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Vegetable dietary fibres made with minimal processing improve health-related faecal parameters in a valid rat model

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Dietary fibre-induced faecal bulking and hydration are important contributors to large bowel function and health, and are affected by the dietary fibre structure. To determine faecal bulk-related parameters for vegetable dietary fibres with retained structure, cold water fragmentation of vegetables was used to make minimally processed vegetable fibres (MPVF) from swede, broccoli and asparagus. A valid adult rat model was used to subject the fibres to processes of hind gut fermentation and faecal accumulation similar to those in humans. All the MPVFs had high faecal bulking indexes (FBIs, mean ± sem: wheat bran (reference), 100 ± 6.0; asparagus 168 ± 5.7; swede 135 ± 6.1; broccoli 135 ± 5.9; broccoli rind 205 ± 10.4), and caused large increases in the theoretical colonic water load at 10 g per 100 g diet (increase over baseline (%): wheat bran, 137 ± 8.3; asparagus, 236 ± 25, swede 193 ± 8.8; broccoli 228 ± 12; broccoli rind 223 ± 8.5). Faecal bulking by MPVFs was much greater than by fermentable extracted polysaccharides such as pectin and raftilose, or by commercial fibres made from highly processed cell walls. The results show natural, non-degraded vegetable fibres with retained botanical structure have beneficial effects not provided by structure-less fermentable dietary fibres. Dietary fibre-deficient diets supplemented with prebiotics cannot, therefore, adequately substitute for varied diets containing adequate vegetables, fruits and wholegrain cereals in which fermentation is associated with enough retained structure to conserve physicochemical properties of benefit to colonic function.
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Food &
Cite this: Food Funct., 2016, 7, 2645
Received 10th December 2015,
Accepted 8th May 2016
DOI: 10.1039/c5fo01526j
Vegetable dietary bres made with minimal
processing improve health-related faecal
parameters in a valid rat model
John Monro,* Suman Mishra, Claire Redman, Sheryl Somereld and Jovyn Ng
Dietary bre-induced faecal bulking and hydration are important contributors to large bowel function and
health, and are aected by the dietary bre structure. To determine faecal bulk-related parameters for
vegetable dietary bres with retained structure, cold water fragmentation of vegetables was used to make
minimally processed vegetable bres (MPVF) from swede, broccoli and asparagus. A valid adult rat model
was used to subject the bres to processes of hind gut fermentation and faecal accumulation similar to
those in humans. All the MPVFs had high faecal bulking indexes (FBIs, mean ± sem: wheat bran (refer-
ence), 100 ± 6.0; asparagus 168 ± 5.7; swede 135 ± 6.1; broccoli 135 ± 5.9; broccoli rind 205 ± 10.4), and
caused large increases in the theoretical colonic water load at 10 g per 100 g diet (increase over baseline
(%): wheat bran, 137 ± 8.3; asparagus, 236 ± 25, swede 193 ± 8.8; broccoli 228 ± 12; broccoli rind 223 ±
8.5). Faecal bulking by MPVFs was much greater than by fermentable extracted polysaccharides such as
pectin and raftilose, or by commercial bres made from highly processed cell walls. The results show
natural, non-degraded vegetable bres with retained botanical structure have benecial eects not
provided by structure-less fermentable dietary bres. Dietary bre-decient diets supplemented with pre-
biotics cannot, therefore, adequately substitute for varied diets containing adequate vegetables, fruits and
wholegrain cereals in which fermentation is associated with enough retained structure to conserve
physicochemical properties of benet to colonic function.
1 Introduction
The properties of both the pre-faecal and faecal masses in the
large intestine play an important role in the entire digestion
as hormonal and neuronal feedback loops from the
colon to the foregut influence processes from appetite and
food intake to gut transit to colonic loading, with diverse
eects on the metabolism of the entire organism.
with the current popular and research emphasis on the eects
of fermentable digestion-resistant carbohydrates (dietary
fibres) as prebiotics, the role of non-fermented bulk has been
relatively neglected. Prebiosis involves fermentative destruc-
tion of fibre, so completely fermentable fibres will undergo a
complete loss of bulk, only partially compensated by increased
biomass due to bacterial growth supported by the fermented
fibre. Unless there is some structural component to the fibre
intake that confers resistance to fermentation and provides
enough structural resilience to maintain volume, with its
associated water load, faecal bulk is likely to fall below the
approximately 150200 g per day indicated for protection
against colorectal cancer.
As dietary fibre, by definition
requires the chain length to be greater than only
310 sugar units, which is far too short for polysaccharide
alignments that generate resistant structures such as plant cell
walls, many prebiotics that qualify as dietary fibres are func-
tionally limited compared with plant cell wall remnants in the
Faecal bulking associated with resistance to fermentation is
a physiological property that modulates the eects of pre-
biotics and may be complementary to them in terms of
health benefits.
Bulking capacity is achieved largely through
hydration, which reduces chemical activity in the distal colon
by dilution.
Colorectal bulk also contributes to the stimuli
that induce the defecation process.
Defecation eliminates
wastes that would produce toxic products of protein putrefac-
tion if allowed to stagnate,
and is followed by movement of
fresh digesta into the colorectal region, where the protective
benefits of fermentation are most required.
Electronic supplementary information (ESI) available. See DOI: 10.1039/
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regular bowel movement also contributes to a sense of
Much of the perceived need for prebiotics associated with
bowel disorders in the modern diet arises because dietary
fibre intakes are inadequate, as many sources of mixed func-
tion dietary fibre have been removed through ingredient
refinement, unhealthy food formulations and poor food
choices. Using prebiotics to restore fibre intake is not,
however, entirely satisfactory because prebiotics often lack
physical structure, so have a more narrow range of functional-
ity than the naturaldietary fibres. They cannot provide the
colon with fermentation-resistant plant cell wall and tissue
remnants, whose morphology plays an important role in faecal
Being plant cell wall material is not, however, sucient to
ensure functionality. Commercial dietary fibre preparations
derived from plant cell walls and used to increase fibre intake
are often functionally deficient because they have been sub-
jected to destructive processing to make them suitable for use
as ingredients in foods such as baked products. Heating that
causes depolymerisation, extraction and loss of pectin, and
loss of structure as the dietary fibre preparations are milled to
very fine powders, will alter hydration properties and lower
resistance to fermentation.
Therefore, unless minimally pro-
cessed, cell wall preparations from vegetables and fruits are
likely to suer a reduced faecal bulking ecacy during
To determine the capacity of minimally processed vegetable
dietary fibres (MPVF) to contribute to distal colonic bulk, a
comparative study was made of the faecal bulking properties
of dietary fibre preparations obtained from vegetables by cold
water maceration. A validated rat model of human faecal
bulking responses was used to assess the potential of the
MPVF to improve faecal bulk and hydration. Several dierent
types of vegetables were used: a stem (swede), a shoot (aspara-
gus), and a flower head (broccoli). The doseresponse relation-
ship was determined and the faecal bulking ecacy compared
with those of a soluble fermentable and a soluble non-fermen-
table polysaccharide and a commercial prebiotic. Finally the
faecal bulking indexes (FBIs) of the materials were determined
to provide a standardised measure of the relative faecal
bulking ecacy of the materials tested.
2 Materials and method
2.1 Dietary fibre preparation
Swedes (Brassica napobrassica), asparagus (Asparagus ocina-
lis), broccoli head (Brassica oleracea), onion (Allium cepa),
parsnip (Pastinaca sativa) and carrot (Daucus carota) were
obtained from commercial growers and were all in sound con-
dition. The onion, parsnip and carrot were not included in the
faecal bulking trials but the hydration properties of all the
fibre preparations were measured. For preparation of broccoli
rind MPVF, broccoli frames (the stalk left after harvesting the
edible flower head) were cut about 10 cm above ground level,
trimmed of leaves, and strips of rind were removed and cut
into 1 cm sections ready for MPVF preparation (below).
The faecal bulking reference material was hard red wheat
bran from a local cereal wholesaler. It was milled in a Retsch
mill with a 1 mm sieve plate and then hand-sieved through a
2 mm sieve for use in the rat diets. Fibrex® sugar beet fibre
(grade 595, <125 μm particle size, Danisco Sugar AB, Malmö,
Sweden) was derived from the wastes of sugar beet so, like the
MPVFs, represents non-woody cell wall material. It is widely
used as a bulking agent in the food industry and was used
directly in the rat diets. Other fibres tested in the hydration
experiment or in the faecal bulking assay were pectin
(Mexpectin; Grinsted Products), psyllium husk (Bronson and
Rosenberg, Germany), Raftilose (Orafti), lactic casein (Fonterra),
starch (New Zealand Starch Ltd, Auckland) and castor sugar
2.2 MPVF preparation
The main aim of the minimal processing was to rupture the
plant cell walls, release and wash away the cell contents, and
dry the remaining fibre (ESI Fig. S1). The vegetables were
washed by hand in cold water containing 100 ppm chlorine.
After washing, they were passed through a Hallde grater with a
4 mm grating disk at a rate of 2 kg per minute. The grated
vegetable was then chopped in a Talsa bowl chopper to
produce a puree. This was added with 2 L water to a disinte-
grator, which chopped at high speed in a sealed container for
5 minutes, producing a fine puree which was then passed
through a colloid mill as the last stage in the size reduction
process. The aperture size was set at 1.75 micron and the vege-
table pulp was manually fed through at a slow speed. By treat-
ing the milled product with Evans Blue stain and viewing
under a microscope, the milling process was shown to be
8590% eective at rupturing the cells. Cells with intact mem-
branes are not stained. The vegetable fibre particles were col-
lected in organza fine mesh bags from the outlet of the colloid
mill, and washed under running cold water until all traces of
colour were removed, leaving a white MPVF preparation. After
washing, the bags were squeezed by hand to remove as much
excess water as possible. The squeezed fibre was spread in
2 cm thick layers in wire mesh drying trays and dried with fan-
forced recirculated air at 50 °C for two days. The dried MPVF
was milled using a Deawner Grinding Mill fitted with a 1 mm
mesh screen and stored in air-tight bags at room temperature
ready for use. The resulting fibre was composed of a range of
particle sizes less than 1 mm.
2.3 Functional intactness of the MPVF
The physical intactness of the MPVF was gauged by micro-
scopic examination and functional intactness by comparing
water retention capacity of the MPVF preparations with
those of commercial dietary fibre preparations using a stan-
dard procedure.
Dietary fibre samples (1.0 g) in duplicate
were hydrated in an excess of water for 16 h. The settled
fibre was centrifuged at 3000gfor 20 min in pre-weighed
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centrifuge tubes. After aspirating the supernatant, the tubes
were reweighed and the weight of tube and fibre subtracted
to obtain a value for retained water. For microscopic exam-
ination freeze dried MPVF was wetted with a few drops of
water and mounted onto a glass slide. Samples were viewed
and imaged using an Olympus Vanox AHT3 light micro-
scope (Olympus Optical, Tokyo, Japan) under bright field
2.4 Faecal bulking analysis
2.4.1 Animals. The properties of faeces from rats fed the
vegetable fibre preparations and wheat bran reference
materials were measured under the conditions of the faecal
bulking index (FBI) assay.
Adult male Sprague Dawley rats
were raised on a standard pellet diet to a weight of 300 ± 50 g.
They were placed individually in hanging mesh-floored cages
in a rack containing 30 cages per side, in a controlled environ-
ment room (12 h lightdark cycle; temperature, 22 ± 1 °C;
humidity, 60 ± 5%; air exchange, 12 times per h). Water was
provided ad libitum. Ethical approval for the trial was obtained
from the AgResearch Grasslands Animal Ethics Committee,
Palmerston North (Application 13069). The animal trials were
conducted under the AgResearch Limited guidelines stated in
the Code of Ethical Conduct for the use of Animals in
Research, Testing and Teaching.
2.4.2 Diets and feeding. The test diets were fed in three
consecutive trials (Table 1). Each trial involved a three day lead
in period followed by a four-day balance period during which
faecal collections were made. After trials 1 and 2 the rats were
randomised and fed a high fibre clean out diet containing
10% sugar beet fibre (Fibrex®) and 5% wheat bran for three
days, before being placed on the lead-in diet for the sub-
sequent trial.
All rats were raised on a standard pelleted diet containing
dietary fibre and were transferred to a powdered high fibre
diet containing 10% sugar beet fibre (Fibrex®) and 5% wheat
bran for 1 week before being fed the trial diets over the course
of three trials. During the assay period, rats (n= 8 per treat-
ment) were fed 25 g per day of a nutritionally complete diet
consisting of a 50% diet base, which provided all the essential
nutrients and was constant for all diets, and 50% sucrose, a
proportion of which was substituted by the component being
tested for its faecal bulking eects (ESI Table S1). The treat-
ments within the three trials are summarised in Table 1. The
cages were arranged in eight consecutive blocks of eight cages,
with each block containing all diets (baseline, reference and
six test diets). Each trial consisted of a three-day lead in
period, and a four-day balance period, during which food
intakes and spillage were accurately recorded and all faeces
collected. A three-day lead in before the balance period was
sucient because of the high background fibre content of the
diet and complete consumption of the 25 g daily ration by the
rats, which were accustomed to the trial conditions. Faeces
were collected daily on a double thickness of blotting paper
beneath the cages over the four-day balance period and dried
under vacuum.
2.4.3 Faecal measurements. The weight of faeces produced
was determined dry and after rehydrating the intact pellets by
imbibition of water. Faecal water-holding capacity was deter-
mined by weighing a subsample (1215 pellets) of the dried
faeces into plastic pots, as a single layer, and adding about
20% more water/sodium azide (0.02%) than was sucient to
saturate them fully. After 2 days at room temperature excess
water was aspirated from the pots, the pots placed on a slope
to gravity drain in situ, and any further water that drained from
the pellets in 30 min was removed with a Pasteur pipette,
before the hydrated pellets were weighed.
The measurements allowed calculation of a number of
faecal parameters (ESI Table S2) including faecal dry matter
per 100 g feed intake, faecal water-holding capacity (ml per g
dry faeces), theoretical faecal water load per 100 g diet
(ml per 100 g feed intake), equivalent hydrated faecal output
(a model of human faecal output; g rehydrated faeces
per 100 g feed intake), the increment in dry and hydrated
faecal bulk per gram of added component, the apparent
survival of MPVF after gut passage, and the faecal bulking
index (FBI; %).
Table 1 Faecal bulking trials conducted
Diet Test component
rate (%)
Trial 1:individual fibre eects
1.1 Swede fibre 10
1.2 Whole swede 10
1.3 Asparagus fibre 10
1.4 Broccoli fibre 10
1.5 Psyllium 2.5
1.6 Pectin 5
1.7 (Reference) Wheat bran 10
1.8 (Baseline) None 0
Trial 2: fibre interactions
2.1 Asparagus fibre 10
2.2 Swede fibre 10
2.3 Swede : asparagus fibres 1 : 1 10
2.4 Swede fibre : psyllium 1 : 1 10
2.5 Swede fibre : wheat bran 1 : 1 10
2.6 Psyllium 5
2.7 (Reference) Wheat bran 10
2.8 (Baseline) None 0
Trial 3: dose response and fibre interactions
3.1 Broccoli fibre 5
3.2 Broccoli fibre 7.5
3.3 Broccoli fibre 10
3.4 Broccoli fibre 12.5
3.5 Broccoli fibre 15
3.6 Broc/Asp/Swede fibres 1 : 1 : 1 10
3.7 (Reference) Wheat bran 10
3.8 (Baseline) None 0
Reference materials from previous trials
Psyllium husk 5
Raftilose 12.5
Sugar beet fibre (Fibrex®) 10
Apple fibre 10
Sucrose 50
Starch 50
Casein 20
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FBIs were calculated as the increase over baseline in re-
hydrated faecal weight induced by a diet component expressed
as a percentage of the increase over baseline due to consump-
tion of the 2 mm hard red wheat bran reference equal in weight
to the dietary component.
The following formula was used to calculate FBI:
where: FBI = faecal bulking index; F
= mass of rehydrated
faeces per 100 g feed intake for test diet; F
= mass of re-
hydrated faeces per 100 g feed intake for baseline diet; F
mass of rehydrated faeces per 100 g feed intake for reference
diet; Tp = proportion of test material in diet; Rp = proportion
of reference material in diet.
2.4.4 Validity of the rat model. The rat is a useful model
because it is a monogastric hind gut fermenter, like humans,
in which any material that escapes digestion enters a bacterial
ecosystem that contains hundreds of species of bacteria with
the collective capacity to utilise any potentially fermentable
Hydrated faecal bulk thus depends more on the
characteristics of the dietary fibre than on the monogastric
host. Production of faeces by rats correlates reasonably with
stool production by humans.
Although the rat produces
faeces as pellets with a lower dry matter content than human
faeces, when they are allowed to imbibe water passively they
attain a moisture content close to that of humans consuming
a mixed diet.
Therefore the model represents the faecal mass
in a non-dehydrated human consuming enough fibre to not be
constipated. All the osmotically active components of the
faecal mass and the original faecal structure remain intact
during the analysis. The procedure is intended to model the
contribution of foods to hydrated bulk in humans consuming
a mixed balanced diet, and not to predict laxation eects in a
system perturbed by very high amounts of osmotic agents and
vigorously fermented carbohydrate.
2.5 Statistical analysis
Standard deviations and standard error of the means were
determined using Microsoft® Excel and post hoc significance
of dierences between means was determined as the
maximum least significant dierence (α< 0.05) using GenStat
Version 17 (VSN International, UK).
3 Results and discussion
The main proposition of this paper is that retained structural
intactness in minimally processed vegetables preserves
physicochemical properties, and that these may partially
persist through the monogastric gut to influence distal colonic
events. The fact that the MPVF preparations exhibited greater
swelling and water retention capacities than commercial
dietary fibre preparations (Fig. 1) indicated that their hydration
properties before ingestion were more intact than those of the
more extensively processed preparations, so that minimally
processedwas a valid descriptor for the vegetable prep-
arations used in this study.
The rat has proved to be a useful model for studying the
properties of dietary fibre after monogastric digestion and
exposure to extensive mixed bacterial fermentation in the hind
gut, and there is a high correlation between the faecal bulking
capacity of fibres in man and the rat.
In the present experi-
ments the rats were mature and had been exposed to mixed
dietary fibre in pre-trial diets, so they readily accepted, and
would have been pre-adapted to the trial diets. The eects of
all test diets were measured as increases over baseline after
adding them to the baseline diet by substitution of sucrose.
The faecal bulking eects of the MPVFs were well within the
linear doseresponse range for faecal bulking eects of
The comparison of the swede fibre (diet 1.1) and whole
swede (diet 1.2) with the baseline in terms of faecal dry matter
(Table 2) and faecal hydration (Table 3) parameters confirmed
that the method of MPVF preparation had had the eect of
concentrating the faecal bulking component of the vegetable.
An idea of the relative faecal bulking ecacy of foods and
food components can be obtained by using wheat bran as a
reference material, as it is well known as an eective, natural,
structured faecal bulking agent in the human diet. Increases
in faecal dry weight induced by the individual MPVFs were sig-
nificantly greater than that induced by wheat bran fed at the
same intake (Table 2: diets 1.1, 10% swede fibre; 1.3, 10%
asparagus fibre; 1.4, 10% broccoli fibre, compared with diet
1.7, 10% wheat bran). The apparent survival of wheat bran was
Fig. 1 Retained functionality indicated by retained water retention
capacity of minimally processed vegetable bres compared with com-
mercially available processed dietary bres. Means ± SD.
FBI ¼Increase over baseline in mass of rehydrated faeces=g of diet component consumed
Increase over baseline in mass of rehydrated faeces=g of wheat bran reference 100
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about 40% averaged across the three trials, which is consistent
with food analyses that have shown wheat bran to be about
43% mainly insoluble dietary fibre, with starch and protein
making up most of the rest of it. It is also consistent with the
fact that wheat bran is a protective seed coating that has
evolved to be highly resistant to bacterial degradation.
Based on the faecal dry weights (Table 2), the apparent
survival of the MPVFs varied from 55 to 71%. In contrast, the
apparent survival of pectin (diet 1.6), a hydrating and fermen-
table polysaccharide, was 14%, while the apparent survival of
psyllium (diet 1.5), a hydrating but relatively non-fermentable
polysaccharide, was 99%. Assuming that pectin was fully
fermented (diet 1.6), we may estimate that every gram of
fermented polysaccharide would increase bacterial biomass
by about 0.14 g. Therefore taking an average apparent survival
(fibre ingested × 100/increase in faecal dry weight) for the
MPVFs of roughly 65% (based on Table 2 values for diets 1.1,
swede fibre; 1.3, asparagus fibre; 1.4, broccoli fibre; 2.1,
asparagus fibre; 2.2, swede fibre; 2.3, swede/asparagus fibres;
3.3, broccoli fibre; 3.6, broccoli/asparagus/swede fibres), we
can estimate conservatively that about 50% of the MPVF had
survived into the faeces. The results of trial 1 show clearly
that in contrast to extracted cell wall polysaccharide in the
form of pectin (apparent survival 14%), the structurally intact
cell walls of MPVF were approximately half fermented, so
were able to make a substantial contribution to residual
faecal mass. Microscopic examination of the faecal material
(Fig. 2) confirmed that the morphology of the parent plant
tissues in the MPVF from broccoli rind survived passage
through the rat gastrointestinal tract, in which it would have
been subjected to gastric and small intestinal digestion, fol-
lowed by fermentation by a full complement of the hind gut
Trial 2 examined combinations of the MPVFs (diet 2.3,
swede/asparagus; diet 2.4, swede/psyllium; diet 2.5, swede/
wheat bran) and it showed that the MPVFs from dierent
sources had approximately additive eects on faecal dry weight
(Table 2), as well as confirming the results of trial 1. At the
same total fibre intake the diets combining swede MPVF with
asparagus MPVF (diet 2.3) and swede MPVF with wheat bran
(diet 2.5) were intermediate between the values for the individ-
ual fibres (diet 2.1, asparagus; diet 2.2, swede; diet 1.7, wheat
bran). Similarly the eects of psyllium and swede fibre in a
1 : 1 mixture of the two (diet 2.4) were approximately additive,
suggesting that the fibre dose-faecal bulking response was
linear with the mixed fibre sources.
Table 2 Changes in faecal parameters related to dry faecal matter
Faecal DW
100 g diet (g)
Increase over BL
per 100 g diet (g)
Increase over BL
Increase per g
component (g)
survival (%)Mean SD Mean SD Mean SD Mean SD
1.1 11.5 0.34 5.50 0.34 47.9 1.6 0.55 0.03 55
1.2 7.80 0.41 1.83 0.41 23.3 4.0 0.18 0.04 18
1.3 13.1 0.36 7.14 0.36 54.4 1.2 0.71 0.04 71
1.4 12.3 0.47 6.35 0.47 51.5 1.7 0.63 0.05 63
1.5 8.44 0.45 2.47 0.45 29.1 3.8 0.99 0.18 99
1.6 6.65 0.29 0.68 0.29 10.1 3.7 0.14 0.06 14
1.7 10.6 0.78 4.65 0.78 43.5 4.1 0.46 0.08 46
1.8 5.97 0.40
LSD 0.52 0.49 3.33 0.09 9.1
p<0.001 <0.001 <0.001 <0.001 <0.001
2.1 13.1 0.60 7.11 0.60 54.3 2.1 0.71 0.06 71
2.2 10.9 0.88 4.90 0.88 44.7 4.6 0.49 0.09 49
2.3 12.0 1.06 6.00 1.06 49.8 4.6 0.60 0.11 60
2.4 15.8 0.95 9.80 0.95 62.0 2.3 0.98 0.10 98
2.5 10.5 0.45 4.49 0.45 42.8 2.5 0.45 0.05 45
2.6 11.0 0.65 5.07 0.65 45.8 3.2 1.01 0.13 101
2.7 9.60 0.70 3.63 0.70 37.5 5.1 0.36 0.07 36
2.8 5.97 0.34
LSD 0.87 0.85 3.89 0.10 9.7
p<0.001 <0.001 <0.001 <0.001 <0.001
3.1 11.3 0.62 4.79 0.62 42.1 3.1 0.96 0.12 96
3.2 13.2 0.64 6.62 0.64 50.2 2.4 0.88 0.09 88
3.3 14.8 1.12 8.22 1.12 55.5 3.7 0.82 0.11 82
3.4 17.3 1.56 10.8 1.56 62.0 3.3 0.86 0.13 86
3.5 20.0 1.19 13.4 1.19 67.1 2.0 0.89 0.08 89
3.6 14.2 0.61 7.70 0.61 54.0 2.0 0.77 0.06 77
3.7 10.5 0.48 3.95 0.48 37.5 2.9 0.39 0.05 39
3.8 6.54 0.38
LSD 1.09 1.06 3.08 0.11 11
P<0.001 <0.001 <0.001 <0.001 <0.001
DW = dry weight; BL = baseline.
Summary of diets in Table 1.
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In trial 3 linearity of the MPVF dose-faecal bulking response
relationship was examined up to 15% broccoli rind MPVF in
2.5% steps (diets 3.13.5). Faecal dry matter increased almost
linearly with increasing MPVF dose, and the apparent survival
of fibre was between 82 and 96%, being 96% for 2.5% MPVF
and 89% for 15% MPVF, which was not a significant dierence
(LSD = 11%; p= 0.05).
Hydrated faecal mass (Table 3) was increased substantially
over the baseline by consuming the MPVFs. Furthermore, the
MPVFs were more eective than an equal weight of wheat bran
(diets 1.1, swede fibre; 1.3, asparagus fibre; 1.4, broccoli fibre
compared with diet 1.7, wheat bran). Diets that contained psy-
llium (diets 1.5, 2.5% psyllium; diet 2.4, 5% psyllium/5%
swede fibre; 2.6, 5% psyllium), however, produced a much
greater increase in hydrated faecal mass per gram of fibre com-
ponent than the MPVFs alone. Pectin fed at twice the intake of
psyllium (diets 1.6, pectin versus diet 1.5, psyllium) had half
the eect on hydrated faecal mass, confirming the persistence
of the physicochemical properties of psyllium and their loss
during fermentation of pectin which, in unfermented form, is
a hydrating polysaccharide.
Increasing MPVF intake in the form of broccoli fibre from
2.5% to 15% of the diet increased the absolute amount of
hydrated faecal mass almost linearly (Table 3: diets 3.13.5)
but did not cause an increase in faecal water per gram of
MPVF consumed (Table 4: trial 3). The pre-ingestion hydration
properties of the MPVF preparations did not, therefore, predict
faecal hydration,
because fermentation in the hind gut
removes much of the polysaccharide responsible for hydration
of undigested vegetable cell walls. The constancy of faecal
hydration per gram of added broccoli fibre did not change sig-
nificantly between intakes of 2.5% and 15% broccoli MPVF
(Table 3: trial 3), suggesting that at all doses the broccoli fibre
had been reduced to a similar physicochemical state by gut fer-
mentation. That is, the highly hydrating pectic polysaccharide
networks of cell walls do not appear to have survived any more
at high versus low MPVF doses within the range tested. These
results are consistent with earlier findings with wheat bran
and low-methoxyl pectin that neither fibre dose nor particle
size greatly aected dietary fibre fermentation in the rat.
increase in hydrated faecal bulk due to the MPVF was due
more to the increase in dry matter, while the water holding
capacity remained more or less constant.
All of the fibre preparations in the diets increased faecal
water holding capacity (Table 4) measured by passive water
imbibition to saturation of the dry faeces. However, based on
Table 3 Changes in faecal parameters related to hydrated faecal mass
Faecal WW
/100 g Increase over BL
(g) Increase over BL (%)
Increase per g
component (g)
Mean SD Mean SD Mean SD Mean SD
1.1 45.7 2.3 28.6 2.3 167 14 2.86 0.23
1.2 29.0 1.9 11.9 1.9 70 11 1.19 0.19
1.3 51.9 2.4 34.8 2.4 204 14 3.48 0.24
1.4 49.4 4.0 32.3 4.0 189 23 3.23 0.40
1.5 37.9 4.8 20.8 4.8 122 28 8.32 1.93
1.6 21.8 2.3 4.7 2.3 28 13 0.94 0.46
1.7 41.0 3.6 23.9 3.6 140 21 2.39 0.36
1.8 17.1 1.0
LSD 3.5 3.5 20 0.87
p<0.001 <0.001 <0.001 <0.001
2.1 57.6 4.5 38.2 4.5 223 26 3.82 0.45
2.2 49.2 5.0 29.8 5.0 174 29 2.98 0.50
2.3 53.3 5.2 33.8 5.2 198 31 3.38 0.52
2.4 103 4.8 83.4 4.8 488 28 8.34 0.48
2.5 45.3 2.7 25.9 2.7 151 16 2.59 0.27
2.6 67.2 8.3 47.8 8.3 279 49 9.55 1.66
2.7 39.4 3.2 19.9 3.2 116 18 1.99 0.32
2.8 19.5 0.9
LSD 5.7 5.6 33 0.82
p<0.001 <0.001 <0.001 <0.001
3.1 44.3 3.5 22.8 3.5 106 16 4.55 0.71
3.2 56.1 4.1 34.5 4.1 160 19 4.60 0.55
3.3 63.3 4.6 41.7 4.6 194 21 4.17 0.46
3.4 81.6 11.6 60.1 11.6 279 54 4.80 0.93
3.5 95.3 10.0 73.7 10.0 342 47 4.91 0.67
3.6 63.6 6.0 42.0 6.0 195 28 4.20 0.60
3.7 44.0 3.1 22.5 3.1 104 14 2.25 0.31
3.8 21.6 1.4
LSD 7.7 7.6 35 0.69
p<0.001 <0.001 <0.001 <0.001
WW = wet weight; BL = baseline.
Summary of diets in Table 1.
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the increase in faecal water per gram of fibre added to 100 g
diet, the fibres fell into four groups: (1) pectin (diet 1.6) had
the least eect (0.81 ml increase per g), presumably because it
was largely fermented; (2) wheat bran caused about 1.9 ml
increase per g, possibly reflecting the limitation to hydration
caused by lignin in its resilient secondary cell wall structure;
(3) MPVFs caused an increase of about 2.53 ml of water held
per g included in the 100 g diet; (4) psyllium caused about
8 ml increase per g (Table 4).
Psyllium led to the greatest increase in theoretical faecal
water load of several hundred percent, because, per gram of
psyllium in the 100 g diet it increased both faecal dry matter
output and faecal water holding capacity. MPVF did not
increase water holding capacity (ml per g faecal dry matter)
greatly, but the combination of the increased dry matter and
its bound water caused the percentage increase over baseline
in faecal water load per 100 g diet to move from 120% increase
at 2.5% broccoli fibre to 402% at 15% broccoli fibre (Table 4
and Fig. 3). All MPVFs alone and in combination with one
another led to about 200% increase in FWL when included at
10% of the diet. Such a large increase in dilution could be
expected to have a biologically significant eect on many
colonic processes.
To allow comparison of the faecal bulking potential of the
test components, faecal bulking indexes (FBIs) were calculated
for the test components in all diets, and compared with some
previous measurements. FBI values express the faecal bulking
eect of a test component as a percentage of the faecal
bulking eect of an equal weight of wheat bran, where bulk is
determined as the weight of fully hydrated pellets. Based on
the FBIs, the following can be seen (Fig. 4):
1. MPVFs were at least as eective as wheat bran in their
faecal bulking capacities. As discussed (above), the ecacy of
the MPVFs relative to wheat bran was due partly to slightly
greater output in faecal dry matter than induced by the wheat
bran reference, and partly due to higher water imbibition by
the dry faeces.
2. Psyllium (diets 1.5 and 2.6) was highly eective as a
faecal bulking agent, much more so than the other fibres
tested. The eectiveness of psyllium reflects the findings
(above) that it has a high apparent survival of hind gut transit,
which increased faecal dry matter, but more so because the
psyllium surviving in the faeces retained a high capacity for
water absorption.
3. The faecal bulking eects of the materials tested were
approximately additive in combination, whether the combi-
nation involved vegetable fibres alone, or vegetable fibres com-
bined with wheat bran or psyllium.
4. Pectin and raftilose, which are disperse polysaccharides
lacking in structure, acting as fermentable hindgut controls,
had very similar and relatively small faecal bulking indexes.
5. Under the conditions in which pectin was fermented,
over 50% of MPVFs survived hind gut transit, which indicates
that MPVF has the capacity to resist fermentation enough for
it to contribute equally to hindgut fermentation and faecal
6. Commercial apple fibre and Fibrex® (sugar beet), which
are both finely ground highly processed dietary fibres, had
about half the FBI of the MPVF, indicating the importance of
retaining structure by minimal processing to achieve a
balanced hind gut functionality.
7. Materials that were, in theory, fully utilized in the foregut
(controls: sugar, starch and casein) had no detectable eect on
faecal bulking. Sugar replacement was therefore a suitable way
of including test components in the diet to measure faecal
8. The faecal bulking indexes for broccoli rind fed at
dierent concentrations in the diet (diets 3.1 to 3.5) were
almost the same, reflecting the fact that the apparent survival
of MPVF was independent of intake within the 2.515% range
tested, and confirming the robustness of the FBI assay.
The present study has demonstrated that minimally pro-
cessed dietary fibres from vegetables are functionally more
balanced than either single fermentable polysaccharides, such
as pectin and raftilose, or highly processed commercial dietary
fibres, such as those derived from sugar beet (Fiberex®) or
apple, because they provide fermentation residues that retain
structure, hydration and bulk. Hydration and bulk influence
rates of digestion and digesta transit, with numerous direct
and indirect connections with health outcomes.
The results
suggest that the current practice of making up for deficient
dietary fibre intakes with prebiotic supplements or pro- and
synbiotics may not be as beneficial as increasing consumption
Fig. 2 Structure remaining in commercial apple bre (A), commercial
sugar beet bre (B), minimally processed asparagus bre (C), broccoli
bre (D), swede bre (E) and wheat bran (F) after passing through the rat
gastrointestinal tract. The bar represents 100 µM.
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Table 4 Changes in faecal hydration properties
Faecal WHC
(ml g
) Faecal moisture (%)
Increase in FWL
100 g diet (%)
Increase in water per g
added component
Mean SD Mean SD Mean SD Mean SD
1.1 2.99 0.18 74.9 1.1 203 19 2.32 0.22
1.2 2.72 0.11 73.1 0.8 88 14 1.01 0.16
1.3 2.96 0.17 74.7 1.1 243 20 2.77 0.23
1.4 3.01 0.32 75.0 1.8 228 34 2.60 0.39
1.5 3.48 0.40 77.5 2.1 161 39 7.34 1.78
1.6 2.27 0.27 69.3 2.5 34 19 0.81 0.42
1.7 2.86 0.11 74.1 0.8 169 26 1.93 0.29
1.8 1.87 0.27 65.0 3.0
LSD 0.29 2.1 28 0.81
p<0.001 <0.001 <0.001 <0.001
2.1 3.40 0.24 77.2 1.2 230 30 3.11 0.40
2.2 3.52 0.17 77.9 0.9 184 31 2.48 0.41
2.3 3.45 0.15 77.5 0.7 206 31 2.78 0.42
2.4 5.53 0.24 84.7 0.6 545 30 7.36 0.40
2.5 3.33 0.08 76.9 0.4 159 16 2.14 0.22
2.6 5.07 0.46 83.5 1.2 316 57 8.53 1.55
2.7 3.10 0.06 75.6 0.3 121 18 1.63 0.25
2.8 2.26 0.10 69.3 0.9
LSD 0.27 0.97 36 0.75
p<0.001 <0.001 <0.001 <0.001
3.1 2.91 0.17 74.4 1.1 120 20 3.59 0.71
3.2 3.26 0.21 76.5 1.2 186 24 3.72 0.55
3.3 3.29 0.18 76.7 1.0 223 24 3.35 0.46
3.4 3.69 0.26 78.6 1.2 328 67 3.94 0.93
3.5 3.77 0.28 79.0 1.2 402 60 4.02 0.67
3.6 3.46 0.27 77.5 1.3 229 36 3.44 0.60
3.7 3.20 0.18 76.1 1.0 123 18 1.85 0.31
3.8 2.30 0.10 69.6 1.0
LSD 0.25 1.3 44 0.61
p<0.001 <0.001 <0.001 <0.001
WHC = water holding capacity; FWL = faecal water load.
Summary of diets in Table 1.
Fig. 3 Eect of minimally processed vegetable bres (MPVF) (broccoli
rind) dose on faecal water load (FWL) per 100 g diet. The baseline diet
contained 3.8% dietary bre. Adding 15% MPVF to the baseline diet
increased FWL by more than 400%. Values are means ± sem.
Fig. 4 Faecal bulking indexes for the components tested in the three
faecal bulking trials and some comparison materials (mean ± sem). The
dotted line shows faecal bulking index for the reference (wheat bran =
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of natural dietary fibre sources, because most supplements
cannot provide the benefits derived from plant morphology in
the gut. Vegetables, fruits and unrefined cereals will provide
mixed function cell wall residues that the hindgut has natu-
rally evolved to process, as well as contributing numerous
other known and unknown beneficial phytochemicals and
nutrients to the diet. Moreover, the mixed polysaccharide
nature of plant cell walls plays an important role in maintain-
ing bacterial diversity in the colon,
conferring resilience on
the microbiome
that allows it to retain its diverse contri-
butions to health.
There was no evidence provided in this study that consum-
ing non-fermentable hydrating polysaccharides, such as psy-
llium, to increase faecal hydration and laxation, impaired
colonic utilisation of co-consumed MPVF. However, more
detailed research should be conducted to determine whether
the persistent high viscosity milieu that non-fermented hydro-
colloids such as psyllium promote in the colon has the eect
of hindering either the bacterial utilisation of fermentable
polysaccharides or the availability of fermentation products to
the host. Should they do so, the benefits of increased laxation
may be counterbalanced by a reduction in benefits of fermen-
tation mediated by short chain fatty acids, such as gut immu-
nity. The advantage of natural vegetable tissue remnants over a
non-fermentable hydrocolloid such as psyllium is that they are
functionally multidimensional, as they can promote bacterial
activity and diversity by supplying mixed polysaccharide sub-
strates, while maintaining enough structured fermentation-
resistant polysaccharides to promote hydration and gut transit,
as the present study has shown.
The results indicate that highly processed fibres produced
for the food industry as ingredients that are compatible with
consumer tastes and baking quality standards may lack the
functionality of the parent fibres. However, as including
dietary fibres in bakery products is a helpful approach to
improving dietary fibre intakes, ways of including either mini-
mally processed fibres or combinations of fibres with comp-
lementary functions in products need to be explored.
A more thorough test of the contrast between minimally pro-
cessed vegetable fibres and highly processed fibres in their
faecal bulking capacity would have been to base the comparison
on the same vegetable matter subjected to minimal and exten-
sive processing. It was not possible in the research program that
yielded the present results but would be worth considering in a
more focused study that quantifies the relationship between
extent of processing, extent of reductions in particle size, aspect
ratio and changes in faecal parameters, with the research
ultimately extended to a human intervention study.
4 Conclusion
The results of this study have shown that the relatively un-
degraded form in which dietary fibre is consumed in whole
vegetables and wheat bran confers beneficial faecal properties
that are unlikely to be obtained from refined, structureless and
highly fermented fibresof which many prebiotics are typical
examples. Therefore, the advice to consume a mixed diet con-
taining vegetables, fruits and wholegrain products should be
heeded before relying on o-the-shelf fibre supplements or
highly processed fibre ingredients to make up any shortfall. A
dietary fibre deficient diet supplemented with structure-less pre-
biotics runs the risk of remaining a functionally-deficient diet.
Conict of interest
The authors disclose no conflict of interest.
BL Baseline
DW Dry weight
FBI Faecal bulking index
FWL Faecal water load
WHC Water holding capacity
MPVF Minimally processed vegetable fibres
Use of the Food Pilot Plant at Massey University for vegetable
processing with advice from the Pilot Plant Manager, Garry
Radford. Justine Shoemark raised the rats and helped with
their care.
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... Plusieurs études montrent que les effets physiologiques des fibres naturelles versus ajoutées (e.g., métabolismes glucidiques et lipidiques) ne sont pas les mêmes (Jones, 2013). En outre il a été récemment montré que les fibres ajoutées ou transformées ont des propriétés physicochimiques détériorées comme une moins bonne capacité de rétention d'eau ou une aptitude différente à fermenter dans le colon (Monro et al., 2016). Et les fibres extraites et purifiées ont perdu leurs composés associés ou "fibres copassengers". ...
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It is usual to define the health potential of a food on the basis of its nutritional composition. This reductionist approach is only partially true and has led nutritionists and technologists to consider the food as a sum of compounds wich can be fractionated and recombined in the form of ultra-processed foods as opposed to normally processed or unprocessed complex foods. Yet the health potential of a food is also its "matrix" effect which plays essential roles on satiety and nutrient release rates in the body. This holistic view of the food considers that the whole is greater than the sum of its parts and that food is not only a sum of nutrients. Especially since epidemiological studies clearly showed that a strong adherence to ultra-processed food, enrich in fat, sugar and salt is associated with significant increases in the risk of chronic diseases.
... Dietary fibre is also abundant in grape pomace (Monro et al., 2016). A lot of studies have revealed that it might be involved in disease prevention and health promotion, including attenuation of blood cholesterol and glucose (Dong et al., 2016), laxative effect (Bliss et al., 2014) and reduction of risk in colon cancer (Vulcan et al., 2015), heart disease (Kim & Je, 2016) and obesity (Han et al., 2015). ...
In this study, we evaluate the effects of high hydrostatic pressure (HHP) and superfine grinding (SFG) treatment on grape pomace. The results showed that the HHP treatment improved physicochemical and antioxidant properties of grape pomace than the SFG treatment did. Moreover, the results of SEM indicated that the HHP-treated grape pomace turned to have more lamellar structure, resulting in more hydrophilic groups exposed to improve WRC, WSC and SDF content. The results of FT-IR spectra indicated that the main components and chemical structure of grape pomace after processing did not significantly change. Therefore, the HHP treatment had better effect in improving the functionality of grape pomace than that of the SFG treatment. The grape pomace treated by the appropriate processing methods could be used as functional foods.
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Purpose For decades, it has been customary to relate human health to the nutritional composition of foods, and from there was born food composition databases, composition labelling scores and the recommendation to eat varied foods. However, individuals can fully address their nutritional needs and become chronically ill. The nutrient balance of a food is only a small part of its overall health potential. In this paper, we discussed the proof of concept that the increased risk of chronic diseases worldwide is primarily associated with the degradation and artificialization of food matrices, rather than only their nutrient contents, based on the assumption that “food matrices govern the metabolic fate of nutrients”. Methods An empirico-inductive proof of concept research design has been used, based on scientific data linking the degree of food processing, food matrices and human health, notably on the glycaemic index, nutrient bioavailability, satiety potential, and synergistic effects. Results We postulate that if the nutrient content is insufficient to fully characterize the diet-global health relationship, one other dimensions is necessary, i.e., the food matrix through the degree of processing. Both matrix and nutrient composition dimensions have been included under the new concept of the 3V index for Real (Vrai), Vegetal (Végétal), and Varied (Varié) foods. The Real metric, reflecting the integrity of the initial food matrix, is the most important, followed by the Vegetal (nutrient origin) and the Varied (“composition” effect) metrics. Conclusion Concerning their effects on health, food matrix comes first, and then nutrient composition, and calorie quality matters more than calorie quantity.
The effects of whole foods and food components on gut microbiota are often investigated in animal models not fed a human-type background diet. In this study, rats were fed basal starch (BS) or quasi human (QH) background diets either unsubstituted (controls) or substituted with inulin, dried kiwifruit or pectin for 28 days. Gut microbiota composition and hydrated faecal bulking potential of the diets were evaluated. In the caecum and colon, relative abundance of bacteria at the phylum, family or genus levels differed considerably between the background diets (BS and QH). Rats fed QH diets had higher Actinobacteria than those rats fed BS diets. Gut microbiota responses to inulin, kiwifruit and pectin depended on the background diet. QH diet led to twice the mass of hydrated faecal bulk than BS diet. Overall, simple laboratory animal diets are unlikely to provide valid predictions of effects of prebiotics added to human diets.
Ultra-processed foods (UPFs) are characterized by the presence of markers of ultra-processing (MUP), either additives (A-MUP) or non-additive ingredients (NA-MUP). The present study aims to characterize the MUP profile of approximately 22,000 UPFs, representative of assortments in French supermarkets. UPFs were ranked according to Siga classification within five UPF technological groups, from C01 to C3, depending on the nature and number of MUPs (MUP1 and MUP2), presence of risk-associated additives, and contents of salt, sugar and/or fat. Then, UPFs were categorized within 10 food categories. The results showed that UPFs contain more NA-MUPs than A-MUPs, on average 1.3 more by UPF. The main MUPs are NA-MUPs, i.e., refined oils (52.5 % of UPFs), extracts and natural aromas (42.7 %), synthetic aromas (26.5 %), glucose syrup (20.0 %), native starches (19.1 %), and dextrose (16.2 %). The NA-MUP/UPF and A-MUP/UPF ratios were not correlated in the 10 food categories. Among UPFs, 19 % contained only one MUP, and 31 % contained more than five MUPs. In conclusion, additives are not a sufficient marker of ultra-processing. It is proposed that NA-MUPs in UPFs should be taken into greater consideration and that foods be scored with indices based on the degree of processing, not compositional scores, which fail to filter MUPs.
Fruits and vegetables are important sources of dietary fiber (DF) with a balanced ratio of insoluble and soluble fractions. The DF obtained from these kinds of plant-based foods possess health-related attributes associated to their physiological and functional properties. Furthermore, they exert antioxidant characteristics derived from the bioactive substances that are linked to DF. This chapter focuses on the content, characteristics and health-related benefits of DF from different parts of fruits and vegetables as well as their by-products obtained after processing. Additionally, cases of food products developed with DF from citrus fruits are described considering their health attributes observed through epidemiological studies.
Structure is a fundamental factor in determining the way that digestible and non-digestible food carbohydrates (mono- and di-saccharides, oligo-saccharides and polysaccharides) influence a range of health outcomes. Much of the influence of carbohydrate structure on health is mediated by its effects on digestive processes throughout the gut. At each region within the gut a hierarchy of carbohydrate-based food structures – monosaccharide, individual polysaccharide, associated polysaccharides, cell walls, plant tissues and food particles – may constrain or enhance digestive processes. The role of carbohydrate structure in health and reformulation for health, through its effects at the gut level, is the focus of this chapter. Emphasis is placed on blood glucose loading, colonic fermentation and distal colonic bulking, because they are at the base of clusters of health outcomes arising from hyperglycaemia, dysbiosis and constipation, respectively. This chapter outlines principles governing choice of carbohydrate ingredients in reformulating for health, based on the role of food structure in function. Precise prescription of formulations is not possible because of the need for empirical testing of products due to the complexity of food component interactions, emergent properties and sensory effects in food products.
The nutrients present in vegetables can be categorized as macro- and micronutrients. Water, carbohydrates, proteins, lipids, and fiber comprise the major macronutrients. Micronutrients are composed of two broader categories, vitamins and minerals. Subsequently, vitamins are further split into water and fat soluble. The epidemiological studies conducted in various parts of the world revealed that consumption of vegetables rich in functional ingredients are associated with reduced risk of chronic disorders. Dietary phytoestrogens have proved to be helpful in reducing the risk of developing certain hormone-stimulated malignancy such as breast and prostate cancers. Dietary fiber promotes the growth of microorganism present in gastrointestinal tract, thus improving human health. This chapter tabulates a summary of food processing effect on nutrients. Substantial quantities of nutrients are lost during processing operations like canning, dehydration, and storage; thus, care should be taken to reduce such losses.
Pour prévenir les maladies chroniques liées à l’industrialisation, l’effet “matrice” d’un aliment participe davantage de son action sur la santé que sa composition nutritionnelle. Il influence notamment la cinétique de libération des nutriments dans le tube digestif, leur biodisponibilité et donc leurs effets métaboliques, mais aussi le sentiment de satiété. Il correspond à une vision holistique de l’aliment reflétant que le tout est supérieur à la somme des parties
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Dietary fibre has been consumed for centuries with known health benefits, but defining dietary fibre is a real challenge. From a functional perspective, dietary fibre is described as supporting laxation, attenuating blood glucose responses and assisting with cholesterol lowering. The problem is different types of dietary fibre have different effects, and new effects are increasingly observed, such as the influence on gut microbiota. Thus, a single definition may need to be described in more generic terms. Rather than being bound by a few functional definitions, we may need to embrace the possibilities of new horizons, and derive a working definition of dietary fibre based on a set of conceptual principles, rather than the limited definitions we have to date. To begin this process, a review of individual fibre types and their physiological effects would be helpful. Dietary fibre is a complex group of substances, and there is a growing interest in specific effects linked to fibre type. Different fractions of dietary fibre have different physiological properties, yet there is a paucity of literature covering the effects of all fibres. This paper describes a range of individual fibre types and identifies gaps in the literature which may expose new directions for a working definition of dietary fibre.
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Complex gene–environment interactions are considered important in the development of obesity. The composition of the gut microbiota can determine the efficacy of energy harvest from food and changes in dietary composition have been associated with changes in the composition of gut microbial populations. The capacity to explore microbiota composition was markedly improved by the development of metagenomic approaches, which have already allowed production of the first human gut microbial gene catalogue and stratifying individuals by their gut genomic profile into different enterotypes, but the analyses were carried out mainly in non-intervention settings. To investigate the temporal relationships between food intake, gut microbiota and metabolic and inflammatory phenotypes, we conducted diet-induced weight-loss and weight-stabilization interventions in a study sample of 38 obese and 11 overweight individuals. Here we report that individuals with reduced microbial gene richness (40%) present more pronounced dys-metabolism and low-grade inflammation, as observed concomitantly in the accompanying paper. Dietary intervention improves low gene richness and clinical phenotypes, but seems to be less efficient for inflammation variables in individuals with lower gene richness. Low gene richness may therefore have predictive potential for the efficacy of intervention.
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Bacteria colonizing the human intestinal tract exhibit a high phylogenetic diversity that reflects their immense metabolic potentials. The catalytic activity of gut microbes has an important impact on gastrointestinal (GI) functions and host health. The microbial conversion of carbohydrates and other food components leads to the formation of a large number of compounds that affect the host metabolome and have beneficial or adverse effects on human health. Metabolomics is a metabolic-biology system approach focused on the metabolic responses understanding of living systems to physio-pathological stimuli by using multivariate statistical data on human body fluids obtained by different instrumental techniques. A metabolomic approach based on an analytical platform could be able to separate, detect, characterize and quantify a wide range of metabolites and its metabolic pathways. This approach has been recently applied to study the metabolic changes triggered in the gut microbiota by specific diet components and diet variations, specific diseases, probiotic and synbiotic food intake. This review describes the metabolomic data obtained by analyzing human fluids by using different techniques and particularly Gas Chromatography Mass Spectrometry Solid-phase Micro Extraction (GC-MS/SPME), Proton Nuclear Magnetic Resonance ((1)H-NMR) Spectroscopy and Fourier Transform Infrared (FTIR) Spectroscopy. This instrumental approach has a good potential in the identification and detection of specific food intake and diseases biomarkers.
Introduction Flow mixing and absorption. The physical problems of extracting nutrients from food items and the possible macroscopic and microscopic solutions. The digestive tube and its limitations. solid to liquid to solid Methods for evaluating the physical properties of digesta Particle size Rheology Viscometry Viscoelastic behaviour Time dependent behaviour Permeametry Hindered settling function Permeability and other measures Methods for evaluating the relationship between motility and flow of digesta Solid and liquid phase markers Reactor mixing Spatiotemporal mapping Physical behaviour of fluid digesta Macroscopic effects Newtonian and non Newtonian behaviour of fluids. Where digesta fit in this system the kinetics of digesta flow Securing efficient absorption from fluids and non-Newtonian fluids, chemical reactor theory and problems Buoyancy Backflow form coiled elements Physical behaviour of solid digesta The continuum between solids and liquids viscoselasticity securing efficient absorption from fluids and from viscoelastic fluids Permeability extrusion of the liquid phase Propulsion and mixing of digesta the interplay between the gut wall and its contents Tension and stretch receptors in the enteric nervous system Maintaining the flow of digesta problems of narrowing and expanding Co-evolution of motility and the physical properties of digesta Micromixing Diffusion. Mucus and the unstirred water layer. Flow in the paravillus space and the crypts. Tight junctions permeability and fluid flow Glycocalyceal signalling of shear The physics of food What is known about how the physical structure of food interacts with the digestive processes e.g starch granule digestion digestion of proteinaceous aggregates eetc ( Dr Allan Hardacre NZ Crop and Food ) Flow and microorganisms Adaptions of micro-organisms to move within digesta and mucus Glycocalyceal signalling Messing with the properties of digesta Adulterating foods with viscoactive substances Nutraceuticals planning the rate of nutrient release. Modulating lumen pressure Microencapsulation and adherence to the gut wall
Hydrocolloids in the form of polymeric ingredients as well as natural biopolymer assemblies provide much of the macroscopic structure of foods. The controlled disassembly of hydrocolloid-structured foods in the digestive tract determines numerous nutritional properties driven by the rates of passage, digestion, absorption, and fermentation. Despite convincing evidence for health benefits of hydrocolloids (particularly dietary fibre) from epidemiology, and numerous in vitro model system studies, the detailed underlying mechanisms operating in the digestive tract are currently understood to only a limited extent. Distinct hydrocolloid-based processes occur in each of the gastric, small intestinal and large intestinal environments, with significant biological cross-talk between the sites. Hydrocolloids offer a major opportunity to tailor nutritional value and provide potential health benefits through control of gastric emptying and ileal brake mechanisms (satiety and potentially obesity), glycemic response (diabetes), plasma cholesterol levels (cardiovascular disease), and carbohydrate fermentation throughout the large intestine (colon cancer). There is often a parallel between the functionality of the plant-based foods which the human digestive tract evolved to digest and the use of extracted hydrocolloids in modern food structuring technology.
Trillions of microbes inhabit the human intestine, forming a complex ecological community that influences normal physiology and susceptibility to disease through its collective metabolic activities and host interactions. Understanding the factors that underlie changes in the composition and function of the gut microbiota will aid in the design of therapies that target it. This goal is formidable. The gut microbiota is immensely diverse, varies between individuals and can fluctuate over time - especially during disease and early development. Viewing the microbiota from an ecological perspective could provide insight into how to promote health by targeting this microbial community in clinical treatments.
An in-vitro model (fermentation and water holding capacity measurement) and a rat model were compared for their ability to predict the action of dietary fibre on stool output in man. A range of different purified or semipurified fibres were studied: wheat bran, pectin, carboxymethylcellulose, xanthan, guar, karaya, tragacanth and gellan. Using equations derived from previous studies, prediction indices from in-vitro studies were compared with the effects of these fibres on stool output in rat and man. The rat model was better as a predictor for stool output (r = 0.94, P < 0.005) in man but the log in-vitro predictive index was significantly correlated with stool output in both rat (r = 0.87, P < 0.02) and man (r = 0.84, P < 0.04). Since in-vitro methods are less expensive and time consuming than animal studies, the log in-vitro predictive index may provide a useful pre-screening device for new dietary fibre sources or detecting changes in the action of dietary fibres during the manufacturing process.
This paper reports the first use of a virtual food component (VFC), which is a value that represents the functional efficacy of a food in the format of a food component, to accurately formulate a functional food and evaluate its efficacy. The effect measured was faecal bulking and the functional food was a cereal bar. The faecal bulking efficacy of ingredients was determined as their content of the VFC, wheat bran equivalents for faecal bulk (WBEfb), which represents faecal bulking efficacy expressed in terms of the amount of wheat bran that would produce an equivalent effect. Using a validated animal model, we measured the faecal bulking efficacy of cereal bar ingredients individually and after combining them in a cereal bar recipe, before and after the combined ingredients had been baked. The sum of the WBEfb contents of the ingredients was 29.7 WBEfb per bar (SEM 2.4). The WBEfb of the recipe mixture before baking was 33.2 WBEfb per bar (SEM 2.4) and after baking was 28.5 WBEfb per bar (SEM 2.9). Faecal bulking efficacy was not related to dietary fibre content. We conclude that the WBEfb content of ingredients can be used to design cereal bars of specified faecal bulking efficacy and that the functionality is resistant to baking. Copyright © 2005 Society of Chemical Industry
Bulk in the distal colon provides protection against a range of large bowel disorders, but a simple standardized measure of the relative bulking efficacy of foods, for use in dietary management of distal colonic bulk, has not been available. This paper describes a faecal bulking index (FBI) for standardized measurement of the relative colonic bulking efficacy of foods relative to a reference material. Faecal bulking index is defined as the mass of fully rehydrated faecal matter accumulated by the distal colon per gram of a food consumed, as a percentage of the matter accumulated from the same weight of a reference food. The FBI of foods was measured after feeding adult rats at moderate levels by partially or completely replacing sucrose in a baseline diet already containing mixed dietary fiber. Faeces were collected, dried, weighed, allowed to imbibe water until fully rehydrated, reweighed and their mass and water holding capacity measured. The FBI was calculated as the increase over baseline in rehydrated faecal mass induced by a test food as a percentage of the increase due to wheat bran (reference). The FBI values were measured for 69 diets including breakfast cereals, breads and other bakery products, fruits, vegetables, food ingredients and polysaccharides. Values for most foods ranged between almost zero for some starch-based foods to about 50 for wheat bran-enriched breakfast cereals, but laxatives based on fermentation-resistant hydrated polysaccharide had FBI values well in excess of 100 (FBI for psyllium = 500). The FBI values allow foods to be ranked according to their faecal bulking efficacy on an equal edible weight basis. They can also be used to calculate the bulking action of any amount of food in terms of equivalents to a reference material such as wheat bran. Wheat bran equivalents allow the cumulative intake of potential distal colonic bulk to be monitored for single foods or mixed meals, and shortfalls to be quantified for dietary modification or supplementation. Measures such as FBI or wheat bran equivalents would prove more useful than dietary fiber in controlling ‘functional foods’ promoted as effective bulking agents.
Dietary lifestyle is relevant for prevention and treatment of various colorectal conditions. Colorectal disorders have significant morbidity and mortality in a western-style community, particularly irritable bowel syndrome (IBS), colorectal cancer, haemorrhoids, constipation and diverticular disease. This review addresses how bowel health can be maintained, what foods and dietary lifestyles are associated with risk for disease and what foods are of real value in management. Bowel health is that state where the individual is satisfied with defaecation, the diet does not create undue risk for disease and lumenal contents maintain an intact and functional mucosa. Bowel health depends on a healthy dietary lifestyle, but in particular on an adequate intake of non-digestable dietary polysaccharide. Diet influences biology in part by altering the lumenal environment. Effects such as high butyrate levels, lowered pH, a predominance of ‘healthy’over ‘unhealthy’ bacteria, rapid intestinal transit, high faecal bulk, a non-leaky epithelial barrier, adsorption of dietary carcinogens by fibre, low bile salt concentrations, reduced generation of toxic bile salts or protein derivatives and provision of certain bioactive substances are seen as beneficial. Diet influences future risk for colorectal cancer (vegetables, animal fats, polysaccharides amongst others) and for diverticular disease (fibre). Adequate fibre and resistant starch can improve constipation and anorectal conditions such as fissure and haemorrhoids. The role of diet in managing patients with IBS is complex. Fibre may worsen symptoms in severe cases of IBS, diverticular disease and inflammatory bowel disease. Certain carbohydrates of limited digestibility/absorbability, such as lactose, fructose and sorbitol, can precipitate IBS symptoms. Low fat, high fibre diets may reduce recurrence of colorectal adenomas. Diet has a significant role to play in colorectal disorders.