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The glycaemic index: Importance of dietary fibre and other food properties

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Abstract

An increasing body of evidence suggests that a low-glycaemic-index (GI) diet has a therapeutic as well as a preventive potential in relation to the insulin resistance syndrome. The implementation of a low-GI diet, however, will require an extended list of low-GI foods to be available on the market. The tailoring of low-GI bread products offers a particular challenge due to their generally high GI and abundance in the diet. Low-GI bread products can be tailored by, for example,enclosure of cereal kernels, sour dough fermentation and/or addition of organic acids, or use of cereal genotypes with elevated contents of amylose or f-glucans. Low-GI cereal foods appear to vary in effect on 'second-meal' glucose tolerance in healthy subjects. In addition to the slow-release properties of such foods, the content of dietary fibre appears to play a role. The low glycaemia to starch in a pasta breakfast (GI 54) promoted a higher glucose tolerance and lowered triacylglycerol levels at a standardized lunch ingested 4 h later, compared with a white-wheat-bread breakfast (GI 100). The metabolic benefits of the low GI properties per se have been demonstrated also in the longer term. Thus, a reduction in dietary GI improved glucose and lipid metabolism and normalized fibrinolytic activity in type 2 diabetics, while maintaining a similar amount and composition of dietary fibre. However, the higher dietary fibre content frequently associated with low-GI foods may add to the metabolic merits of a low-GI diet. Consequently, a low-GI barley meal rich in dietary fibre (GI 53) improved glucose tolerance from evening meal to breakfast, whereas an evening meal with pasta had no effect (GI 54). The exchange of common high-GI bread for low-GI high-fibre bread, as the only dietary modification, improved insulin economy in women at risk of type 2 diabetes. These results are in accordance with epidemiological evidence of a reduced risk of type 2 diabetes with a low-GI diet rich in cereal fibre. It is concluded that low-GI cereal foods developed should preferably be rich in dietary fibre.
Proceedings of the Nutrition Society (2003), 62, 201–206 DOI:10.1079/PNS2002239
© The Authors 2003
Abbreviations: GI, glycaemic index; RS, resistant starch.
*Corresponding author: Professor Inger Björck, fax + 46 46 222 4532, email inger.bjorck@inl.lth.se
CAB Int ernational PNSProceedings of Nutritio n Society ( 2003)0029-6651 © Nutrition Society 20 03 621PNS 239 Nutrients co ntributing to the fibre effectI. Björck and H. Liljeberg Elmståhl2012066© Nutr ition Socie ty 2003
The glycaemic index: importance of dietary fibre and other food properties
Inger Björck* and Helena Liljeberg Elmståhl
Department of Applied Nutrition and Food Chemistry, Centre for Chemistry and Chemical Engineering, Lund University,
PO Box 124, SE-221 00 Lund, Sweden
Profes sor Inger Björck, fax + 46 46 222 4532, e mail inger.bj orck@inl. lth.se
An increasing body of evidence suggests that a low-glycaemic-index (GI) diet has a therapeutic
as well as a preventive potential in relation to the insulin resistance syndrome. The implementation
of a low-GI diet, however, will require an extended list of low-GI foods to be available on the
market. The tailoring of low-GI bread products offers a particular challenge due to their generally
high GI and abundance in the diet. Low-GI bread products can be tailored by, for example,
enclosure of cereal kernels, sourdough fermentation and/or addition of organic acids, or use of
cereal genotypes with elevated contents of amylose or β-glucans. Low-GI cereal foods appear to
vary in effect on ‘second-meal’ glucose tolerance in healthy subjects. In addition to the slow-
release properties of such foods, the content of dietary fibre appears to play a role. The low
glycaemia to starch in a pasta breakfast (GI 54) promoted a higher glucose tolerance and lowered
triacylglycerol levels at a standardized lunch ingested 4 h later, compared with a white-wheat-
bread breakfast (GI 100). The metabolic benefits of the low GI properties per se have been
demonstrated also in the longer term. Thus, a reduction in dietary GI improved glucose and lipid
metabolism and normalized fibrinolytic activity in type 2 diabetics, while maintaining a similar
amount and composition of dietary fibre. However, the higher dietary fibre content frequently
associated with low-GI foods may add to the metabolic merits of a low-GI diet. Consequently, a
low-GI barley meal rich in dietary fibre (GI 53) improved glucose tolerance from evening meal to
breakfast, whereas an evening meal with pasta had no effect (GI 54). The exchange of common
high-GI bread for low-GI high-fibre bread, as the only dietary modification, improved insulin
economy in women at risk of type 2 diabetes. These results are in accordance with epidemiological
evidence of a reduced risk of type 2 diabetes with a low-GI diet rich in cereal fibre. It is concluded
that low-GI cereal foods developed should preferably be rich in dietary fibre.
Glycaemic response: Product tailoring: Diabetes mellitus: Dietary fibre
GI, gl ycaemic in dex; RS, res istant star ch.
Diseases related to insulin resistance are common causes of
death in Western societies, and the current increase in type 2
diabetes is being referred to as an epidemic. During the last
10 years an important number of studies have identified a
low-glycaemic-index (GI) diet as beneficial in relation to the
insulin-resistance syndrome. Several semi-long-term dietary
interventions are available for healthy subjects and for
subjects with metabolic disease. With a few exceptions, these
studies have shown that a low-GI diet not only improves
certain metabolic consequences of insulin resistance, but also
reduces insulin resistance per se (Del Prato et al. 1994). In
addition to improvements in glucose and lipid metabolism
(Jenkins et al. 1987; Brand et al. 1991; Järvi et al. 1999) there
are indications of improvements in the fibrinolytic activity
(Järvi et al. 1999), suggesting a beneficial role in diabetes and
cardiovascular disease. Based on this evidence, the Food and
Agriculture Organization/World Health Organization (1998)
expert consultation on dietary carbohydrates strongly
advocates the relevance of the GI concept, in particular for
subjects with impaired glucose tolerance.
In relation to mechanisms for the metabolic advantages of
low-GI foods, these may derive from the slow-release prop-
erties in the upper gastrointestinal tract, and in particular to
the lowered insulin demand (Jenkins et al. 1990). Another
possible mechanism relates to their generally higher content
of indigestible carbohydrates, for example, dietary fibre and
resistant starch (RS), which increases the fermentative
activity in the colon. Consequently, propionic acid has been
implicated as a moderator of hepatic glucose (Venter et al.
1990) and lipid metabolism (Wolever et al. 1989).
The therapeutic value of a low-GI diet in diabetes has
been demonstrated in both type 1 and type 2 patients (Brand
202 I. Björck and H. Liljeberg Elmståhl
Miller, 1994). Dietary interventions with low-GI foods thus
appear to lower the glycosylated haemoglobin fraction
HbA1c and the incidence of hypoglycaemic episodes in
juvenile (Gilbertsson et al. 2001) and maturity-onset
diabetes (Giacco et al. 2000). However, in some of the semi-
long-term metabolic studies performed the low-GI regimens
are characterised by a higher dietary fibre content (Giacco
et al. 2000), making it difficult to assign the beneficial
effects entirely to the low GI properties per se. With the
purpose of addressing this issue, an intervention study was
performed in type 2 diabetics where differences in GI
between the high- and low-GI diets were achieved in the
absence of differences in nutrient composition (Järvi et al.
1999). The GI differences between test periods were
obtained by modifying the structural features of the foods;
thus maintaining approximately identical amount and
composition of dietary fibre in the low- and high-GI dietary
periods. Apart from the facilitated control of blood glucose
and lowered LDL-cholesterol, a dramatic lowering of
plasminogen activator inhibitor 1 levels was observed
during the low-GI period. These data suggest that the GI
characteristics of the diet per se are indeed important, and
that the low-GI period normalized a risk factor for throm-
bosis, in the absence of a change in dietary fibre intake. It
should be pointed out, however, that even in the absence of
a difference in dietary fibre low-GI foods frequently contain
a higher amount of RS (Björck et al. 2000), which may add
to the metabolic advantages of low-GI diets.
As for the preventive potential, prospective studies
indicate that a low-GI diet, and/or a diet rich in whole-grain
products reduce the risk of type 2 diabetes (Salmerón et al.
1997a,b). There are also data to suggest a negative
correlation between serum HDL-cholesterol and dietary GI
(Frost et al. 1999). In fact, in the study by Frost et al.
(1999), dietary GI was a stronger predictor of serum HDL-
cholesterol than dietary fat. Moreover, there is evidence that
a low-GI diet may reduce the risk of myocardial infarction
in women (Liu et al. 2000).
The findings of Salmerón et al. (1997a,b) raise the
question whether dietary fibre, or at least cereal fibre,
could be a more important preventive factor than the GI
characteristics, and the most commonly consumed whole-
grain products, such as flour-based bread and breakfast
cereals, have high, rather than low, GI (Foster-Powell et al.
2002).
Accumulating data thus substantiate the therapeutic and
preventive efficacy of low-GI foods in general in relation to
the metabolic syndrome, and that cereal fibre may have a
preventive effect. However, the implementation of the GI
concept in dietary advice will require a much wider range of
low-GI products. In particular, there is a shortage of low-GI
cereal foods. On the basis of the experimental and epidemi-
ological evidence referred to earlier, the development of
low-GI high-fibre cereal products seems particularly
relevant from a metabolic perspective.
Tailoring of low-glycaemic-index cereal foods with focus
on bread products
In most European countries, bread constitutes a major
source of dietary carbohydrates. Consequently, there is a
need for new technologies that can be used to modulate the
GI of bread, with the focus on wholegrain bread. One
obvious alternative would be to encourage the use of more
or less intact cereal kernels and kernel-based breads are
usually characterised by a low GI (Liljeberg et al. 1992;
Liljeberg & Björck, 1994). The mechanism for this effect is
an obstructed amylolysis, due to botanical encapsulation of
starch and/or a limited extent of starch swelling. However,
the challenge for the food industry will be to find tech-
nologies that can be used to lower the GI of meal-based
bread, since the difference in GI properties between
wholemeal bread from common cereals and white bread is
usually marginal (Jenkins et al. 1986; Liljeberg et al. 1992).
Potential of barley genotypes
In a study by Åkerberg et al. (1998) wholegrain barley
flours with different amylose contents were subjected to
conventional baking (45 min, 200°), or low-temperature
long-duration baking conditions (20 h, 120°), i.e. pumper-
nickel-baking conditions. An increased holding temperature
with a wet temperature of 100°, as during low-temperature
long-duration baking, promotes growth of crystalline
amylose, a phenomenon known as annealing (Eerlingen
et al. 1993). Using high-amylose barley flour and these
baking conditions it was possible to reduce the GI predicted
from the in vitro rate of starch hydrolysis and the measured
GI by approximately 30 % (Table 1). It was also found that
baking at annealing conditions increased RS content to a
high level (10 % on total starch basis). The use of high-
amylose barley thus makes it possible to produce a low-GI
bread from flour-based ingredients. Moreover, such bread
products can be produced with elevated contents of RS, with
potential beneficial effects on colonic health (Scheppach
et al. 1992).
The development of whole-grain low-GI foods could also
involve cereal genotypes with high levels of viscous fibre.
One example of such a genotype is Prowashonupana barley,
which contains as much as 190 g β-glucans/kg. Such flour
was included at different levels in mixtures with white
wheat and baked into flat bread (E Rossi, H Elmståhl, H
Larsson and I Björck, unpublished results). The levels were
0 (i.e. pure wheat), 350, 500 and 750 g Prowashonupana
barley/kg. In parallel with the measurement of GI in healthy
subjects, the fluidity index of the corresponding in vitro
enzymic digesta was measured using a very simple
Bostwick consistometer. The digesta were prepared by
incubating the products with enzymes in simulated in
vivo conditions (Granfeldt et al. 1992). The lower the
fluidity index, the higher the viscosity. The results showed
that the inclusion of Prowashonupana flour lowered the
fluidity index of the digesta, and as a consequence
lowered GI compared with the flat bread with no added
Prowashonupana flour by 30, 40 and 50 % at the 350, 500
and 750 g/kg levels of inclusion, respectively. By including
Prowashonupana flour in flat bread it was thus possible to
substantially lower GI compared with white bread or a
product containing 500 g common barley/kg in a mixture
with white wheat. However, the commercial dehulling and
desprouting procedure must be carefully controlled to
maintain the viscosity of the β-glucans, and with some
Nutrients contributing to the fibre effect 203
commercial batches, inclusion of Prowashonupana at a level
of 500 g/kg failed to affect either the fluidity or the
glycaemic properties of the bread. Consequently, the
amount of β-glucan added to a product may be a poor
predictor of the glycaemic effect associated with a processed
food product. However, the study shows that the GI of
barley bread containing variable amounts of β-glucans can
be predicted with good accuracy from measurement of
fluidity in an in vitro system. It also demonstrates a
potential for cereal genotypes rich in β-glucans.
Sourdough baking and addition of organic acids
Another process that could be used to lower the GI of
wholegrain bread is sourdough fermentation. In a study in
which white bread was used as a vehicle for organic acids,
white bread with vinegar was given in a breakfast meal to
healthy subjects, using white bread with no acid as a control
(Liljeberg & Björck, 1998). The amount of acetic acid added
was selected to mimic the level reached during sourdough
fermentation, and the presence of acetic acid lowered the
postprandial metabolic responses (GI 64, insulin index 65).
A lowered rate of glucose delivery to the blood might be
secondary to a lowered rate of gastric emptying. Para-
cetamol is used as a marker of gastric emptying, as it is not
absorbed in the stomach but instead rapidly absorbed in the
upper duodenum. The appearance of paracetamol in the
blood was slower following ingestion of the bread with
acetic acid, suggesting that this acid delays gastric emptying
rate (Liljeberg & Björck, 1998). When added to wholegrain
barley bread lactic acid also appears to lower glycaemia in
healthy subjects, when tested at a level similar to that
achieved using a homo-fermentative starter culture
(Liljeberg et al. 1995). However, in contrast to acetic acid
and sodium propionate, the lowered glycaemia with lactic
acid-containing bread could not be assigned to a lowered
gastric emptying rate using paracetamol as a marker (Fig. 1).
Instead, the lowering of GI could be predicted from meas-
urement of the rate of in vitro starch hydrolysis, suggesting
that lactic acid interferes with the digestive process. In order
to investigate the mechanism for the prohibitive effect on
amylolysis, wheat starch–gluten mixtures were treated with
lactic acid before or after heat treatment at simulated baking
conditions and the enzyme availability tested using an
in vitro method previously shown to predict GI with good
accuracy (Granfeldt et al. 1992). The presence of lactic acid
during heat treatment lowered the predicted GI, but only in
the presence of gluten (Östman et al. 2002). A decrease in
pH per se had no impact. Furthermore, the addition of lactic
acid after heat treatment was not effective, suggesting that
lactic acid does not act as a classical enzyme inhibitor.
Homogenisation of the mixture removed the enzyme barrier,
and it is possible that lactic acid induces interactions
between starch and gluten, leading to reduced starch
availability.
Table 1. Effect of barley genotype and baking conditions on resistant starch (RS) content, in vitro starch hydrolysis rate (hydrolysis index; HI)
and predicted and determined glycaemic index (GI) (from Granfeldt et al. 1992; Åkerberg et al. 1998)
(Values are means with their standard errors of the means)
Amylose content
of wholemeal
bread* (%)
45 min and 200° 20h and 120°
RS* (%) HI (%)
Predicted
GI
Determined
GI RS* (%) HI (%)
Predicted
GI
Determined
GI
Mean SEM Mean SEM Mean Mean SEM Mean SEM Mean SEM Mean Mean SEM
Waxy†
(BZ-489-30)
Ordinary†
(8775)
Ordinary†
(Glacier)
High-amylose†
(Glacier)
3
23
33
44
0·6
b
2·4
c
1·6
d
3·5
e
0·0
0·1
0·0
0·1
112·3
ab
109·3
a
95·1
ab
92·8
ab
11·6
10·4
5·7
5·8
105·0
102·4
90·2
88·2
99·4
a
12·2
2·5
c
6·2
f
6·0
f
10·3
g
0·1
0·2
0·1
0·1
101·9
c
95·8
ab
88·1
b
73·0
c
8·0
5·9
5·8
6·0
96·0
90·8
84·1
71·1
70·7
b
8·8
a, b, c, d, e, f, g
Mean values with unlike superscript letters were significantly different (P<0·05).
*Content on a total starch basis.
†Wholemeal barley–white wheat (70:30, w/w).
a
b
a
b
a
a
a
a
b
a
a
b
100
80
60
40
20
0
0 15 30457095
Period after meal (min)
Change in serum paracetamol (µmol/l)
Fig. 1. Serum paracetamol responses in healthy subjects following
a breakfast meal with wholegrain barley bread alone () or with
the addition of lactic acid (––) or sodium propionate ().
a,b
Mean values with unlike superscript letters were significantly differ-
ent (P < 0·05). (From Liljeberg & Björck, 1996.)
204 I. Björck and H. Liljeberg Elmståhl
Thus, sourdough fermentation or the addition of organic
acids represent other methods that can be used to lower the
GI of bread products.
Importance of glycaemic index properties v. dietary fibre
content
Second-meal effects
Which types of low-GI cereals are preferable, and could
there be differences in metabolic advantages between low-
GI products? One mechanism that could account for the
metabolic benefits of a low-GI diet might be secondary to
the so-called ‘second-meal phenomenon’. The finding that a
low-GI meal improves glucose tolerance to the following
meal was reported first by Jenkins et al. (1980). The
phenomenon can be seen from breakfast to lunch (Jenkins
et al. 1982), but also from the evening meal to breakfast
(Wolever et al. 1988). In a study by Liljeberg et al. (1999)
the effects of three different cereal breakfasts on glucose
tolerance at a standardized lunch ingested 4 h later was
measured in healthy subjects (Table 2). The test breakfasts
had GI in the lower range (from 52 to 64) and consisted of
pasta, a fibre-rich mixed barley meal or white bread with
vinegar. A breakfast consisting of a carbohydrate-equivalent
amount of white bread was used as reference. In the case of
the spaghetti and the mixed barley-based breakfast, the
lunch produced only 60 or 70 % of the corresponding
glycaemic response after the reference breakfast. The pasta
breakfast also significantly lowered the insulin response at
lunch (P < 0·05). In contrast, no significant effect was noted
at lunch in the case of the breakfast with white bread +
vinegar. The net increment in glycaemia when commencing
the lunch in the case of the pasta and the barley breakfasts
was an indicator of a prolonged absorption. This finding
might suggest that in addition to low GI properties, as calcu-
lated by the 90 (Liljeberg & Björck, 1998) or 120 min
(Wolever et al. 1991) glucose areas under the curves, the
presence of a late glycaemic response may promote a 4h
second-meal effect. It seems that even though the dietary
fibre and RS contents are low (Liljeberg et al. 1999), the
pasta breakfast is capable of lowering glucose tolerance at
lunch (Liljeberg et al. 1999; Liljeberg & Björck, 2000). The
pasta breakfast also lowered triacylglycerol levels after the
standardized lunch (Liljeberg & Björck, 2000). Similar
information may be useful in the development of cereal
products with optimal carbohydrate release profiles. The
finding that a low GI per se has a beneficial effect on
glucose tolerance is in agreement with results from a semi-
long-term intervention in subjects with non-insulin-
dependent diabetes mellitus (Järvi et al. 1999), in which a
lowering of dietary GI, in the absence of difference in
dietary fibre, markedly improved metabolic variables
relating to insulin resistance.
In another study the effects of three evening meals
containing cereal on glucose tolerance at a following stand-
ardized white-bread breakfast were evaluated (Y Granfeldt,
W Xaomei and I Björk, unpublished results). The evening
meals were served at 22.00 hours to healthy subjects and
consisted of white bread or two low-GI meals (spaghetti GI
54, insulin index 53; barley kernels GI 53, insulin index 49).
The low-GI evening meals were thus matched with respect
to GI and insulin index, but were very different in the
content of indigestible carbohydrates, i.e. dietary fibre and
RS. When compared with the white-bread evening meal,
only the low-GI barley evening meal, rich in indigestible
carbohydrates, improved glucose tolerance the following
morning. The reduction in glucose and insulin areas under
the curve at the standardized breakfast meal was approxi-
mately 25 %. No blunting effect was noted following pasta
as the evening meal, which was in contrast to the finding
that pasta markedly improved glucose tolerance from
breakfast to lunch (Liljeberg et al. 1999; Liljeberg & Björck,
2000). A possible mechanism could be that the barley meal
promotes a higher fermentative activity in the colon, which
may act to suppress non-esterified fatty acid levels, and
hence improve glucose tolerance 10 h later, i.e. at the time of
the breakfast meal. It has also been reported that an evening
meal with barley, but not rice, improves glucose tolerance
and lowers non-esterified fatty acids the following morning
(Thorburn et al. 1993). On the basis that this overnight
phenomenon contributes to the long-term benefits of a low-
GI diet, the new generation of cereal products should,
therefore, not only have a low GI and a slow release profile
of the digestible carbohydrates fraction, but preferably also
be rich in indigestible and fermentable carbohydrates. This
added value of low-GI cereal products rich in dietary fibre
could provide one mechanism for the epidemiological
evidence that a high content of cereal fibre, in addition to a
low glycaemic load, protect against development of type 2
diabetes (Salmerón et al. 1997a,b).
Metabolic potential of low-glycaemic-index fibre-rich bread
products in women at risk of type 2 diabetes
Another important issue in relation to product tailoring and
optimisation of dietary GI relates to the magnitude of the
dietary change necessary to achieve the required metabolic
effect. To address this question, the semi-long-term
potential of modulating only the GI of the bread products
was studied in women at risk of type 2 diabetes (H Liljeberg
Elmståhl, A Frid, L Groop and I Björk, unpublished results).
The bread products were commercial high-GI products or
two types of modulated low-GI bread, one light and one
dark. Both low-GI bread products were based on intact rye
kernels and baked using sourdough fermentation. The
Table 2. Incremental blood glucose and insulin areas under the
curve (AUC) in healthy human subjects after a standardized lunch
meal following various cereal breakfasts
Breakfast
Standardized lunch
incremental (AUC) (%)
GI II Glucose Insulin
White bread
Spaghetti
Barley, rich in amylose
and β-glucans
White bread + vinegar
100
52
60
64
100
42
70
65
100
64*
72*
79 NS
100
69*
82 NS
79 NS
GI, glycaemic index; II, insulin index.
Mean values were significantly different from those for subjects receiving white
bread as breakfast: *P<0·05.
Nutrients contributing to the fibre effect 205
lighter bread contained fewer intact kernels, and instead had
added oat ß-glucans. Both the light and the dark bread had
similar GI of about 55. The commonly-consumed high-GI
bread products were thus replaced by experimental bread
products with lower GI and a higher content of indigestible
carbohydrates. The test subjects were women (about 31
years of age) with a history of gestational diabetes. These
women showed a genetic disposition for type 2 diabetes
during pregnancy, with a high risk of developing diabetes
later in life. An oral glucose tolerance test was performed
before inclusion in the study. Subjects diagnosed with
diabetes were excluded, and only those with impaired
glucose tolerance were recruited. Seven of the eight women
participants completed the study. The bread was included in
the breakfast, lunch and late-evening meals, and the amount
of carbohydrates provided during the two test periods was
standardized for each individual. A crossover design was
used, with 3-week intervention periods and a 3-week
washout period. The glucose and insulin responses to an
intravenous glucose challenge were measured before and
after each intervention period. No significant difference was
noted in the 1 h insulin areas under the curve over the inter-
vention period with the high-GI bread. In contrast, all
women displayed a decrease in insulin response over the
period with the low-GI bread. The mean decrease was
substantial (about 40 %). No differences were noted in the
corresponding blood glucose responses to the intravenous
glucose challenge, and the results indicated that replacing
the usual high-GI bread with the modified low-GI high-fibre
bread improved insulin economy in women at risk of type 2
diabetes. It remains to be established whether these low-GI
bread products may actually postpone development of type
2 diabetes. These experimental data are, however, in line
with epidemiological evidence of a lowered risk for type 2
diabetes with a low-GI diet rich in cereal fibre (Salmerón
et al. 1997a,b).
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... All three spaghetti pastas also produced a lower GL value compared to the reference foods without significant differences between them. Thus, our data do not support the popular idea of a reduced glycemic response elicited by increasing fiber content in foods, such as in the case of spaghetti pastas, which is in agreement with others [26,46,47,49,52,53]. The inconsistencies reported for fibers' effects on postprandial glycemia may be due to the fact that when soluble fibers are added to foods, their molecular weight vary and interactions with other compounds can occur. ...
... The inconsistencies reported for fibers' effects on postprandial glycemia may be due to the fact that when soluble fibers are added to foods, their molecular weight vary and interactions with other compounds can occur. It may also be that only certain types of fiber, mainly soluble (i.e., vegetable gums, derived from fruits, legumes, and psyllium), may influence the GI of foods through a reduced rate of gastric emptying as they make the chyme (partly digested food coming from the stomach) more viscous [46,53]. Other possible explanations may be that glycemic response is not significantly related to soluble dietary fiber content or that soluble fibers' effects are masked when they interact with other compounds, or that they are not as important in controlling postprandial glycemia. ...
... Other possible explanations may be that glycemic response is not significantly related to soluble dietary fiber content or that soluble fibers' effects are masked when they interact with other compounds, or that they are not as important in controlling postprandial glycemia. Finally, it may also be considered that the postprandial glucose-lowering effects of fiber, particularly soluble fiber, will be markedly observed when added to some high GI foods, such as breads [46,53,54], and not to low GI foods, such as spaghetti pastas. ...
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This randomized, single blind, cross-over study investigated the glycemic responses to three spaghetti No 7 types differing in dietary protein and soluble fiber content. Fourteen clinically and metabolically healthy, fasting individuals (25 � 1 years; ten women; BMI 23 � 1 kg/m2) received isoglucidic test meals (50 g available carbohydrate) and 50 g glucose reference, in random order. GI was calculated using the FAO/WHO method. Capillary blood glucose and salivary insulin samples were collected at 0, 15, 30, 45, 60, and 120 min. Subjective appetite ratings (hunger, fullness, and desire to eat) were assessed by visual analogue scales (VAS, 100 mm) at baseline and 120 min. All three spaghetti types (regular, whole wheat, and high soluble fiber–low carbohydrates) provided low GI values (33, 38, and 41, respectively, on glucose scale) and lower peak glucose values compared to glucose or white bread. No differences were observed between spaghetti No 7 types for fasting glucose, fasting and post-test-meal insulin concentrations, blood pressure (systolic and diastolic), and subjective appetite. Conclusions: all spaghetti No 7 types, regardless of soluble fiber and/or protein content, attenuated postprandial glycemic response, which may offer advantages to glycemic control.
... The trapezoid rule was used to calculate the 120 min positive iAUC after breakfast [22]. We chose to analyze the postprandial glucose response in connection with breakfast to minimize potential second meal effects [23]. Following the guidelines of the International Diabetes Federation At the start of each of the two study periods, participants attended outpatient units at a community hospital and a university hospital in Sweden, where the CGM thin-wire sensor was inserted in accordance with the manufacturer's instructions. ...
... The trapezoid rule was used to calculate the 120 min positive iAUC after breakfast [22]. We chose to analyze the postprandial glucose response in connection with breakfast to minimize potential second meal effects [23]. Following the guidelines of the International Diabetes Federation and the American Diabetes Association, we used 7.8 mmol/L and 3.9 mmol/L as cut-off levels for high and low glucose concentrations [24,25]. ...
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This is an observational study of interstitial glucose (IG) concentrations, IG variability and dietary intake under free-living conditions in 46 females with obesity but without diabetes. We used continuous glucose monitoring, open-ended food recording and step monitoring during regular dietary intake followed by a low-energy diet (LED). Thirty-nine participants completed both study periods. The mean BMI at baseline was 43.6 ± 6.2 kg/m2. Three weeks of LED resulted in a mean weight loss of 5.2% with a significant reduction in diurnal IG concentration but with greater glycemic variability observed during LED. The mean 24 h IG concentration decreased from 5.8 ± 0.5 mmol/L during the regular diet period to 5.4 ± 0.5 mmol/L (p < 0.001) during LED, while the mean amplitude of glycemic excursion increased from 1.5 ± 0.7 to 1.7 ± 0.7 mmol/L (p = 0.031). The positive incremental area under the curve at breakfast was significantly larger for LED compared to regular diet. The daily fiber intake and the glycemic index of breakfast meals were significantly associated with the glycemic variability during regular dietary intake. In conclusion, the 24 h mean IG concentration was lower but with more pronounced glycemic variability during LED compared to a regular diet.
... In this study, use of sourdough had no effect on the glycemic response of fresh pasta, contrary to what was found in literature for bread, which reported how sourdough fermentation or the addition of organic acids had been used to lower the glycemic index [36]. This, as organic acids were thought to delay gastric emptying (mainly acetic acid), or to promote starch-gluten interactions which reduce starch bioavailability (mainly lactic acid) after heat treatment [26]. ...
... It is worth mentioning that the increase in postprandial glycemia is not only related to the GI of a food but also to the amount of carbohydrates in the serving size of that food. Thus, another index, glycemic load (GL), was used [36]. In this study GL was calculated as the product of GI a and the grams of available carbohydrate in 160 g of cooked pasta (standard serving size) divided by 100. ...
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The use of wholemeal flour and sourdough fermentation in different food matrices has received considerable attention in recent years due to its resulting health benefits. In this study, a semolina-based and a wholemeal semolina-based sourdough were prepared and added to the formulation of gnocchetti-type fresh pasta. Four types of gnocchetti were made, using semolina plus semolina-based sourdough (SS), semolina plus wholemeal semolina-based sourdough (SWS), semolina alone (S), and semolina plus wholemeal semolina (WS). The latter two were used as controls. The digestibility of starch was studied both in vitro and in vivo, and the glycemic response (GR) and glycemic load (GL) were determined. Starch digestibility, both in vivo and in vitro, was higher in wholemeal semolina than semolina pasta and the resulting GR values (mg dL−1 min−1) were also higher (2209 and 2277 for WS and SWS; 1584 and 1553 for S and SS, respectively). The use of sourdough significantly reduced the rapidly digestible starch (RDS) content and increased the inaccessible digestible starch (IDS) content. The addition of sourdough to the formulation had no effect on the GR values, but led to a reduction of the GL of the pasta. These are the first data on the GR and GL of fresh pasta made with sourdough.
... La viscosidad se determina por el peso molecular y la estructura química y tienen esta característica de formar geles por los polímeros que la constituyen independientemente de su concentración. Esta capacidad gelificante es responsable de diversos efectos además de la retención de agua como funciones metabólicas, disminuir niveles de glicemia [13][14][15][16][17][18] postprandiales, de colesterol y triglicéridos Entre las fibras solubles se encuentran la pectina, ciertas hemicelulosas, gomas, mucilagos, betaglucanos y polisacáridos de algas. ...
... Esto es lo que justifica la absorción disminuida de nutrientes como glucosa impidiendo la elevación de la misma en la sangre. Este efecto de aplanamiento de la curva de glucosa es lo que justifica la recomendación en la que se debe aumentar la ingesta de fibra en el caso de pacientes diabéticos 16 especialmente la de tipo soluble . ...
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Anteriormente se consideraba poca importancia de la fibra alimentaria solo para mejorar los problemas de estreñimiento pero actualmente se han descuLa fibra no tiene contenido calórico, lo que la hace tener más ventajas con el resto de los carbohidratos y las moléculas de su composición al ser tan grandes y complejas, resisten la acción de las enzimas que tratan de descomponerlas para ser utilizadas en nuestro organismo. Las únicas calorías que aportan son proporcionadas por los ácidos grasos liberados al ser fermentada por la flora intestinal.bierto otras funciones en la dieta.
... Generally, foods that contain high dietary fiber have small glycemic indices. A low glycemic index meal rich in dietary fiber can improve glucose tolerance (35). Therefore, consistent dietary fiber intake is associated with low risk of metabolic syndrome, although evidences from cohort data are insufficient (36,37). ...
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It has been suggested that long working hours are associated with various diseases through dietary patterns. However, few studies have reported the association between working hours and dietary habits. Thus, the objective of this cross-sectional study was to explore the difference in dietary fiber intake by working hours. Data of a total of 10,760 workers in South Korea who participated in the Korea National Health and Nutrition Survey (KNHANES), a nation-wide survey, were analyzed to determine different distributions of dietary fiber insufficiency using multiple logistic regression models. Fiber insufficiency proportion was different from working hour groups. 70.1% of the total population eat fiber insufficiently. Working <40 h group showed 66.8% of fiber insufficiency. But working more than 52 h group marked 73.2% of fiber insufficiency. Logistic regression analysis of 10,760 nation-wide study participants revealed that working for 41–52 h a week (OR: 1.32, 95% CI: 1.18–1.47) and working for over 52 h a week (OR: 1.42, 95% CI: 1.25–1.62) were significantly associated with insufficient fiber intake compared to workers with standard working hours (30–40 h a week). These associations were still robust in an adjusted model, with working for 41–52 h a week (OR: 1.13, 95% CI: 1.01–1.27) and working for over 52 h (OR: 1.26, 95% CI: 1.09–1.45) showing high associations with dietary fiber insufficiency. Those with long working hours tend to have insufficient intake of dietary fiber. To promote desirable dietary habits, intervention programs on working conditions should be considered.
... Moreover, we demonstrated that the consumption of products with medium GI increased the likelihood to be diagnosed with PCOS by threefold [31]. Unlike products with low GI, products with high and medium GI usually contain only few fiber and complex carbohydrates [60], resulting in their different effects on glucose and insulin levels and eventually on androgen levels [53,57]. ...
Article
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The roles of dietary macronutrients and physical activity (PA) in patients with PCOS have not been sufficiently reported, especially in adolescent girls. To address this knowledge gap, we evaluated the associations between serum concentrations of total testosterone (tT), free testosterone (fT), androstenedione (A), dehydroepiandrosterone-sulfate (DHEA-S), sex hormone-binding globulin (SHBG) and dietary macronutrients intake as well as different types and levels of PA. The study population consisted of 96 girls of Caucasian ancestry, aged 14-18 years: 61 participants with polycystic ovary syndrome (PCOS) and 35 healthy controls. Serum tT, fT, A, DHEA-S, and SHBG were determined in fasting blood. Macronutrient intake and PA levels were assessed by using the three-day food record method and the Beliefs and Eating Habits Questionnaire (KomPAN), respectively. We found several positive correlations between dietary macronutrients such as total fat, saturated fatty acids (SFA), monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA), and hormonal parameters across the entire cohort and in healthy girls. A positive correlation between SHBG and total protein consumption as well as an inverse correlation between SHBG and carbohydrate intake could be determined. No correlation between androgens and macronutrients was found in the PCOS group. In contrast, we observed an inverse correlation between androgen concentrations (except of DHEA-S) and "work/school" and/or "leisure time" PA only in PCOS patients. Moreover, the hormone levels differed according to PA intensity. In conclusion, the impact of diet and PA was strikingly different in adolescents with and without PCOS. These findings indicate that disturbed hormonal homeostasis in PCOS, at least in the youngest patients, likely "overtrump" dietary influences, and otherwise, PA offers a therapeutic potential that requires further evaluation of the long-term effects in randomized studies. (ClinicalTrial.gov Identifier: NCT04738409.) Citation: Mizgier, M.; Watrowski, R.; Opydo-Szymaczek, J.; Jodłowska-Siewert, E.; Lombardi, G.; Kędzia, W.; Jarząbek-Bielecka, G.
... However, when bread (starch food) is taken with AECs in any order, the peak reached is lower than that of 'bread only' group in the;glucose response curve'. The reason for the last observation may be due to the -glucosidase inhibitory property polyphenol or the flavonoid component of AECs that delay the digestion of the starch-food ( Bjorck and Liljeberg, 2003 ;Lunde et al ., 2011 ). Although, after 120 minutes, the blood glucose levels of all the treatments did not return to the baseline, they were close to the baseline. ...
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High glycaemic index diet and α-glucosidase activity have been implicated in postprandial hyperglycaemia. Regulation of α-glucosidase activity and high glycaemic index diet has promising consequence on curbing the prevalence of type-2 diabetes mellitus. The present study investigated inhibitory effect of aqueous extract of Camellia sinensis (green tea) on α-glucosidase activity and glycaemic index of white bread. In vitro inhibition of α-glucosidase activity using p-nitrophenyl glucopyranoside as substrate and Camellia sinensis aqueous extract as inhibitor was investigated. Likewise, in vivo study on effect of the tea on glycaemic index of white bread using 30 healthy participants was carried out. The outcomes of the investigation revealed that Camellia sinensis aqueous extract reduced the activity of α-glucosidase to 17.50% with IC50 of 202.12 µg/mL. The mode of inhibition was mixed competitive. It also lowered the glycaemic index (GI) of white bread by 39.71% when bread consumption was delayed for 5 minutes after the extract consumption. In conclusion, report has shown that agent that reduces postprandial hyperglycaemia has an important role to play in the handling type-2 diabetes mellitus. This agent does this by lowering the GI of carbohydrate-rich food and/or inhibiting the activities of α-glucosidase enzyme. This study shows that aqueous extract of Camellia sinensis has a great potential to reduce the undue postprandial hyperglycaemia.
Article
The aim of this study was to carry out a systematic review of clinical trials followed by meta-analysis, to evaluate the effect of sourdough bread on glycemic control and appetite and satiety regulators such as leptin, ghrelin, GLP-1 (glucagon-like peptide-1), GLP-2 (glucagon-like peptide-2), NPY (neuropeptide Y), AgRP (agouti-related protein), PYY (peptide YY), and GIP (glucose-dependent insulinotropic polypeptide). Clinical trials compared the intake of sourdough bread to that of an industrially fermented one or control glucose solution in adults over 18 years of age. This systematic review included all randomized, parallel, or crossover trials published up to June 2021 in the EMBASE, MEDLINE, Scopus, and Web of Science databases. After the selection process, 18 studies were included. The analysis of the final average difference of the change in serum glucose after 60 minutes for the intervention indicated that the consumption of sourdough bread has a lower impact on blood glucose compared to that of industrial bread or glucose (MD = -0.29, IC 95% = [-0.46; -0.12]; I2 = 0%). The evaluation of blood glucose 120 minutes after the consumption of the intervention also indicated a lower increment in blood glucose when compared to the consumption of other types of bread or the same amount of glucose (MD = -0.21, IC 95% = [-0.32; -0.09]; I2 = 0%). The certainty of evidence varied from low to very low. The results showed that sourdough is effective in reducing the increment of postprandial glycemia, especially when prepared with whole wheat flour, although it does not reduce fasting serum insulin, nor does it change plasma PYY.
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Background : Currently, the increase in the nutritional value of food constitutes a major challenge in global nutrition, which is mainly aimed at preventing malnutrition and related diseases. Among the foods that are subject to this challenge, wheat bread, the traditional staple food of many populations worldwide, is often denigrated because of its low nutritional value due to the poor manufacturing practices that use baker’s yeast. Methods : Research was conducted on a wide range of databases (MEDLINE via PubMed, SpringerLink, Scopus, and Science Direct), over the period from 1970 to 2020, using the keywords : Wheat bread, sourdough, Lactic acid bacteria, yeasts, quality characteristics, nutritional value. Results : All reviewed publications proposed the use of sourdough during bread-making as an alternative to baker’s yeast. Its effectiveness has been proven through its capacity to improve the nutritional composition of wheat bread, which remains capable to satisfy the daily nutritional requirements in macronutrients and micronutrients, along with its sensory characteristics in terms of taste, flavor, volume, texture, and shelf life. Interestingly, the consumption of sourdough bread as a staple food prevents diabetes, gluten intolerance, and mineral deficiency, which are major global public health problems. Conclusion : The use of sourdough in the bread production industry may become a future innovative technology, considering the changes in the human diet, caused by the increase in the production of processed foods, rapid urbanization, and changing lifestyles.
Article
The incorporation of yoghurt as a starter in sourdough wheat bread, to improve technological and nutritional properties, was investigated. Two bread dough matrices were considered: endosperm wheat flour and blended with whole-grain flour. Two fermentation’s types were performed, two-stage sourdough bread and yeast bread fermentation. Compared with yeast dough, yoghurt-sourdough fermentation promoted considerable changes in chemical composition, particularly when whole-grain flour was conjoined with wheat flour: higher protein proteolysis degree, increase of peptide and free amino nitrogen content, solubilization of phenolic compounds (46–53%), increase of DPPH radical scavenging (54–65%) and ferric-reducing power (85–88%), were observed. As a baking ingredient, yoghurt-sourdough improved the bread crumb softness (15–12%) and delayed the staling (40–35%). Nutritionally, the glycemic index was reduced (18–32%) while protein digestibility (6–12%) and free amino acids bioavailability (50–100%) were enhanced. The addition of yoghurt and sourdough fermentation techniques offered a promising tool to improve wheat bread's technological and functional properties.
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Objective: To examine prospectively the relationship between glycemic diets, low fiber intake, and risk of non-insulin-dependent diabetes mellitus. Design: Cohort study. Setting: In 1986, a total of 65173 US women 40 to 65 years of age and free from diagnosed cardiovascular disease, cancer, and diabetes completed a detailed dietary questionnaire from which we calculated usual intake of total and specific sources of dietary fiber, dietary glycemic index, and glycemic load. Main outcome measure: Non-insulin-dependent diabetes mellitus. Results: During 6 years of follow-up, 915 incident cases of diabetes were documented. The dietary glycemic index was positively associated with risk of diabetes after adjustment for age, body mass index, smoking, physical activity, family history of diabetes, alcohol and cereal fiber intake, and total energy intake. Comparing the highest with the lowest quintile, the relative risk (RR) of diabetes was 1.37 (95% confidence interval [CI], 1.09-1.71, P trend=.005). The glycemic load (an indicator of a global dietary insulin demand) was also positively associated with diabetes (RR= 1.47; 95% CI, 1.16-1.86, P trend=.003). Cereal fiber intake was inversely associated with risk of diabetes when comparing the extreme quintiles (RR=0.72, 95% CI, 0.58-0.90, P trend=.001). The combination of a high glycemic load and a low cereal fiber intake further increased the risk of diabetes (RR=2.50, 95% CI, 1.14-5.51) when compared with a low glycemic load and high cereal fiber intake. Conclusions: Our results support the hypothesis that diets with a high glycemic load and a low cereal fiber content increase risk of diabetes in women. Further, they suggest that grains should be consumed in a minimally refined form to reduce the incidence of diabetes.
Article
To define those patients most likely to benefit from the hypolipidemic effect of low-glycemic-index (GI) traditional starchy foods, 30 hyperlipidemic patients were studied for 3 mo. During the middle month, low-GI foods were substituted for those with a higher GI with minimal change in dietary macronutrient and fiber content. Only in the group (24 patients) with raised triglyceride levels (types IIb, III, and IV) were significant lipid reductions seen: total cholesterol 8.8 +/- 1.5% (p less than 0.001), LDL cholesterol 9.1 +/- 2.4% (p less than 0.001), and serum triglyceride 19.3 +/- 3.2% (p less than 0.001) with no change in HDL cholesterol. The percentage reduction in serum triglyceride related to the initial triglyceride levels (r = 0.56, p less than 0.01). The small weight loss (0.4 kg) on the low-GI diet did not relate to the lipid changes. Low-GI diets may be of use in the management of lipid abnormalities associated with hypertriglyceridemia.
Article
The possible effects of organic acids or an organic salt on the rate of gastric emptying was studied to identify the cause for reduced postmeal responses of blood glucose and insulin to foods containing such components, eg, sourdough bread. Paracetamol was included in bread products with added lactic acid or sodium propionate and used as a marker for the rate of gastric emptying in healthy subjects. In parallel, postprandial glycemia, insulinemia, and satiety were evaluated. The influence of lactic acid, propionic acid, and sodium propionate was also studied in rats after they were tube-fed with glucose solutions. The bread products with lactic acid or sodium propionate both lowered blood glucose and insulin responses. The bread with sodium propionate also prolonged satiety. The reason for the lowered metabolic responses with sodium propionate was probably a lowered gastric emptying rate, as judged from reduced blood paracetamol concentrations; there was no such effect observed with bread with added lactic acid. A similar amount of lactic acid in solution tube-fed to rats did not affect the disappearance of glucose from the stomach. In contrast with the finding in humans, sodium propionate had no effect on the rate of gastric emptying in rats whereas an equimolar solution of propionic acid reduced gastric emptying rate in rats. Possibly, less of this acid was produced in the gastric contents after a bolus load of a sodium propionate solution (in rats) than in an eating situation. Also, the pH and/or the osmolarity may be important, and when provided in excessive amounts, lactic acid reduced the gastric emptying rate in rats. A hydrochloric acid solution of similar pH was much less effective in this respect.
Article
To define those patients most likely to benefit from the hypolipidemic effect of low-glycemic-index (GI) traditional starchy foods, 30 hyperlipidemic patients were studied for 3 mo. During the middle month, low-GI foods were substituted for those with a higher GI with minimal change in dietary macronutrient and fiber content. Only in the group (24 patients) with raised triglyceride levels (types IIb, III, and IV) were significant lipid reductions seen: total cholesterol 8.8 ± 1.5% (p < 0.001), LDL cholesterol 9.1 ± 2.4% (p < 0.001), and serum triglyceride 19.3 ± 3.2% (p < 0.001) with no change in HDL cholesterol. The percentage reduction in serum triglyceride related to the initial triglyceride levels (r = 0.56, p < 0.01). The small weight loss (0.4 kg) on the low-GI diet did not relate to the lipid changes. Low-GI diets may be of use in the management of lipid abnormalities associated with hypertriglyceridemia.
Article
Objective. —To examine prospectively the relationship between glycemic diets, low fiber intake, and risk of non—insulin-dependent diabetes mellitus.Desing. —Cohort study.Setting. —In 1986, a total of 65173 US women 40 to 65 years of age and free from diagnosed cardiovascular disease, cancer, and diabetes completed a detailed dietary questionnaire from which we calculated usual intake of total and specific sources of dietary fiber, dietary glycemic index, and glycemic load.Main Outcome Measure. —Non—insulin-dependent diabetes mellitus.Results. —During 6 years of follow-up, 915 incident cases of diabetes were documented. The dietary glycemic index was positively associated with risk of diabetes after adjustment for age, body mass index, smoking, physical activity, family history of diabetes, alcohol and cereal fiber intake, and total energy intake. Comparing the highest with the lowest quintile, the relative risk (RR) of diabetes was 1.37 (95% confidence interval [CI], 1.09-1.71, Ptrend=.005). The glycemic load (an indicator of a global dietary insulin demand) was also positively associated with diabetes (RR=1.47; 95% CI, 1.16-1.86, Ptrend=.003). Cereal fiber intake was inversely associated with risk of diabetes when comparing the extreme quintiles (RR=0.72,95% CI, 0.58-0.90, Ptrend=.001). The combination of a high glycemic load and a low cereal fiber intake further increased the risk of diabetes (RR=2.50, 95% CI, 1.14-5.51) when compared with a low glycemic load and high cereal fiber intake.Conclusions. —Our results support the hypothesis that diets with a high glycemic load and a low cereal fiber content increase risk of diabetes in women. Further, they suggest that grains should be consumed in a minimally refined form to reduce the incidence of diabetes.
Article
Fermentation of undigested carbohydrate produces short-chain fatty acids (SCFA), some of which have been shown to reduce hepatic glucose production (HGP) in animals. The aim of this study was to examine whether carbohydrate fermentation decreases HGP in man. Ten healthy subjects consumed 90-g carbohydrate portions of either brown rice or barley for dinner in random order 1 week apart. The following morning, glucose kinetics were measured basally and during an oral glucose tolerance test (OGTT). HGP was calculated as the difference between the total rate of glucose appearance (calculated from % enrichment of 6,6 dideuterated glucose [6,6 D2 glucose]) and the rate of appearance of gut-derived glucose (calculated from 6-3H glucose in the glucose drink). To detect fermentation, breath H2 content was measured by end-expiratory sampling of alveolar air. Significantly more breath H2 was produced after barley consumption (24 ± 4 v 4 ± 1 ppm, P < .001), indicating that barley contains more fermentable carbohydrate than rice. Glucose tolerance improved after the barley meal, with the peak OGTT plasma glucose concentration being 0.7 mmol/L lower than that after the rice meal (7.7 ± 0.4 v 8.4 ± 0.3 mmol/L, P < .05). This was primarily due to a 30% reduction in HGP (area under the curve, 909 ± 116 v 1,295 ± 157 μmol/kg; P < .01). No difference in the rates of glucose disappearance or gut glucose absorption was observed. However, serum free fatty acid (FFA) concentrations were significantly reduced the morning after the barley meal. In summary, carbohydrate fermentation enhances the suppression of HGP and FFA levels by oral glucose in man. Fermentation of carbohydrate may therefore play a role in improving postprandial glycemia after high-fiber, high-carbohydrate diets.