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Glycaemic index of selected staples commonly eaten in the Caribbean and the effects of boiling v. crushing

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Integrating information about the glycaemic index (GI) of foods into the Caribbean diet is limited by the lack of data. Therefore, we determined the GI of eight staple foods eaten in the Caribbean and the effect on GI of crushing selected tubers. Groups of eight to ten healthy volunteers participated in three studies at two sites. GI was determined using a standard method with white bread and adjusted relative to glucose. The mean area under the glucose response curve elicited by white bread was similar for the different groups of subjects. In study 1, the GI of cassava (Manihot esculenta; 94 (sem 11)) was significantly higher than those of breadfruit (Artocarpus altilis; 60 (sem 9)), cooking 'green' banana (Musa spp.; 65 (sem 11)) and sadha roti (65 (sem 9)) (P=0.018). There was no significant difference in the GI of the foods in study 2: dasheen (Colocasia esculenta var. esculenta; 77 (sem 10)), eddoes (Colocasia esculenta var. antiquorum; 61 (sem 10)), Irish potato (Solanum tuberosum; 71 (sem 8)), tannia (Xanthosoma sagittifolium; 60 (sem 5)) and white yam (Dioscorea alata; 62 (sem 6)), and, in study 3, crushing did not significantly affect the GI of dasheen, tannia or Irish potato. However, when the results from studies 2 and 3 were pooled, the GI of dasheen (76 (sem 7)) was significantly greater than that of tannia (55 (sem 5); P=0.015) with potato being intermediate (69 (sem 6)). We conclude that dasheen and cassava are high-GI foods, whereas the other tubers studied and sadha roti are intermediate-GI foods. Given the regular usage of cassava and dasheen in Caribbean diets we speculate that these diets would tend to be high GI, although this could be reduced by foods such as sadha roti and white yam. The range of GI between the staples is sufficiently large that health benefits may be accrued by replacing high-GI staples with intermediate-GI staples in the Caribbean diet.
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Glycaemic index of selected staples commonly eaten in the
Caribbean and the effects of boiling v. crushing
D. Dan Ramdath
1
, Rene
´
e L. C. Isaacs
2
, Surujpal Teelucksingh
3
and Thomas M. S. Wolever
2
*
1
Department of Preclinical Sciences, Faculty of Medical Sciences, The University of the West Indies, St Augustine,
Trinidad and Tobago
2
Department of Nutritional Sciences, University of Toronto, Faculty of Medicine, Toronto, Ontario, M5A 3E2,
Canada
3
Clinical Medical Sciences, Faculty of Medical Sciences, The University of the West Indies, St Augustine,
Trinidad and Tobago
(Received 22 July 2003 – Revised 22 January 2004 Accepted 11 February 2004)
Integrating information about the glycaemic index (GI) of foods into the Caribbean diet is limited by the lack of data. Therefore, we deter-
mined the GI of eight staple foods eaten in the Caribbean and the effect on GI of crushing selected tubers. Groups of eight to ten healthy
volunteers participated in three studies at two sites. GI was determined using a standard method with white bread and adjusted relative to
glucose. The mean area under the glucose response curve elicited by white bread was similar for the different groups of subjects. In study
1, the GI of cassava (Manihot esculenta;94(
SEM 11)) was significantly higher than those of breadfruit (Artocarpus altilis;60(SEM 9)),
cooking ‘green’ banana (Musa spp.; 65 (
SEM 11)) and sadha roti (65 (SEM 9)) (P¼ 0·018). There was no significant difference in the GI of
the foods in study 2: dasheen (Colocasia esculenta var. esculenta; 77 (
SEM 10)), eddoes (Colocasia esculenta var. antiquorum; 61 (SEM
10)), Irish potato (Solanum tuberosum;71(SEM 8)), tannia (Xanthosoma sagittifolium;60(SEM 5)) and white yam (Dioscorea alata;62
(
SEM 6)), and, in study 3, crushing did not significantly affect the GI of dasheen, tannia or Irish potato. However, when the results from
studies 2 and 3 were pooled, the GI of dasheen (76 (
SEM 7)) was significantly greater than that of tannia (55 (SEM 5); P¼ 0·015) with potato
being intermediate (69 (
SEM 6)). We conclude that dasheen and cassava are high-GI foods, whereas the other tubers studied and sadha roti
are intermediate-GI foods. Given the regular usage of cassava and dasheen in Caribbean diets we speculate that these diets would tend to
be high GI, although this could be reduced by foods such as sadha roti and white yam. The range of GI between the staples is sufficiently
large that health benefits may be accrued by replacing high-GI staples with intermediate-GI staples in the Caribbean diet.
Glycaemic index: Caribbean: Diabetes: Glucose
The glycaemic index (GI) is a classification of the glu-
cose-rising potential of carbohydrate foods relative to glu-
cose (Wolever et al. 1991). Recent studies have shown
that the regular consumption of diets containing high-GI
foods is associated with an increased risk for type 2 dia-
betes mellitus (Salmeron et al. 1997a,b) and CHD (Ford
& Liu, 2001; Liu & Manson, 2001). In contrast, the
inclusion of low-GI foods in the diet, with no change
in the total amount of carbohydrate consumed, may
improve blood glucose control (Brand et al. 1992),
reduce serum triacylglycerols (Jenkins et al. 1987), pro-
long endurance during physical activity (Thomas et al.
1991) and improve insulin sensitivity (Byrnes et al.
1995; Frost et al. 1998). The GI may therefore provide
the rationale for choosing carbohydrate foods for meal
plans created for individuals with diabetes (Food and
Agriculture Organization of the United Nations, 1998).
In addition, low-GI diets could be incorporated into
health promotion messages for the reduction of risk for
type 2 diabetes and CHD.
In the Caribbean, type 2 diabetes and CHD are the lead-
ing causes of morbidity and mortality. In Trinidad and
Tobago the prevalence of diabetes is the highest in the
Caribbean and approximately six times higher than that in
North America (Gulliford et al. 1995; Gulliford, 1996).
The annual financial cost of admission for diabetes has
been conservatively estimated at TT$ 10·66 million (UK
£1·24 million) (Gulliford et al. 1995). Predominantly a
migrant population from Africa and South Asia, the Carib-
bean has in turn seeded a secondary wave of migrants to
many metropolitan areas of North America and Europe.
In developed countries, migrant Caribbean populations con-
tinue to have a high incidence of diabetes wherever they
have settled (Cruickshank et al. 1991; Cooper et al. 1997).
* Corresponding author: Professor Thomas Wolever, fax þ 1 416 978 5882, email thomas.wolever@utoronto.ca
Abbreviations: AUC, area under the glucose response curve; GI, glycaemic index; RS, resistant starch.
British Journal of Nutrition (2004), 91, 971–977 DOI: 10.1079/BJN20041125
q The Authors 2004
Caribbean guidelines for the dietary management of
diabetes and CHD risk reduction are based on six food
groups, and the main dietary staples are ‘ground pro-
visions’ and ‘grains and cereals’ (Caribbean Food and
Nutrition Institute, 1994). Foods in the former group
include tubers, breadfruit (Artocarpus altilis) and cooking
‘green’ banana (Musa spp.), which is a different variety
from dessert banana and is eaten in the immature stage.
These provisions are usually cooked by boiling, but may
also be crushed after being boiled. Another important
source of carbohydrate is sadha roti; a wheat-based lea-
vened bread, which is commonly eaten in Caribbean
islands with a large South Asian population. The GI of
these foods are not known and as such their inclusion in
the menus for individuals with diabetes has been based
mainly on reducing fat intakes and increasing intakes of
complex carbohydrates (Caribbean Food and Nutrition
Institute, 1994). An understanding of the physiological
basis of carbohydrate exchange, as classified by the GI,
may assist in optimising healthy food choices in the Carib-
bean and in emigrant populations. As such, knowledge of
the GI of staples commonly used by Caribbean individuals
could contribute to evidence-based meal planning and
implementation of culturally sensitive risk-reduction diet-
ary interventions.
In the present two-centre study the GI for boiled tubers,
breadfruit, cooking banana, and sadha roti were determined
in healthy volunteers. In another study the effect of crush-
ing on the GI of selected tubers was also evaluated, since
preparation methods and differing starch characteristics
can both affect GI (Soh & Brand-Miller, 1999).
Methods
Study design
Parallel studies were conducted at the Department of Pre-
clinical Sciences, University of the West Indies, Trinidad
and Tobago (site 1) and at the Department of Nutritional
Sciences, University of Toronto, Canada (site 2) using a
standard protocol as outlined by Wolever et al. (1991).
The respective institutional ethics review committee
approved the protocols and informed consent was obtained
from all volunteers. The power of the tests with ten sub-
jects was set at 80 % to detect a 22 % difference in areas
under the glucose response curves (AUC) between the
foods. This calculation assumed a variation of 22 %
within subjects (Wolever et al. 1991).
Reference food
White bread was prepared at both study sites using the
recipe previously described (Wolever et al. 1994). In the
absence of a bread maker at site 1 the ingredients were
manually mixed and kneaded over a 3 h period, and
baked in an electric oven at 1908C for 35 min. At both
study sites loaves were cooled at room temperature for
1 h, weighed, cut into 50 g available carbohydrate portions
(discarding the crust ends), placed in plastic bags and
frozen. Before consumption the bread was warmed for
1 min in a microwave oven.
Test foods and preparation
These included breadfruit, cassava (Manihot esculenta),
dasheen (Colocasia esculenta var. esculenta), eddoes
(Colocasia esculenta var. antiquorum), cooking ‘green’
banana, tannia (Xanthosoma sagittifolium), Irish potato
(Solanum tuberosum), and white yam (Dioscorea alata).
Additionally, the leavened wheat-based bread, sadha roti,
was tested. Foods eaten at site 1 were obtained on the
day of harvest. With the exception of Irish potatoes, the
foods eaten at site 2 were obtained from the local immi-
grant market and were usually about 1 week post-harvest.
In all cases the inedible portions of the tubers were
removed and discarded; for cassava and breadfruit this
included both the peel and core. For the remaining tubers
and cooking ‘green’ banana the peel was removed. The
edible portions were washed and allowed to air dry at
room temperature for 10 min; they were then cut into
chunks of approximately 25 mm, and 50 g available carbo-
hydrate portions (see Table 1) were boiled with minimal
water and a pinch of salt. With the exception of breadfruit
(18 and 8 min) and green banana (15 and 8 min) the tubers
were cooked by gently boiling with the lid of the cooking
vessel on for 20 min, followed by simmering heat and the
lid off for a further 10 min. At site 1 the test foods
(except sadha roti) were prepared in weekly batches,
allowed to cool at room temperature (about 258C) for
10 min and stored in plastic bags at 2 208C. These were
thawed at room temperature and warmed for 1 min in a
Table 1. Composition of test foods (per 50 g available carbohydrate)*
Food Weight (g) Protein (g) Fat (g) Total carbohydrate (g) Fibre (g)
Dasheen† 131 0·4 0·3 52·1 2·2
Eddoes† 221 4·9 0·7 53·4 3·4
Irish potato† 151 1·9 0·2 53·8 3·8
Tannia† 135 2·6 0·3 52·0 2·0
White yam† 300 5·8 0·2 52·1 2·1
White flour‡ 67 6·9 0·7 51·8 1·8
Cassava‡ 159 4·9 0·6 54·0 4·0
Green banana‡ 223 2·7 1·0 54·9 4·9
Breadfruit‡ 216 2·4 0·4 53·2 3·2
* Available carbohydrate was calculated by difference.
Proximate and dietary analysis using standard AOAC methods.
Taken from Food Composition for the Caribbean (Caribbean Food and Nutrition Institute, 1998).
D. D. Ramdath et al.972
microwave oven before consumption. At site 2 the test
tubers were prepared on the day before each test, allowed
to cool (228C) for 10 min and refrigerated; they were
heated in a microwave oven for 1 min before being
served. At site 1 sadha roti was prepared on the test day
from 67·3 g portions of white flour (Five Roses; ADM
Agri-Industries Ltd, Decatur, IL, USA). The flour was
dry mixed with 1 g salt and 1 g baking powder. Following
the addition of approximately 50 ml water the mixture was
kneaded to produce a soft dough. A ball of dough was then
flattened with a rolling pin to approximately 150 mm in cir-
cumference and 12·5 mm thick. It was then evenly cooked
on a hot plate at moderate heat for 5 min, turning occasion-
ally until done.
Study 1
At site 1, eight normal volunteers (age 25·4 (
SEM 1·5)
years; four male, four female; BMI 21·5 (
SEM 0·8) kg/m
2
)
ate cassava, breadfruit, cooking ‘green’ banana and sadha
roti. The portion sizes were based on published values
for total carbohydrate and dietary fibre (Caribbean Food
and Nutrition Institute, 1998) and available carbohydrate
was calculated by difference (Table 1).
Study 2
At site 2, ten normal volunteers (age 29 (
SEM 4) years; four
male, six female; BMI 21·9 (
SEM 0·8) kg/m
2
) ate dasheen,
eddoes, white yam, tannia and Irish potato. The portion
sizes were based on proximate (ash, acid hydrolysis for
fat, 1008C oven for moisture, Dumas method (N £ 5·70)
for protein, total carbohydrate by difference) and total diet-
ary fibre analysis (gravimetric method) using standard
AOAC methods (Association of Official Analytical Che-
mists, 1995) with available carbohydrate being defined as
total carbohydrate minus total dietary fibre (Table 1).
Study 3
At site 2 the tubers from study 2 with the highest and
lowest GI values were chosen. Irish potato was used as a
comparison or reference food in order to validate the pro-
cedure used to study the effects of crushing on the selected
tubers. Six of the volunteers from study 2 participated in
study 3. Available carbohydrate portions (50 g) of the
foods were boiled and either left uncrushed or crushed
before storage in the refrigerator, as in study 2.
Experimental procedure
Following 12 h overnight fasts volunteers ate 50 g available
carbohydrate portions of the foods weekly. They each
started and ended with white bread; the second white
bread and the test foods were randomly eaten. At site 1
all foods were taken with 250 ml water, at site 2 the volun-
teers chose water or unsweetened tea or coffee, but the
chosen beverage was constant for all studies. Fingerpick
capillary blood samples were taken before starting the
meals. Volunteers were then asked to consume the foods
within 10 min and to remain seated for the duration of
the test. Further blood samples were taken at 15, 30, 45,
60, 90, and 120 min. Blood samples were taken into
fluoro-oxalate tubes and either stored at 2 208C (site 2)
or quickly centrifuged to obtain plasma which was stored
at 2 208C (site 1). At site 1 capillary plasma glucose was
measured using a commercial hexokinase end-point
method with blank correction (Sigma Chemical Co., St
Louis, MO, USA). Capillary whole-blood glucose was
measured at site 2 using an automatic analyser (2300 Stat
Glucose Analyser; YSI Inc., Yellow Springs, OH, USA).
All glucose assays were performed within 48 h of
sampling. At both sites the inter-assay and intra-assay
CV for the glucose assay were approximately 3 %.
Statistical analysis
Incremental AUC ignoring area beneath the fasting level
were calculated geometrically (Wolever et al. 1991). The
AUC for each food was expressed as a percentage of the
mean area for the three white-bread tests and the resulting
values averaged to give the food GI based on white bread.
Because it is now the preferred practice to report GI values
using glucose, this was derived by multiplying the white-
bread-based GI by 0·71 (since the GI of white bread is
71 when glucose has the reference GI of 100; Wolever
et al. 2003). The test-food GI for each subject was aver-
aged to give the mean GI for each test food. The AUC
for pooled repeated white-bread tests were compared
using one-way ANOVA. The AUC and GI values were
not normally distributed and so statistical analysis was per-
formed by using Friedman’s ANOVA by ranks with Dun-
nett’s post hoc test. The blood glucose concentrations at
each time point were compared using conventional two-
way ANOVA, followed by Tukey’s test to protect for mul-
tiple comparisons. Differences were considered statistically
significant at P, 0·05.
Results
The blood glucose response curves of the test foods and
white bread for studies 1 and 2 are shown in Fig. 1. The
mean, standard deviation and CV of the AUC values for
repeated white-bread tests are given in Table 2 for each
volunteer and each site. There was no significant difference
between the mean AUC (P¼ 0·5) or the mean CV
(P¼ 0·09) between the different centres. However, differ-
ences between subjects at each site were highly significant
(P, 0·001).
Table 3 shows the AUC, the white-bread-based GI
values, as well as the glucose-based GI results for the
test foods. Two-way ANOVA showed there was no signifi-
cant effect of subject on GI in any of the three studies. In
study 1 cassava was found to have a significantly higher
(x
2
11·9, degrees of freedom 4; P¼ 0·018) ranked GI
than the other foods tested at site 1. In study 2 the differ-
ences in AUC and GI among the foods tested were not stat-
istically significant.
The blood glucose response curves for the three boiled
(whole and crushed) tubers compared with the response
for white bread are shown in Fig. 1. Table 4 shows the
AUC and GI values for the boiled þ uncrushed and
Glycaemic index of Caribbean staples 973
boiled þ crushed tubers compared with the response for
white bread. The AUC and the GI values of uncrushed
and crushed preparations of the foods tested were not sig-
nificantly different. When data for boiled whole dasheen,
Irish potato and tannia from both studies (study 2 and 3)
were pooled, their GI values, respectively, were 76 (
SEM
7), 69 (SEM 6) and 55 (SEM 5), with the difference between
dasheen and tannia being statistically significant
(P¼ 0·015).
Discussion
The GI values of staples commonly eaten in the Caribbean
were determined in the present two-centre study using a
standard protocol. The foods selected for testing were
based on 24 h recalls (Wolever et al. 2002), food balance
sheets (Sinha, 1995) and discussions with nutrition prac-
titioners in the Caribbean. There was good concordance
between the two centres with respect to the mean and
within-subject variation of glycaemic responses elicited
by white bread. Although there was significant variation
in the glucose response to white bread between subjects,
there was no significant variation in GI values between
subjects. Additionally, in a recent study white bread
made from flour obtained at the respective study sites
was shown to have comparable GI (Wolever et al. 2003).
Based on the mean GI values obtained for dasheen (77
and 75), tannia (60 and 50) and Irish potato (71 and 66)
in studies 2 and 3, the average between-study standard
deviation was 6·6, which is less than the average
between-laboratory standard deviation of 9 previously
reported (Wolever et al. 2003). We did not undertake
measurements of insulin in the present study due to finan-
cial constraints but also because our main objective was to
generate GI data for Caribbean foods.
Fig. 1. Blood glucose responses in groups of eight to ten normal subjects elicited by test foods (green banana (a), breadfruit (b), cassava (c),
roti (d), tannia (e), Irish potato (f), dasheen (g), eddoe (h), crushed tannia (i), crushed Irish potato (j), crushed dasheen (k), yam (l)) (W, O)
compared with white bread (X) consumed by the same subjects. For (i) to (k), the results for uncrushed tubers are shown (W) as well as those
for crushed tubers (O). Mean values are shown, with standard errors of the mean represented by vertical bars. Bars have not been shown if
they are smaller than the symbol or overlap other symbols or bars. Mean values were significantly different from that for white bread
(P, 0·05): * uncrushed foods; † crushed foods.
Table 2. Incremental areas under the glucose response curve
(mmol £ min/l) for white bread
Volunteer
Code no. 1 no. 2 no. 3 Mean
SD CV (%)
Site 1
101 203 179 218 200 20 10
102 167 156 223 182 36 20
103 117 105 102 108 8 7
104 103 120 96 106 12 11
105 252 251 231 245 12 5
106 221 266 199 228 34 15
107 158 171 187 172 15 9
108 238 288 197 241 46 19
Mean 182 192 182 185 23 12
SEM 20 24 19 19 5 2
Site 2
201 146 148 123 139 14 10
202 462 393 452 435 37 9
203 85 97 179 120 51 43
204 71 80 86 79 7 10
205 212 135 134 160 45 28
206 121 125 205 150 47 32
207 167 127 147 147 20 14
208 75 114 120 103 24 24
209 116 131 96 114 18 15
210 158 190 142 163 24 15
Mean 161 154 168 161 29 20
SEM 36 28 33 32 5 4
D. D. Ramdath et al.974
The method used to measure glucose and the type of
blood samples analysed differed at the two study sites.
However, results from a multi-centre study, which included
both study sites, showed that derivation of GI is not
affected by the analytical method used for glucose determi-
nation (Wolever et al. 2003). Additionally, GI values
obtained from capillary whole blood or plasma were not
different and produced a smaller standard deviation in
comparison with venous blood (Wolever et al. 2003). At
site 2, volunteers were allowed the choice of water,
unsweetened tea or coffee, whereas at site 1 all meals
were eaten with water. The former practice does not
affect the glucose AUC significantly (Young & Wolever,
1998), and is considered acceptable providing that volun-
teers keep constant their chosen drink for the duration of
the GI studies (Wolever et al. 1991).
We were unable to detect significant differences in gly-
caemic response between the tubers in the individual
studies, despite apparently large-enough differences in
mean AUC: 26 % in study 2, dasheen v. eddoe; 34 % in
study 3, uncrushed dasheen v. crushed tannia. The original
power analysis indicates that the probabilities of failing to
detect differences of 26 and 34 %, respectively, are 0·16
and 0·04. Thus, in study 2 the largest difference between
tubers, 26 %, was such that there was a relatively high
chance (0·16, or about 1:6) of failing to detect it. On the
other hand, in study 3 it is improbable (P, 0·05) that the
failure to detect the 34 % difference in AUC was due to
chance, and hence is more probably due to the existence
of greater variability than expected. However, when the
results for the whole tubers in studies 2 and 3 were
pooled, the difference in GI between dasheen and tannia
became significant. Even if a very conservative Bonferroni
correction is applied to the pooled data to adjust for the fact
that the same data were used for two statistical tests, the
difference is still significant (P¼ 0·03).
The tubers reported in the present paper have not been
studied previously, so it was important to calibrate our
studies with a food, preferably a tuber, with a known
GI. Irish potato was chosen for this purpose. The GI
values obtained for Irish potato in studies 2 and 3 (71
and 66) not only agree with each other but also are similar
to GI values we have previously published for boiled or
baked Prince Edward Island, white and new potatoes
(range 5570) (Jenkins et al. 1981, 1983; Wolever et al.
1994).
The studies showed that the nine different test foods
have GI values which varied over a 1·5-fold range. The
reason for the relative differences is not known; however,
one possibility is that the physical and chemical character-
istics of the starch in these foods vary. Further work is
therefore needed to determine the characteristics of the
starch in the various tubers. The cookcoolingre-warm-
ing cycle to which the tubers were subjected could have
affected the amount of resistant starch (RS) they contained.
About 7 % of the starch in reheated boiled potatoes escapes
digestion in the small intestine starch compared with about
3 % in freshly cooked potato (Englyst & Cummings, 1987),
a difference which seems too small to have a detectable
effect on glycaemic responses. The RS content of foods
similar to those reported here (roti, yam, eddoes, cassava,
Table 3. Incremental areas under the glucose response curve (AUC) and glycaemic index (GI) for test foods and white bread in study 1 and study 2
(Mean values and standard errors of the mean)
Study 1 Study 2
Green
banana Breadfruit Cassava Roti White bread Dasheen Eddoe Irish potato Tannia White yam White bread
Mean
SEM Mean SEM Mean SEM Mean SEM Mean SEM Mean SEM Mean SEM Mean SEM Mean SEM Mean SEM Mean SEM
AUC 171 38 142 12 243* 39 172 33 185 19 168 33 125 23 151 24 137 33 134 20 161 32
GI
wb
92 16 83 13 133* 16 91 13 100† 109 14 86 14 101 11 84 7 88 9 100†
GI 65 11 60 9 94* 11 65 9 71† 77 10 61 10 71 8 60 5 62 6 71†
GI
wb
, GI based on bread reference (i.e. GI of white bread ¼ 100).
* Mean value was significantly different from those for the other test foods (P, 0·01).
†No
SEM shown because of zero degrees of freedom for a defined value.
Glycaemic index of Caribbean staples 975
potato) is low, with a range of 1·8 3·4 g/11 g dry weight
(Platel & Shurpalekar, 1994). More recently, the effect of
RS on GI was examined using barley (about 15 % RS),
and there was no significant effect on GI after adjusting
for RS content (Wolever et al. 2003).
The finding that crushing did not result in significant
differences in GI suggests that this procedure did not
affect the foods’ physical structure sufficiently to produce
elevated glycaemic responses. The GI for Irish potato did
not increase when it was crushed in these studies. This is
consistent with the findings of a previous study in which
the GI of boiled Prince Edward Island potatoes (64) did
not increase significantly when the potatoes were mashed
(74) (Wolever et al. 1994).
Using published criteria (Brand-Miller et al. 2003b)itis
possible to classify dasheen and cassava as being high-GI
foods, whereas the other tubers studied (i.e. yam, tannia,
eddoes, and Irish potato, cooking ‘green’ banana, and
breadfruit) and roti can be designated intermediate-GI
foods. Food consumption patterns are not available for
most Caribbean countries; however, of the staple foods
tested, cassava, dasheen, Irish potato, yam and roti are
probably eaten more often than ‘green’ banana, breadfruit,
eddoes and tannia. When the former are added to the other
frequently used staples (bread and rice) it becomes appar-
ent that the Caribbean diet is probably one with a high GI.
This is supported by the finding of a mean diet GI of 58 in
a sample of healthy individuals in Trinidad and Tobago
(Wolever et al. 2002), which can be compared with
median values of 52 and 50, respectively for middle-aged
men and women in the USA (Salmeron et al. 1997a,b).
The range of GI between staples is sufficiently large, and
could result in beneficial health effects if those consuming
a Caribbean diet reduced their intakes of staples with high
GI and increased the consumption of those with intermedi-
ate GI. This is particularly important since small changes
in diet GI are associated with a significant reduction in
CHD risk (Liu et al. 2000), diabetes risk (Salmeron et al.
1997a,b) and improvements in insulin sensitivity and gly-
caemic control (Frost et al. 1998; Wolever & Mehling,
2002; Brand-Miller et al. 2003a). Ideally, low-GI Carib-
bean staples need to be identified and their usage pro-
moted; however, this will require further studies. The
findings of the present study can provide useful guidance
for health workers involved in meal planning for diabetics
and diabetes education programmes, especially in Carib-
bean countries and in Caribbean migrants. It can also be
used to achieve healthy eating and plan chronic-disease
risk-reduction programmes in high-risk populations.
It should now be possible to advocate for evidence-based
changes in the type and frequency of staples used by Car-
ibbean individuals.
Acknowledgements
The present work was partially supported by grants from
the Caribbean Health Research Council and the University
of the West Indies (St Augustine) Research and Publication
Funds. We thank Mr B. Mahabir, Ms N. Ramdhanie, Ms
A. Williams, Mr C. Bridgemohan, the National Herbarium
of Trinidad and Tobago, and the volunteers for their valu-
able contributions.
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Table 4. Effect of crushing tubers on incremental area under the glucose curve (AUC; mmol £ min/l) and glycaemic index (GI)
Uncrushed
dasheen
Uncrushed
Irish potato
Uncrushed
tannia
Crushed
dasheen
Crushed Irish
potato
Crushed
tannia White bread
Mean
SEM Mean SEM Mean SEM Mean SEM Mean SEM Mean SEM Mean SEM
AUC 155 40 130 23 112 29 129 15 127 13 103 13 145 22
GI
wb
105 17 93 14 71 11 93 8 94 9 74 7 100*
GI 75 12 66 10 50 8 66 6 66 7 52 5 71*
GI
wb
, GI based on bread reference (i.e. GI of white bread ¼ 100).
*No
SEM shown because of zero degrees of freedom for a defined value.
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Glycaemic index of Caribbean staples 977
... In total, the meta-analysis involved fifty-seven articles, as exhibited in Figure 1. According to the Cochrane Collaboration tool, eleven trials [6,24,29,32,33,37,38,42,48,51,54] were categorized as being at a low risk of bias, while forty-four were categorized as unclear [17,[19][20][21][22][23]25,27,28,30,31,[34][35][36][39][40][41][43][44][45][46][47]49,50,52,53,[55][56][57][58][59][60][61][62], and two were categorized as being at a high risk of bias [18,26]. Details about the risk of bias are supplied in Figures 2 and 3. ...
... Among fifty-seven included studies, forty-eight were selected for discussion of the relationship between chemical properties and GI value . The remaining studies were used for the selection of low-GI carbohydrate-based foods [55][56][57][58][59][60][61][62]. All studies reported changes in glycemic index, four studies [7,[17][18][19] reported changes in amylose content to GI, ten studies [9][10][11][12][13][20][21][22][23][24] reported changes in resistant starch (RS) content to GI, fifteen studies reported a change in dietary fibre content to GI, fifteen studies reported a change in fat content to GI, fifteen studies reported a change in protein content to GI, twelve studies reported a change in phenol content to GI, ten studies reported a change in flavonoid content to GI, five studies reported a change in cereal type to GI, six studies reported a change in tuber type to GI, two studies reported a change in fruit type to GI, and four studies reported a change in legume type to GI. Detailed characteristics of eligible studies are presented in Tables 2 and 3. Thiranusornkij et al. 2019 [12] Odenigbo et al. 2012 [24] Ek et al. 2013 [45] Hidayat et al. 2017 [46] Singh et al. 2011 [47] Kumar et al. 2019 [10] Srikaeo and Sangkhiaw 2014 [11] Darandakumbura et al. 2013 [14] Ayerdi et al. 2005 [13] Oboh and Ogbebor 2010 [48] Vahini et al. ...
... Only one study used both in vitro and in vivo data experiments [11]. The in vivo studies involved healthy participants, and some studies used rats [51,58]. The PICOS of this research is defined as Participants, Interventions, Comparisons, Outcomes, and Study Design. ...
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The chemical properties that serve as major determinants for the glycemic index (GI) of starchy food and recommended low-GI, carbohydrate-based foods have remained enigmatic. This present work performed a systematic assessment of linkages between chemical properties of foods and GI, and selected low-GI starchy foods. The data were sourced from literature published in various scientific journals. In total, 57 relevant studies and 936 data points were integrated into a database. Both in vitro and in vivo studies on GI values were included. The database was subsequently subjected to a meta-analysis. Meta-analysis from in vitro studies revealed that the two significant factors responsible for the GI of starchy foods were resistant starch and phenolic content (respectively, standardized mean difference (SMD): −2.52, 95% confidence interval (95%CI): −3.29 to −1.75, p (p-value) < 0.001; SMD: −0.72, 95%CI: −1.26 to −0.17, p = 0.005), while the lowest-GI crop type was legumes. Subgroup analysis restricted to the crop species with significant low GI found two crops, i.e., sorghum (SMD: −0.69, 95%CI: −2.33 to 0.96, p < 0.001) and red kidney bean (SMD: −0.39, 95%CI: −2.37 to 1.59, p = 0.001). Meta-analysis from in vivo studies revealed that the two significant factors responsible for the GI of starchy foods were flavonoid and phenolic content (respectively, SMD: −0.67, 95%CI: −0.87 to −0.47, p < 0.001; SMD: −0.63, 95%CI: −1.15 to −0.11, p = 0.009), while the lowest-GI crop type was fruit (banana). In conclusion, resistant starch and phenolic content may have a desirable impact on the GI of starchy food, while sorghum and red kidney bean are found to have low GI.
... In addition to antioxidants, taro phytochemicals display immunomodulatory, antioxidant, antitumoral, antimetastatic, antimutagenic, anti-hyperglycemic, and anti-hypercholesterolemic bioactivities. Moreover, taro is a potential alternative staple source, with a lower glycemic index than potato, and its consumption may decrease the incidence and prevalence of several diseases, including certain types of cancers [13,[15][16][17]. ...
... In addition, the presence of soluble and non-soluble dietary fibers can improve intestinal transit and possibly aid in colorectal cancer prevention. As a result of its gluten-free nature, taro flour has arisen as a promising substitute for wheat flour, boosting the Brazilian market for gluten-free derivatives [13,15,16,[27][28][29]. ...
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Taro corms contain valuable bioactive molecules effective against cancer and cancer-related risk factors, such as carcinogens and biological agents, several pathophysiological conditions, including oxidative stress and inflammation, while controlling metabolic dysfunctions and boosting the immunological response. Such broad effects are achieved by the taro health-influencing compounds displaying antitumoral, antimutagenic, immunomodulatory, anti-inflammatory, antioxidant, anti-hyperglycemic, and anti-hyperlipidemic activities. Taro bioactivities are attributed to the combination of tarin, taro-4-I polysaccharide, taro polysaccharides 1 and 2 (TPS-1 and TPS-2), A-1/B-2 α-amylase inhibitors, monogalactosyldiacylglycerols (MGDGs), digalactosyldiacylglycerols (DGDGs), polyphenols, and nonphenolic antioxidants. Most of these compounds have been purified and successfully challenged in vitro and in vivo, proving their involvement in the aforementioned activities. Although these health-promoting effects have been recognized since ancient times, as well as other valuable features of taro for food profit, such as hypo-allergenicity, gluten-free, and carbohydrates with medium-glycemic index, taro crop remains underexploited. The popularization of taro intake should be considered a dietary intervention strategy to be applied to improve the overall health status of the organism and as supportive therapy to manage tumorigenesis.
... Human studies related to breadfruit in the diet have mainly focused on the glycemic index (GI) measurement. Several researchers [11][12][13], indicated that breadfruit had a low glycemic index as compared to many common staples such as wheat, cassava, yam and potatoes. However, the literature is somewhat complicated by a study in 1995 that reported the death of four male Hooded Lister rats after consumption of breadfruit seed extracts [14] that led to the classification of breadfruit as a "hazardous plant" by the United States Food and Drug Administration (FDA). ...
... There was no reported death, sickness, or malnutrition of the mice after consuming a breadfruit diet for 3 weeks. Similar to our findings, human studies related to breadfruit have not reported any discomfort or death after consuming breadfruit [11][12][13]27]. This is also Fig 7. Comparison of iNOS expression between ileums of breadfruit (BF)-and 5LG4-fed mice. ...
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Breadfruit is a traditional staple crop from Pacific islands with the potential to improve worldwide food security and mitigate diabetes. Flour produced from breadfruit is a gluten-free, low glycemic index, nutrient dense and complete protein option for modern foods but basic scientific knowledge of health impacts of a breadfruit-based diet in animals and humans was lacking. We designed a series of studies to provide basic and fundamental data on impacts of a breadfruit-based diet through an in vitro and in vivo model. Cooked breadfruit flour was digested through a multi-stage enzyme digestion model to estimate protein digestibility in comparison to wheat flour. Breadfruit protein was found to be easier to digest than wheat protein in the enzyme digestion model. The flour digestions were applied to Caco-2 cells to test the cytotoxicity and to measure the immunogenicity through cytokine expression. No significant differences were observed for immune factors and cytokines (IL-4, IL-10, IL-8, TNF-α, IFN-γ) on Caco-2 cells between the breadfruit and wheat groups. A breadfruit-based rodent chow was formulated by substitution of all of the wheat in the standard formulation with breadfruit. The diets were isocaloric, nutrient equivalent and used to feed male and female C57BL/6 mice for 21 days. No sign of malnutrition, discomfort, illness or death was observed among the mice because of the diet. The histology and the cytokine expression of the mice ileum from both groups were analyzed and showed similar results. The expression of major bacteria was measured in the colon and showed similar results. Mice fed the breadfruit diet had a significantly higher growth rate and body weight than standard diet fed mice. No negative health outcomes were observed in studies with in vitro or in vivo models and breadfruit flour is a healthy alternative to other starches for modern foods.
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Background: Glycemic index (GI) measures postprandial blood sugar after consumption of carbohydrate-rich foodstuff. Kenya is yet to fully embrace this concept in prevention and management of diabetes mellitus. Objective: To review and tabulate GIs of locally consumed foods in order to improve dietary management of diabetes mellitus. Methodology: A literature search was conducted using Google scholar and PubMed databases which identified 7 articles on glycemic index values of Kenyan foods published between 2002 and 2020. Two articles failed to meet the inclusion criteria and five proceeded for review. Key search words used included GI, glycemic load and glycemic response combined with Kenya. The data was reported depending on whether the testing involved healthy individuals or patients suffering from diabetes mellitus. Results: Nine individual foods and 7 mixed meals were identified. Low GI foods included beans and whole maize ugali consumed alongside cowpea leaves. High GI foods included whole maize ugali eaten with beef, boiled rice, boiled cassava and cassava-sorghum ugali eaten with silver fish. Conclusion: Proper meal mixing is important in diabetes management. Cowpea leaves and beans possess GI lowering potential. This information can be used to improve guidance on food choices for diabetes patients.
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This research aimed to study granular and molecular structures, physicochemical and functional properties of the starch extracted from a novel, dasheen type of taro conserved and cultivated by several generations of Kunabi tribes of Joida, Karnataka, India. This article is protected by copyright. All rights reserved
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In modern agriculture, horticultural crops are an integral component and play a vital role in sustaining human life. Although conventional approaches have contributed to the enhanced agricultural production, innovative breeding technology is required to further increase horticultural and nutritious crop worldwide. Genome editing has revolutionized the plant world by precisely edit the targeted modification of plant genome, including model plants, agricultural and horticultural crops. Recent advances in Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR/associated protein 9 (Cas9) genome editing tool have emerged as an efficient targeted modification in most fruit, vegetable and ornamental plants thus promising to accelerate crop improvement due to its high accuracy and efficiency. Several reports of the development of improved fruit, vegetable and ornamental plants using CRISPR/Cas9 tool has been documented. CRISPR/Cas9 genome editing efficiency depends on several factors such as promoter sequence, RNA polymerase specificity, Cas9 expression, types of vectors, guide RNA expression etc. In the present review, we summarize the applications of CRISPR/Cas9 genome editing system in fruit, vegetable and ornamental crops. This article also provides its origin, mechanism, an existing pitfall and future possibilities for bright future in development of horticultural crops.
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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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To define those patients most likely to benefit from the hypolipidemic effect of low-glycemic-index (GI) traditional starchy foods, 30 hyperlipidemic patients were studied for 3 mo. During the middle month, low-GI foods were substituted for those with a higher GI with minimal change in dietary macronutrient and fiber content. Only in the group (24 patients) with raised triglyceride levels (types IIb, III, and IV) were significant lipid reductions seen: total cholesterol 8.8 +/- 1.5% (p less than 0.001), LDL cholesterol 9.1 +/- 2.4% (p less than 0.001), and serum triglyceride 19.3 +/- 3.2% (p less than 0.001) with no change in HDL cholesterol. The percentage reduction in serum triglyceride related to the initial triglyceride levels (r = 0.56, p less than 0.01). The small weight loss (0.4 kg) on the low-GI diet did not relate to the lipid changes. Low-GI diets may be of use in the management of lipid abnormalities associated with hypertriglyceridemia.
Article
To define those patients most likely to benefit from the hypolipidemic effect of low-glycemic-index (GI) traditional starchy foods, 30 hyperlipidemic patients were studied for 3 mo. During the middle month, low-GI foods were substituted for those with a higher GI with minimal change in dietary macronutrient and fiber content. Only in the group (24 patients) with raised triglyceride levels (types IIb, III, and IV) were significant lipid reductions seen: total cholesterol 8.8 ± 1.5% (p < 0.001), LDL cholesterol 9.1 ± 2.4% (p < 0.001), and serum triglyceride 19.3 ± 3.2% (p < 0.001) with no change in HDL cholesterol. The percentage reduction in serum triglyceride related to the initial triglyceride levels (r = 0.56, p < 0.01). The small weight loss (0.4 kg) on the low-GI diet did not relate to the lipid changes. Low-GI diets may be of use in the management of lipid abnormalities associated with hypertriglyceridemia.
Article
Objective. —To examine prospectively the relationship between glycemic diets, low fiber intake, and risk of non—insulin-dependent diabetes mellitus.Desing. —Cohort study.Setting. —In 1986, a total of 65173 US women 40 to 65 years of age and free from diagnosed cardiovascular disease, cancer, and diabetes completed a detailed dietary questionnaire from which we calculated usual intake of total and specific sources of dietary fiber, dietary glycemic index, and glycemic load.Main Outcome Measure. —Non—insulin-dependent diabetes mellitus.Results. —During 6 years of follow-up, 915 incident cases of diabetes were documented. The dietary glycemic index was positively associated with risk of diabetes after adjustment for age, body mass index, smoking, physical activity, family history of diabetes, alcohol and cereal fiber intake, and total energy intake. Comparing the highest with the lowest quintile, the relative risk (RR) of diabetes was 1.37 (95% confidence interval [CI], 1.09-1.71, Ptrend=.005). The glycemic load (an indicator of a global dietary insulin demand) was also positively associated with diabetes (RR=1.47; 95% CI, 1.16-1.86, Ptrend=.003). Cereal fiber intake was inversely associated with risk of diabetes when comparing the extreme quintiles (RR=0.72,95% CI, 0.58-0.90, Ptrend=.001). The combination of a high glycemic load and a low cereal fiber intake further increased the risk of diabetes (RR=2.50, 95% CI, 1.14-5.51) when compared with a low glycemic load and high cereal fiber intake.Conclusions. —Our results support the hypothesis that diets with a high glycemic load and a low cereal fiber content increase risk of diabetes in women. Further, they suggest that grains should be consumed in a minimally refined form to reduce the incidence of diabetes.
Article
Background This study aimed to describe trends in age-specific mortality from diabetes mellitus, hypertension, cerebrovascular disease and ischaemic heart disease in Trinidad and Tobago between 1953 and 1992 and to relate them to earlier changes in infant mortality rates. Methods Average annual age-specific mortality rates per 100 000 were calculated for 5-year time periods from 1953–1957 to 1988–1992 and plotted by mid-year of birth for cohorts born 1874–1882 to 1944–1952. Regression analyses were performed to test associations between adult mortality rates, and infant mortality rates for the same birth cohorts and period of death. Results Infant mortality declined from 180 per 1000 in 1901 to 10 per 1000 in 1992. Age-standardized mortality from diabetes mellitus increased, in men, from 60 in 1958–1962 to 278 in 1988–1992, in women the increase was from 89 to 303. Mortality from hypertension declined, in men, from 232 in 1953–1957 to 73 in 1988–1992, and in women, from 206 to 67. Cerebrovascular mortality increased, in men, from 341 in 1953–1957 to 451 in 1963–1967 before declining to 224 In 1988–1992. In women cerebrovascular mortality increased from 292 in 1953–1957 to 361 in 1963–1967 before declining to 196 in 1988–1992. There was evidence of a deceleration in cerebrovascular mortality for cohorts born after 1908–1918. Ischaemic heart disease mortality remained constant. Mid-cohort infant mortality rates were not associated with adult mortality after adjusting for age and period of death. Conclusions Declining infant mortality was subsequently associated with declining mortality from cerebrovascular disease and hypertensive disease and increasing mortality from diabetes mellitus but there was no association with ischaemic heart disease mortality. These relationships were confounded by secular changes associated with year of death.
Article
Countries of English-speaking Caribbean in the last thirty years have experienced an unprecedented epidemiological transition. Malnutrition in children and infectious diseases, once the major public health problems, have considerably declined and have been replaced by obesity and chronic noncommunicable diseases such as diabetes, hypertension, stroke, coronary heart disease and cancers. Countries of the Caribbean are net importers of food. During this period of time total food availability has greatly improved but from health point of view this improvement is highly skewed. The increase in the availability of total calories has been almost entirely due to increase in total fat, most of which is from foods from animal sources. While cereals are adequately available, none of the countries meets the recommended population goals for fruits, vegetables, roots, tubers and legumes and they lack upwards of fifty per cent of their needs. Indeed, an ecological study of food availability and disease pattern clearly shows a significant positive relationship between the increase in total calories and diabetes, and between total fat and coronary heart disease and cancers of prostate, breast and colon. A significant inverse relationship can also be noticed between consumption of roots, tubers, fruits and vegetables and heart disease and colorectal cancer. An important feature of this rapid transition in the Caribbean is that the complex problem of obesity and chronic diseases has followed right on the heels of nutritional deficiencies and infectious diseases. During this period of time, economies have not improved much, and almost all countries have incurred massive external debt and are reeling under economic structural adjustment programs. Although very much reduced, the threat of undernutrition and infectious diseases is still lurking in the background and may erupt into epidemic proportions under the fragile economic systems. Thus these countries are finding themselves torn between holding the reins of nutritional deficiencies and infectious diseases from resurfacing and making a frontal attack on the so called “diseases of affluence” with the resources only of developing countries. While eating properly is an individual choice, a variety of factors influence the choice. This paper suggests a series of strategies for appropriate policy development, private sector involvement, health care restructuring and public education programs.
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Low glycaemic index diets reduce blood glucose and lipid levels in humans but glycaemic index values are only available for a small number of foods. Thus, we determined the glycaemic index of 102 complex carbohydrate foods in patients with diabetes. The values varied from 37 for bean thread noodles to 127 for Rice Chex cereal (p<0.001). There were no significant differences between the values of 14 different commercial leavened, wheat breads, which had a mean glycaemic index of 97. This supports the validity of using white bread as the standard food with an arbitrary glycaemic index of 100. There were significant differences between the glycaemic index values of individual foods in the following groups: rye breads, cakes, corn products, cookies, crackers, grains, pasta, potato, soups, legumes and breakfast cereals. Legumes and pasta tended to have low glycaemic index values. The glycaemic index values of the foods were weakly negatively related to their protein (r=−0.407; p<0.001) and dietary fibre (r=0.322; p<0.001) content but not fat (r=−0.054, ns). Thus, there are sufficient differences between the glycaemic responses of complex carbohydrate foods to make the glycaemic index classification a useful supplement to food tables in planning diets for patients with metabolic disorders such as diabetes or hyperlipidaemia.
Article
To study the effect of volume and type of beverage consumed with a meal on blood glucose (BG) responses, 12 normal subjects ate a standard test meal, Diabetes Screening Product (DSP), with 50, 250, 500, 750 or 1000ml water, or 250ml coffee or tea on separate days after overnight fasts. Water volumes were tested twice, making 12 tests done by each subject in a randomized block design. Finger-prick blood was taken before and 15, 30, 45, 60, 90 and 120min after starting to eat. The mean and variation of BG responses were compared by 2-way ANOVA. Mean BG 15min after DSP plus 500ml water was 0.6mmol/L greater than after DSP plus 50ml water (p<0.05). At 30min, BG was 0.5–0.7mmol/L greater after 500 and 750ml water than 50, 250, and 1000ml (p<0.005). At 90min, BG was 0.3mmol/L greater after 50 and 250ml water than after 500 and 750ml (p<0.005). At 120min, BG was 0.5mmol/L greater after 50ml than 500 and 750ml (p<0.001). Coffee and tea resulted in greater 45min BG than the same volume of water (p<0.005), while BG 60min after coffee was greater than after both tea and water (p<0.05). Volume and type of beverage did not significantly affect the incremental area under the curve or the variability of BG. We conclude that, in normal subjects, the volume and type of beverage consumed with a test meal influences the pattern of blood glucose response but has no effect on the incremental area under the glycaemic response curve. Since the volume, but not the type of beverage, affected the blood glucose concentration 2h after eating, a standardized meal volume should be used when testing an individual's carbohydrate tolerance status.
Article
To determine whether low-glycemic index (GI) diets have clinical utility in overweight patients with non-insulin-dependent diabetes mellitus (NIDDM). Six patients with NIDDM were studied on both high- and low-GI diets of 6-wk duration with metabolic diets with a randomized crossover design. Both diets were of similar composition (57% carbohydrate, 23% fat, and 34 g/day dietary fiber), but the low-GI diet had a GI of 58 compared with 86 for the high-GI diet. Small and similar amounts of weight were lost on both diets: 2.5 kg on high-GI diet and 1.8 kg on low-GI diet. On the low-GI diet, the mean level of serum fructosamine, as an index of overall blood glucose control, was lower than on the high-GI diet by 8% (P less than 0.05), and total serum cholesterol was lower by 7% (P less than 0.01). In overweight patients with NIDDM, reducing diet GI improves overall blood glucose and lipid control.
Article
The frequency of non-insulin-dependent diabetes mellitus (NIDDM) and of high blood pressure (or hypertension) is higher in some ethnic groups than in others for reasons that remain unclear. To investigate the mechanisms leading to these ethnic differences, plasma C-peptide and insulin concentrations were measured after overnight fast and during an oral glucose tolerance test in subjects aged 45-74 years sampled from the practice lists of two north west London health centres. Ethnic group was defined by grandparental origin as Afro-Caribbean in 106, Gujerati Indian in 107, and white European in 101. The total age-adjusted prevalence of NIDDM was 29% in the Afro-Caribbean, 30% in the Gujerati, and 3% in the white groups, respectively. Fasting C-peptide and insulin concentrations increased from the subgroup with normal glucose tolerance, through impaired glucose tolerance, to new NIDDM, and were lower again in subjects with known NIDDM. The odds ratio for new NIDDM was 1.87 (95% confidence interval 1.26-2.77) per 1 SD increase in fasting C-peptide, which was the most powerful independent indicator of new NIDDM (p = 0.0005) and accounted for the effect of ethnic group. Fasting insulin had a similarly strong effect. There was no relation between any index of insulin secretion and blood pressure or hypertension. There were differences among the ethnic groups in the C-peptide response relative to the insulin response. These results suggest that factors determining insulin secretion and its hepatic clearance, possibly including dietary fat, are the main causes of ethnic variation in rates of new NIDDM.