
Fiber and Functional Gastrointestinal Disorders
e physiological characteristics (and potential health bene ts)
of each di erent ber type, in turn, depends on its proportion of
soluble- and insoluble carbohydrate components. For example,
ber types that are high in soluble, viscous ber may slow rates
of glucose and lipid absorption from the small intestine, likely by
sequestering bile acids and monoglycerides during passage through
the intestinal lumen ( 39 ). Soluble ber (pectin, beta-glucan (from
oats and barley), ispaghula / psyllium) is believed to be bene cial
in lowering blood cholesterol and plaque-forming low-density
lipoprotein levels by interrupting the enterohepatic circulation of
bile salts, thereby increasing hepatic conversion of cholesterol into
newly synthesized bile acids and decreasing serum LDL ( 18 – 20 ).
Dietary ber can contribute to net metabolizable energy, depend-
ing on how readily it is fermented. For example, fermentable ber
contributes 8 kJ / g (resistant starch (8.8 kJ / g), fructo-oligosaccha-
rides (8.4 kJ / g ), and inulin (8.8 kJ / g)) and non-fermentable ber
contributes (0 kJ / g) ( 40 ). Tabl e 2 lists popular commercially avail-
able supplements by type of ber.
How fi ber affects GI function
Fiber has been advocated for improved bowel function since the
early 1970s ( 41 ). In a 1980 Nature article, Stephen and Cummings
( 42 ) demonstrated that the actions of soluble and insoluble bers
in the colon depend on the extent to which they are digested. In
an elegant study they showed that insoluble ber alters colonic
function by increasing fecal water content and fecal bulk.
e mechanism for this e ect was unclear, however, as insolu-
ble ber has no appreciable water holding capacity, is minimally
fermented (no appreciable increase in biomass), and accelerates
colonic transit in germ-free rats ( 43,44 ). It was later determined
that insoluble ber (e.g., wheat bran) increases fecal mass and
colonic transit rate through mechanical stimulation / irritation of
gut mucosa, inducing secretion and peristalsis ( 45 ). An additional
study showed that both particle size and shape were important,
with large, coarse particles providing greater laxative e cacy than
ne, smooth particles (no e ect) ( 46 ). Taken together, these data
support that insoluble ber can have a signi cant laxative e ect,
but only if the particles are of su cient size and coarseness.
Soluble non-viscous ber and soluble viscous ber that is readily
fermented increase stool bulk by increasing biomass and fermen-
tation by-products, such as gas and SCFAs ( 42 ). On the basis of
such observations, it has been proposed that ber improves FGIDs
through the acceleration of oro-anal transit and by decreasing
intra-colon pressure ( 47,48 ). Of course, it is also possible that it is
through secondary e ects on the microbiota, low-grade in amma-
tion, or permeability that ber exerts e ects on sensation as well
as transit ( Figure 1 ) ( 49 ). e consumption of ber may actually
retard gas transit, by decreasing bolus propulsion to the rectum
( 50 ). us, in addition to increasing gas production by colonic
ora, ber ingestion may elicit gaseous or bloating symptoms by
promoting gas retention.
Soluble viscous ber that is minimally fermented has a high
water-holding / gel-forming capacity that is preserved through-
out the large bowel, normalizing stool form (so ens hard stool in
constipation, rms loose / liquid stool in diarrhea) ( 51,52 ). Viscous
bers that are FDA approved for laxation include methylcellulose,
calcium polycarbophil, and psyllium. Stool consistency is highly
correlated with stool water content, and a relatively small change in
stool water content (increase of 4.7 % ) can lead to a relatively large
stool so ening e ect (4.6-fold di erence in viscosity) ( 51 ).
Fiber also has extra-colonic e ects, and the data on gastric emp-
tying are mixed ( 53 – 57 ). In general, high doses ( ≥ 7 g) of wheat bran,
inulin, and psyllium tend to delay gastric emptying, whereas lower
doses do not show a signi cant e ect. Delayed gastric emptying
may be due to increased viscosity of gastric contents, which reduces
pyloric ow. Increased viscosity reduces sedimentation of solids in
liquids and thus impairs the ability of the antrum to preferentially
empty liquids faster than solids ( 58,59 ). is delay in gastric emp-
tying, together with a possible impairment of nutrient absorption
in the small intestine may delay intragastric redistribution, which
normally occurs as nutrients enter the duodenum ( 60 ). is could
explain the tendency towards the higher antral / fundal ratios seen
with bran, leading to the sensation of distension and bloating ( 61 ).
Effects of SCFAs
Using in vitro fermentation models to produce estimates of in vivo
ber fermentation, there is evidence that soluble bers increase the
rate of fermentation, increase SCFA production, lower pH, and
increase hydrogen gas production ( 62 ). In fact, di erences in fer-
mentation rates, gas production, and SCFA production have been
observed for various ber preparations (wheat dextrin, psyllium,
inulin), which may in turn explain their clinically observed di erent
gastrointestinal tolerances. Of the SCFAs, butyrate is the preferred
energy source for the colonic mucosa cells and exerts e ects on
myenteric neurons and motility ( 63 ), supporting one mechanism by
which a high ber diet accelerates colonic transit ( 64 ). Recent work
has found that speci c SCFAs such as butyrate alter the proportion
of ChAT immune reactive myenteric neurons and increase choliner-
gic-mediated colonic circular smooth muscle contraction in animals
( 63 ). Butyrate has also been shown to suppress colonic in ammation
by the inhibition of the IFN- γ / STAT1 signaling pathway ( 65 – 67 ).
SCFAs may also be shown to exert e ects on the GI tract
outside the colon. Exposure of the proximal colon in healthy
Fiber
Fiber
Fermentation
Short chain
fatty acids (SCFA)
(Butyrate, propionate,
acetate)
Stool
bulking
↑ Osmotic
load
Acceleration
of transit time
Increased
biomass
Effects on
inflammation
and permeability
Likely mechanism of action of fiber
on intestinal transit time and visceral hypersensitivity
Microbiome
changes
Luminal
pH ↓
Pain,
bloating,
flatulence
Gas
production
(CH4, H2, CO2)
Figure 1 . Likely mechanism of action of fi ber on intestinal transit time and
visceral hypersensitivity.
The American Journal of GASTROENTEROLOGY VOLUME 108 | MAY 2013 www.amjgastro.com
720
ROLE OF FOOD IN FUNCTIONAL GASTROINTESTINAL DISORDERS
Eswaran et al
Table 1 . Naturally occurring fi ber types
Fiber type Chain length Sources Potential benefi ts for IBS
a Potential risks for IBS
a
Soluble highly fermentable
oligosaccharides
(includes FOS, GOS)
Short-chain
carbohydrates
• Legumes / pulses
Nuts and seeds
• Wheat, rye
• Onions, garlic,
artichoke
• Laxation: weak laxative effect.
• Transit time: does not hasten transit time.
• Balance of bacteria: selective growth of
certain microbiota, e.g., Bifi dobactia.
• SCFA: very rapidly fermented in terminal
ileum and proximal colon to produce SCFA.
• Gas production: high
• In patients with IBS the rapid
fermentation may contribute to
gas, fl atus and gastrointestinal
symptoms.
• A number of studies have been
undertaken in IBS — with mixed
results ( 37 ).
Soluble highly fermentable
‘ fi ber ’ (e.g., RS, pectin,
guar gum, and inulin)
Long-chain
carbohydrates
• Legumes / pulses
• Rye bread, barley
• Firm bananas
• Buckwheat
groats (kashi),
millet, oats
• Cooked and
cooled-pasta,
potato and rice.
• Laxation: Mild laxative effect.
• Transit time: Does not hasten gut transit.
Can slow absorption from the small
intestine.
• Balance of bacteria: Increases overall
bacterial species but not selective for
bifi dobacteria.
• SCFA: Rapidly fermented in proximal colon
to produce SCFA. RS is good an excellent
substrate for the production of the SCFA
butyrate.
• Gas production: moderate
• In patients with IBS the rapid
fermentation may contribute to
gas, fl atus, and gastrointestinal
symptoms
• No well-designed studies have been
undertaken in IBS.
Intermediate soluble
fermentable ‘ fi b e r ’
(psyllium / ispaghula)
and oats.
Long-chain
carbohydrates
Seed of the plant
Plantago ovata ,
and oats
• Laxation: good laxative effect.
• Transit time: does hasten transit time.
• Balance of bacteria: increases overall
bacterial species but little evidence for
selective growth
• SCFA: moderately fermented along length
of colon to produce SCFA.
• Gas production: moderate.
• In patients with IBS studies have
shown some positive effect on
laxation.
• Side-effects of gas / fl atus has
produced mixed results for some
patients with IBS ( 38 ) .
Insoluble slowly fermentable
‘ fi ber ’ (e.g., wheat bran,
lignin (fl ax), fruit,
and vegetables)
Long-chain
carbohydrates
• Some vegetables
and fruit
• Wheat bran
• Wholegrain cereal
• Rye
• Brown rice,
wholemeal
pasta, quinoa
• Flax seed.
• Laxation: good laxative effect.
• Transit time: does hasten transit time.
• Balance of bacteria: increases overall
bacterial species but little evidence for
selective growth
• SCFA: slowly fermented to produce SCFA
along the length of the colon.
• Gas production: moderate-high
• In patients with IBS wheat bran
has not been shown to be effective.
A major side-effect has been
excessive gas / wind and bloating
( 39 ). This may be due to the
presence of high quantities of
fructans also associated with the
wheat bran ( 40 ).
• Symptoms associated with wheat
bran may not be acceptable to many
patients.
Insoluble, non-fermentable
‘ fi ber ’
(e.g. cellulose, sterculia,
and methylcellulose)
Long-chain
carbohydrates
• High fi ber grains
and cereals
• Nuts, seeds
• Skins of fruit and
vegetables.
• Laxation: good laxative effect.
• Transit time: does hasten transit time.
• Balance of bacteria: no evidence
for selective growth.
• SCFA: poorly fermented.
• Gas production: low
• Less gas / wind forming properties
• This fi ber type may have better
characteristics for treating
constipation in IBS patients.
However, few well designed
studies have been conducted.
FOS, fructo-oligosaccarides; GOS, galacto-oligosaccarides; IBS, irritable bowel syndrome; RS, resistant starch; SCFA, short chain fatty acids.
Information given in this table is a simplifi ed overview that summarizes the different physiological effects of the different fi ber types. More detailed information about this
area may be obtained by key reviews cited in this paper ( 26 – 35,42 – 44,73,74,77 ).
a Using standard (not excessive) doses of these carbohydrates .
© 2013 by the American College of Gastroenterology The American Journal of GASTROENTEROLOGY
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ROLE OF FOOD IN FUNCTIONAL GASTROINTESTINAL DISORDERS
Fiber and Functional Gastrointestinal Disorders
volunteers to SCFAs results in marked dose-dependent relaxa-
tion of the proximal stomach, and triggers transient LES relaxa-
tions ( 68,69 ). Similar e ects have been observed in patients with
gastroesophageal re ux disease on a diet high in indigestible
carbohydrates (10 g ber / day), signi cantly increasing the rate
of transient LES relaxations, number of acid re ux episodes,
and symptoms of gastroesophageal re ux disease ( 70 ).
Interaction with microbiota
ere is also evidence that changes in the complex gastrointes-
tinal environment by ingested ber in uence fecal microbiota
pro les, perhaps because of the varied production of SCFAs
and / or decreases in colonic pH, promoting the growth of ben-
e cial bacteria ( Figure 1 ). Short-chain carbohydrates (inulin,
fructo-oligosaccharides / galacto-oligosaccharide) and other solu-
ble bers are fermented in the distal small intestine and proximal
colon by endogenous bacteria to energy and metabolic substrates
(SCFAs), and the presence of these carbohydrates may produce
selective changes in the composition of the microbiota, inducing
di erent fermentation patterns. As such, carbohydrates such as
inulin are regarded as prebiotics, which may stimulate or alter the
preferential growth of health-promoting species already residing
in the colon (especially, but not exclusively, lactobacilli and bi do-
bacteria) ( 71 – 75 ), leading to potential bene ts in irritable bowel
syndrome (IBS) ( 76 ).
Fiber for chronic constipation
In addition to adequate uid intake and exercise, a high ber diet
is o en the rst recommendation a patient will receive for chronic
constipation, as a lack of dietary ber is believed to contribute to
constipation ( 77 – 79 ). Although 50 % of patients think ber does
not completely relieve their constipation and almost two-thirds of
respondents are not completely satis ed with the ability of ber to
improve their quality of life ( 80 ), current guidelines recommend
the use of ber in both dietary and supplement form for the early
management of constipation ( 81 ) ( Table 3 ( 82 )). It is apparent
from trials identi ed by systematic reviews that there is a relative
paucity of high quality evidence to support this approach, espe-
cially for insoluble ber. Soluble ber is thought to increase stool
bulk and weight and therefore stool frequency ( 3,83 ). Insoluble
ber such as bran is thought to accelerate intestinal transit time,
thereby increasing stool frequency ( 43,45,84 ). Finally, there is a
particular lack of evidence of e cacy of ber for individual con-
stipation subtypes (obstructive, metabolic, neurological, diet-
related, myogenic, drug-related, and pelvic oor dysfunction).
us, the remainder of this discussion will focus on ber as a
treatment for chronic idiopathic constipation (CIC), or constipa-
tion unrelated to anatomic, medication-related, or readily identi-
able physiological causes.
Fiber supplements. In an attempt to make sense of the divergent
data addressing the role of ber as a treatment for constipation, a
number of systematic reviews and meta-analyses with varying se-
lection criteria have been published ( 2,85,86 ). ese analyses have
found that most studies su er from small sample sizes and poor
study design with non-rigorous outcomes and high risk of bias.
Acknowledging the inherent heterogeneity of the data, there does
appear to be a signi cant improvement in constipation symptoms
Table 2 . Commercially available fi ber preparations
Fiber category Type Brand Serving size Amount of fi ber per serving
Soluble highly fermentable
oligosaccharides
FOS Orafti-P95 Powder 8 g / day 7.5 g
Soluble highly fermentable fi ber Inulin FiberChoice
Fibersure
Benefi ber (Canada)
Metamucil clear
Choice
2 Tablets
1 teaspoon
Varies
4 – 5 g
Wheat dextrin Benefi ber (USA) 2 Teaspoon powder 3 g
Partially hydrogenated guar
gum (PHGG)
Resistant starch
Benefi ber (formerly)
Hi-Maize
Powder
15 – 20 g powder
7 – 9 g
Soluble intermediate fermentable
fi ber
Ispaghula / psyllium
Oat Bran
Metamucil
Konsyl
Quaker oats
1 Tsp
Powder, caplet, wafer
40
g dry
3 g
4 g (2 g soluble)
Insoluble, minimally fermentable
fi ber
Wheat Bran Available in supermarket − 15 g Coarse powder
− 19 g Bran-pellets
6.5 g
4.5 g
Insoluble, non-fermentable fi ber Methylcellulose
a Citrucel Varies 0.5 – 2 g
Karaya gum / sterculia
b Normacol
Normafi b
1 – 2 Sachets daily or bid 7 g Per sachet
FOS, fructo-oligosaccarides.
a Derivatives of insoluble fi bers (e.g., esters of cellulose) are generally used. These derivatives are soluble in cold water.
b Sterculia gum is available as granules which should be swallowed whole with plenty of water.
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ROLE OF FOOD IN FUNCTIONAL GASTROINTESTINAL DISORDERS
Eswaran et al
Di culty of defecation was also signi cantly reduced with rye
bread ( P < 0.001), and stools were so er ( P < 0.001). However,
there were higher symptoms scores for gastrointestinal side e ects
such as abdominal pain, atulence, borborygmi, and bloating
with rye bread compared with low ber bread (mean di erence in
scores = 1.6, P < 0.001). Note that rye is partially fermentable, and
the high dose (37 g / day) was started day 1 without a gradual intro-
duction of ber.
Little human data exist on other commercially available ber
preparations ( Ta ble 3 ). For example, one study of methylcellulose
in constipated patients resulted in statistically signi cant increases
in stool frequency, water content, and fecal solids but this was
neither randomized or placebo controlled ( 95 ).
Fiber e ects on constipation subtype. Non-response to supple-
mentary ber may be a marker of refractory constipation or con-
stipation subtype, though there are few studies that have assessed
the e cacy of ber for slow transit constipation or dyssynergic
defecation. One non-randomized study demonstrated 88 % of
patients with slow transit and 63 % of patients with a disorder of
defecation did not respond to dietary ber treatment (30 g of ber
per day), whereas 85 % of patients without a pathological nding
improved or became symptom free ( 96 ). Approximately half of
patients with symptoms refractory to supplementary ber have a
prolonged intestinal transit time ( 97 ). us, ber intake is not a
panacea for all CIC patients.
Dietary ber. Patients o en nd ber supplements inconvenient
and unpalatable with the occurrence of gas or bloating o en a
reason for lack of compliance or discontinuation of therapy ( 98 ).
Comparatively, few clinical trials have evaluated dietary ber that
is naturally occurring as opposed to supplemental ber, likely
because food contains not only ber but other non-absorbable
sugars (i.e., polyols, fructans, and galacto-oligosaccharides) or
chemicals, which may exert laxative e ects. For example, a recent
prospective, randomized-controlled 8-week single-blind cross-
over study examined treatment with dried plums (prunes, 6 g / day
ber) compared with psyllium (6 g / day ber) in 40 patients ( 99 ).
Dried plums not only contain ber but also sorbitol and fructans,
non-absorbable carbohydrates that, when fermented by colonic
bacteria, create an osmotic load that can dramatically alter stool
frequency and consistency ( 100 ). Treatment with dried plums
resulted in a greater improvement in constipation symptoms
as re ected by a signi cant increase in the number of complete
spontaneous bowel movements and in stool consistency (so er
stools) when compared to treatment with psyllium. Also, more
subjects reported subjective improvement in overall constipa-
tion symptoms, although the mean global constipation symptom
scores were similar between groups and psyllium also improved
constipation symptoms when compared with baseline.
Conclusion. As there may be some bene t and little risk of seri-
ous adverse events, increasing dietary ber or the addition of ber
supplements seems a reasonable initial strategy in the manage-
ment of CIC patients. Patients may enjoy improvements in bowel
and abdominal discomfort compared with placebo for soluble
ber (psyllium, inulin). e paucity of high quality data highlights
the need for further large, methodologically rigorous, randomized
controlled trials (RCTs) utilizing validated outcome measures as
de ned by the Rome Foundation and regulatory agencies such
as the US Food and Drug Administration and the European
Medicines Agency ( 87 ).
e most recent summary of available RCTs studying the
e ects of both soluble and insoluble ber in patients with CIC
was performed in 2011 by Suares et al ( 88 ). Six studies were found
eligible for inclusion, including one RCT, which utilized a cross-
over design. It should be noted that studies which recruited patients
with drug-induced constipation, institutionalized patients, or those
that enrolled a heterogeneous group of patients (e.g., both CIC
and IBS with constipation (IBS-C)) were excluded. None of these
was at low risk of bias, the majority of them were small, and none
accounted for baseline dietary ber consumption or change in ber
consumption during the study. Amounts of ber in these studies
ranged between 10 – 20 g of ber / day with a treatment duration
from 2 to 8 weeks. e settings were mostly tertiary care centers and
subjects were predominantly female. Four of the eligible trials used
soluble ber (3 with psyllium, 1 with inulin and malto-dextrin)
( 89 – 92 ). e largest trial was a single-blind RCT with 201 primary
care patients who underwent treatment over a 2-week period ( 89 ).
Eighty-seven percent of patients allocated to psyllium reported an
improvement in symptoms, compared with 47 % of patients receiv-
ing placebo ( P < 0.001). ere was also a signi cant response in
abdominal pain / discomfort and straining on defecation. Similar
e ects were seen among the other three trials of soluble ber. In
one study, pain with defecation was signi cantly reduced with psyl-
lium, but 18 % of psyllium patients reported abdominal pain as a
side e ect as compared with 0 % of placebo ( 90 ).
Two studies used insoluble ber, wheat bran in one study ( 93 )
and rye bread in the other ( 94 ). In the 24 patients recruited to
receive 20 g of bran per day or placebo, no statistically signi cant
di erence in response (de ned as having no further straining at
stool) occurred with active treatment. For the rye bread study,
29 female participants consumed rye bread (37 g / day ber) or
low ber bread (6.6 g / day ber) over a 3-week period. Following
the intervention period, the mean di erence in number of stools
per day was 0.3 higher for the patients randomized to rye bread
compared with those assigned to low- ber bread ( P = 0.001).
Table 3 . Commonly used therapeutics for constipation and level
and grade of evidence ( 82 )
Treatment modalities commonly
used for constipation
Recommendation level and grade
of evidence
Bulking agents
• Psyllium / ispaghula Level II; grade B
• Calcium polycarbophil Level III; grade C
• Bran Level III; grade C
• Methycellulose Level III; grade C
© 2013 by the American College of Gastroenterology The American Journal of GASTROENTEROLOGY
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ROLE OF FOOD IN FUNCTIONAL GASTROINTESTINAL DISORDERS
Fiber and Functional Gastrointestinal Disorders
movement frequency and consistency. E ects on other symptoms
commonly reported by CIC patients such as abdominal pain or
bloating are more variable. Non-evidence based but practical ad-
vice on initiating therapy with ber supplements includes starting
at a nominal dose and slowly titrating up as tolerated over the
course of weeks to a target dose of 20 – 30 g of total dietary and
supplementary ber per day ( Table 2 ). It is also reasonable to rec-
ommend clearing hard stool with an osmotic laxative before initi-
ating ber therapy, which may avoid cramping pain. Occasionally,
patients will experience marked worsening of their constipation
related symptoms with ber. When this occurs, there are some
data to suggest that signi cantly delayed colon transit or dyssyn-
ergic defecation might be present ( 96,97 ).
Fiber for IBS. Historically, increasing dietary ber intake has
been a standard recommendation for patients with IBS, but the
e cacy of ber for IBS is more nuanced than appreciated by
most clinicians. Ever since Burkitt et al. ( 41 ) rst suggested that
ber might protect people in rural areas from certain gastroin-
testinal disorders, the practice of advising ber supplementation
in FGIDs has become widespread and remains standard operat-
ing procedure. However, the use of ber for IBS has historically
been, and still remains, controversial. Although some believe that
the highly processed, low ber western diet is at the root of IBS,
others believe that “ roughage ” can exacerbate or even cause IBS
symptoms ( 41,101 ). ese divergent views are likely the result of
the inherent heterogeneity of IBS, confusion as to what we refer
to as ber, the paucity of high quality studies, and con icting his-
torical data. In 1977, Manning et al. ( 102 ) examined the e ect of a
6-week high- or low- ber diet on abdominal pain and bowel fre-
quency in 26 IBS patients. Participants in this single-blind RCT
ingested an additional 20 g of wheat bran per day on the high
ber diet. e investigators found signi cant improvement in
pain frequency ( P < 0.05) and pain severity ( P ~ 0.01). Bowel habit
was regarded as “ improved ” in the high ber group ( P < 0.05),
and bowel frequency improved modestly as well ( P < 0.02). An-
other seminal RCT of psyllium in 80 IBS patients signi cantly
improved constipation ( P = 0.026) and transit time ( P = 0.001)
but did not signi cantly improve bloating and abdominal pain
( 103 ). A subsequent non-randomized study investigated the util-
ity of “ high- ber ” diets (30 g of ber / day) for the treatment of
72 IBS patients (all subtypes). is study reported improvement
in hard stools, bowel frequency, and urgency but no change in
abdominal distension, diarrhea, or atulence ( 104 ). Finally, an
o en-cited patient survey of 100 IBS patients found that 55 % felt
worse and only 10 % felt better on bran ( 105 ).
Fiber intake in IBS. A recent survey found that most general
practitioners believe that ber de ciency is the main cause of IBS
symptoms and 94 % would institute dietary therapy based on this
assumption ( 106 ). However, patients with FGIDs do not seem to
consume less dietary ber than healthy controls, suggesting symp-
toms are unlikely to be related to altered diet composition ( 107 ).
A recent Swedish abstract that compared the nutrition intake in
patients with IBS with the general population actually found the
intake of dietary ber to be higher in the IBS group (19 vs. 16 g /
day, P < 0.001) compared with controls ( 108 ). e authors con-
cluded that although IBS patients may have a self-imposed limited
diet and avoid trigger foods, their mean average daily ber intake
is essentially similar to that of a matched healthy control popula-
tion and in accordance with current nutrition recommendations.
Fiber supplements in IBS. e use of ber or bulking agents
for treatment of IBS has been summarized in two meta-analy-
ses ( 109,110 ), four systematic reviews ( 37,111 – 113 ), and two
comprehensive narrative reviews ( 114,115 ). All noted signi -
cant quality shortcomings in the published studies, including
heterogeneous patient populations, varied outcome measures,
di erent types of ber supplements, small sample size, and dif-
culties with blinding. Other widely variable factors included
the amount of soluble (5 – 30 g) and insoluble (4.1 – 36 g) ber
added to the diet and the duration of study intervention (3 – 16
weeks). Most of the trials that report the use of these agents do
not adhere to the recommendations made by the Rome foun-
dation for the design of treatment trials for the functional GI
disorders ( 87 ), although this is largely because the majority of
these trials were conducted long before these guidelines were in
place. Finally, most studies evaluated supplementary ber and
not increased dietary ber, and rarely reported on IBS subtype
or baseline dietary ber consumption.
e most recent Cochrane analysis concluded that bulking
agents were not bene cial for the treatment of IBS ( 112 ). is anal-
ysis, which included 12 papers with an intervention period lasting
4 – 16 weeks, reiterated the problems with the quality of available
data. e authors ’ conclusions from the pooled data suggested
that bulking agents provided no bene t for the treatment of IBS.
e studies either showed no signi cance or did not address spe-
ci c outcomes, including abdominal pain, improvement in global
assessment, and IBS symptom scores. Only seven of the included
studies had more than 30 patients and all studies had quality
limitations (i.e., method of randomization, double-blinding, con-
cealment of treatment allocation, description of withdrawals).
In a systematic review and meta-analysis by Ford et al. , ( 109 )
12 trials and 591 patients were included that evaluated the e -
cacy of various forms of ber with placebo or, in one study, a low
ber diet as treatment for IBS. Only 3 of these 12 studies reported
on IBS subtype. Two of the studies included only IBS-C patients
and another had 49 % IBS-C patients. e ber preparations used
included bran ( ve studies), ispaghula / psyllium (six studies), and
one unspeci ed. Overall, 52 % of IBS patients assigned to ber
had persistent symptoms or no improvement in symptoms a er
treatment compared with 57 % assigned to placebo or a low ber
diet (relative risk (RR) 0.87, 95 % con dence interval (CI) = 0.76 –
1.00, P = 0.05). ere was no statistically signi cant heterogeneity
detected between studies ( I 2 = 14.2 % , P = 0.31). e number needed
to treat (NNT) with ber to prevent one patient with persistent
symptoms was 11 (95 % CI = 5 – 100). ere was no evidence of
funnel plot asymmetry, suggesting no publication bias. However,
only seven of the 12 studies scored 4 or more on the Jadad scale.
When only these seven higher quality studies were included in the
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724
ROLE OF FOOD IN FUNCTIONAL GASTROINTESTINAL DISORDERS
Eswaran et al
patients reporting no change. In primary-care, psyllium led to
improvement in 25 % , deterioration in 19 % and no change in
56 % , which was not signi cantly di erent to secondary-care. e
authors concluded that although the approach of advising bran
for patients with IBS is not especially bene cial, it may be better
tolerated in primary care settings.
Although few adequately powered, methodologically rigorous
studies have examined the role of commercially available bers other
than psyllium for the treatment of IBS symptoms, there are some data
to suggest that preparations such as partially hydrolyzed guar gum
(formerly Bene ber, Novartis Consumer Health Inc., Parsippany, NJ)
and calcium polycarbophil (Fibercon, P zer, New York, NY) may
be helpful and well tolerated ( 118 – 120 ). It should be noted that each
caplet of calcium polycarbophil contains roughly 0.5 g of ber, thus
multiple pills may be required to see an appreciable e ect.
Dietary ber. In contrast to the larger number of studies of ber
supplementation, few studies have examined the e ect of increas-
ing ber intake in the form of ordinary foods ( 121 – 123 ). ere
are reports of improvement of IBS symptoms on both high- ber
and low- ber diets, a result attributed to a placebo or Hawthorne
e ect. In fact, a number of contrarian studies had suggested that
popular sources of dietary ber, such as bran, cereals, vegetables,
and fruits, might actually aggravate symptoms in IBS as these
foods also contain large amounts of FODMAPs (e.g., fructans, ex-
cess fructose, galacto-oligosaccharide, and sugar polyols) ( 124 ).
e symptoms that appeared to be aggravated most commonly
were atulence, bloating, and abdominal pain.
CONCLUSION
Success in nding an e ective treatment strategy for treating
functional GI disorders is a challenging area of clinical manage-
ment. One of the aims of this review was to highlight the impor-
tance of assessing the fermentation characteristics of each ber
type when choosing a suitable strategy for patients. When ber
is recommended for FGIDs, use of a soluble supplement such as
ispaghula / psyllium is best supported by the available evidence. In
constipated patients, it can be helpful for pre-existing hard stool
to be eliminated (e.g., with an osmotic laxative) before initiat-
ing ber therapy. Fiber should be started at a nominal dose and
slowly titrated up as tolerated over the course of weeks to a tar-
get dose of 20 – 30 g of total dietary and supplementary ber per
day. Even when used judiciously, ber can exacerbate problems
with abdominal distension, atulence, constipation, and diarrhea
( 105,125,126 ). It is clear that rather than extrapolating from the
studies undertaken in healthy individuals, further research in
functional GI patients should be performed with rigorous end-
points, strict inclusion criteria, and IBS subtype in mind.
ACKNOWLEDGMENTS
e authors would speci cally like to thank Dr John McRorie for
his contributions and edits to the “ Fiber metabolism ” section of the
manuscript.
analysis, the borderline treatment bene t for ber was no longer
evident (RR of persistent symptoms (0.90, 95 % CI = 0.75 – 1.08).
e data would suggest that all types of ber supplementation
are not created equally, at least not as it pertains to the treatment of
IBS. In ve studies (221 patients), which compared insoluble bran
with placebo or a low ber diet, bran failed to improve overall IBS
symptoms (RR of persistent or unimproved symptoms 1.02, 95 %
CI = 0.82 – 1.27) ( 109 ). On the other hand, six studies (321 patients)
evaluated soluble ber (ispaghula / psyllium) vs. placebo. Ispaghula
was e ective at improving overall IBS symptoms (RR of persistent
or unimproved symptoms 0.78, 95 % CI = 0.63 – 0.96). e NNT for
ispaghula to prevent one patient from experiencing persistent symp-
toms was 6 (95 % CI = 3 – 50). ere was no evidence of funnel plot
asymmetry and 5 / 6 studies scored 4 or more on the Jadad scale.
One key di erence between the Ford and Cochrane reviews was
the method of analysis ( 109,112 ). Both analyses had similar strict
inclusion criteria, but Ford et al. ( 109 ) did not use an intention-
to-treat analyses, and used persistent symptoms a er treatment as
an outcome measure. is may explain why this group found
psyllium to have a small but statistically signi cant bene t for IBS.
e most recent comparative e ectiveness trial evaluated the rela-
tive e cacy of psyllium / ispaghula, 10 g ( n = 85), bran, 10 g ( n = 97),
or rice our (placebo) ( n = 93), twice daily (mixed with food, pref-
erably yogurt) over 12 weeks in 164 primary care IBS patients
( 116 ). is study was not included in the reviews mentioned above.
At 1 month, 57 % of patients taking psyllium experienced adequate
symptom relief for 2 / 4 weeks of treatment compared with 40 % with
bran (NNT = 6, 95 % CI = 4 – 104) and 35 % with placebo (NNT = 5,
95 % CI = 3 – 15). e di erence between psyllium and placebo, how-
ever, was no longer signi cant at 3 months. Bran provided bene ts
over placebo only at 3 months. Over 60 % of subjects randomized to
psyllium or bran reported moderate adverse events, the most com-
mon of which were constipation and diarrhea. Interpretation of the
results at 2 and 3 months of treatment are complicated by the high
drop-out rates (29 % and 40 % , respectively). e overall likelihood
of side e ects was similar among the three groups.
It is important to recognize that most of the data on the e cacy
of ber for IBS come from referral centers. Studies conducted in
referral centers are likely to be biased against ber supplemen-
tation, as patients who improve with ber are less likely to be
referred to a tertiary care center. us, it is possible that results
of trials evaluating from referral centers could underestimate the
bene ts of ber for IBS. Only a few studies have included primary
care patients exclusively ( 105,116 ), and only one has addressed
this potential di erence in response speci cally. Miller et al.
( 117 ) recruited consecutive patients meeting Rome I criteria for
IBS from primary and secondary clinics until 100 had completed
questionnaires. Twenty-seven percent of primary care patients
said that bran had improved their symptoms compared with 22 %
who claimed it had made them worse. Ten percent of secondary
care patients attributed improvement to bran, while 55 % of these
patients felt it exacerbed their symptoms. About half of primary
care patients (51 % ), reported that bran had no positive or nega-
tive e ect on their symptoms compared with 33 % of secondary
© 2013 by the American College of Gastroenterology The American Journal of GASTROENTEROLOGY
725
ROLE OF FOOD IN FUNCTIONAL GASTROINTESTINAL DISORDERS
Fiber and Functional Gastrointestinal Disorders
CONFLICT OF INTEREST
Guarantor of the article : William D. Chey, MD, AGAF, FACG, FACP.
Speci c author contributions: Dr Eswaran dra ed the
manuscript and prepared the tables. Dr Muir contributed to the
writing, referencing, and preparation of the manuscript and tables.
Dr Chey proofed and nalized the text. All authors approved the
nal dra submitted.
Financial support : None.
Potential competing interests: Dr Eswaran and Jane Muir have no
potential competing interests. William D. Chey is a consultant for
N e s t l é / P r o m e t h e u s .
REFERENCES
1 . B o u c h o u c h a M , F a y e A , S a v a r i e a u B et al. E ect of an oral bulking agent
and a rectal laxative administered alone or in combination for the treatment
of constipation . Gastroenterol Clin Biol 2004 ; 28 : 438 – 43 .
2 . R a m k u m a r D , R a o S S . E cacy and safety of traditional medical
therapies for chronic constipation: systematic review . Am J Gastroenterol
2005 ; 100 : 936 – 71 .
3 . M c R o r i e J W , D a g g y B P , M o r e l J G et al. Psyllium is superior to docusate
sodium for treatment of chronic constipation . Aliment Pharmacol er
1998 ; 12 : 491 – 7 .
4 . Mehmood MH , Aziz N , Ghayur MN et al. Pharmacological basis for the
medicinal use of psyllium husk (Ispaghula) in constipation and diarrhea .
Dig Dis Sci 2011 ; 56 : 1460 – 71 .
5 . W a s h i n g t o n N , H a r r i s M , M u s s e l l w h i t e A et al. Moderation of lactulose-
induced diarrhea by psyllium: e ects on motility and fermentation .
Am J Clin Nutr 1998 ; 67 : 317 – 21 .
6 . Wenzl HH , Fine KD , Schiller LR et al. Determinants of decreased fecal
consistency in patients with diarrhea . Gastroenterology 1995 ; 108 :
1729 – 38 .
7 . Qvitzau S , Matzen P , Madsen P . Treatment of chronic diarrhoea: loperamide
versus ispaghula husk and calcium . Scand J Gastroenterol 1988 ; 23 : 1237 – 40 .
8 . H e a t h e r D J , H o w e l l L , M o n t a n a M et al. E ect of a bulk-forming cathartic
on diarrhea in tube-fed patients . Heart Lung 1991 ; 20 : 409 – 13 .
9 . E h e r e r A J , S a n t a A n a C A , P o r t e r J et al. E ect of psyllium, calcium
polycarbophil, and wheat bran on secretory diarrhea induced by
phenolphthalein . Gastroenterology 1993 ; 104 : 1007 – 12 .
1 0 . M u r p h y J , S t a c e y D , C r o o k J et al. Testing control of radiation-induced
diarrhea with a psyllium bulking agent: a pilot study . Can Oncol Nurs J
2000 ; 10 : 96 – 100 .
1 1 . S m a l l e y J R , K l i s h W J , C a m p b e l l M A et al. Use of psyllium in the manage-
ment of chronic nonspeci c diarrhea of childhood . J Pediatr Gastroenterol
Nutr 1982 ; 1 : 361 – 3 .
1 2 . S h e r m a n D S , F i s h D N . M a n a g e m e n t o f p r o t e a s e i n h i b i t o r - a s s o c i a t e d
diarrhea . Clin Infect Dis 2000 ; 30 : 908 – 14 .
1 3 . F e r n a n d e z - B a n a r e s F , H i n o j o s a J , S a n c h e z - L o m b r a n a J L et al. Randomized
clinical trial of Plantago ovata seeds (dietary ber) as compared with
mesalamine in maintaining remission in ulcerative colitis. Spanish group
for the study of Crohn’s disease and ulcerative colitis (GETECCU) .
Am J Gastroenterol 1999 ; 94 : 427 – 33 .
1 4 . F u j i m o r i S , G u d i s K , M i t s u i K et al. A randomized controlled trial on
the e cacy of synbiotic versus probiotic or prebiotic treatment to improve
the quality of life in patients with ulcerative colitis . Nutrition 2009 ; 25 :
520 – 5 .
15 . Fujimori S , Tatsuguchi A , Gudis K et al. High dose probiotic and prebiotic
cotherapy for remission induction of active Crohn’s disease . J Gastroenterol
Hepatol 2007 ; 22 : 1199 – 204 .
16 . Pittler MH , Ernst E . Dietary supplements for body-weight reduction: a
systematic review . Am J Clin Nutr 2004 ; 79 : 529 – 36 .
17 . Salas-Salvado J , Farres X , Luque X et al. E ect of two doses of a mixture
of soluble bres on body weight and metabolic variables in overweight or
obese patients: a randomised trial . Br J Nutr 2008 ; 99 : 1380 – 7 .
18 . Rodriguez-Moran M , Guerrero-Romero F , Lazcano-Burciaga G . Lipid- and
glucose-lowering e cacy of Plantago Psyllium in type II diabetes .
J Diabetes Complications 1998 ; 12 : 273 – 8 .
1 9 . M o r e y r a A E , W i l s o n A C , K o r a y m A . E ect of combining psyllium ber
with simvastatin in lowering cholesterol . Arch Intern Med 2005 ; 165 :
1161 – 6 .
2 0 . R o m e r o A L , W e s t K L , Z e r n T et al. e seeds from Plantago ovata lower
plasma lipids by altering hepatic and bile acid metabolism in guinea pigs .
J Nutr 2002 ; 132 : 1194 – 8 .
2 1 . d e B o c k M , D e r r a i k J G , B r e n n a n C M et al. Psyllium supplementation
in adolescents improves fat distribution & lipid pro le: a randomized,
participant-blinded, placebo-controlled, crossover trial . PLoS One
2012 ; 7 : e41735 .
2 2 . A n d e r s o n J W , A l l g o o d L D , T u r n e r J et al. E ects of psyllium on glucose and
serum lipid responses in men with type 2 diabetes and hypercholestero-
lemia . Am J Clin Nutr 1999 ; 70 : 466 – 73 .
23 . Levin EG , Miller VT , Muesing RA et al. Comparison of psyllium
hydrophilic mucilloid and cellulose as adjuncts to a prudent diet in the
treatment of mild to moderate hypercholesterolemia . Arch Intern Med
1990 ; 150 : 1822 – 7 .
2 4 . P a s t o r s J G , B l a i s d e l l P W , B a l m T K et al. Psyllium ber reduces rise in
postprandial glucose and insulin concentrations in patients with non-
insulin-dependent diabetes . Am J Clin Nutr 1991 ; 53 : 1431 – 5 .
2 5 . S i e r r a M , G a r c i a J J , F e r n a n d e z N et al. erapeutic e ects of psyllium in
type 2 diabetic patients . Eur J Clin Nutr 2002 ; 56 : 830 – 42 .
26 . Slavin JL . Position of the American Dietetic Association: health implica-
tions of dietary ber . J Am Diet Assoc 2008 ; 108 : 1716 – 31 .
27 . Cummings JH , Macfarlane GT . e control and consequences of bacterial
fermentation in the human colon . J Appl Bacteriol 1991 ; 70 : 443 – 59 .
28 . Cummings JH , Macfarlane GT , Englyst HN . Prebiotic digestion and
fermentation . Am J Clin Nutr 2001 ; 73 : 415S – 20S .
2 9 . T o d e s c o T , R a o A V , B o s e l l o O et al. Propionate lowers blood glucose and
alters lipid metabolism in healthy subjects . Am J Clin Nutr 1991 ; 54 : 860 – 5 .
3 0 . T o p p i n g D L , C l i on PM . Short-chain fatty acids and human colonic
function: roles of resistant starch and nonstarch polysaccharides .
Physiol Rev 2001 ; 81 : 1031 – 64 .
31 . Roediger WE . Utilization of nutrients by isolated epithelial cells of the rat
colon . Gastroenterology 1982 ; 83 : 424 – 9 .
3 2 . F l a m m G , G l i n s m a n n W , K r i t c h e v s k y D et al. Inulin and oligofructose as
dietary ber: a review of the evidence . Crit Rev Food Sci Nutr 2001 ; 41 : 353 – 62 .
33 . Davies GJ , Crowder M , Reid B et al. Bowel function measurements of
individuals with di erent eating patterns . Gut 1986 ; 27 : 164 – 9 .
3 4 . M c R o r i e J , G r e e n w o o d - V a n M e e r v e l d B , R u d o l p h C . C h a r a c t e r i z a t i o n o f
propagating contractions in proximal colon of ambulatory mini pigs .
Dig Dis Sci 1998 ; 43 : 957 – 63 .
35 . Heizer WD , Southern S , McGovern S . e role of diet in symptoms of
irritable bowel syndrome in adults: a narrative review . J Am Diet Assoc
2009 ; 109 : 1204 – 14 .
3 6 . C h o u i n a r d L E . e role of psyllium bre supplementation in treating
irritable bowel syndrome . Can J Diet Pract Res 2011 ; 72 : e107 – 14 .
3 7 . B i j k e r k C J , M u r i s J W , K n o t t n e r u s J A et al. Systematic review: the role of
di erent types of bre in the treatment of irritable bowel syndrome .
Aliment Pharmacol er 2004 ; 19 : 245 – 51 .
38 . Biesiekierski JR , Rosella O , Rose R et al. Q u a n t i cation of fructans,
galacto-oligosacharides and other short-chain carbohydrates in processed
grains and cereals . J Hum Nutr Diet 2011 ; 24 : 154 – 76 .
3 9 . H u n t R , F e d o r a k R , F r o h l i c h J et al. erapeutic role of dietary bre .
Can Fam Physician 1993 ; 39 : 897 – 900 , 3 – 10 .
40 . Elia M , Cummings JH . Physiological aspects of energy metabolism and
gastrointestinal e ects of carbohydrates . Eur J Clin Nutr 2007 ; 61 (Suppl 1) :
S40 – 74 .
4 1 . B u r k i t t D P , W a l k e r A R , P a i n t e r N S . E ect of dietary bre on stools and
the transit-times, and its role in the causation of disease . Lancet
1972 ; 2 : 1408 – 12 .
42 . Stephen AM , Cummings JH . Mechanism of action of dietary bre in the
human colon . Nature 1980 ; 284 : 283 – 4 .
43 . Tomlin J , Read NW . The relation between bacterial degradation of
viscous polysaccharides and stool output in human beings . Br J Nutr
1988 ; 60 : 467 – 75 .
44 . Riottot M , Sacquet E , Leprince C . E ect of wheat bran upon gastro-
intestinal transit in germ-free and conventional rats . Digestion 1984 ; 29 :
3 7 – 4 1 .
45 . Tomlin J , Read NW . Laxative properties of indigestible plastic particles .
BMJ 1988 ; 297 : 1175 – 6 .
4 6 . L e w i s S J , H e a t o n K W . R o u g h a g e r e v i s i t e d : t h e e ect on intestinal func-
tion of inert plastic particles of di erent sizes and shape . Dig Dis Sci
1999 ; 44 : 744 – 8 .
47 . Camilleri M . Management of the irritable bowel syndrome .
Gastroenterology 2001 ; 120 : 652 – 68 .
The American Journal of GASTROENTEROLOGY VOLUME 108 | MAY 2013 www.amjgastro.com
726
ROLE OF FOOD IN FUNCTIONAL GASTROINTESTINAL DISORDERS
Eswaran et al
7 5 . R o b e r f r o i d M B , V a n L o o J A , G i b s o n G R . e bi dogenic nature of chicory
inulin and its hydrolysis products . J Nutr 1998 ; 128 : 11 – 9 .
7 6 . S i l k D B , D a v i s A , V u l e v i c J et al. Clinical trial: the e ects of a trans-
galactooligosaccharide prebiotic on faecal microbiota and symptoms in
irritable bowel syndrome . Aliment Pharmacol er 2009 ; 29 : 508 – 18 .
7 7 . T r o w e l l H . D e nition of dietary ber and hypotheses that it is a protective
factor in certain diseases . Am J Clin Nutr 1976 ; 29 : 417 – 27 .
7 8 . B u r k i t t D P , M e i s n e r P . H o w t o m a n a g e c o n s t i p a t i o n w i t h h i g h - ber diet .
Geriatrics 1979 ; 34 : 33 – 5 , 8 – 40 .
7 9 . Tu c k e r D M , S a n d s t e a d H H , L o g a n J r G M et al. D i e t a r y ber and personality
factors as determinants of stool output . Gastroenterology 1981 ; 81 : 879 – 83 .
80 . Johanson JF , Kralstein J . Chronic constipation: a survey of the patient
perspective . Aliment Pharmacol er 2007 ; 25 : 599 – 608 .
81 . Locke 3rd GR , Pemberton JH , Phillips SF . AGA technical review on con-
stipation. American Gastroenterological Association . Gastroenterology
2000 ; 119 : 1766 – 78 .
82 . Rao SS . Constipation: evaluation and treatment of colonic and anorectal
motility disorders . Gastroenterol Clin North Am 2007 ; 36 : 687 – 711 , x .
8 3 . M a r t e a u P , F l o u r i e B , C h e r b u t C et al. Digestibility and bulking e ect of
ispaghula husks in healthy humans . Gut 1994 ; 35 : 1747 – 52 .
84 . Payler DK , Pomare EW , Heaton KW et al. e e ect of wheat bran on
intestinal transit . Gut 1975 ; 16 : 209 – 13 .
8 5 . T r a m o n t e S M , B r a n d M B , M u l r o w C D et al. e treatment of chronic
constipation in adults. A systematic review . J Gen Intern Med 1997 ; 12 :
15 – 24 .
86 . Jones MP , Talley NJ , Nuyts G et al. Lack of objective evidence of e cacy of
laxatives in chronic constipation . Dig Dis Sci 2002 ; 47 : 2222 – 30 .
8 7 . I r v i n e E J , W h i t e h e a d W E , C h e y W D et al. Design of treatment trials
for functional gastrointestinal disorders . Gastroenterology 2006 ; 130 :
1538 – 51 .
8 8 . S u a r e s N C , F o r d A C . S y s t e m a t i c r e v i e w : t h e e ects of bre in the
management of chronic idiopathic constipation . Aliment Pharmacol er
2011 ; 33 : 895 – 901 .
8 9 . F e n n G C , W i l k i n s o n P D , L e e C E et al. A general practice study of the
e cacy of Regulan in functional constipation . Br J Clin Pract 1986 ; 40 :
192 – 7 .
9 0 . A s h r a f W , P a r k F , L o f J et al. E ects of psyllium therapy on stool
characteristics, colon transit and anorectal function in chronic idiopathic
constipation . Aliment Pharmacol er 1995 ; 9 : 639 – 47 .
91 . Nunes F , Nunes C , Levis E . A double-blind trial of a celandin, aloevera
and psyllium laxative preparation in adult patients with constipation .
Rev Bras Med 2005 ; 62 : 352 – 7 .
9 2 . L o p e z R o m a n J , M a r t i n e z G o n z a l v e z A , L u q u e A . E f e c t o d e l a i n g e s t a
de un preparado lacteo con bra dietetica sobre el estrenimiento cronic
primario idiopatico . Nutr Hosp 2008 ; 23 : 12 – 9 .
93 . Badiali D , Corazziari E , Habib FI et al. E ect of wheat bran in treatment
of chronic nonorganic constipation. A double-blind controlled trial .
Dig Dis Sci 1995 ; 40 : 349 – 56 .
9 4 . H o n g i s t o S M , P a a j a n e n L , S a x e l i n M et al. A combination of bre-rich
rye bread and yoghurt containing Lactobacillus GG improves bowel
function in women with self-reported constipation . Eur J Clin Nutr
2006 ; 60 : 319 – 24 .
9 5 . H a m i l t o n J W , W a g n e r J , B u r d i c k B B et al. Clinical evaluation of
methylcellulose as a bulk laxative . Dig Dis Sci 1988 ; 33 : 993 – 8 .
96 . Voderholzer WA , Schatke W , Muhldorfer BE et al. Clinical response
to dietary ber treatment of chronic constipation . Am J Gastroenterol
1997 ; 92 : 95 – 8 .
9 7 . M e r t z H , N a l i b o B , Mayer E . Physiology of refractory chronic
constipation . Am J Gastroenterol 1999 ; 94 : 609 – 15 .
98 . Schiller LR . Review article: the therapy of constipation . Aliment Pharmacol
er 2001 ; 15 : 749 – 63 .
9 9 . A t t a l u r i A , D o n a h o e R , V a l e s t i n J et al. Randomised clinical trial: dried
plums (prunes) vs. psyllium for constipation . Aliment Pharmacol er
2011 ; 33 : 822 – 8 .
100 . McRorie J , Zorich N , Riccardi K et al. E ects of olestra and sorbitol
consumption on objective measures of diarrhea: impact of stool viscosity
on common gastrointestinal symptoms . Regul Toxicol Pharmacol
2000 ; 31 : 59 – 67 .
101 . Painter NS . Irritable or irritated bowel . Br Med J 1972 ; 2 : 46 .
102 . Manning AP , Heaton KW , Harvey RF . Wheat bre and irritable bowel
syndrome. A controlled trial . Lancet 1977 ; 2 : 417 – 8 .
103 . Prior A , Whorwell PJ . Double blind study of ispaghula in irritable bowel
syndrome . Gut 1987 ; 28 : 1510 – 3 .
48 . Camilleri M , Heading RC , ompson WG . Clinical perspectives,
mechanisms, diagnosis and management of irritable bowel syndrome .
Aliment Pharmacol er 2002 ; 16 : 1407 – 30 .
4 9 . H a m e r H M , J o n k e r s D , V e n e m a K et al. Review article: the role of butyrate
on colonic function . Aliment Pharmacol er 2008 ; 27 : 104 – 19 .
5 0 . G o n l a c h a n v i t S , C o l e s k i R , O w y a n g C et al. Inhibitory actions of a high
bre diet on intestinal gas transit in healthy volunteers . Gut 2004 ; 53 : 1577 – 82 .
5 1 . M c R o r i e J , P e p p l e S , R u d o l p h C . E ects of ber laxatives and calcium
docusate on regional water content and viscosity of digesta in the large
intestine of the pig . Dig Dis Sci 1998 ; 43 : 738 – 45 .
5 2 . M a r l e t t J A , F i s c h e r M H . e active fraction of psyllium seed husk .
Proc Nutr Soc 2003 ; 62 : 207 – 9 .
5 3 . B e r g m a n n J F , C h a s s a n y O , P e t i t A et al. Correlation between echographic
gastric emptying and appetite: in uence of psyllium . Gut 1992 ; 33 : 1042 – 3 .
5 4 . R i g a u d D , P a y c h a F , M e u l e m a n s A et al. E ect of psyllium on gastric
emptying, hunger feeling and food intake in normal volunteers:
a double blind study . Eur J Clin Nutr 1998 ; 52 : 239 – 45 .
5 5 . B i a n c h i M , C a p u r s o L . E ects of guar gum, ispaghula and microcrystalline
cellulose on abdominal symptoms, gastric emptying, orocaecal
transit time and gas production in healthy volunteers . Dig Liver Dis
2002 ; 34 (Suppl 2) : S129 – 33 .
5 6 . F r o s t G S , B r y n e s A E , D h i l l o W S et al. e e ects of ber enrichment of
pasta and fat content on gastric emptying, GLP-1, glucose, and insulin
responses to a meal . Eur J Clin Nutr 2003 ; 57 : 293 – 8 .
5 7 . K a w a s a k i N , S u z u k i Y , U r a s h i m a M et al. E ect of gelatinization on gastric
emptying and absorption . Hepatogastroenterology 2008 ; 55 : 1843 – 5 .
58 . Grimes DS , Goddard J . Gastric emptying of wholemeal and white bread .
Gut 1977 ; 18 : 725 – 9 .
5 9 . M e y e r J H , G u Y , E l a s h o J et al. E ects of viscosity and uid out ow on
postcibal gastric emptying of solids . Am J Physiol 1986 ; 250 : G161 – 4 .
6 0 . R u s s e l l J , B a s s P . C a n i n e g a s t r i c e m p t y i n g o f ber meals: in uence of meal
viscosity and antroduodenal motility . Am J Physiol 1985 ; 249 : G662 – 7 .
61 . Vincent R , Roberts A , Frier M et al. E ect of bran particle size on gastric
emptying and small bowel transit in humans: a scintigraphic study .
Gut 1995 ; 37 : 216 – 9 .
6 2 . T i m m D A , S t e w a r t M L , H o s p a t t a n k a r A et al. Wheat dextrin, psyllium,
and inulin produce distinct fermentation patterns, gas volumes, and short-
chain fatty acid pro les in vitro . J Med Food 2010 ; 13 : 961 – 6 .
63 . Soret R , Chevalier J , De Coppet P et al. Short-chain fatty acids regulate the
enteric neurons and control gastrointestinal motility in rats .
Gastroenterology 2010 ; 138 : 1772 – 82 .
64 . Jouet P , Sabate JM , Co n B et al. Fermentation of starch stimulates
propagated contractions in the human colon . Neurogastroenterol Motil
2011 ; 23 : 450 – 6 , e176 .
6 5 . Z i m m e r m a n M A , S i n g h N , M a r t i n P M et al. Butyrate suppresses colonic
in ammation through HDAC1-dependent Fas Upregulation and Fas-
mediated apoptosis of T cells . Am J Physiol Gastrointest Liver Physiol
2012 ; 302 : 61405 – 15 .
6 6 . K l a m p f e r L , H u a n g J , S a s a z u k i T et al. Inhibition of interferon gamma
signaling by the short chain fatty acid butyrate . Mol Cancer Res 2003 ; 1 :
855 – 62 .
6 7 . S t e m p e l j M , K e d i n g e r M , A u g e n l i c h t L et al. E s s e n t i a l r o l e o f t h e J A K /
STAT1 signaling pathway in the expression of inducible nitric-oxide
synthase in intestinal epithelial cells and its regulation by butyrate . J Biol
Chem 2007 ; 282 : 9797 – 804 .
6 8 . R o p e r t A , C h e r b u t C , R o z é C et al. Colonic fermentation and proximal
gastric tone in humans . Gastroenterology 1996 ; 111 : 289 – 96 .
6 9 . P i c h e T , Z e r b i b F , V a r a n n e s S B et al. Modulation by colonic fermentation
of LES function in humans . Am J Physiol Gastrointest Liver Physiol
2000 ; 278 : G578 – 84 .
70 . Piche T , des Varannes SB , Sacher-Huvelin S et al. Colonic fermentation
in uences lower esophageal sphincter function in gastroesophageal re ux
disease . Gastroenterology 2003 ; 124 : 894 – 902 .
71 . Roberfroid M . Prebiotics: the concept revisited . J Nutr 2007 ; 137 : 830S – 7S .
7 2 . G i b s o n G R , B e a t t y E R , W a n g X et al. Selective stimulation of bi dobacteria
in the human colon by oligofructose and inulin . Gastroenterology
1995 ; 108 : 975 – 82 .
7 3 . B o u h n i k Y , F l o u r i e B , R i o t t o t M et al. E ects of fructo-oligosaccharides
ingestion on fecal bi dobacteria and selected metabolic indexes of colon
carcinogenesis in healthy humans . Nutr Cancer 1996 ; 26 : 21 – 9 .
7 4 . K l e e s s e n B , S y k u r a B , Z u n H J et al. E ects of inulin and lactose on fecal
micro ora, microbial activity, and bowel habit in elderly constipated
persons . Am J Clin Nutr 1997 ; 65 : 1397 – 402 .
© 2013 by the American College of Gastroenterology The American Journal of GASTROENTEROLOGY
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ROLE OF FOOD IN FUNCTIONAL GASTROINTESTINAL DISORDERS
Fiber and Functional Gastrointestinal Disorders
1 0 4 . L a m b e r t J P , B r u n t P W , M o w a t N A et al. e value of prescribed
‘ high- bre ’ diets for the treatment of the irritable bowel syndrome .
Eur J Clin Nutr 1991 ; 45 : 601 – 9 .
1 0 5 . F r a n c i s C Y , W h o r w e l l P J . B r a n a n d i r r i t a b l e b o w e l s y n d r o m e : t i m e f o r
r e a p p r a i s a l . e Lancet 1994 ; 344 : 39 – 40 .
1 0 6 . B i j k e r k C J , d e W i t N J , S t a l m a n W A et al. Irritable bowel syndrome in
primary care: the patients ’ and doctors ’ views on symptoms, etiology and
management . Can J Gastroenterol 2003 ; 17 : 363 – 8 , quiz 405 – 6 .
1 0 7 . S a i t o Y A , L o c k e # # 3 r d G R , W e a v e r A L et al. Diet and functional
gastrointestinal disorders: a population-based case-control study .
Am J Gastroenterol 2005 ; 100 : 2743 – 8 .
1 0 8 . B o h n N , S t o r s r u d S , L i n d h A et al. Nutrition intake in patients with
irritable bowel syndrome (IBS) compared with the general population .
Gastroenterology 2011 ; 140 : S305 .
1 0 9 . F o r d A C , T a l l e y N J , S p i e g e l B M et al. E ect of bre, antispasmodics, and
peppermint oil in the treatment of irritable bowel syndrome: systematic
review and meta-analysis . BMJ 2008 ; 337 : a2313 .
110 . Lesbros-Panto i c k o v a D , M i c h e t t i P , F r i e d M et al. Meta-analysis:
e treatment of irritable bowel syndrome . Aliment Pharmacol er
2004 ; 20 : 1253 – 69 .
111 . Brandt LJ , Chey WD , Foxx-Orenstein AE et al. An evidence-based
position statement on the management of irritable bowel syndrome .
Am J Gastroenterol 2009 ; 104 (Suppl 1) : S1 – 35 .
1 1 2 . R u e p e r t L , Q u a r t e r o A O , d e W i t N J et al. Bulking agents, antispasmodics
and antidepressants for the treatment of irritable bowel syndrome .
Cochrane Database Syst Rev 2011 , CD003460 .
1 1 3 . J a i l w a l a J , I m p e r i a l e T F , K r o e n k e K . P h a r m a c o l o g i c t r e a t m e n t o f t h e i r r i t a -
ble bowel syndrome: a systematic review of randomized, controlled trials .
Ann Intern Med 2000 ; 133 : 136 – 47 .
1 1 4 . Z u c k e r m a n M J . e role of ber in the treatment of irritable bowel syndrome:
therapeutic recommendations . J Clin Gastroenterol 2006 ; 40 : 104 – 8 .
115 . Akehurst R , Kaltenthaler E . Treatment of irritable bowel syndrome:
a review of randomised controlled trials . Gut 2001 ; 48 : 272 – 82 .
1 1 6 . B i j k e r k C J , d e W i t N J , M u r i s J W et al. Soluble or insoluble bre in irritable
bowel syndrome in primary care? Randomised placebo controlled trial .
BMJ 2009 ; 339 : b3154 .
117 . Miller V , Lea R , Agrawal A et al. Bran and irritable bowel syndrome:
the primary-care perspective . Dig Liver Dis 2006 ; 38 : 737 – 40 .
1 1 8 . P a r i s i G , B o t t o n a E , C a r r a r a M et al. T r e a t m e n t e ects of partially
hydrolyzed guar gum on symptoms and quality of life of patients with
irritable bowel syndrome. A multicenter randomized open trial .
Dig Dis Sci 2005 ; 50 : 1107 – 12 .
1 1 9 . P a r i s i G C , Z i l l i M , M i a n i M P et al. H i g h - ber diet supplementation in
patients with irritable bowel syndrome (IBS): a multicenter, randomized,
open trial comparison between wheat bran diet and partially hydrolyzed
guar gum (PHGG) . Dig Dis Sci 2002 ; 47 : 1697 – 704 .
120 . Toskes PP , Connery KL , Ritchey TW . Calcium polycarbophil compared
with placebo in irritable bowel syndrome . Aliment Pharmacol er
1993 ; 7 : 87 – 92 .
121 . Aller R , de Luis DA , Izaola O et al. E ects of a high- ber diet on
symptoms of irritable bowel syndrome: a randomized clinical trial .
Nutrition 2004 ; 20 : 735 – 7 .
1 2 2 . L u c e y M R , C l a r k M L , L o w n d e s J et al. I s b r a n e cacious in irritable
bowel syndrome? A double blind placebo controlled crossover study .
Gut 1987 ; 28 : 221 – 5 .
1 2 3 . V i l l a g r a s a M , B o i x J , H u m b e r t P et al. Aleatory clinical study comparing
otilonium bromide with a ber-rich diet in the treatment of irritable bowel
syndrome . Ital J Gastroenterol 1991 ; 23 : 67 – 70 .
124 . Shepherd SJ , Parker FC , Muir JG et al. Dietary triggers of abdominal
symptoms in patients with irritable bowel syndrome: randomized
placebo-controlled evidence . Clin Gastroenterol Hepatol 2008 ; 6 :
765 – 71 .
1 2 5 . N a n d a R R J , S m i t h H , D u d l e y C R , J e w e l l D P . F o o d i n t o l e r a n c e a n d t h e
irritable bowel syndrome . Gut 1989 ; 30 : 1099 – 104 .
126 . King TS , Elia M , Hunter JO . Abnormal colonic fermentation in irritable
bowel syndrome . Lancet 1998 ; 352 : 1187 – 9 .
