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The Postprandial Glycemic and Insulinemic Effects of Three Cooked Vegetables : Corchorus Olitorius , Spinacia Oleracea , and Daucus Carota on Steamed White Rice

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Abstract

Background: Eatingcooked vegetables with rice is quite common in Jordan and worldwide. Dietary fibers of vegetables are expected to play a role in the glycemic control of meals. Aim: To study the postprandial glycemic and insulinemic effect of three cooked vegetables: mulukhiyah leaves (Corchorus olitorius), spinach (Spinacia oleracea) and carrots (Daucus carota). Methods: The postprandial glycemic and insulinemic effect of the threecooked vegetables on steamed rice were studied by runningtheoral glucose tolerance tests on apparently healthy young adults, each of who served as his own control, using white bread as the reference. Insulin sensitivity was measured by calculating the composite insulin sensitivity index. Results: The glycemic index (GI) of rice (84.2±10.5%) ingested with chicken broth was significantly lowered only by eating 120 g of mulukhiyah leaves (ML) and not by either carrots or spinach. The insulinemic index (II) of steamed white rice eaten with broth was significantly lowered by120 g of ML (61.7± 9.2%) and 150 g of spinach (42.9± 9.0%). Insulin sensitivity was only improved by spinach. All results are expressed as means ± SEM and are considered statistically significant at P<0.05. The results also suggested that there was no significant difference between the calculated relative GI and relative II responses of the three cooked vegetables at the two assigned levels, each eaten with rice and broth compared to the corresponding GI or the II values of the individual foods from which they were composed of. Conclusions: Eating a relatively high portion of mulukhiyah leaves improves the glycemic response to white rice whereas only higher levels of carrots tended to improve the glycemic response of white rice, and spinach at either level had no apparent effect. While insulin level was lowered by the three tested vegetables, its sensitivity was improved by eating spinach only. © 2013 DAR Publishers? University of Jordan. All Rights Reserved.
The Postprandial Glycemic and Insulinemic Effects
of Three Cooked Vegetables: Corchorus Olitorius, Spinacia
Oleracea, and Daucus Carota on Steamed White Rice
1. Faculty of Agriculture, The University of Jordan.
2. Msc in Dietetics and Human Nutrition, Faculty of Agricultrue, The University of Jordan.
* Correspondence should be addressed to:
Prof. Ahmad Faqih
E-mail: Faqiham@ju.edu.jo
© 2013 DAR Publishers University of Jordan. All Rights Reserved.
Ahmad Faqih*1 and Buthaina Al-Khatib2
Abstract
Background: Eatingcooked vegetables with rice is quite common in Jordan and worldwide. Dietary
fibers of vegetables are expected to play a role in the glycemic control of meals.
Aim: To study the postprandial glycemic and insulinemic effect of three cooked vegetables: mulukhiyah
leaves (Corchorus olitorius), spinach (Spinacia oleracea) and carrots (Daucus carota).
Methods: The postprandial glycemic and insulinemic effect of the threecooked vegetables on steamed
rice were studied by runningtheoral glucose tolerance tests on apparently healthy young adults, each of
who served as his own control, using white bread as the reference. Insulin sensitivity was measured by
calculating the composite insulin sensitivity index.
Results: The glycemic index (GI) of rice (84.2±10.5%) ingested with chicken broth was significantly
lowered only by eating 120 g of mulukhiyah leaves (ML) and not by either carrots or spinach. The
insulinemic index (II) of steamed white rice eaten with broth was significantly lowered by120 g of ML
(61.7± 9.2%) and 150 g of spinach (42.9± 9.0%). Insulin sensitivity was only improved by spinach. All
results are expressed as means ± SEM and are considered statistically significant at P<0.05.
The results also suggested that there was no significant difference between the calculated relative GI and
relative II responses of the three cooked vegetables at the two assigned levels, each eaten with rice and
broth compared to the corresponding GI or the II values of the individual foods from which they were
composed of.
Conclusions: Eating a relatively high portion of mulukhiyah leaves improves the glycemic response to
white rice whereas only higher levels of carrots tended to improve the glycemic response of white rice,
and spinach at either level had no apparent effect. While insulin level was lowered by the three tested
vegetables, its sensitivity was improved by eating spinach only.
Keywords: Glycemic index, insulinemic index, mulukhiyah leaves, spinach, carrots, insulin sensitivity.
(J Med J 2013; Vol. 47 (2):161- 175)
Received Accepted
February 2, 2012 December 16, 2011
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Introduction
Dietary fibers which by definition cannot be
digested by humans play an important role in
improving the glycemic control. Water-
soluble dietary fibers are more effective than
insoluble fibers.1, 2 Part of this control can be
ascribed to glucagon-like peptide-1(GLP-1)
which is secreted by intestinal L-cells and to
ghrelin which is secreted by the stomach. It is
well established that GLP-1slows the gastric
emptying rate and consequently slows down
the rate of glucose absorption into the blood
stream which plays an important role in
glucose control and diabetes treatment3. It
also stimulates glucose-dependent insulin
secretion in addition to decreasing the
production of glucagon. Furthermore, insulin
sensitivity can be increased by some fibers.4, 5
Ghrelin, an appetite-stimulating hormone is
down regulated by soluble fibers by delaying
gastric emptying.6 Glucose-dependent
insulintropic polypeptide (GIP) is secreted by
K-cells of the intestine and as the name
indicates its function is to stimulate insulin
secretion. GIP and GLP-1 are called incretins
and thus both have the incretin effect,
meaning that a higher amount of insulin is
secreted when an equivalent amount of
glucose is administered orally than
intravenously.5 Tahrani and colleagues
summarize the difference between GIP and
GLP-1 as follows, “unlike GLP-1, GIP has no
effect on α-cells that secrete glucagon and has
no impact on food intake, satiety, gastric
emptying, or body weight.”5
The postprandial glycemic and insulinemic
effect of foods can be studied in terms of their
effect on the glycemic index (GI) and
insulinemic index (II) on cooked rice as in our
study. The GI refers to the incremental area
under the glucose response curve after an
amount of carbohydrate from a test food
relative to that of a control food that is
consumed.7 The area under the curve for
glucose (AUCg) is calculated to reflect the
total rise in blood glucose level after the test
food. The glycemic index is calculated by
dividing the AUCg resulting from eating a
fixed amount of carbohydrates (50 g) of the
test food by the AUCg resulting from eating a
similar amount of carbohydrates from the
reference food and multiplying the answer by
100.7The use of a reference food is essential
for reducing the confounding influence of
differences in the physical characteristics of
the subject.8 Jenkins and his co-workers 8 first
introduced the concept of the glycemic index
(GI) in 1981.
Recent studies show a positive impact of low-
GI diets on hunger ratings,9 resting energy
expenditure, nitrogen balance, fat loss,10 and
weight loss.6,11,12 In 2007, the World Health
Organization (WHO) and Food and
Agriculture Organization (FAO) 13 updated the
1998 recommendations about carbohydrates in
human nutrition by recommending to people
from industrialized countries to base their diets
on foods with low GI (< 55%), in order to
prevent the most common diseases of
affluence, notably obesity, coronary heart
disease, and diabetes.
The development of insulinemic indices (IIs)
for foods has also been reported as necessary
to supplement the GI tables used in the dietary
management of diabetes mellitus.14 It has been
widely assumed that the insulin response is
proportional to the glucose response, and
therefore the glycemic response is an accurate
predictor of the insulin response.15 The II of
foods can also be determined from the
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corresponding incremental blood insulin
areas.16
Traditionally, many Middle Eastern dishes are
prepared from cooked rice along with
vegetables in different amounts and various
methods. For this report, carrots, spinach, and
mulukhiyah leaves were selected. The GI and
II have been widely determined from single
food items, which may not necessarily predict
their GI and II in mixed dishes.17 Besides,
people do not usually eat single food items.16
Thus, additional research is needed to
determine the glycemic index of mixed dishes
rather than the single foods that comprise
them. The glycemic and insulinemic response
elicited by a meal is termed the relative
glycemic response (RGR) and the relative
insulinemic response (RIR), respectively.
Wolever and Bolognesi18 developed an
equation to estimate the RGR and RIR of a
meal from the individual GI, II, and the
amount of carbohydrate content of the meal
components. The equation was found to
explain 90% of the variation in mean glucose
responses conducted by mixed meals in normal
subjects.18
The objective of the present study was to
determine the glycemic and insulinemic
indices of mulukhiyah leaves (Corchorus
olitorius), spinach (Spinacia oleracea), or
carrots (Daucus carota) when eaten at two
different levels with steamed white rice and
chicken broth.
Materials and Methods
Preparation of Test Foods: White rice,
chicken, mulukhiyah leaves, spinach, and
carrots were purchased from a local market in
Amman, Jordan. All vegetables were washed
with water. Spinach (medium size leaves) was
chopped into small square pieces (about 3
cm2), mulukhiyah leaves were chopped into
small pieces, and carrots of medium length
(about 80 g for each) were peeled and chopped
to round slices (about 5mm). All vegetables
were weighed, put into polyethylene bags, and
kept frozen until used within three weeks.
Chicken broth (B) was prepared separately by
using young chickens (age 42 days, about 2
kg) without skin and bones, using two liters of
water and 30 grams of salt per one kilogram of
chicken and were boiled for a period of 20
minutes. Chicken broth was served in 200 mL
disposable plastic cups along with steamed
white rice and with each vegetable dish at two
different levels.
Rice (R; American white rice, medium-grain;
trade mark: Sun White) was weighted by an
electronic balance,put in a household steam
cooker, covered with aluminum foil, and left
for a period of four hours until it became
tender but firm. Sunflower oil (5 g) and table
salt (5 g) were added to each serving of white
rice, the average weight of which before
steaming (and after steaming) was as follows:
60g (150g), 55g (138g ), 50g (125g), and 40g
(100g).
Each vegetable dish was prepared either at a
low level equivalent to one cup of raw
vegetables or half a cup of cooked vegetables
or at a high level to about twice or three times
the low level per serving. The average amount
of one serving and the method of preparation
of each dish were determined by a pilot study
of five neighboring housewives.
Each serving of frozen vegetables was
prepared by adding 40 mL of filtered water and
5g of salt and boiled for 20 min. for the low
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level. For the high level, the amount of water
and salt were doubled for carrots and tripled
for spinach and mulukhiyah leaves andthen
cooked for 20 min.
Subjects: Fifteen apparently healthy adults (3
men and 12 women) with a mean (±SEM) age
of 25.4 (±1.82) and a normal BMI of 21.6
(±0.97) volunteered to participate in the
study.Thus, the inclusion criteria stipulated
that all subjects should be apparently healthy
and young, with a normal BMI in addition to
having a normal oral glucose tolerance test
(OGTT) based on the results of the (OGTT)
that was conducted on the control (white
bread) as explained in the experimental design
section. All participants were informed about
the experimental protocol and the purpose of
the study before they signed a written consent
form. The protocol of the study was approved
by the scientific committees of the Nutrition
and Food Science Department at the Faculty of
Agriculture and the Faculty of Graduate
Studies at the University of Jordan.
Experimental Design: Oral glucose tolerance
tests (OGTT) were applied following 10–12
hours of overnight fasting. To clarify the
experimental design referring to tables 2, 3,
and 4, we noticethat there are4 food dishes
that comprise every set of test vegetables,
namely bread (the reference) and 3 other
dishes, all of which need a conduction of a
total of 4 glucose tolerance tests. For each
OGTT to be conducted for each food dish,
each subject serves as his/her own control by
completing the four OGTT srequired for the 4
food dishes that comprise every set of
testvege tables. The reference is assigned a
glycemic index of 100 and aninsulinemic
index of 100.The reference is considered “the
control”. For a certain study subject called
“x”, “x” is subjected to the first OGTT for the
reference food. The area under the curve for
glucose (AUCg) is assigned the value of 100
and similarly giving the area under the curve
for insulin (AUCi) the value of 100. Then
after a rest of 2 to 3 days, a second glucose
tolerance test forrice and broth is conducted
for person “x” to be followed after the rest
period bythe third and the fourth oral glucose
tolerance tests for the two different levels
(portions) of each vegetable, respectively.
This makes person “x” a control for himself
since he was first subjected to the oral glucose
tolerance testusing bread as a control with
which we compare the postprandial glycemic
and insulinemic response of the other test
foodsfor every set of the test vegetables. This
protocol was repeated (replicated) five times
for every food (bread, rice and broth with
each vegetable at two different levels) for
every set of vegetables. This means that 5
different persons (replicates) are needed for
any one of the foods for any particular set of
vegetable. Less than 5 persons are needed in
the few cases whereby a certain person who
was subjected to OGTT for the reference
bread chose to sit for the food dishes that
comprise a different vegetable set, without
repeating OGTT for bread which he was
already subjected to.
The first OGTT test was applied on the
reference, local Arabic white bread (85g, free
from sugar and any other additives) containing
50 grams of carbohydrates and prepared from
straight grade flour with an extraction rate of
about 77%. It was consumed thoroughly using
a cup of plain water (200 mL) to wash down
any food residue in the mouth. All foods, other
than bread, were served warm. The second
OGTT was run on a portion of steamed
American white rice (R;60 g) containing 50 g
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of carbohydrates and was eaten along with a
cup (200 mL) of warm chicken broth (B)
which was beneficial to wash down any
residue in the mouth similar to that of water
used with the reference. The third and fourth
OGTTs were run on the cooked vegetables
each eaten at two different levels with steamed
R+B. The four OGTTs for every vegetable
were replicated (repeated)for each of the
corresponding five subjects, having Arabic
white bread as the control for each of the 3
vegetables as shown in table 3 and table 4.
Thus, each of the five subjects served as his
own control by being subjected to 3 OGTTs
for every vegetable and a fourth OGTT for the
reference (Arabic white bread). Subjects were
tested at the same time in the morning but on
four non-successive days.
The portion size of white bread (85g), rice
(60g), and the combined portions of rice and
vegetables in each test dish were based on the
proximate analysis that we determined
according to AOAC methods as shown in table
1.19 The portions of rice and raw vegetables
were combined to give a total of 50 g
carbohydrates (table 1b). The initial venous
blood sample (0 time) was taken at the fasting
state and at 30, 60, 90, and 120 min thereafter.
The test food was completely ingested within
10 to 15 minutes using plain water for bread
and chicken broth for rice alone or for rice
eaten with vegetables; plain water and chicken
broth helped in ingesting any food residue
from the oral cavity. Serum glucose was
determined in duplicate by the enzymatic
colorimetric method using a hexokinase
reagent kit (Roche Diagnostics, GmbH, D-
68298 Mannheim, Germany). Serum insulin
was determined by an
electrochemiluminescence immunoassay
(ECLIA), using an atomic analyzer (Modular
Analytics E170, Roche) with commercial
analysis kits (Cobas; Roche Diagnostics,
Diagnostic GmbH, SandhoferStrasse 116, D-
68305Mannheim, Germany). All instruments
were calibrated accordingly to ensure the
accuracy of the results. Areas under the curve
for glucose (AUCg) and insulin (AUCi) were
calculated excluding the areas below the
fasting levels.8The observed glycemic index
(GI), insulinemic index (II), relative glycemic
response (RGR), and relative insulinemic
response (RIR) were calculated.20
Based on OGTT, the following formula was
used to calculate the composite insulin
sensitivity index (CISI):21
CISI= 10,000/ [(fasting G × fasting I) ×
(mean G (0-120 min) × mean I (0-120 min)]
where G = Glucose and I = Insulin.
Statistical Analysis: AUC, GI, II, and CISI
were calculated using Microsoft Office Excel
2003. Statistical analysis was performed using
Statistical Package for Social Sciences
software (SPSS, version 9.0, 2004).22 All
results were expressed as means ± standard
error of the mean (SEM) and were considered
statistically significant at the 5% level
(P<0.05). A separate analysis for each dish was
performed. Differences in GI, II, AUC, CISI,
and peaks of glucose and insulin
concentrations between the test dishes were
subjected to a one-way analysis of variance
(ANOVA). Results which exceeded 2 SEM of
the total mean were considered out-layers and
were excluded, leaving the number of
replicates (n) for certain OGTT data of each of
the tested vegetable equal to 4 and not 5 and
for the combined rice and bread equal to 13
and not 15 (table 3 and table 4).
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Table (1):Proximate Composition of 100 g of Tested Food Items Energy
Kcal/100g
Carbohydrates
(N.F.E.)1
(%)
Crude
fibers
(%)
Ash
(%)
Crude
fat
(%)
Crude
protein
(%)
Moisture
(%)
Food item
278.0 58.6 0.4 1.6 1.2 8.2 30.0 White Arabic bread
357.4 83.3 0.8 0.6 0.6 4.7 10.0 White rice (medium
grain)
31.8 6.6 1.0 0.8 0.2 0.9 90.5 Carrots
56.8 7.5 1.3 2.5 0.8 4.9 83.0 Mulukhiyah leaves
27.1 3.2 0.9 1.4 0.3 2.9 91.3 Spinach
1. Carbohydrates are calculated by difference as nitrogen free extract (N.F.E)
2. Values are based on fresh weight basis. 3. Mulukhiyah is Corchorus olitorius.
Table (1b): The Combined Amounts of Raw White Rice and Tested Vegetables in Different
Portion Sizes that Give a Total of 50 Grams of Carbohydrates.*
Test Vegetable The Lower Vegetable Level
(Rice + Vegetable, g) The higher Vegetable Level
(Rice + Vegetable, g)
Rice, g Vegetable, g Rice, g Vegetable, g
Carrots 50 130 40 260
Mulkhiyah leaves 55 40 50 120
Spinach 58 50 55 150
* Based on Table 1 for carbohydrate content.
Results and Discussion
The mean values for fasting serum glucose level
for bread in normal fasting subjects expressed
during the 120 minutes period of OGTT in
addition to AUCg, GI, and RGR are presented
in tables 2 and 4. All subjects exhibited normal
glucose and insulin responses to ingested bread
as based on the OGTT data obtained. The mean
values for serum insulin response in normal
fasting subjects for bread and for all test foods
are presented in tables 3 and 4 which also show
the serum insulin response, the calculated
AUCi, the II, and the RIR. Results are further
discussed in the following paragraphs.
The Glycemic and Insulinemic Responses to
Rice (R) Ingested with Broth (B): The
glycemic and insulinemic responses (GI and II)
to R+B were tested for each test vegetable
group (tables 2 and 3) and then they were
calculated for all subjects combined, in which
case the GI value of R+ B (93.4 ± 1.3%)
tended to be lower but not significantly
different from that of bread. In contrast, the
corresponding II for all subjects combined
(86.6 ± 2.5%) was significantly lower than that
of bread. The results of GI and II cannot be
compared directly with the results obtained
from other studies because of a number of
reasons, including variation in varieties of rice
used,23processing conditions,24, 25food structure
such as particle size and shape,26 and the
proportion of starch type between amylose and
amylopectin.27,28
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Table (4): Glycemic Index, Relative Glycemic Response, Insulinemic Index, Relative
Insulinemic Response, and Composite
Insulin Sensitivity Index for OGTT as Affected by the Tested Vegetables (Means ± SEM).
Test dishes GI (%) RGR (%) II (%) RIR (%) CISI
1. Carrots:
Bread
Rice (R,60g ) +chicken broth (B, 200mL)
Rice (R,50g) +B with carrots (130g)
Rice (R,40g) +B with carrots (260g)
2. Mulukhiyah leaves (ML):
Bread
Rice (R,60g ) +chicken broth (B, 200mL)
Rice (R,55g) +B with ML (40g)
Rice (R,50g) +B with The ML (120g)
3. Spinach :
Bread
Rice (R,60g ) + chicken broth (B, 200mL)
Rice (R,58g) +B with spinach (50g)
Rice (R,55g) +B with spinach (150g)
4. R + B, combined subjects
Bread (reference)
Rice+ Chicken broth (R+B)
100 a
92.7 ± 12.1 a
101.3 ± 12. a
83.3 ± 12.1 a
100 a
84.2 ± 10.5 a
88.1 ± 12.1 a
34.1 ± 12.1 b
100 a
100.1± 12.8a
89.8 ± 12.8 a
95.6 ± 12.8 a
100 a
93.4 ± 1.3 a
95.1 ± 10.8 a
102.8 ± 10. a
84.2 ± 10.8 a
87.9 ± 9.3 a
91.9 ± 10.8 a
43.4 ± 10.8 b
100.6 ±11.4a
93.0 ± 11.4 a
98.1 ± 11.4 a
100 a
92.0 ± 8.9 a
67.5 ± 7.7 b
84.2± 8.9 ab
100 a
81.0 ± 9.0 b
73.7± 7.7 cb
61.7 ± 9.2 c
100 a
76.1 ±7.7 ab
76.5± 7.7 ab
42.9 ± 9.0 c
100 a
86.6 ± 2.5 b
7.9 ±1.1 a
9.6 ±3.3 a
12.2 ±5.2 a
10.8 ± 4.6 a
10.5 ±5.2 a
9.1 ±2.3 a
9.9 ±2.3 a
9.0 ±2.3 a
7.5 ±2.6 a
8.8 ±4.2 a
11.2 ±6.4 ab
17.8 ±5.1 b
7.9 ±1.1 a
9.6 ±3.3 a
12.2 ±5.2 a
10.8 ± 4.6 a
10.5 ±5.2 a
9.1 ±2.3 a
9.9 ±2.3 a
9.0 ±2.3 a
7.5 ±2.6 a
8.8 ±4.2 a
11.2 ±6.4 ab
17.8 ±5.1 b
1. One way ANOVA adjusted for multiple pair-wise comparisons by least significant test was performed for
every treatment.
2. Means in the same column for each group of test dishes with different superscripts are significantly
different (P˂ 0.05).
3. GI: Glycemic index, RGR: Relative glycemic response, II: Insulinemic index, RGR: Relative insulinemic
response, CISI: Composite insulin sensitivity index.
4. 4. For rice + chicken broth, all subjects for the bread and R+B in the three groups were combined
together.
The small amount of fat (5g of sunflower oil)
that was added to steamed rice in addition to
thesmall amount fat that arises from chicken
broth are partially responsible for the lower
value of GI and II obtained in this study. Fats
and oils slow the rate of gastric emptying of
food (here rice) carbohydrates and their
absorption,29 leading to lowered blood glucose
level, lowered GI%, and lowered II%.
The Glycemic and Insulinemic Responses of
Carrots (Cr) Ingested with R and B: The
glycemic indices produced byeating carrots
with rice and chicken broth at two different
levels were not significantly different from one
another or from the GI of the reference white
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bread (table 4). However, due to the increased
sample size, the difference became significant
as was discussed above. The observed GI
values were 101.3% and 83.3% for the higher
(260g) and the lower (130g) levels of carrots,
respectively, with a tendency of the higher
level to lower blood glucose (P=0.08). In
contrast to the GI, the postprandial II of the
lower level of Cr+R+B (67.5%) was
significantly lower than that of bread, R+B,
and the higher level of Cr+R+B (table 4). The
tendency to decrease blood glucose because it
wasaffected by the increase of the ingested
amount of carrots is consistent with what was
reported by Gustafsson, et al30 who found that
the larger the carrot portion, the lower the
glucose and insulin responses and the higher
the satiety scores that were obtained. This
lowering effect was related to the increase in
the amount of dietary fiber resulting from
increasing carrots in the dish.30During the
cooking of the carrots, physicochemical
properties of dietary fiber may be modified
and, as a consequence, certain physiological
effects may also change. For example,
glycosidic linkages in the dietary fiber can be
broken, resulting in the solubilization of
dietary fiber or its loss.31
Carrots (Daucus carota) are an important root
vegetable and are usually used for juice
production. Carrots get their characteristic and
bright orange color from β-carotene which
ismetabolized to vitamin A by humans when
bile salts are present in the intestine. Carrots
are rich in dietary fibers, antioxidants, and
minerals.32 To evaluate the effect of the dosage
on the metabolic response to vegetables added
to a mixed lunch meal, Gustafsson and his
colleagues 30 chose carrots as an example.
They found that the larger the carrot portion,
the lower the glucose and insulin responses
and the higher the satiety scores. In the revised
GI tables (2008),33 the mean GI value for
peeled and boiled carrots was 32 when using
glucose as a reference and 70 when using
white bread as a reference.
Results in table 4 show that whereas the larger
portion of carrots tended (p> 0.05) to lower the
insulinemic index of R+B to 84.2 ±7.7%, the
smaller portion significantly lowered (p> 0.05)
it II to 67.5 ±7.7%. Insulin response seems to
be a complex system as was explained before.
Incretin hormones play an important role in
insulin regulation; the hormone glucose-
dependent insulinotropic polypeptide (GIP)
and glucagon-like-peptide 1 (GLP-1) are
potent determinants of the postprandial insulin
release that occurs when blood glucose
increases.34The incretin hormones are essential
in the regulation of postprandial glycemia.35
Orskov and associates36noticed that plasma
insulin responses correlate significantly with
GIP and GLP-1 responses in healthy
volunteers. Further research work is required to
clarify the glycemic and insulinemic effect of
carrots.
The Glycemic and Insulinemic Responses to
Mulukhiyah LeavesIngested with R and B
(MLRB): Whereas the higher portion of ML
(120g) significantly lowered the GI % of R+B
from 84.2% to 34.1%, the lower level had no
effect (table 4). The corresponding II (table 4)
of R+B when eaten with ML both the lower
and higher levels were 73.7% and 61.7%,
respectively.
Insulin sensitivity as measured by CISI was
not affected by ML (table 4). This finding is in
agreement with the general conclusion arrived
at in 2005 by Innami and colleagues.37They
found that the viscous soluble dietary fibers
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that were extracted from ML had significantly
suppressed the blood glucose level in arat due
largely to the delayed absorption of glucose
from the intestinal membrane in the upper
digestive tract caused by the α-glucosidase
inhibitor present in the viscous soluble dietary
fibers of ML. This mechanism was further
confirmed in 2009 by Phuwapraisirisan and
colleagues 38 who were able to isolate from ML
new flavonol glycosides, corchorusides A and
B, which acted as α -glucosidase inhibitors.38
Mulukhiyah (Corchorus olitorius) is
commonly cultivated locally as a popular
seasonal vegetable. It is native to Egypt and the
Middle East. The stem of the plant is an
important source of fiber.39 Recently, it has
been found that the strong antioxidant activity
of the leaves of mulukhiyah is attributed to
some of its antioxidative phenolic
compounds.40 Whereas a large amount of
water-soluble polysaccharides are present in
mulukhiyah leaves,39 dietary fibers obtained
from their leaves have a high water-holding
capacity.41 The leaves are usually cooked as
fresh, frozen, or dried.
The Glycemic and Insulinemic Responses of
Spinach (S) Ingested with R +B (SRB): The
observed mean postprandial GI produced by
the two levels of spinach, 50g and 150 g,
ingested with R+B were 89.8% and 95.6%,
respectively (table 4). In contrast, it can be
observed that the higher level of spinach
lowered significantly the insulinemic response
of R+B to 42.9 ±9.0%, and the lower level had
no effect (table 4).
The findings from this study demonstrate that
spinach eaten with rice and chicken broth does
not apparently improve the postprandial
glycemic response in healthy subjects at the
two different levels used. This can be
explained by the observation that spinach
improved insulin sensitivity: CISI value was
increased significantly from 8.8 ±4.2 for R+B
alone to 17.8 ±5.1 for R=B eaten with the
higher portion of spinach (table 4), but at the
same time it decreased the amount of insulin
produced as exemplified in the AUCi, with a
net result of no change in its glycemic effect.
In other words, the apparent decrease in blood
glucose level that might have resulted due to
the improved insulin sensitivity obtained was
abolished by the lower insulin amount that
was produced by the higher portion of spinach.
Another possible explanation can be ascribed
to the smaller amount of spinach we used. It is
a coincident that Gustafsson and colleagues 42
used a large spinach portion (250 g) containing
7.2 g of fibers which resulted in a low
postprandial glycemic effect and not their 150g
portion. They did not calculate insulin
sensitivity which should have shed some light
on the physiological mechanism of the
lowering glycemic effect of spinach. Thus,
further studies are needed to have some depth
to explain this finding.
Spinach (Spinacia oleracea) is an edible
flowering plant of the family amaranthaceae.
It is native to central and southwestern Asia.43
It is a rich source of vitamin A, vitamin
C,vitamin E, and vitamin K, and it is especially
high in lutein. Gustafsson and his colleagues 42
evaluated the satiety effect of spinach in mixed
meals, using a control meal without spinach
and a test meal with spinach, both meals were
balanced regarding their energy (2000 kJ),
digestible carbohydrates (59 g) and similar
protein and fat content. They found that the
largest spinach portions (250 g in a 2000 KJ
meal) reduced the post-prandial glucose
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response in adult subjects.42
Relative Glycemic and Insulinemic Response:
Relative glycemic and relative insulinemic
response (RGR) values of the means for all the
vegetable-based dishes revealed the same
pattern of significance parallel to the GI and II
values of the individual foods from which they
were prepared (table 4). These results are in
line with what Wolever and colleagues 17
found that GI is a significant determinant of
the glycemic responses of mixed meals.
In conclusion,the glycemic and insulin
micresponses of rice and chicken broth are
improved when eaten with cooked leaves of
mulukhiyah. Whereas higher levels of cooked
carrots tended to improve the glycemic
response of rice and chicken broth, spinach
had no apparent effect on the blood glucose
level in spite of the fact it apparently
improved insulin sensitivity. It was further
noticed that there was no difference between
the calculated relative glycemic response for
all the vegetable-based dishes and the GI
values of the individual foods from which
they were prepared, suggesting that the GI is a
significant determinant of the glycemic
response of mixed meals.
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ﻡﺪﻟﺍ ﲔﻟﻮﺴﻧﺇﻭ ﺯﻮﻛﻮﻠﻏ ﻰﻠﻋ ﺓﻮﻬﻄﳌﺍ ﺦﻧﺎﺒﺴﻟﺍﻭ ﺔﻴﺧﻮﻠﳌﺍﻭ ﺭﺰﳉﺍ ﻝﻭﺎﻨﺗ ﲑﺛﺄﺗ
ﺯﺭﻸﻟ ﺭﺎﺨﺒﻟﺎﺑ ﻮﻬﻄﳌﺍ
ﻪﻴﻘﻔﻟﺍ ﺪﲪﺃ،
1
ﺐﻴﻄﳋﺍ ﺔﻨﻴﺜﺑﻭ
2
1- ،ﺔﻋﺍﺭﺰﻟﺍﺔﻴﻠﻛ ،ﺫﺎﺘﺳﺍﺔﻴﻧﺩﺭﻷﺍ ﺔﻌﻣﺎﳉﺍ؛ 2 - ،ﺔﻋﺍﺭﺰﻟﺍ ﺔﻴﻠﻛ ،ﺔﻳﺬﻐﺗ ﲑﺘﺴﺟﺎﻣ ﺔﻴﻧﺩﺭﻷﺍ ﺔﻌﻣﺎﳉﺍ
ﺺﺨﻠﳌﺍ
ﺔﻴﻔﻠﳋﺍ
:ﱂﺎﻌﻟﺍ ﻥﺍﺪﻠﺑ ﻦﻣ ﻩﲑﻏﻭ ﻥﺩﺭﻷﺍ ﺯﺭﻷﺍ ﻊﻣ ﺕﺍﻭﺍﺮﻀﳋﺍ ﻝﻭﺎﻨﺗ ﻊﻴﺸﻳ. ﺐﻌﻠﺗﻭ ﲔﻟﻮﺴﻧﺇﻭ ﺯﻮﻛﻮﻠﻏ ﻢﻴﻈﻨﺗ ﺍﺭﻭﺩ ﺔﻴﺋﺍﺬﻐﻟﺍ ﻑﺎﻴﻟﻷﺍ
ﺔﺻﺎﺧ ﻱﺮﻜﺴﻟﺍ ﻰﺿﺮﻣﻭ ﺀﺎﺤﺻﻷﺍ ﻯﺪﻟ ﻡﺪﻟﺍ.
ﻑﺪﳍﺍ
: ﺮﺷﺆﻣ ﻰﻠﻋ ﺓﻮﻬﻄﳌﺍ ﺭﺰﳉﺍﻭ ﺦﻧﺎﺒﺴﻟﺍﻭ ﺔﻴﺧﻮﻠﳌﺍ ﻦﻣ ﻞﻛ ﻝﻭﺎﻨﺘﻟ ﺮﺷﺎﺒﳌﺍ ﲑﺛﺄﺘﻟﺍ ﺔﻓﺮﻌﻣ ﱃﺇ ﺔﺳﺍﺭﺪﻟﺍ ﺖﻓﺪﻫ ﻢﺟﺎﻨﻟﺍ ﻡﺪﻟﺍ ﲔﻟﻮﺴﻧﺇﻭ ﺮﻜ
ﺯﺭﻷﺍ ﻊﻣ ﺕﺍﻭﺍﺮﻀﳋﺍ ﻩﺬﻫ ﻝﻭﺎﻨﺗ ﻦﻋ ﻭﺭﺎﺨﺒﻟﺎﺑ ﻮﻬﻄﳌﺍ ﺝﺎﺟﺪﻟﺍ ﻕﺮﻣ ﻊﻣ ﻝﻭﺎﻨﺘﳌﺍ.
ﺔﻘﻳﺮﻄﻟﺍ
: ﻩﺬﻫ ﻝﻭﺎﻨﺗ ﻦﻋ ﻢﺟﺎﻨﻟﺍ ﻡﺪﻟﺍ ﲔﻟﻮﺴﻧﺇﻭ ﺮﻜﺳ ﺮﺷﺆﻣ ﻰﻠﻋ ﺦﻧﺎﺒﺴﻟﺍﻭ ﺔﻴﺧﻮﻠﳌﺍﻭ ﺭﺰﳉﺍ ﲑﺛﺄﺗ ﺔﺳﺍﺭﺪﻟ ﻡﺪﻟﺍ ﺯﻮﻛﻮﻠﻏ ﻞﻤﲢ ﺭﺎﺒﺘﺧﺍ ﻱﺮﺟﺃ
ﳌﺍ ﺾﻴﺑﻻﺍ ﺯﺭﻷﺍ ﻊﻣ ﺓﻮﻬﻄﳌﺍ ﺕﺍﻭﺍﺮﻀﳋﺍﺝﺎﺟﺪﻟﺍ ﻕﺮﻣ ﻊﻣ ﻝﻭﺎﻨﺘﳌﺍ ﺭﺎﺨﺒﻟﺎﺑ ﻮﻬﻄ .ّﺤ ﺻ ﺃ ﺹﺎﺨﺷﺃ ﺔﺳﺍﺭﺪﻟﺍ ﻩﺬﳍ ﻉﻮﻄﺗﻥﻮﻐﻟﺎﺑ ﺀﺎ، ﻎﻠﺑ
ﻢﻫﺭﺎﻤﻋﺃ ﻂﺳﻮﺘﻣ25.4 ﺔﻨﺳ)± 1.28 ﺱﺎﻴﻘﻟﺍ ﺄﻄﺧ ﻝﺪﻌﻣ( ﻂﺳﻮﺘﻣ ﻎﻠﺑ ﺎﻤﻛ ،ﺔﺒﺴﻧ ﻢﻬﻣﺎﺴﺟﺃ ﺔﻠﺘﻛ21.6 ﻢﻐﻛ/2 )± 1.0( ﻊﺘﲤﻭ ،
ﺯﻮﻛﻮﻠﻐﻟﺍ ﻞﻤﲢ ﺭﺎﺒﺘﺧﻻ ﺔﻴﻌﻴﺒﻃ ﺞﺋﺎﺘﻨﺑ ﻢﻬﻌﻴﲨ.
ﺞﺋﺎﺘﻨﻟﺍ
: ﺔﻠﺘﻛ ﺮﺷﺆﻣ ﺾﻔﳔﺍ ﻝﻭﺎﻨﺘﺑ ﻕﺮﳌﺍ ﻊﻣ ﺯﺭﻸﻟ ﻡﺪﻟﺍ ﺮﻜﺳ120 ﻝﻭﺎﻨﺘﺑ ﺽﺎﻔﳔﻻﺍ ﱃﺇ ﺮﺷﺆﳌﺍ ﺍﺬﻫ ﻝﺎﻣﻭ ،ﺔﻴﺧﻮﻠﳌﺍ ﻦﻣ ﻢﻏ260 ﻢﻏ
ﻮﻬﻄﳌﺍ ﺦﻧﺎﺒﺴﻟﺍ ﻝﻭﺎﻨﺘﺑ ﺎﻳﺮﻫﺎﻇ ﺮﺛﺄﺘﻳ ﻪﻨﻜﻟﻭ ،ﻮﻬﻄﳌﺍ ﺭﺰﳉﺍ ﻦﻣ .ﻡﺪﻟﺍ ﲔﻟﻮﺴﻧﺇ ﺮﺷﺆﻣ ﺎﻣﺃ، ﻝﻭﺎﻨﺘﺑ ﺱﻮﻤﻠﻣ ﻞﻜﺸﺑ ﺾﻔﳔﺍ ﺪﻘﻓ120 ﻢﻏ
ﻭﺃ ﺔﻴﺧﻮﻠﳌﺍ ﻦﻣ130 ﻭﺃ ﺭﺰﳉﺍ ﻦﻣ ﻢﻏ150 ﻢﻏﻂﻘﻓ ﺦﻧﺎﺒﺴﻟﺍ ﻝﻭﺎﻨﺘﺑ ﻱﺮﻫﻮﺟ ﻞﻜﺸﺑ ﲔﻟﻮﺴﻧﻹﺍ ﺔﻴﺳﺎﺴﺣ ﺖﻨﺴﲢ ﺪﻗﻭ ﺦﻧﺎﺒﺴﻟﺍ .
ﺕﺎﺟﺎﺘﻨﺘﺳﻻﺍ
:ﻭﺫ ﻦﺴﲢ ﺙﺪﺣ ﺍﺬﻫ ﻦﻜﻟﻭ ،ﺔﻴﺧﻮﻠﳌﺍ ﻦﻣ ﺎﻴﺒﺴﻧ ﺔﻴﻟﺎﻋ ﺔﻴﻤﻛ ﻊﻣ ﻪﻟﻭﺎﻨﺗ ﲔﺣ ﺥﻮﺒﻄﳌﺍ ﺯﺭﻸﻟ ﻡﺪﻟﺍ ﺮﻜﺳ ﺮﺷﺆﳌ ﺔﻳﻮﻨﻌﻣ ﺔﻟﻻﺩ
ﺘﻳ ﻪﻨﻜﻟﻭ ،ﺭﺰﳉﺍ ﻦﻣ ﻰﻠﻋﻷﺍ ﺔﻴﻤﻜﻟﺍ ﻊﻣ ﻪﻟﻭﺎﻨﺘﺑ ﻦﺴﺤﺘﻟﺍ ﱃﺇ ﻝﺎﻣ ﺮﺷﺆﳌﺍﺦﻧﺎﺒﺴﻟﺍ ﻊﻣ ﻪﻟﻭﺎﻨﺘﺑ ﺎﻳﺮﻫﺎﻇ ﺮﺛﺄ . ﲔﻟﻮﺴﻧﺇ ﺮﺷﺆﻣ ﻯﻮﺘﺴﻣ ﺾﻔﳔﺍ
ﻝﻭﺎﻨﺘﺑ ﻻﺇ ﻦﺴﺤﺘﺗ ﻢﻠﻓ ﺯﺭﻷﺍ ﻝﻭﺎﻨﺗ ﻦﻋ ﺔﲨﺎﻨﻟﺍ ﲔﻟﻮﺴﻧﻹﺍ ﺔﻴﺳﺎﺴﺣ ﺎﻣﺃ ،ﺕﺍﻭﺍﺮﻀﳋﺍ ﻩﺬﻫ ﻦﻣ ﻱﺃ ﻊﻣ ﻪﻟﻭﺎﻨﺗ ﲔﺣ ﺔﻳﻮﻨﻌﻣ ﺔﻟﻻﺪﺑ ﺯﺭﻸﻟ ﻡﺪﻟﺍ
ﺦﻧﺎﺒﺴﻟﺍ.
ﺔﻟﺍﺪﻟﺍ ﺕﺎﻤﻠﻜﻟﺍ: ،ﺔﻴﺧﻮﻠﳌﺍ ،ﻡﺪﻟﺍ ﲔﻟﻮﺴﻧﺍ ﺮﺷﺆﻣ ،ﻡﺪﻟﺍ ﺮﻜﺳ ﺔﻠﺘﻛ ﺮﺷﺆﻣﲔﻟﻮﺴﻧﻷﺍ ﺔﻴﺳﺎﺴﺣ ،ﺭﺰﺟ ،ﺦﻧﺎﺒ.
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