The Effect of Nopal (Opuntia Ficus Indica) on Postprandial Blood Glucose, Incretins, and Antioxidant Activity in Mexican Patients with Type 2 Diabetes after Consumption of Two Different Composition Breakfasts

Abstract

Nopal is a plant used in traditional Mexican medicine to treat diabetes. However, there is insufficient scientific evidence to demonstrate whether nopal can regulate postprandial glucose. The purpose for conducting this study was to evaluate the glycemic index, insulinemic index, glucose-dependent insulinotropic peptide (GIP) index, and the glucagon-like peptide 1 (GLP-1) index, and the effect of nopal on patients with type 2 diabetes after consumption of a high-carbohydrate breakfast (HCB) or high-soy-protein breakfast (HSPB) on the postprandial response of glucose, insulin, GIP, GLP-1, and antioxidant activity. In study 1, the glycemic index, insulinemic index, GIP index, and GLP-1 index were calculated for seven healthy participants who consumed 50 g of available carbohydrates from glucose or dehydrated nopal. In study 2, 14 patients with type 2 diabetes consumed nopal in HCB or HSPB with or without 300 g steamed nopal. The glycemic index of nopal was 32.5±4, insulinemic index was 36.1±6, GIP index was 6.5±3.0, and GLP-1 index was 25.9±18. For those patients with type 2 diabetes who consumed the HCB+nopal, there was significantly lower area under the curve for glucose (287±30) than for those who consumed the HCB only (443±49), and lower incremental area under the curve for insulin (5,952±833 vs 7,313±1,090), and those patients with type 2 diabetes who consumed the HSPB avoided postprandial blood glucose peaks. Consumption of the HSPB+nopal significantly reduced the postprandial peaks of GIP concentration at 30 and 45 minutes and increased the antioxidant activity after 2 hours measured by the 2,2-diphenyl-1-picrilhidracyl method. These findings suggest that nopal could reduce postprandial blood glucose, serum insulin, and plasma GIP peaks, as well as increase antioxidant activity in healthy people and patients with type 2 diabetes.

Full text

RESEARCH
Research and Practice Innovations
The Effect of Nopal (Opuntia Ficus Indica)on
Postprandial Blood Glucose, Incretins, and
Antioxidant Activity in Mexican Patients with
Type 2 Diabetes after Consumption of Two
Different Composition Breakfasts
Patricia López-Romero; Edgar Pichardo-Ontiveros; Azalia Avila-Nava, MSc; Natalia Vázquez-Manjarrez; Armando R. Tovar, PhD;
José Pedraza-Chaverri, PhD; Nimbe Torres, PhD
ARTICLE INFORMATION
Article history:
Accepted 19 February 2014
Keywords:
Nopal
Antioxidant activity
Diabetes
Glucose-dependent insulinotropic peptide (GIP)
Glycemic control
2212-2672/Copyright ª2014 by the Academy of
Nutrition and Dietetics.
http://dx.doi.org/10.1016/j.jand.2014.06.352
ABSTRACT
Nopal is a plant used in traditional Mexican medicine to treat diabetes. However, there
is insufficient scientific evidence to demonstrate whether nopal can regulate post-
prandial glucose. The purpose for conducting this study was to evaluate the glycemic
index, insulinemic index, glucose-dependent insulinotropic peptide (GIP) index, and the
glucagon-like peptide 1 (GLP-1) index, and the effect of nopal on patients with type 2
diabetes after consumption of a high-carbohydrate breakfast (HCB) or high-soy-protein
breakfast (HSPB) on the postprandial response of glucose, insulin, GIP, GLP-1, and
antioxidant activity. In study 1, the glycemic index, insulinemic index, GIP index, and
GLP-1 index were calculated for seven healthy participants who consumed 50 g of
available carbohydrates from glucose or dehydrated nopal. In study 2, 14 patients with
type 2 diabetes consumed nopal in HCB or HSPB with or without 300 g steamed nopal.
The glycemic index of nopal was 32.54, insulinemic index was 36.16, GIP index was
6.53.0, and GLP-1 index was 25.918. For those patients with type 2 diabetes who
consumed the HCBþnopal, there was significantly lower area under the curve for
glucose (28730) than for those who consumed the HCB only (44349), and lower
incremental area under the curve for insulin (5,952833 vs 7,3131,090), and those
patients with type 2 diabetes who consumed the HSPB avoided postprandial blood
glucose peaks. Consumption of the HSPBþnopal significantly reduced the postprandial
peaks of GIP concentration at 30 and 45 minutes and increased the antioxidant activity
after 2 hours measured by the 2,2-diphenyl-1-picrilhidracyl method. These findings
suggest that nopal could reduce postprandial blood glucose, serum insulin, and plasma
GIP peaks, as well as increase antioxidant activity in healthy people and patients with
type 2 diabetes.
J Acad Nutr Diet. 2014;-:---.
THE CACTUS OPUNTIA, WHICH IS ALSO KNOWN AS
nopal, is native to central Mexico
1
and the pads are
eaten as a vegetable. Cactus plants have long served
as a source of food for people, and they have long
been used in traditional Mexican medicine for treating dia-
betes. Nopal is considered a functional food because it is a
proven source of dietary fiber
2
and bioactive compounds
with antioxidant activity, such as flavonoids, flavonols, car-
otenes, and ascorbic acid,
3
in addition to being low in calo-
ries (27 kcal/100 g). The current epidemic of obesity and
diabetes has led to a search for functional foods that could
aid in ameliorating these pathologies. In the case of dia-
betes, consuming high-calorie meals can lead to exagger-
ated postprandial peaks in blood glucose and in lipids that
generate reactive oxygen species,
4,5
which results in inflam-
mation
5
and endothelial dysfunction.
6
In addition, post-
prandial glucose homeostasis is controlled not only by
direct stimulation of insulin release by absorbed nutrients,
but also through secretion of incretin hormones, that is,
glucagon-like peptide-1 (GLP-1) and glucose-dependent in-
sulinotropic peptide (GIP).
7
These incretins are released
from enteroendocrine cells and are responsible for at least
50% of the total insulin
8
secreted after the ingestion of
food.
9
Therefore, the purpose of conducting this study was
first to evaluate the glycemic index, insulinemic index, GIP
index, and GLP-1 index, and second, to evaluate the meta-
bolic effect of steamed nopal on postprandial peaks of
glucose, insulin, GIP, and antioxidant activity after the
ª2014 by the Academy of Nutrition and Dietetics. JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS 1

consumption of a high-carbohydrate breakfast (HCB) or
high-soy-protein breakfast (HSPB).
MATERIALS AND METHODS
Ethics Statement
All of the procedures were conducted with an adequate un-
derstanding by, and the written consent of, the participants.
The study was approved by the Ethics Committee of Humans
by the Instituto Nacional de Ciencias Médicas y Nutrición and
was in compliance with the Declaration of Helsinki. The study
was registered in the Institutional Committee for Human
Biomedical Research (no. 118).
Participants
Two separate studies were performed using two separate
groups of participants. Study 1 was performed to determine
the glycemic index of nopal. This study included seven
healthy, nonsmoking, nonmedicated, normal-weight volun-
teers (three men and four women, meanstandard error of
mean [SEM]¼26.31.2 years of age), with a meanSEM body
mass index (calculated as kg/m
2
) of 23.50.8, according to
the recommendations of the Joint Food and Agricultural Or-
ganization of the United Nations/World Health Organization
Expert Consultation.
10
Study 2 was performed to evaluate the effect of nopal on
postprandial blood glucose after the consumption of two
different types of breakfasts. This study included 14 out-
patients (four men and 10 women) who were diagnosed with
type 2 diabetes with durations of <8 years. Patients with type
2 diabetes were treated with metformin only and were be-
tween 40 and 60 years old (meanSEM¼482.1 years of
age), with a body mass index <30 (meanSEM¼28.91).
They did not have dyslipidemia, hypertension, or severe
hypoglycemic episodes during the past year. Their glycosy-
lated hemoglobin levels were <8% (meanSEM¼6.5%0.2%),
and their fasting serum glucose concentration was 100 to
120 mg/dL (6.7 mmol/L). Patients with type 2 diabetes
were studied on four separate occasions. The day of the study,
patients with type 2 diabetes were instructed not to take
their morning doses of metformin. In this study, we included
seven adults without diabetes who were recruited through
fliers as a control group, including four men and three
women within the age range of 25 to 54 years old (mean-
SEM¼24.11.2 years) with a BMI 25 (meanSEM¼
22.20.6) for the past 6 months. No participant received any
compensation for participation in the study. Exclusion
criteria included current cigarette smoker, presence of known
medical problem, or currently being on any medication.
Test Meals: Study 1
The test meal was composed of a portion of nopal containing
50 g of available carbohydrates, which is defined as total
carbohydrates minus dietary fiber, according to the recom-
mendation of the Joint Food and Agricultural Organization of
the United Nations/World Health Organization Expert
Consultation.
10
Because raw nopal contains a significant
amount of water, dehydrated nopal was utilized to determine
the glycemic index. Fresh nopal was obtained from Milpa
Alta, México City, and dried for 48 hours at 55C.
The chemical composition in the dry basis was as follows:
carbohydrates, 24.8%; insoluble fiber, 32.2%; soluble fiber,
4.8%; fat, <1.9%; and protein, 15.4%.
Test Meals: Study 2
The HCB contained 300 kcal and comprised 89% carbohy-
drates, 6% protein, and 5% fat, in the form of apple juice
(240 mL), white bread (55.6 g), and strawberry jam (21 g).
The HSPB contained 344 kcal and comprised 42.4% carbo-
hydrates, 40.7% protein, and 16.9% fat, in the form of soy
hamburger (61.5 g) and soymilk beverage (230 mL). The HSPB
was designed based on previous studies that have demon-
strated that soy protein reduces the postprandial peaks of
insulin and increases insulin sensitivity.
11,12
The HCBþnopal or the HSPBþnopal contained the foods
described here, with the addition of 300 g steamed nopal cut
into small pieces (2.0- to 2.5-cm cubes), the traditional form
consumed in Mexican cuisine. Raw nopal was cooked in a
steamer for 11 minutes over a medium heat, and final cooked
weight was approximately 250 g. It was then served as side
dish. The chemical composition in fresh weight basis was
determined according to Association of Analytic Commu-
nities methods: carbohydrates, 1.4%; insoluble fiber, 1.7%;
soluble fiber, 0.17%; fat, negligible; and protein, 1.1%. Nopal
was always obtained from the same location during the same
season and harvested at the same time of day to minimize
chemical variability.
Protocol
Each participant arrived in the morning after a 12-hour
overnight fast and consumed the test meal as described
here for either study 1 or study 2. All participants consumed
the meal in the same order, and the washout period between
test meals was 1 week. All participants completed the study.
The test meals were consumed within 10 minutes and only
within each selected study. Capillary blood samples for
glucose determination in healthy participants were obtained
intermittently using a finger-stick before and at 15, 30, 45, 60,
90, and 120 minutes after commencing the test meals. Whole
blood glucose was measured using an automatic analyzer
(Model 2700, YSI Inc.). An additional sample in patients with
type 2 diabetes was collected at 150 minutes. Venous blood
samples were also obtained at the same time as capillary
blood to measure serum insulin, plasma GIP, GLP-1, and
antioxidant activity. The insulin concentration was measured
using a human radioimmunoassay kit (Linco Research Inc.).
GIP and GLP-1 were determined in blood samples that were
collected in tubes containing ethylenediamine tetraacetic
acid. Immediately after the blood collection, 30
m
L of the
dipeptidyl peptidase 4 inhibitor for the GLP-1 measurement
(Linco’s DPP IV inhibitor) was added. Plasma was removed
after centrifugation and stored at 20C. The incretins were
analyzed using the Human Gut Hormone Panel (LINCOplex
Kit, Linco Research, Inc). The antioxidant capacity was
determined by the method of 2,2-diphenyl-1-picrilhidracyl,
which has been described previously.
13
Statistical Analysis
Calculation of the glycemic index and incremental area under
the curve (IAUC), excluding the area below fasting, were
calculated using the trapezoid rule.
14
Data are expressed as meanSEM. Analysis of repeated
measures was used to determine the diet and timing effects
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on the glucose, insulin, GIP, and GLP-1 concentrations. Stu-
dent’sttest was used to compare the IAUC among the groups.
For all of the statistical tests, a Pvalue <0.05 was considered
to be significant. Statistical analysis was performed with
Prism 6.0b for Mac OSXb (GraphPad Software Inc). Power
analysis indicated that with seven individuals, the study had
sufficient power to detect medium to small effects (0.80).
RESULTS
Study 1
The ingestion of 50 g of available carbohydrates from nopal
resulted in a significant reduction (P<0.001) in the IAUC of
blood glucose (71.43.5) with respect to the 50 g of glucose
(231.717.4), as demonstrated in Figure 1A, which resulted in
a glycemic index of nopal of 32.54.0, a value that is
considered to be low.
15
With respect to insulin, the IAUC for
nopal was 7.81.0 and was significantly different (P<0.05)
with respect to the glucose (25.55.8). The insulinemic index
was 36.16.1, which is also considered low, as demonstrated
in Figure 1B.
As shown in Figure 1C, low levels of GIP (8.61.4 pg/mL
[1.80.3 pmol/L]) were observed after a 12-hour fast. After
50 g oral glucose, the GIP concentration rapidly increased
within 45 minutes and reached a maximum value of
76.313.4 pg/mL (15.92.8 pmol/L). The consumption of
nopal did not increase the GIP concentration in the 2-hour
period, which had a value of 12.517.3 pg/mL (2.6 to 3.6
pmol/L). There was a significant reduction in the IAUC for
plasma GIP after the consumption of 50 g of available car-
bohydrate from nopal in comparison with 50 g glucose
(1,370235 vs 88.519.3; P<0.01), as demonstrated in
AB
CD
Figure 1. (A) Blood glucose, (B) serum insulin, (C) plasma glucose-dependent insulinotropic peptide (GIP), and (D) glucagon-like protein
1 (GLP-1) concentrations at fasting state and 15, 30, 45, 60, 90, and 120 minutes after the consumption of 50 g oral glucose or 50 g
available carbohydrates (CHO) from nopal. Values were obtained in seven healthy adults without diabetes.
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Figure 1C. As shown in Figure 1D, the GLP-1 concentration
was low (43.915.8 pg/mL [13.34.8 pmol/L]) after 12 hours
of fasting. The consumption of 50 g glucose triggered a rapid
increase in GLP-1 to 79.117.1 pg/mL (245.2 pmol/L) within
45 minutes. In contrast, the 50 g of available carbohydrates
from nopal did not produce a peak in the GLP-1, instead, the
values remained constant (approximately 56 to 59 pg/mL [17
to 18 pmol/L]) during the 2-hour period.
Study 2
Effect of Steamed Nopal on Blood Glucose after
Ingesting an HCB or HSPB. Patients with type 2 diabetes
had a higher fasting blood glucose concentration (104.53.6
mg/dL [5.80.2 mmol/L]) compared with healthy partici-
pants (721.1 mg/dL [40.06 mmol/L]), as demonstrated in
Figure 2A. The consumption of an HCB in patients with type 2
diabetes gradually increased blood glucose concentration,
reaching a maximum value of 183.89 mg/dL (10.20.5
mmol/L) at 60 minutes, and the consumption of an
HCBþnopal significantly decreased the postprandial peaks of
glucose at 45 and 60 minutes (P<0.01), as demonstrated in
Figure 2A. The IAUC for glucose in the group with an
HCBþnopal was significantly lower (28730) than the group
with an HCB (44349; P<0.001 (inset, Figure 2A).
The consumption of an HCB by healthy participants grad-
ually increased blood glucose concentration, reaching a
maximum value of 120.71.8 mg/dL (6.70.1 mmol/L) at 30
minutes, and the consumption of an HCBþnopal reached a
maximum value of 106.35.4 mg/dL (5.90.3 mmol/L).
Therefore, the inclusion of nopal significantly decreased the
postprandial peaks of glucose at 30, 45, and 60 minutes
(P<0.05), as demonstrated in Figure 2A. There was no dif-
ference in the IAUC for glucose in healthy participants after
the consumption of both breakfasts.
With respect to the HSPB, patients with type 2 diabetes
had a higher fasting blood glucose (99.15.4 mg/dL [5.50.3
mmol/L]) than healthy participants (73.91.8 mg/dL [4.10.1
mmol/L]), as demonstrated in Figure 2B. Interestingly, the
HSPB with and without nopal produced a smaller postprandial
blood glucose peak (126.15.4 mg/dL [7.00.3 mmol/L]) than
the HCB at 30, 45, 60, 90 (P<0.001), and 120 minutes (P<0.01);
therefore, it was more effective in reducing the postprandial
glucose peaks. No significant differences were observed be-
tween the HSPB and HSPBþnopal. The IAUC for blood glucose
in patients with type 2 diabetes was similar in the HSPB
(12421) and HSPBþnopal (91.921).
Effect of Steamed Nopal on Serum Insulin after
Ingesting an HCB
The fasting serum insulin concentration in patients with
type 2 diabetes was higher (233
m
IU/mL [13818 pmol/L])
than in healthy participants (92
m
IU/mL [5412 pmol/L]), as
demonstrated in Figure 2C.
There was no difference in insulin concentration in both
over time; however, the IAUC for insulin concentration
was lower in the HCBþnopal group (5,953834) compared
with the HCB breakfast group (7,3131091) ( P<0.05) (inset,
Figure 2C).
There was no significant difference in insulin concentration
over time in the HCB or HCBþnopal groups in healthy
participants.
Effect of Steamed Nopal on Serum Insulin after
Ingesting an HSPB
The fasting serum insulin concentration in patients with type
2 diabetes was higher (22.42
m
IU/mL [134.412 pmol/L])
than in healthy participants (13.21.8
m
IU/mL [79.210.8
pmol/L]), as demonstrated in Figure 2D. After the consump-
tion of an HSPB, the insulin concentration in patients with
type 2 diabetes increased during the postprandial period,
reaching a maximum value at 90 minutes. There was no
significant difference in insulin concentration over time or in
the IAUC between the HSPB and the HSPBþnopal groups in
patients with type 2 diabetes (inset Figure 2D), and
HSPBþnopal significantly reduced the IAUC for insulin in
healthy participants (inset, Figure 2D).
Effect of Steamed Nopal on Plasma GIP after
Ingesting an HCB
Patients with type 2 diabetes had higher fasting plasma GIP
concentration (70.114.9 pg/mL [14.63.1 pmol/L]) compared
with healthy participants (22.14.8 pg/mL [4.61 pmol/L]).
Fifteen minutes after consuming an HCB, patients with type 2
diabetes had a rapid increase in GIP concentration, which
reached a maximum value (170.422.1 pg/mL [35.54.6 pmol/
L]) at 60 minutes. Consuming the HCBþnopal reduced the
postprandial peaks of GIP between 30 and 60 minutes, as
demonstrated in Figure 3A. The consumption of an HCBþnopal
by healthy participants significantly reduced the GIP peak at 60
minutes compared with the HCB group (P<0.05), as demon-
strated in Figure 3A. There was no significant difference in the
IAUC in patients with type 2 diabetes after the consumption of
an HCBþnopal, but in healthy participants, there was a sig-
nificant difference (P<0.01) compared with the HCB group
(2,842802 pg/mL [592167 pmol/L] vs 8,2521,171 pg/mL
[1,719244 pmol/L]).
Effect of Steamed Nopal on Plasma GIP after
Ingesting an HSPB
Fastingplasma GIP concentrations were similar in patients with
type 2 diabetes and in healthy participants (35.15.3 pg/mL
[7.321.1 pm o l / L] a nd ( 26 .1 5.3 pg/mL [5.431.1 pmol/L],
respectively). Fifteen minutes after theconsumption of an HSPB,
patients with type 2 diabetes had a rapid increase in GIP con-
centration, which reached a maximum value (137.312 pg/mL
[28.62.5 pmol/L]) after 30 minutes, as demonstrated in
Figure 3B. In patients with type 2 diabetes, consumption of an
HSPBþnopal significantly reduced the GIP concentration at 30
and 40 minutes (P<0.00 at 30 minutes and P<0.05 at 45 mi-
nutes). There was a significant reduction (P<0.01) in the IAUC
after the consumption of the HSPBþnopal compared with the
HSPB (1,744258 vs 2,448229) in patients with type 2 dia-
betes. In healthy participants, there was an increase in the GIP
plasma concentrations starting after 15 minutes of HSPB
ingestion, with a maximum peak (14416.3 pg/mL [30.03.4
pmol/L]) after90 minutes. There was no significant difference in
the IAUCbetween the HSPBand HSPBþnopal (inset, Figure 3B).
Effect of Steamed Nopal on Plasma GLP-1 after
Ingesting an HCB or HSPB
The GLP-1 concentration in patients with type 2 diabetes
was 15.53 pg/mL (4.70.9 pmol/L) after 12 hours of fasting,
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4JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS -- 2014 Volume -Number -

AB
CD
Figure 2. Fasting and postprandial blood glucose and increase in the incremental area under the curve (IAUC) for blood glucose
after the consumption of a high-carbohydrate breakfast (HCB) (A) or a high-soy-protein breakfast (HSPB) (B) with or without 300 g of
steamed nopal (N); *P<0.05, **P<0.01. We also show fasting and postprandial serum insulin and IAUC after the consumption of an
HCB (C) or HSPB (D) with or without 300 g steamed nopal. Values were obtained in seven healthy adults without diabetes and in 14
patients with type 2 diabetes (PT2D). Values are meanstandard error of mean. HCB-D¼HCB-patients with type 2 diabetes; HCB-
H¼HCB-healthy subjects; HCBþN-D¼HCBþnopal-patients with type 2 diabetes; HCBþN-H¼HCBþnopal-healthy subjects; HSPB-
D¼HSPB-patients with type 2 diabetes; HSPB-H¼HSPB-healthy subjects; HSPBþN-D¼HSPBþnopal-patients with type 2 diabetes;
HSPBþN-H¼HSPBþnopal-healthy subjects.
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AB
C
Figure 3. Fasting and postprandial glucose-dependent insulinotropic peptide (GIP) and incremental area under the curve (IAUC)
after the consumption of a high-carbohydrate breakfast (HCB) (A) or a high soy-protein breakfast (HSPB) (B) with or without 300 g
steamed nopal (N) in 7 healthy adults without diabetes and in 14 patients with type 2 diabetes (PT2D); *P<0.05, **P<0.01,
***P<0.001. (C) Plasma antioxidant activity after 2 hours of consuming the HCB or the HSPB in PT2D and healthy adults without
diabetes. HCB-D¼HCB-patients with type 2 diabetes; HCB-H¼HCB-healthy subjects; HCBþN-D¼HCBþnopal-patients with type 2
diabetes; HCBþN-H¼HCBþnopal-healthy subjects; HSPB-D¼HSPB-patients with type 2 diabetes; HSPB-H¼HSPB-healthy subjects;
HSPBþN-D¼HSPBþnopal-patients with type 2 diabetes; HSPBþN-H¼HSPBþnopal-healthy subjects. a >b>c>d.
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and GLP-1 concentration in healthy subjects was 310.4 pg/
mL (9.41.2 pmol/L). After the consumption of the
HCBþnopal or HSPBþnopal, there was no effect on GLP-1 in
patients with type 2 diabetes or healthy participants (data
not shown).
Serum Antioxidant Activity after Ingesting Nopal in
an HCB or HSPB
Healthy participants showed similar antioxidant activity
(9.2%6.4%) compared with patients with type 2 diabetes
(7.7%1.6%) at 120 minutes regardless of the breakfast
consumed. The inclusion of nopal increased the antioxidant
activity in healthy participants and in patients with type 2
diabetes and was more evident after the consumption of the
HSPB (Figure 3C).
DISCUSSION
Excessive and prolonged postprandial blood glucose peaks
are a serious health problem for individuals with diabetes. As
a result, changes in lifestyle have been suggested as the main
strategy for controlling the biochemical abnormalities that
are associated with type 2 diabetes.
16
We developed a dietary
strategy including the use of the inexpensive regional food
nopal to minimize postprandial glucose peaks. Our results
show that nopal has low glycemic and insulinemic indexes
that could be recommended for patients with type 2 diabetes.
Interestingly, the low glycemic index and insulinemic index
of nopal were associated with a dramatic reduction of
the IAUC for the total plasma GIP concentration. These
results suggest that nopal could regulate blood glucose and
serum insulin concentrations by modulating GIP levels.
Interestingly, the inclusion of steamed nopal in the HCB
significantly reduced postprandial blood glucose peaks.
Remarkably, the HSPB and HSPBþnopal helped prevent
postprandial blood glucose peaks. These results are impor-
tant because recommendations from the American Diabetes
Association are for patients with type 2 diabetes to maintain,
“blood glucose levels in the normal range or as close to
normal as is safely possible.”
17
The European Diabetes Policy
Group has set the maximum postprandial glucose peak to not
exceed 135 mg/dL (7.5 mmol/L) to reduce arterial risk and
160 mg/dL (9.0 mmol/L) to reduce microvascular risk.
18
The
inclusion of nopal in the HCB in patients with type 2 diabetes
reduced blood glucose by 36 mg/dL (2 mmol/L), reaching a
value near that recommended by the European Diabetes
Policy Group. The presence of nopal in the HSPB helped
significantly to avoid blood glucose peaks reaching a value of
127 mg/dL (7.07 mmol/L) at 60 minutes, a value below that
recommended by the European Diabetes Policy Group. Nopal
consumption significantly reduced the IAUC for serum insulin
in patients with type 2 diabetes after ingesting the HCB and
prevented an increase in insulin levels after consuming an
HSPB.
In this study, GIP levels seemed to be significantly
increased in patients with type 2 diabetes in the postprandial
state compared with those in healthy participants, and the
insulinotropic effect of GIP was maintained and associated
with insulin concentration in patients with type 2 diabetes
because the insulin levels increased as the GIP increased.
However, the postprandial blood glucose concentra-
tion remained high, which indicates insulin resistance.
Interestingly, the inclusion of nopal in the HCB or HSPB
significantly reduced the postprandial peaks of the total GIP
in patients with type 2 diabetes and in healthy participants.
One limitation of the study was the difference in age and sex;
patients with type 2 diabetes were older than healthy
subjects.
It is recommended to include two or three medium nopales
(approximately 250 g after cooking) in a salad, soup, grilled,
nopal juice, or as side dish for patients with type 2 diabetes
and 1
1
/
2
to 2 medium nopales for healthy people. Nopal can
be found in ethnic grocery stores in the United States, mainly
in Southern California and Texas. Another option is to
consume dehydrated nopal (13.7 g) dried at low temperature
(no higher than 55C to maintain antioxidant activity), which
is equivalent to 300 g raw nopal.
There is considerable evidence from in vitro and in vivo
studies that hyperglycemia results in the generation of
reactive oxygen species and consequently increased oxidative
stress. The presence of polyphenols (such as quercetin, iso-
rhamnetin, and kaempferol; vitamin C) and beta carotenes in
nopal contributes to nopal antioxidant activity. We demon-
strated that consumption of nopal provides antioxidant ac-
tivity in the serum of both healthy people and patients with
type 2 diabetes 2 hours after consumption. The consumption
of nopal could have a compensatory effect on the decreased
endogenous antioxidants during type 2 diabetes.
CONCLUSIONS
The current epidemic of diabetes has led to a search for
functional foods that could aid in ameliorating this pathol-
ogy. Nopal has long been used in traditional Mexican med-
icine to control diabetes, however, there was insufficient
scientific evidence regarding the ability of this plant to help
control postprandial blood glucose peaks. Our results show
that nopal has low glycemic, insulinemic, and GIP indexes
and could be recommended for patients with type 2
diabetes. The inclusion of nopal in an HCB had anti-
hyperglycemic and antihyperinsulinemic effects, and in the
HSPB, it prevented postprandial blood glucose peaks. The
consumption of nopal increased the antioxidant activity in
both healthy people and patients with type 2 diabetes.
Nopal is not a complete replacement for prescription blood
glucose drugs, but the findings in this study support the
traditional use of nopal for the safe management of glucose
without any side effects.
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AUTHOR INFORMATION
P. López-Romero is an assistant researcher, E. Pichardo-Ontiveros is an assistant researcher, A. Avila-Nava is an assistant researcher, N. Vázquez-
Manjarrez is an assistant researcher, A. R. Tovar is a professor, and N. Torres is a professor, Departamento de Fisiología de la Nutrición, Instituto
Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Vasco de Quiroga, México. J. Pedraza-Chaverri is a professor, Departamento de
Biología, Facultad de Química, Edificio F, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, Coyoacan, México.
Address correspondence to: Nimbe Torres, PhD, Departamento de Fisiología de la Nutrición, Instituto Nacional de Ciencias Médicas y Nutrición
Salvador Zubirán, Vasco de Quiroga, No. 15, Sección XVI, 14000, México. E-mail: nimbester@gmail.com
STATEMENT OF POTENTIAL CONFLICT OF INTEREST
No potential conflict of interest was reported by the authors.
FUNDING/SUPPORT
This study was supported by the Instituto de Ciencia y Tecnología del Distrito Federal, Fundación Produce 2010 and Nutriva de México S.A. de
C.V. Aguascalientes, Ags. México. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the
manuscript.
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