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Glycemic Index Determination of Vegetable and Fruits in Healthy Bangladeshi Subjects 393
Mal J Nutr 17(3): 393 - 399, 2011
Short Communication
Glycemic Index Determination of Vegetable and Fruits in
Healthy Bangladeshi Subjects
Fatema K1, Sumi N1, Rahman F1, Kobura K1 & Ali L2
1Dept of Epidemiology, Bangladesh Institute of Health Sciences (BIHS), 125/1 Darus Salam, Mirpur,
Dhaka-1216, Bangladesh
2Dept of Biochemistry & Cell Biology, Bangladesh Institute of Health Sciences 125/1 Darus Salam,
Mirpur, Dhaka-1216, Bangladesh
ABSTRACT
Introduction: Fruits and vegetables are an important part of the diet especially
for their complex carbohydrates, dietary fibre and micronutrients. The present
study investigated the glycemic index (GI) of a vegetable [carrot (Daucas carota)]
and fruits [banana (Chapa kola) Musa Sp. and plum (Bau kul) Zizyphus mauritiana] of
Bangladeshi origin. Methods: Fourteen healthy Bangladeshi subjects, comprising
7 males and, 7 females, with mean age of 26 ± 3 years, BMI 22 ± 3 kg/m2, waist-
hip ratio of 0.89 ± 0.01 and 0.84 ± 0.04 respectively for males and females. Under
a cross-over design, they consumed equi-carbohydrate amounts (25 g of total
available carbohydrate) of the test foods and two times glucose as reference
food (25 g of total carbohydrate), with a run in period of 7 days between the
consecutive items. Serum glucose levels were determined at 0, 30, 60, 90, and 120
min. The GIs was calculated. Results: The carrot, banana and plum samples
showed significantly lower serum glucose values (incremental area under the
curve 30.4 + 12.6, 37.3 + 19.2 and 41.8 + 20.7 respectively) than glucose (132.7±
36.0). The carrot showed a lower GI value than banana and plum respectively (23
± 9, 30 ± 18 and 32 ± 15). Conclusion: The vegetable and fruit samples tested of
Bangladesh origin were shown to have comparatively low GI values.
Keywords: Carbohydrate, diet, fruits, glycemic index, glycemic load, vegetables
* Correspondence author: Kaniz Fatema; Email: kfatema@bihs.edu.bd; kanizfatemadina@pushti.org
INTRODUCTION
Dietary guidelines recommend increased
intake of dietary fibre for better control and
proper management of chronic diseases
such as diabetes mellitus, cardiovascular
disease and cancer (Food and Nutrition
Research Institute, Phillipines, 2000). The
physical and chemical properties of dietary
fibre, for example, its viscosity and fibrous
structure, have an important role in the
release and absorption of nutrients in spite
of having different amounts of
carbohydrates. Post-prandial glycemia is
influenced by both the amount and the type
of carbohydrates in the foods. The nature of
carbohydrates is best described by their
glycemic indices (GIs) (WHO, 2010). GI is
defined as the incremental area under the
blood glucose response curve following
consumption of a food portion containing
50 g of available carbohydrates relative to
Fatema K, Sumi N, Rahman F, Kobura K & Ali L
394
that produced by a portion of a control food
(either glucose or white bread) containing
the same amount of carbohydrate. GI is a
useful indicator to rank the biological
response of dietary carbohydrates and can
be converted to a practical tool referred to as
the glycemic load (GL) for routine dietary
advice. The GL is determined by multiplying
the GI of a food by the grams of
carbohydrates in a serving (Foster-Powell,
Holt & Brand- Miller, 2002).
Recent evidence suggests that high GI/
GL diets may increase the risk for
cardiovascular diseases (Liu et al., 2000;
Amano et al., 2004) and type 2 diabetes
(Hodge et al., 2004; Schulze et al., 2004). Due
to inherent botanical differences of foods
from different countries, the GI of food
products can differ (Foster-Powell et al.,
2002). Emphasis has been given on the need
for individual countries to carry out their
own GI testing, particularly with raw
agricultural products like vegetables, fruits
and rice which are more likely to vary from
one geographical location to another
(Rahman et al., 2011; Fatema et al., 2011).
This study was conducted with carrot
(Daucas carota), banana (Musa Sp.) and plum
(Zizyphus mauritiana) which are very
commonly consumed in Bangladesh
(Razzaque & Hossain, 2007).
The nutritional value of these fruits and
vegetables makes them an excellent choice
for both weight control and general health.
Carrot contains 87% of water, is rich in
calcium and high in fibre (BCSIR, 2009).
Plum is a good source of vitamin C (BCSIR,
2009). Both the banana and the plum are the
richest sources of calcium (BCSIR, 2009). The
objectives of the study were to determine
blood glucose response after consuming
three types of Bangladeshi vegetables and
fruits as well as their GI and GL values in
healthy Bangladeshi respondents.
METHODS
Fourteen healthy subjects constituted the
sample for this study after obtaining their
informed consent. The inclusion criteria for
the selection of the subjects were age
between 18 to 45 years, BMI below 25 kgm2,
not on any medication and with a fasting
blood glucose <110 mg per dl (6.1 mmol per
L) (WHO, 1980). They were requested to
maintain their usual daily food intake and
activity schedule throughout the study
period.
The protocol was approved by the
Ethical Review Committee of the Diabetic
Association of Bangladesh.
The subjects were requested to go
through the study protocol on five separate
occasions (one trial for each test food and
two repeated trials for the reference food) in
the morning after a 10–12 h overnight fast.
The test with the reference food was repeated
to obtain at least two values in each subject,
thus improving the precision (Brouns et al.,
2005). The test and reference meals were
given to the subjects under a cross-over
design with a wash out period of 7 days to
avoid the ‘second meal effect’. The subjects
were advised to rely on recommended
standard carbohydrate diet and also
instructed not to eat legumes in the meal
preceding the fast (Table 1).
An intravenous cannula was inserted
into a superficial vein in the forearm on the
day of experiment to draw the fasting (0 hr)
blood sample of the subjects. Subjects were
requested to consume the test food with 250
ml plain water (during the protocol of the
test foods) or the glucose in 250 ml of water
(during the protocol of the reference food) in
random order at a comfortable place within
10 min of each intake. Further blood samples
were drawn at 30, 60, 90 and 120 min after
the initial intake of sample. All the
information and data obtained were
recorded in a predesigned Case Record Form.
Blood samples were centrifuged at 3000 rpm
for 15 min. The separated plasma was
allocated into labeled Eppendorf tubes and
preserved at –70°C until biochemical
analysis. Serum glucose was analysed by
glucose oxidase (GOD-PAD) method using
reagents from SERA PAK, USA.
Glycemic Index Determination of Vegetable and Fruits in Healthy Bangladeshi Subjects 395
All analyses were done using the SPSS
version 11.5. The incremental areas under
the curve (iAUC) were calculated by the
standardised criteria, ignoring the area
below the baseline level. The average iAUC
for the two glucose tests was used as the
reference value and each subject’s GI for each
food was calculated. The GL for each food
was calculated using serving size practised
in Bangladesh. Significance between the
mean values of GI was calculated using
paired t-test. All parametric variables are
expressed as M ± SD and non-proportional
data are expressed in percentages with p<
0.05 and p< 0.001 considered as statistically
significant.
RESULTS
The participants consisted of 7 males and 7
females aged 26 ± 3 years (mean ± SD). Their
mean BMI was 22 ± 3 kg/m2, while their mean
waist-hip ratio for the males and females
were 0.89 ± 0.01 and 0.84 ± 0.04 respectively.
A significantly different pattern of blood
glucose response was observed during the 2
h of dietary regime (Figure 1). The lower
serum glucose responses to carrot (p<0.001)
at 30 and 60 min showed a significant
difference compared to glucose. The banana
showed a significantly lower serum glucose
value compared to glucose at 30 min
(p<0.001), 60 min (p<0.01) and 90 min
(p<0.05). The banana also showed both
significantly lower and higher serum
glucose values compared to carrot at 30 min
(p<0.05) and at 60 min (p<0.01) respectively.
There were significant lower serum glucose
responses to plum (p<0.001) at 30 min and
(p<0.01) at 60 min compared to glucose. The
plum showed higher (p<0.05) significant
differences compared to carrot at 30 and 60
min and was also significantly higher
(p<0.001) at 30 min compared to the banana.
The iAUC values of carrot, banana and plum
were significantly lower than that of glucose
(incremental area under the curve 30.4 ± 12.6
in carrot, 37.3 ± 19.2 in banana and 41.8 ±
20.7 in plum vs 132.7± 36.0 in glucose;
(p<0.0001) (Table-2).
Judged against the mean values of the
international table (GI: High > 70, Medium
56-69 and low < 55; GL: High > 20, Medium
11-19 and low < 10), the carrot had a lower
GI value than the banana and plum
[(mean±SD): 23 ± 9 in carrot, 30 ± 18 in
banana and 32 ± 15 in plum]. The GL of
carrot, banana and plum were 1, 2 and 1.4
respectively (Table-2).
DISCUSSION
The results showed that even at a constant
amount of available carbohydrate in the test
foods (25 g available carbohydrate), there
were significant variations in the glycemic
response, confirming that equi-carbohydrate
portions of different foods may not
Table 1. Nutrient composition of the Test Meals (g per 100 g)
Sample Moisture Ash Protein Fat Crude CHO Vit-c Iron Calcium Energy
(%) (%) (%) (%) Fiber (%) (%) (%) (%) (Kcal/100gm)
(%) (Calculation)
Carrot 87.00 0.30 1.51 0.92 1.0 9.27 6.00 0.80 31.72 51.40
Banana 74.04 0.66 2.84 0.60 0.40 21.46 15.00 0.50 40.00 102.60
(Chapa kola)
Plum(Bau kul) 80.00 0.25 1.50 0.18 0.50 17.57 27.01 1.50 49.11 77.90
Source: Values were taken from Institute of Food Science and Technology (BCSIR), Dhaka, Bangladesh
2009.
Determination of the macronutrient and micronutrient analysis was done by the AOAC method.
Fatema K, Sumi N, Rahman F, Kobura K & Ali L
396
necessarily have the same glycemic effect on
human subjects. The blood glucose response
after consuming carrot was significantly
lower when compared with glucose
(p<0.001). The banana and plum also
showed lower glycemic responses compared
to glucose. These lower glycemic responses
were also reflected in their GI values.
In order to give good dietary advice, it is
necessary to know the glycemic index of
different foodstuffs in different ethnic and
cultural settings. The GI of carrot has been
studied in Australia (low GI) but in Canada,
it was found to show a high GI on a healthy
population study compared with the
reference food glucose, respectively ( Brand-
Miller et al., 1998). A low GI of ripe banana
was reported in USA (Brand et al., 1990). Low
GIs after consumption of raw plum were
reported in Canada, and in Italy on type 2
diabetic subjects compared with the reference
food glucose, respectively. These
discrepancies between studies may be due
partly to the fibre content (Augustin et al.,
2002), variations in botanical sources (Brand-
Miller et al., 1992) and the moisture content
of the fruits and vegetables. This also seems
to depend on the adaptation of the gut to
specific food types in different populations
(Larsen, Rasmussen & Rasmussen, 2000).
In this study we have also calculated
the glycemic load (GL) values which express
the glycemic effect of realistic serving sizes
of different foods. The GL can be defined as
the product of the glycemic index (GI) of a
food and the amount of carbohydrate in a
serving (Foster-Powell et al., 2002). Based on
the serving size in Bangladeshi society, the
test vegetables and fruits can be considered
as very low GL food. So, based on the quality
and quantity of carbohydrates, these fruits
and vegetables would be very beneficial for
diabetic patients as well as for healthy
subjects (USDA,USDHHS, 2000).
Fibre rich foods with a low postprandial
glycemic response are generally considered
valuable. High fibre is believed to be able to
reduce the blood glucose response and hence
lower the GI value. Vegetables and fruits
are excellent components of a diet because
of their high nutritional values (particularly
with respect to micronutrients). To prescribe
Figure 1. Comparison of three test foods with a reference food (n-14)
Glycemic Index Determination of Vegetable and Fruits in Healthy Bangladeshi Subjects 397
Table 2. Glycemic responses of the study subjects at different time intervals after ingestion of test meals (n=14)
Test foods Serum glucose (mmol/l) iAUC GI GL
(mmol/l) (M±SD)
0 min 30 min 60 min 90 min 120 min
Glucose 4.9 ± 0.5 7.4 ± 0.9 6.5 ± 1.1 5.0 ± 0.7 4.5 ± 0.5 132.7 ± 36.0
(100) (149 ± 14) (132 ± 21) (103 ± 14) (93 ± 7)
Carrot 4.8 ± 0.3 5.7 ± 0.4 4.9 ± 0.5 4.8 ± 0.4 4.8 ± 0.4 30.4 ± 12.6 23 ± 9 1
(100) (117 ± 6) (100 ± 8) (99 ± 9) (98 ± 6) a***
a*** a***
Banana (Chapa kola) 4.8 ± 0.3 5.3 ± 0.5 5.5 ± 0.6 4.5 ± 0.5 4.5 ± 0.3 37.3 ± 19.2 30 ± 18 2
(100) (110 ± 8) (115 ± 13) (95 ± 10 ) (95 ± 4) a***
a***b* a**b** a*
Plum (Bau kul) 5.1 ± 0.4 6.1 ± 0.6 5.3 ± 0.5 4.9 ± 0.5 4.8 ± 0.3 41.8 ± 20.7 32 ± 15 1.4
(100) (122 ± 11) (106 ± 6) (97 ± 6) (95 ± 4) a***
a*** b* c*** a**b*
Results expressed as mean ± SD; *p < 0.05 and **p < 0.01 was taken as the level of significance in paired students t-test; a, Glucose;
b, Carrot; c, Banana; d, Plum. Carrot, Banana and Plum have 9.27/100 g, 21.46 /100 g and 17.57 /100 g of carbohydrate respectively. To
calculate GL, serving size for Carrot was 50 g/serve and for Banana and Plum were 25 g/serve; n, Number of subjects; iAUC, Increment
area under the curve. There were no statistically significant differences in GI & GL values.
Fatema K, Sumi N, Rahman F, Kobura K & Ali L
398
a particular food, it is important to consider
how rapidly the glucose level rises and falls
as abrupt rises may lead to unusual demand
for insulin secretion from pancreatic
β
cells.
The results of three test meals have shown
that at pos-prandial stage after two hours,
all the foods maintained the serum glucose
levels at the same level.
The study limitations include purchase
of the test foods at different times. This might
have led to possible differences in glycemic
index values, possibly owing to seasonal
variations.
ACKNOWLEDGEMENT
The study was supported by grants from the
International Program in the Chemical
Science (IPICS), Uppsala University, Sweden
and Biomedical Research Group (BMRG) of
BIRDEM. We express our gratitude to all
the subjects who participated in this study.
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