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Acute effects of raisin consumption on glucose and insulin reponses in healthy individuals

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Raisins are popular snacks with a favourable nutrient profile, being high in dietary fibre, polyphenols and a number of vitamins and minerals, in addition to being rich in fructose. In light of evidence demonstrating improvements in glycaemic control with moderate fructose intake and low-glycaemic index (GI) fruits, our aim was to determine the GI, insulin index (II) and postprandial responses to raisins in an acute feeding setting. A total of ten healthy participants (four male and six female) consumed breakfast study meals on four occasions over a 2- to 8-week period: meal 1: white bread (WB) (108 g WB; 50 g available carbohydrate) served as the control and was consumed on two separate occasions; meal 2: raisins (R50) (69 g raisins; 50 g available carbohydrate); and meal 3: raisins (R20) (one serving, 28 g raisins; 20 g available carbohydrate). Postprandial glucose and insulin were measured over a 2 h period for the determination of GI, glycaemic load (GL) and II. The raisin meals, R50 and R20, resulted in significantly reduced postprandial glucose and insulin responses when compared with WB (P < 0·05). Furthermore, raisins were determined to be low-GI, -GL and -II foods. The favourable effect of raisins on postprandial glycaemic response, their insulin-sparing effect and low GI combined with their other metabolic benefits may indicate that raisins are a healthy choice not only for the general population but also for individuals with diabetes or insulin resistance.
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HUMAN AND CLINICAL NUTRITION
Acute effects of raisin consumption on glucose and insulin reponses
in healthy individuals
Amin Esfahani
1,2,3
, Joanne Lam
1
and Cyril W. C. Kendall
2,3,4
*
1
School of Medicine, New York Medical College, Valhalla, NY, USA
2
Clinical Nutrition and Risk Factor Modication Center, St Michaels Hospital, Toronto, ON, Canada
3
Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
4
College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada
(Received 11 July 2013 Final revision received 8 September 2013 Accepted 4 October 2013)
Journal of Nutritional Science (2014), vol. 3, e1, page 1 of 6 doi:10.1017/jns.2013.33
Abstract
Raisins are popular snacks with a favourable nutrient prole, being high in dietary bre, polyphenols and a number of vitamins and minerals, in addition to
being rich in fructose. In light of evidence demonstrating improvements in glycaemic control with moderate fructose intake and low-glycaemic index (GI)
fruits, our aim was to determine the GI, insulin index (II) and postprandial responses to raisins in an acute feeding setting. A total of ten healthy participants
(four male and six female) consumed breakfast study meals on four occasions over a 2- to 8-week period: meal 1: white bread (WB) (108 g WB; 50 g
available carbohydrate) served as the control and was consumed on two separate occasions; meal 2: raisins (R50) (69 g raisins; 50 g available carbohydrate);
and meal 3: raisins (R20) (one serving, 28 g raisins; 20 g available carbohydrate). Postprandial glucose and insulin were measured over a 2 h period for the
determination of GI, glycaemic load (GL) and II. The raisin meals, R50 and R20, resulted in signicantly reduced postprandial glucose and insulin
responses when compared with WB (P<0·05). Furthermore, raisins were determined to be low-GI, -GL and -II foods. The favourable effect of raisins
on postprandial glycaemic response, their insulin-sparing effect and low GI combined with their other metabolic benets may indicate that raisins are a
healthy choice not only for the general population but also for individuals with diabetes or insulin resistance.
Key words: Raisins: Dried fruit: Glycaemic index: Glycaemic load
Raisins are one of the most commonly consumed dried fruits,
are eaten across the globe, and have a unique nutrient prole
that may confer distinctive health benets when compared
with other fruit. Raisins are a rich source of polyphenols
and phenolic acids, which may serve as antioxidants and pro-
mote an anti-inammatory environment with potential health
benets
(13)
. Raisins are also high in dietary bre and prebio-
tics, such as inulin, which have been shown to produce a heal-
thier colonic microora prole in addition to possibly aiding
weight management and reducing the risk of CVD
(4)
. A clini-
cal study found that raisins as part of a healthy diet improved
blood lipids and reduced other risk factors for CVD
(5)
.
Raisins are also high in fructose, which has a low glycaemic
index (GI). While concerns have been raised that fructose may
have adverse metabolic effects and promote weight gain, a
recent meta-analysis
(6)
demonstrated that moderate intakes of
fructose may improve glycaemic control, without harming car-
diometabolic risk factors
(6)
. This is especially important in light
of recent evidence demonstrating that low-GI fruits may
improve glycaemic and cardiovascular markers, including
HbA1c and blood pressure
(7)
.
Given that raisins are the most commonly consumed dried
fruit, are high in fructose and the controversy surrounding the
cardiometabolic effects of fructose, we investigated the effect
Abbreviations: GI, glycaemic index; GL, glycaemic load; iAUC, incremental AUC; R20, raisins (20 g available carbohydrate); R50, raisins (50 g available carbohydrate); WB,
white bread.
*Corresponding author: Dr Cyril W. C. Kendall, fax +1 416 978 5310, email cyril.kendall@utoronto.ca
© The Author(s) 2014. The online version of this article is published within an Open Access environment subject to the conditions of the Creative
Commons Attribution license <http://creativecommons.org/licenses/by/3.0/>.
JNS
JOURNAL OF NUTRITIONAL SCIENCE
1
of raisins on postprandial glycaemia and insulinaemia in an
acute feeding study.
Methods
Participants
Inclusion criteria included men or non-pregnant women aged
1875 years who were in good health. Individuals with a
known history of AIDS, hepatitis, diabetes or a heart con-
dition, or individuals taking medication or with any condition
that might make participation dangerous to the individual or
affect the results were excluded.
A total of ten participants were studied. Using the tdistri-
bution and assuming an average CV of within-individual vari-
ation of incremental AUC (iAUC) values of 25 %, n10
participants has 80 % power to detect a 33 % difference in
iAUC with two-tailed P<0·05.
Protocol
The study was open-label with a partial randomised, cross-
over design using standard GI methodology (ISO
26642:2010; International Organization for Standardization).
Eligible participants were studied on four separate days over
a period of 28 weeks with an interval of no less than 40 h
and no more than 2 weeks between tests. On each test day,
participants came to the clinic in the morning after a 1014
h overnight fast. Participants were asked to maintain stable
dietary and activity habits throughout their participation in
the study. If any participant was not feeling well or had not
complied with the preceding experimental conditions, the
test was not carried out and was rescheduled for another
day. On each test occasion participants were weighed, and
two fasting blood samples were obtained by nger-stick at
5-min intervals. Finger-stick blood samples were collected
from hands warmed with an electric heating pad for 35
min before each sample. Blood samples were collected into
two separate vials: one (two or three drops of blood) for glu-
cose analysis and the other (between six and eight drops of
blood) for insulin. After the second fasting sample was col-
lected the participant was provided with the test meal. At
the rst bite, a timer was started and additional blood samples
were taken at 15, 30, 45, 60, 90 and 120 min. Before and
during the test, a blood glucose test record was lled out
with the participants initials, identication number, date,
body weight, test meal, beverage, time of starting to eat,
time it took to eat, time and composition of last meal, and
any unusual activities. During the 2 h test, participants
remained seated quietly. After the last blood sample had
been obtained participants were offered a snack and then
allowed to leave.
The present study was conducted according to the guide-
lines laid down in the Declaration of Helsinki and all pro-
cedures involving human subjects/patients were approved by
the Western Institutional Review Board
®
. Written informed
consent was obtained from all participants before the start
of the study.
Study meals
Each participant participated in a total of four breakfast study
meals. Two test meals were consumed: meal 1: R50, consisting
of 50 g available carbohydrate from raisins; and meal 2: R20,
consisting of 20 g available carbohydrate from raisins, which
is one standard serving (28 g) of raisins. The control white
bread (WB) meal, which provided 50 g available carbohydrate,
was consumed twice. The macronutrient proles of the study
meals are provided in Table 1. The order of the test meals was
randomised.
Palatability
After consuming a meal, participants rated its palatability using
a visual analogue scale anchored at very unpalatableat one
end (0) and very palatableat the other (100). Therefore, the
higher the number, the higher was the perceived palatability
of the product.
Blood samples
The nger-stick samples for glucose analysis were placed in
a refrigerator and at the end of the test transferred to a
20°C freezer until analysed, which was performed within
5 d. A YSI model 2300 STAT analyser (YSI Life Sciences)
was used for glucose analysis. For insulin analysis, the micro-
vette tubes were centrifuged and the serum transferred to
labelled polypropylene tubes and stored at 20°C before analy-
sis. Insulin levels were measured using a Human Insulin ELISA
Kit (Alpco Diagnostics).
Data analysis
Data were entered into a spreadsheet by two different individ-
uals and the values compared with assure accurate transcrip-
tion. Incremental areas under the glucose and insulin
response curves (AUC), ignoring area below fasting, were cal-
culated. For the purposes of the AUC calculation, fasting
Table 1. Nutrient content of test meals
Test meal Abbreviation Amount (g) Protein (g) Fat (g) Total CHO (g) Dietary fibre (g) Available CHO (g)
White bread WB 108·09·30·852·02·050·0
Raisins (50 g CHO) R50 69·01·70 53·43·450·0
Raisins (one serving) R20 28·00·70 21·71·420·3
CHO, carbohydrate.
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glucose and fasting insulin were taken to be the mean of the
rst measurement of the blood glucose concentrations and
serum insulin concentrations at times 5 min and 0 min.
The GI and insulin index were calculated by expressing each
participants AUC for the test food as a percentage of the
same participants mean AUC for the two white bread con-
trols. Values >2 SD above the mean were excluded. The
blood glucose and serum insulin concentrations at each time,
AUC, GI and insulin index values were subjected to repeated-
measures ANOVA examining for the main effects of test meal
and the meal × participant interaction. After demonstration of
signicant heterogeneity, the signicance of the differences
between individual means was assessed using Tukeys test to
adjust for multiple comparisons. Means differing by more
than the LSD (least signicant difference) were statistically sig-
nicant, two-tailed P<0·05.
Glycaemic load (GL) was calculated using the formula:
GL = GI × g of available carbohydrate in the portion.
Glycaemic index classification
Using the classication of Brand-Miller for the glucose scale,
products with a GI of 55 or lower are classied as being
low GI; those with a GI of 56 to 69 are classied as medium,
while those with a GI of 70 or greater are classied as high GI.
Results
A total of ten participants (four male and six female) with a
mean age of 39 (SD 11) years and an average BMI of 26·4
(SD 6·2) kg/m
2
completed the study.
Within-subject variation of reference food
The mean within-subject CV of the iAUC values after the two
repeated WB tests was 17·0±3·6 % and was thus considered
technically satisfactory (average intra-subject variation of less
than 30 %).
Palatability
Palatability scores are presented in Table 2. The subjective
palatability of the R50 and R20 meals was higher than that
of the WB control. However, this difference did not reach stat-
istical signicance.
Postprandial glucose response and glycaemic index
Postprandial incremental glucose levels after the R50 meal
were signicantly higher than those after the WB meal at 15
and 30 min. At 60, 90 and 120 min, however, the postprandial
incremental glucose levels after R50 were signicantly lower
than after WB (Fig. 1). iAUC were signicantly lower after
both raisin meals than after WB (Fig. 2). The nal GI and
GL values are presented in Table 2.
Fig. 2. Incremental AUC (iAUC) for glucose after consumption of three meals
containing 50, 50 and 20 g of available carbohydrates from white bread (WB),
raisins (R50) and raisins (R20), respectively. Values are means, with standard
errors represented by vertical bars.
a,b,c
Mean values with unlike letters were
significantly different (P<0·05).
Fig. 1. Postprandial glucose responses to three meals containing 50, 50 and
20 g of available carbohydrates from white bread (), raisins () and raisins
(Δ), respectively. Values are means, with standard errors represented by ver-
tical bars.
a,b,c
Mean values at a specific time point with unlike letters were sig-
nificantly different (P<0·05).
Table 2. Palatability, glycaemic index (GI), GI category, glycaemic load (GL), GL category and insulin index
(Mean values with their standard errors)
Palatability
(mm) GI Insulin index
Test meal Abbreviation Mean SEM Mean SEM GI category* GL GL category Mean SEM
White bread WB 63·0
a
10·071·0
a
High 35·5
a
High 71·0
a
Raisins (50 g CHO) R50 75·0
a
6·049·0
b
4·0Low24·5
b
N/A 38·0
b
3·0
Raisins (one serving) R20 72·0
a
6·0 N/A N/A 9·9
c
Low N/A
CHO, carbohydrate; N/A, not applicable.
a,b,c
Mean values within a column with unlike superscript letters were significantly different (P<0·05).
* Category from GI Factor (Atkinson et al.
(27)
).
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Postprandial insulin response and insulin index
There was no signicant difference between the WB and
R50 meals in incremental postprandial insulin levels at 15
and 30 min. However, insulin levels were signicantly lower
at 45, 60 90 and 120 min with the R50 meal compared with
WB (Fig. 3). iAUC were also signicantly lower with raisins
compared with the WB control (Fig. 4). The nal insulin
index values are presented in Table 2.
Discussion
The present study demonstrates that raisins are a low-GI and
-insulin index fruit that provides a favourable postprandial glu-
cose and insulin response. In terms of postprandial glucose
response, raisins elicited a swifter response compared with
WB for the rst 30 min. This, however, was followed by a
sharp decline and an overall lower AUC for glucose when
compared with WB (P<0·05), which is commonly observed
with other fruits. This postprandial glucose response pattern
may be explained by the high sucrose content of raisins. The
sucrose would be rapidly digested and the glucose rapidly
absorbed relative to starch. However, the fructose, which is
responsible for 50 % of the available carbohydrate content
of raisins, would not contribute to the rise in blood glucose.
Evidence from other studies suggests that the benets of fruc-
tose on glycaemic control may extend beyond simple replace-
ment of glucose. Moore et al.
(8)
demonstrated that the addition
of only 7·5 g of fructose, levels which are slightly lower than
the fructose content of one serving of raisins, to 75 g of glu-
cose as part of an oral glucose tolerance test signicantly low-
ered the glucose response when compared with 75 g glucose
with no added fructose
(8)
. A potential mechanism of action
for this improved glycaemic response with fructose ingestion
may be enhanced hepatic glucose uptake. Fructose ingestion
increases the hepatic concentrations of fructose-1-phosphate
(rst product of hepatic fructose metabolism), which in turn
competes with fructose-6-phosphate for binding to glucoki-
nase regulatory protein (GKRP). This leads to the release of
glucokinase (rate-limiting enzyme in the hepatic metabolism
of glucose) from GKRP, causing hepatic metabolism and
further uptake of glucose and thus lower postprandial glucose
concentrations
(8,9)
. This glycaemic advantage with moderate
intakes of fructose over glucose is not a novel nding, and
has been reported in both healthy individuals and patients
with diabetes in the 1970s and 1980s
(1012)
. A recent
meta-analysis put this link into perspective by demonstrating
that small doses of fructose < 10 g/meal or < 36 g/d can sig-
nicantly improve serum levels of HbA1c and fasting glucose
levels
(6)
. Furthermore, this daily intake level was not associated
with any adverse metabolic effects that have been linked to
high intake of fructose such as dyslipidaemia
(6)
.
Also of interest is the low GI of raisins as determined by the
present study (49 based on the glucose scale). A previous study
by Jenkins et al.
(13)
reported the GI of raisins to be 64.
However, this study was conducted on only six subjects.
More recently a study by Kim et al.
(14)
reported GI values of
49 in sedentary individuals, 49 in individuals with prediabetes
and 55 in aerobically trained adults. These results are very
similar to the GI value determined for raisins in the present
study. The health benets of low-GI fruit were demonstrated
in a recent secondary analysis of a clinical intervention that
showed that low-GI fruit consumption as part of a low-GI
diet was associated with statistically signicant reductions in
HbA1c, systolic blood pressure and overall CHD risk
(7)
. The
original randomised clinical trial assessed the effects of a
low-GI v. a high-bre diet on glycaemic control in patients
with type 2 diabetes and included fruit intake advice as part
of the dietary intervention
(15)
. The secondary analysis included
152 patients and demonstrated that the GI of fruit was an
independent predictor of HbA1c reduction and that the lowest
quartile of GI intake led to the greatest reduction in HbA1c
(7)
.
It is important to note that in this study grapes were con-
sidered high-GI foods (GI > 90 based on the bread scale).
However, the present study suggests that raisins have a low
GI (GI < 70 based on the bread scale). The present study
also demonstrated that both serving sizes of raisins studied
(69 and 28 g) are low-GL foods. The benecial effects of
low-GI and -GL foods on diabetes and risk of CVD have
Fig. 4. Incremental AUC (iAUC) for insulin after consumption of three meals
containing 50, 50 and 20 g of available carbohydrates from white bread
(WB), raisins (R50) and raisins (R20), respectively. Values are means, with
standard errors represented by vertical bars.
a,b,c
Mean values with unlike
letters were significantly different (P<0·05).
Fig. 3. Postprandial insulin responses to three meals containing 50, 50 and
20 g of available carbohydrates from white bread (), raisins ( ) and raisins
(), respectively. Values are means, with standard errors represented by ver-
tical bars.
a,b,c
Mean values at a specific time point with unlike letters were sig-
nificantly different (P<0·05).
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been demonstrated by a number of large cohort studies
(1618)
.
Lastly, the type and amount of bre present in raisins should
not be overlooked as another component that may account for
the lowered glycaemic response. Overall, the present ndings
support the notion that incorporation of raisins as part of a
healthy, low-GI diet in patients with diabetes or impaired glu-
cose tolerance can potentially improve glycaemic management
and provide additional cardiovascular benets.
The present study also demonstrated that raisins lead to a
lower postprandial insulin response when compared with
WB. This insulin-sparing effect may also be in part due to
the fructose content of raisins. Fructose is not an insulin secre-
tagogue and, unlike glucose, does not require insulin for cell
entry
(19)
. The insulin-sparing effects of fructose have been
demonstrated in a number of other studies
(2022)
. While long-
term impacts of raisins on insulin control require further inves-
tigation, the present study suggests that raisins, through acute
postprandial insulin-sparing effects, may be a healthy food
choice in patients with insulin resistance or diabetes.
The major limitation of the present study, as with all acute
feeding studies, is the inability to translate these acute ndings
to long-term benets. However, at least in terms of the ben-
ecial effect of fructose on glycaemic management, previous
studies have shown that these effects are sustainable over a
longer period of time
(23,24)
. Another shortcoming is the sample
size. While the use of ten subjects has been validated by a
number of studies, nevertheless this sample size reduces the
study precision and may lead to exaggerated associations.
While the potential benets of moderate consumption of
fructose on glucose control have been overshadowed by the
adverse outcomes, especially on serum lipids
(23,25,26)
, asso-
ciated with overconsumption and over-utilisation of high-
fructose corn syrup in the everyday diet, the benets of
fructose as a component of whole fruits should not be over-
looked. Raisins are popular snacks that are readily accessible
at a reasonable price. Their nutrient prole, being high in anti-
oxidants, dietary bre, prebiotics, vitamins and minerals,
indicate that they could contribute to overall health. While
long-term studies are needed, the present study demonstrates
that in addition to the aforementioned benets, raisins can
acutely improve postprandial glycaemic control and, as a
low-GI food, may serve as a healthy snack, when used in mod-
eration, in the diets of healthy individuals and for those with
diabetes or impaired glucose tolerance.
Acknowledgements
The present study was supported by Sun-Maid Growers of
California, Kingsburg, CA, USA. The authors wish to thank
Dr Arianna Carughi, Health & Nutrition Research Coordinator,
Sun-Maid Growers of California, for assistance with the study.
C. W. C. K. provided the establishment of funding, study
design, data gathering and manuscript preparation. A. E. and
J. L. were involved with data gathering and manuscript
preparation.
C. W. C. K. has received research grants, travel funding,
consultant fees, honoraria or has served on the scientic advi-
sory board for Abbott, Advanced Food Materials Network,
Almond Board of California, American Peanut Council,
American Pistachio Growers, Barilla, California Strawberry
Commission, Canadian Institutes of Health Research, Canola
Council of Canada, Danone, General Mills, Hain Celestial,
International Tree Nut Council, Kellogg, Loblaw Brands
Ltd, Nutrition Impact, Oldways, Orafti, Paramount Farms,
Pulse Canada, Saskatchewan Pulse Growers, Solae,
Sun-Maid Growers of California and Unilever. A. E. and
J. L. have no conicts of interest.
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... Whole fruits are typically low GI foods. The current investigation classified both raisin varieties (Sultanas and Corinthian) as high GI foods, which is in contrast to results from other studies, but as low GL foods which is in agreement with others (20,(42)(43)(44)(45)(46)(47)(48). The reason for this discrepancy may be the different variety of raisins used in studies originating from Canada, USA, and Australia (41,42,46,47), made from different grapes, containing about 11 g less sugars compared to the Greek varieties tested. ...
... The current investigation classified both raisin varieties (Sultanas and Corinthian) as high GI foods, which is in contrast to results from other studies, but as low GL foods which is in agreement with others (20,(42)(43)(44)(45)(46)(47)(48). The reason for this discrepancy may be the different variety of raisins used in studies originating from Canada, USA, and Australia (41,42,46,47), made from different grapes, containing about 11 g less sugars compared to the Greek varieties tested. Greek raisins contain predominantly fructose and glucose at almost equal amounts, and low amounts of sucrose and maltose (49). ...
Article
Goat milk yogurt (GMY) and raisins are popular foods with a favorable nutrient profile. Our aim was to determine the glycemic index (GI) and postprandial responses to GMY containing ACE-I peptides carrying the RPKHPINHQ isracidin fragment and two Greek raisin varieties in an acute feeding setting. A total of 12 healthy participants (four male and eight female) consumed breakfast study foods containing 25g available carbohydrate on seven occasions over a 3- to 9-week period: food 1: D-glucose (25g) served as the control and was consumed on three separate occasions; food 2: GMY (617.28g); food 3: Corinthian raisins (37.76g); food 4: Sultana raisins (37.48g); and food 5: GMY & C (308.64g GMY & 18.88g C). Postprandial glucose was measured over a 2h period for the determination of GI and glycemic load (GL). Subjective appetite ratings (hunger, fullness, and desire to eat) were assessed by visual analogue scales (VAS, 100mm) at 0-120min. Blood pressure (systolic and diastolic; BP) was measured at baseline and 120min. GMY provided low GI (26), C and S provided high GI/low GL (75/10 and 70/9, respectively), and GMYC provided low GI (47) values on glucose scale compared to D-glucose. Peak blood glucose rise was significantly lower only for GMY and GMYC compared to reference food (D-Glucose), as well as C, and S (P for all < 0.05). No differences were observed between test foods for fasting glucose, BP, and subjective appetite. In conclusion, GMY and GMYC attenuated postprandial glycemic responses, which may offer advantages to glycemic control.
... [39] On the other hand, intake of raisins with HCD; in this study, markedly reduced the blood glucose, insulin, cholesterol, TG, and LDL levels, whereas HDL significantly elevated. These findings were similar to that of Puglisi, et al. [40] and Esfahani, et al. [41] Raisins contain a significant amount of polyphenols and dietary fibers that can potentially decrease both plasma TG and LDLC by reducing apo E and inhibition of microsomal triglyceride transfer protein, respectively, as shown with lyophilized grape powder supplementation. [40,42] The decrease of both glucose and insulin levels in HCD and raisins administrated group of this work was in agreement with the previous study of Esfahani et al. [41] who documented that fructose constitutes about 50% of carbohydrate content of raisins and has a low glycemic index. ...
... These findings were similar to that of Puglisi, et al. [40] and Esfahani, et al. [41] Raisins contain a significant amount of polyphenols and dietary fibers that can potentially decrease both plasma TG and LDLC by reducing apo E and inhibition of microsomal triglyceride transfer protein, respectively, as shown with lyophilized grape powder supplementation. [40,42] The decrease of both glucose and insulin levels in HCD and raisins administrated group of this work was in agreement with the previous study of Esfahani et al. [41] who documented that fructose constitutes about 50% of carbohydrate content of raisins and has a low glycemic index. Fructose intake elevates the concentration of "fructose-1-phosphate" in the liver which competes with "fructose-6-phosphate" for binding to glucokinase regulatory protein. ...
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Background: Statins are among the first line of pharmacological treatment of lipid disorders and lowering serum cholesterol, but they have many side effects. Aim: The study aim was to evaluate the role of raisins in protecting the thyroid function and structure in a rat model of hypercholesterolemia, through biochemical and histopathological investigation. Materials and methods: Thirty male rats were randomly divided into three groups (n = 10 each) of albino rats included the control, high cholesterol diet (HCD)-fed for 13 weeks and HCD plus Raisins were included in this study. Blood levels of glucose, insulin, cholesterol, lipids, thyroid-stimulating hormone (TSH), T3, T4, oxidants/anti-oxidants were assessed. Thyroid gland was processed and examined histopathologically using light and electron microscopy. Results: Feeding HCD resulted in hypercholesterolemia in rats after 13 weeks as evidence by lipid profile. Ingestion of raisins along with HCD resulted in a significant (P < 0.001) decrease in the levels of insulin, blood glucose, thyroxine (T4) and malondialdehyde (MDA), while the levels of TSH, T3 and total anti-oxidant capacity significantly (P < 0.001) elevated. Raisins histologically alleviated the HCD-induced structural changes in the thyroid glands that included degenerated mitochondria and increased lipid droplets in the cytoplasm. Conclusions: Simultaneous administration of raisins along with HCD, administrated for a short time, could modulate the negative effect on thyroid gland structure and function.
... Glycemic index values for raisins have been found to be low in several groups such as healthy adults, healthy sedentary individuals and prediabetic adults [48,49]. A randomized crossover study carried out with healthy and diabetic subjects that received 74 g of Corinthian currants or 50 g of glucose as a reference food showed that currants intake reduced postprandial glucose and insulin responses, both in healthy and diabetic subjects [50]. ...
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Alzheimer’s disease (AD) is associated with brain amyloid‐β (Aβ) peptide accumulation and neuroinflammation. Currants, a low glycemic index dried fruit, and their components display pleiotropic neuroprotective effects in AD. We examined how diet containing 5% Corinthian currant paste (CurD) administered in 1-month-old 5xFAD mice for 1, 3, and 6 months affects Aβ levels and neuroinflammation in comparison to control diet (ConD) or sugar-matched diet containing 3.5% glucose/fructose (GFD). No change in serum glucose or insulin levels was observed among the three groups. CurD administered for 3 months reduced brain Aβ42 levels in male mice as compared to ConD and GFD, but after 6 months, Aβ42 levels were increased in mice both on CurD and GFD compared to ConD. CurD for 3 months also reduced TNFα and IL-1β levels in male and female mouse cortex homogenates compared to ConD and GFD. However, after 6 months, TNFα levels were increased in cortex homogenates of mice both on CurD and GFD as compared to ConD. A similar pattern was observed for TNFα-expressing cells, mostly co-expressing the microglial marker CD11b, in mouse hippocampus. IL-1β levels were similarly increased in the brain of all groups after 6 months. Furthermore, a time dependent decrease of secreted TNFα levels was found in BV2 microglial cells treated with currant phenolic extract as compared to glucose/fructose solution. Overall, our findings suggest that a short-term currant consumption reduces neuroinflammation in 5xFAD mice as compared to sugar-matched or control diet, but longer-term intake of currant or sugar-matched diet enhances neuroinflammation.
... Insulin resistance was unchanged in both the dates and the raisins groups over the study period. The consumption of fruit with a low glycemic index and high fiber content, such as raisins, has been shown to decrease insulin resistance in acute studies [25]; however, there was no improvement seen here in insulin resistance (IR), insulin sensitivity (IS) or glycemic control, perhaps because the study was too short in duration for any changes in glycemic control to become evident. In addition, with the concern that the additional prolonged glycemic load may affect the beta cell, there were no changes in beta cell function as determined by HOMA-B or the composite measure of beta cell function, the disposition index. ...
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Objective: Date fruit has been reported to have benefits in type 2 diabetes (T2D), though there is a concern, given the high sugar content, about its effects on glycemic control. Design and setting: Prospective, interventional, randomized, parallel study. Participants: In total, 79 patients with T2D (39 male and 40 female). Intervention: Participants were randomly allocated to either 60 g date fruit or 60 g raisins daily of the equivalent glycemic index (amount split, given as midmorning and midafternoon snack) for 12 weeks. Main outcome measures: The primary outcome was to investigate the effect of date fruit on HbA1c and fasting blood glucose, and their variability, in patients with T2D in comparison to the same glycemic load of raisins. The secondary outcomes were to determine whether date fruit affected cardiovascular risk by measuring fasting lipids, C-reactive protein (CRP), blood pressure, and insulin resistance (IR) as measured by Homeostatic Model Assessment (HOMA-IR). Results: In total, 61 (27 female and 34 male) of 79 patients completed the study. There was no difference between or within groups for HbA1c or HbA1c variability, fasting glucose or glucose variability, insulin resistance (HOMA-IR), insulin sensitivity (HOMA-S), beta cell function (HOMA-B), the disposition index, lipids, systolic (SBP) or diastolic blood pressure (DBP), or C-reactive protein (CRP) (p > 0.05). Conclusion: No improvement in glycemic indices was seen following supplementation of 60 g daily date fruit or raisins, though neither had a deleterious effect on glycemic control over a 12-week period, indicating their safety when consumed in T2D. Additionally, no beneficial therapeutic effects of date fruit on other cardiovascular indices in T2D were seen.
... This increase persisted in both the sensitivity and per protocol analyses. Dried fruits have a low to moderate glycemic index, and the acute glycemic response to carbohydrate-rich meals is attenuated by replacement of refined starches with dried fruits (46)(47)(48)(49)(50) . The lower postprandial glycemic response is likely due to partial glucose replacement by fructose, which does not contribute substantially to blood glucose and may even stimulate hepatic glucose uptake (51) . ...
Article
Fruit intake is associated with lower risk of cardiometabolic diseases. However, effects of dried fruits on cardiometabolic health are not well researched. We investigated the effect of daily dried fruit consumption compared to a carbohydrate-rich snack on cardiometabolic disease risk factors in adults with increased cardiometabolic risk. A two-period randomized crossover trial was conducted in adults (n=55) with elevated BMI and at least one additional risk factor for cardiometabolic disease to compare the effects of consuming 3/4 cup/d mixed dried fruits (plums, figs, dates, and raisins) or a calorie- and carbohydrate-matched control snack for 4 weeks. The primary outcome was low-density lipoprotein cholesterol (LDL-C); secondary outcomes included other lipids and lipoproteins, glucose and insulin, C-reactive protein, blood pressure, and vascular stiffness. Linear mixed models were used for data analysis. Lipid and lipoprotein concentrations did not differ between conditions, however dried fruit increased LDL-C (0.10 mmol/L, 95% CI: 0.01, 0.20) compared to baseline. Compared to the control, dried fruit increased mean fasting glucose (0.08 mmol/L, 95% CI: 0.005, 0.16; P =0.038). Vascular outcomes, fasting insulin, and C-reactive protein did not differ between conditions. Mean weight changes did not differ ( P =0.55) but tended to increase after both conditions (dried fruit: 0.3 kg, 95% CI: -0.09, 0.65; control: 0.4 kg, 95% CI: 0.01, 0.75). Thus, short-term daily consumption of a large portion of mixed dried plums, figs, dates, and raisins, without structured dietary guidance, did not improve cardiometabolic risk factors, compared to carbohydrate-rich snacks, in adults with increased baseline cardiometabolic risk.
... Raisin has high amounts of fructose, which has a low Glycemic Index (GI). Although concerns have been raised that high amounts of fructose, especially among diabetic patients, may have adverse metabolic effects (Sievenpiper et al., 2012), the authors in this study used 36 g/day of raisin, which was higher than its standard serving size for diabetic patients (Esfahani et al., 2014). This might be the reason for increasing inflammatory mediators after 24 weeks of intervention. ...
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Grapes contain different polyphenols and might prevent inflammation by reducing Nitric Oxide (NO) inactivation through antioxidative enzymes. The aim of this article was to demonstrate the effects of grape polyphenols on the selected inflammatory mediators, such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-a), and high-sensitivity C-reactive protein (hs-CRP). To find papers assessing the effects of grape polyphenols on inflammatory mediators, electronic data bases, including ISI web of science, PubMed/Medline, SCOPUS, and Google scholar, were searched up to March 2019. Delphi checklist was used for evaluating the qualities of the included articles. The protocol was registered in PROSPERO (No. CRD42019116695). The mean changes in the intervention and control groups were calculated by subtracting the end values from the baselines. Then, the difference between the two changes was measured and utilized as the effect size in meta-analysis. 9 and 8 articles were included in the systematic review and meta-analysis, respectively. Our results indicated that grape polyphenols did not reduce hs-CRP levels, but omission of one article could lead to a significant reduction in hs-CRP (Weight Mean Difference (WMD): -0.54 mg/L, 95 % CI: -1.02, -0.06; P=0.026, I2=0.0 %). Regarding IL-6 and TNF-α, no significant changes were observed in the intervention compared to the control group (WMD: 0.04 pg/mL, 95 % CI: -0.02, 0.28; P=0.744, I2=0.0 %, WMD: -0.10 pg/mL, 95 % CI: -0.25, 0.05; P=0.183, I2=0.0 %, respectively). We found no beneficial effects of grape polyphenols on the selected inflammatory mediators. Still, more studies with higher doses of polyphenols, longer treatment durations, different sources of grape polyphenols, and larger numbers of participants are required.
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In 2019 and 2020, and especially during the COVID-19 pandemic, the number of households owning dogs increased considerably, and many of these pets were new puppies acquired during the lockdowns in the UK. With such a rise in puppy ownership, it has never been more important to ensure that these puppies receive adequate nutrition throughout their weaning and growth periods, and beyond. In this article, the nutritional considerations of growing puppies will be discussed, along with current pet food trends and how to ensure puppies are receiving a complete and balanced diet.
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Two studies investigating the impact of dried fruits eaten as a snack on weight control were designed to examine the effects of prunes and raisins on appetite (phase 1), and whether prunes undermine weight loss, due to the increase in energy density on drying, when included in a structured weight loss programme (phase 2). Phase 1 compared the effect on appetite of equi-weight or equi-caloric snacks of prunes (100 or 140 g) and raisins (100 or 111 g) with a control condition (100 g/335 kcal jelly babies), in a pre-load, cross-over design (n = 40 analysed). A significant effect of condition on food intake was observed, with significantly lower weight of food consumed in the 140 g prune group versus control, and on Area Under the Curve (AUC) fullness, due to a greater effect in the 140 g prune group versus control. In phase 2, change in bodyweight and waist circumference were measured in a 12-week randomised, parallel-groups intervention study (n = 100 analysed, 50 per group). Prunes (females: 140 g, males: 171 g/day) replaced usual snacks whilst following a weight loss programme. The active control group followed the same programme and participants were instructed on healthy snacking. A significant reduction in mean bodyweight in the prune group versus baseline was consistent with the phase 1 evidence that prunes can aid appetite control, although it could also be explained by overall diet in the context of a structured weight loss programme. Prunes did not produce a detrimental effect on mean weight loss over 12 weeks versus control (prune group: −1.99 kg; active control: −1.53 kg), nor on decrease in waist circumference (prune group: −2.40 cm; active control: −1.74 cm). No additional benefit on weight loss was seen (between-group difference was non-significant). The daily intake of prunes was well-tolerated. Phase 1 demonstrated that prune snacks produced beneficial changes in appetite. Phase 2 demonstrated that prunes did not undermine weight management, and this warrants further study.
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There are dilemmas in the minds of consumers with respect to sugar consumption – they would like to consume sugars for sweetness, but in a healthy (and perhaps guilt free!) way. In a sense, consumers believe that if sugar does not appear as an ingredient on the product label, but is intrinsic in the food (and will appear as a nutrient), it is ‘good’. As an ingredient, however, it is viewed as a ‘bad chemical’ associated with tooth decay and obesity. The reality is that unless processing induced modifications have occurred, the sugar molecule within a plant tissue is the same molecule structure as present in purified sugar. The same calorific value. However, there is an argument that humans eat too refined food and that if sugars were eaten in their natural context (e.g. within a fruit), their presence and concentration would be in harmony (where different nutrients complement and balance the sugar concentration) with the human body. This reflects the process of eating, satiety, presence of other nutrients (including water) and the associated impact of the indigestible components of plant foods on the transit/nutrient bioavailability control and thus benefits through the gut. The authors explore these issues in this article and seek to provide a scientific basis to different sides of the argument – sugar is good or bad depending on how (in which format and how much/how concentrated) it is consumed. More importantly perhaps, how should sugar consumption – an important nutrient – be managed to optimize the benefits but reduce the disadvantages? © 2020 Society of Chemical Industry
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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.
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Contrary to concerns that fructose may have adverse metabolic effects, there is evidence that small, ‘catalytic’ doses ( ≤ 10 g/meal) of fructose decrease the glycaemic response to high-glycaemic index meals in human subjects. To assess the longer-term effects of ‘catalytic’ doses of fructose, we undertook a meta-analysis of controlled feeding trials. We searched MEDLINE, EMBASE, CINAHL and the Cochrane Library. Analyses included all controlled feeding trials ≥ 7 d featuring ‘catalytic’ fructose doses ( ≤ 36 g/d) in isoenergetic exchange for other carbohydrates. Data were pooled by the generic inverse variance method using random-effects models and expressed as mean differences (MD) with 95 % CI. Heterogeneity was assessed by the Q statistic and quantified by I 2. The Heyland Methodological Quality Score assessed study quality. A total of six feeding trials (n 118) met the eligibility criteria. ‘Catalytic’ doses of fructose significantly reduced HbA1c (MD − 0·40, 95 % CI − 0·72, − 0·08) and fasting glucose (MD − 0·25, 95 % CI − 0·44, − 0·07). This benefit was seen in the absence of adverse effects on fasting insulin, body weight, TAG or uric acid. Subgroup and sensitivity analyses showed evidence of effect modification under certain conditions. The small number of trials and their relatively short duration limit the strength of the conclusions. In conclusion, this small meta-analysis shows that ‘catalytic’ fructose doses ( ≤ 36 g/d) may improve glycaemic control without adverse effects on body weight, TAG, insulin and uric acid. There is a need for larger, longer ( ≥ 6 months) trials using ‘catalytic’ fructose to confirm these results.
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Sugar has been suggested to promote obesity, diabetes and coronary heart disease (CHD), yet fruit, despite containing sugars, may also have a low glycaemic index (GI) and all fruits are generally recommended for good health. We therefore assessed the effect of fruit with special emphasis on low GI fruit intake in type 2 diabetes. This secondary analysis involved 152 type 2 diabetic participants treated with glucose-lowering agents who completed either 6 months of high fibre or low GI dietary advice, including fruit advice, in a parallel design. Change in low GI fruit intake ranged from -3.1 to 2.7 servings/day. The increase in low GI fruit intake significantly predicted reductions in HbA(1c) (r = -0.206, p =0.011), systolic blood pressure (r = -0.183, p = 0.024) and CHD risk (r = -0.213, p = 0.008). Change in total fruit intake ranged from -3.7 to 3.2 servings/day and was not related to study outcomes. In a regression analysis including the eight major carbohydrate foods or classes of foods emphasised in the low GI diet, only low GI fruit and bread contributed independently and significantly to predicting change in HbA(1c). Furthermore, comparing the highest with the lowest quartile of low GI fruit intake, the percentage change in HbA(1c) was reduced by -0.5% HbA(1c) units (95% CI 0.2-0.8 HbA(1c) units, p < 0.001). Low GI fruit consumption as part of a low GI diet was associated with lower HbA(1c), blood pressure and CHD risk and supports a role for low GI fruit consumption in the management of type 2 diabetes. ClinicalTrials.gov NCT00438698.
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Studies in animals have documented that, compared with glucose, dietary fructose induces dyslipidemia and insulin resistance. To assess the relative effects of these dietary sugars during sustained consumption in humans, overweight and obese subjects consumed glucose- or fructose-sweetened beverages providing 25% of energy requirements for 10 weeks. Although both groups exhibited similar weight gain during the intervention, visceral adipose volume was significantly increased only in subjects consuming fructose. Fasting plasma triglyceride concentrations increased by approximately 10% during 10 weeks of glucose consumption but not after fructose consumption. In contrast, hepatic de novo lipogenesis (DNL) and the 23-hour postprandial triglyceride AUC were increased specifically during fructose consumption. Similarly, markers of altered lipid metabolism and lipoprotein remodeling, including fasting apoB, LDL, small dense LDL, oxidized LDL, and postprandial concentrations of remnant-like particle-triglyceride and -cholesterol significantly increased during fructose but not glucose consumption. In addition, fasting plasma glucose and insulin levels increased and insulin sensitivity decreased in subjects consuming fructose but not in those consuming glucose. These data suggest that dietary fructose specifically increases DNL, promotes dyslipidemia, decreases insulin sensitivity, and increases visceral adiposity in overweight/obese adults.
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Clinical trials using antihyperglycemic medications to improve glycemic control have not demonstrated the anticipated cardiovascular benefits. Low-glycemic index diets may improve both glycemic control and cardiovascular risk factors for patients with type 2 diabetes but debate over their effectiveness continues due to trial limitations. To test the effects of low-glycemic index diets on glycemic control and cardiovascular risk factors in patients with type 2 diabetes. A randomized, parallel study design at a Canadian university hospital research center of 210 participants with type 2 diabetes treated with antihyperglycemic medications who were recruited by newspaper advertisement and randomly assigned to receive 1 of 2 diet treatments each for 6 months between September 16, 2004, and May 22, 2007. High-cereal fiber or low-glycemic index dietary advice. Absolute change in glycated hemoglobin A(1c) (HbA(1c)), with fasting blood glucose and cardiovascular disease risk factors as secondary measures. In the intention-to-treat analysis, HbA(1c) decreased by -0.18% absolute HbA(1c) units (95% confidence interval [CI], -0.29% to -0.07%) in the high-cereal fiber diet compared with -0.50% absolute HbA(1c) units (95% CI, -0.61% to -0.39%) in the low-glycemic index diet (P < .001). There was also an increase of high-density lipoprotein cholesterol in the low-glycemic index diet by 1.7 mg/dL (95% CI, 0.8-2.6 mg/dL) compared with a decrease of high-density lipoprotein cholesterol by -0.2 mg/dL (95% CI, -0.9 to 0.5 mg/dL) in the high-cereal fiber diet (P = .005). The reduction in dietary glycemic index related positively to the reduction in HbA(1c) concentration (r = 0.35, P < .001) and negatively to the increase in high-density lipoprotein cholesterol (r = -0.19, P = .009). In patients with type 2 diabetes, 6-month treatment with a low-glycemic index diet resulted in moderately lower HbA(1c) levels compared with a high-cereal fiber diet. Trial Registration clinicaltrials.gov identifier: NCT00438698.
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
Studies in both healthy and diabetic subjects demonstrated that fructose produced a smaller postprandial rise in plasma glucose and serum insulin than other common carbohydrates. Substitution of dietary fructose for other carbohydrates produced a 13% reduction in mean plasma glucose in a study of type 1 and type 2 diabetic subjects. However, there is concern that fructose may aggravate lipemia. In 1 study, day-long plasma triglycerides in healthy men were 32% greater while they consumed a high-fructose diet than while they consumed a high-glucose diet. There is also concern that fructose may be a factor contributing to the growing worldwide prevalence of obesity. Fructose stimulates insulin secretion less than does glucose and glucose-containing carbohydrates. Because insulin increases leptin release, lower circulating insulin and leptin after fructose ingestion might inhibit appetite less than consumption of other carbohydrates and lead to increased energy intake. However, there is no convincing experimental evidence that dietary fructose actually does increase energy intake. There is also no evidence that fructose accelerates protein glycation. High fructose intake has been associated with increased risk of gout in men and increased risk of kidney stones. Dietary fructose appears to have adverse effects on postprandial serum triglycerides, so adding fructose in large amounts to the diet is undesirable. Glucose may be a suitable replacement sugar. The fructose that occurs naturally in fruits and vegetables provides only a modest amount of dietary fructose and should not be of concern.
Article
The objective of this study was to determine the glycemic index (GI) and insulin index (II) of raisins and evaluate if these values are similar in different populations. The study subjects consisted of 10 healthy sedentary individuals (S; age, 25.7 +/- 1.3 years; body mass index [BMI] = 23.3 +/- 1.7 kg/m(2)), 11 aerobically trained adults (A; age, 23.1 +/- 1.0 years; BMI = 24.1 +/- 0.3 kg/m(2)), and 10 prediabetic adults (P; age, 50.0 +/- 2.6 years; BMI = 32.6 +/- 1.9 kg/m(2)). Subjects consumed 50 g of available carbohydrate from raisins and from a glucose solution (reference food) on 2 separate occasions. Serum glucose and insulin concentrations were measured from capillary fingerstick blood samples at baseline and at 15, 30, 45, 60, 90, and 120 minutes (and 150 and 180 minutes for P group) postprandially. The GI of raisins was low (GI, < or = 55) in the S (49.4 +/- 7.4) and P (49.6 +/- 4.8) groups and was moderate (GI, 55-69) in the A group (62.3 +/- 10.5), but there were no differences among the subject groups (P = .437). The II of raisins was 47.3 +/- 9.4, 51.9 +/- 6.5, and 54.4 +/- 8.9 for the S, A, and P groups, respectively. On average, the A group secreted 2- to 2.5-fold less insulin per gram of carbohydrate compared with the S and P groups (P < .05). Thus, raisins are a low to moderate GI food, with a correspondingly low II. The lower insulin response in the A group compared with the other groups suggests enhanced insulin sensitivity.