Glycative Stress Research
Online edition : ISSN 2188-3610
Print edition : ISSN 2188-3602
Received : July 14, 2022
Accepted : August 11, 2022
Published online : September 30, 2022
doi:10.24659/gsr.9.3_118

Original article

Effect of Yokan intake on postprandial blood glucose
Masayuki Yagi 1), Akari Yoshimura 1), Takuya Yokoi 2), Yutaka Aoyama 2), Kaoru Masuda 2),
Chieko Sakiyama 1), Mari Ogura 1), Yoshikazu Yonei 1)
1) Anti-Aging Medical Research Center and Glycative Stress Research Center, Faculty of Life and Medical Sciences,
Doshisha University, Kyoto, Japan
2) Toraya Confectionery Co. Ltd., Tokyo, Japan

Abstract

Persistent postprandial hyperglycemia contributes to increased glycative stress. Therefore, it is important to understand theeffects of carbohydrates in food on postprandial glycative stress. In this study, we evaluated the effects of Yokan, a Japanese
confectionery (Wagashi) made of sugar, azuki beans, and agar, on glycative stress by comparing blood glucose changes after
intake of Yokan, sugar water, and rice.
The subjects were 16 healthy 20 ~30 year men and women who attended the briefing session in advance and gave their writtenconsent to participate in the study. The test foods were rice (A) as the reference food, Yokan (B, C, D) as the test food, andsugar water (E) with 50 g of carbohydrate, and the subsequent blood glucose changes were verified. FreeStyle Libre Pro wasused for the study, and glucose concentrations in tissue interstitial fluid were measured as blood glucose levels. Blood glucose
was collected prior to 120 min after intake of the test food. Results were evaluated by blood glucose change (ΔBG), maximum
blood glucose (ΔCmax) and area under the glucose curve (iAUC). Study results were analyzed using multiple testing with the
Bonferroni method.
The study was free of adverse events and no subjects met the exclusion criteria for analysis. The glucose change curve forthe 16 subjects was higher for test foods E > A > B, C, and D, in that order. ΔBG after intake of A was higher than B, C, andD at 90 and 120 min, respectively. ΔBG in B was lower than that of E after 45 min. ΔBG in C tended to be lower than thatof E after 45 min. The iAUCs were higher in the order A > E > B > C > D, with significantly lower values for B, C, and D
compared to A. The iAUC of D tended to be lower than that of E. The ΔCmax was higher in the order of E > D > A > B and C.
The ΔCmax of B and C tended to be lower than that of E.
The factors that caused the lower ΔBG, iAUC, and ΔCmax in test foods B, C, and D compared to A and E were presumed tobe the effects of the azuki bean component and agar in Yokan, and changes in structure and function during food processing.
From the perspective of glycemic index (GI), the effects of sugar on Yokan intake were considered comparable to thoseof common foods. Yokan may be a functional food with less effect on glycative stress compared to rice or sugar intake if
consumed in appropriate amounts.

KEY WORDS: glycative stress, postprandial blood glucose, Yokan, azuki beans

Introduction
Glycative stress is one of the negative effects on the
body caused by the generation and accumulation of advanced
glycation end products (AGEs) 1). Glycative stress is involvedin aging and various age-related diseases, and is a factor in
the development of skin aging, diabetic complications,
osteoporosis, and dementia. There are several ways to reduce

glycative stress, i.e., suppressing hyperglycemia, inhibiting
glycation reactions, and promoting the breakdown andexcretion of AGEs 2, 3). Even in healthy individuals, rapid
postprandial hyperglycemia causes an increase in blood
aldehydes, which in turn increases glycative stress 4, 5).
Therefore, it is important to understand the effect ofcarbohydrates in foods on postprandial glycemic index (GI),and elevation as a countermeasure against glycative stress.

Contact Address: Professor Masayuki Yagi, PhD
Anti-Aging Medical Research Center, and Glycative Stress Research Center,
Faculty of Life and Medical Sciences, Doshisha University
1-3, Tataramiyakodani, Kyotanabe-shi, Kyoto, 610-0321 Japan
TEL & FAX: +81-774-65-6394 e-mail: myagi@mail.doshisha.ac.jp
Co-authors: Yoshimura A, ctuh2036@mail4.doshisha.ac.jp;
Yokoi T, t.yokoi@toraya-group.co.jp; Aoyama Y, aoyama@toraya-group.co.jp;
Masuda K, kaoru.masuda@toraya-group.co.jp; Sakiyama C, csakiyam@mail.doshisha.ac.jp;
Ogura M, m-ogura@po.kbu.ac.jp; Yonei Y, yyonei@mail.doshisha.ac.jp_ 118 _

Glycative Stress Research 2022; 9 (3) : 118-125(c) Society for Glycative Stress ResearchGlycative Stress Research

To control postprandial hyperglycemia, it is important to
reduce carbohydrate intake, select low GI foods that causea slow rise in postprandial blood glucose levels 6), eat foods
rich in protein, fat, acetic acid, and dietary fiber alongwith carbohydrates 7), and eat vegetables first rather thancarbohydrates 8). Confectionery is consumed mainly as asnack or dessert, and often contains a lot of sugar and has
a strong sweet taste. Excessive intake of sugar-rich foods
is a factor in the development of dental caries, obesity, andmetabolic syndrome 9). While, the consumption of sweets assnacks improves attention and memory 10, 11). Furthermore,
it has been reported that confectioneries can enhancecommunication and creativity in group activities 12). The
purpose of this study was to evaluate the effect of Yokan,a Japanese confectionery (Wagashi) made of sugar, azuki
beans, and agar as main ingredients, on glycative stress after
intake of Yokan, sugar-water, and steamed rice as test foods
with a unified carbohydrate content of 50 g.

the study. All subjects were healthy and free from chronic
physical diseases. Subjects who have been fully informed ofthe purpose and content of the study, are competent to consent,
understand the study well, volunteer to participate, and are able
to consent to participation in the study in writing. They wereable to come to the office on the designated study date and beable to complete the study. Those who have been approved by
the study investigator as suitable participated in the study.

Survey items and examination details
Subjects completed a subject background survey, inwhich they self -reported their age, medical history, andfood allergies, concurrently underwent blood tests (Table 2).
The test was performed using FreeStyle Libre Pro(Abbott Laboratories, Chicago, IL, USA), and the glucose
concentration in the tissue interstitial fluid measured during
the study period was used as the blood glucose level 13).

Study protocol

Methods

As previously reported 14-18), this study was conductedin accordance with the unified protocol by the Japanese
Association for the Study of GI 19). During the study period,
subjects were instructed to observe to the following.
Avoid an irregular lifestyle, such as lack of sleep andbinge eating and drinking, and lead a normal life. Diet,

Subjects

Sixteen subjects met the following selection criteria( Table 1 ). Males and females between the ages of 20 and
30 years at the time of obtaining consent to participate inTable 1. Subjects profile.
Unit
Number of subjects
Age

years

Body weightkg

Body height
BMI

cm

Total

Male

Female168822.5 ± 0.9

22.6 ± 0.7

22.4 ± 1.0

166.0 ± 10.1

174.4 ± 4.1

157.6 ± 6.6

21.2 ± 2.8

22.3 ± 2.6

20.2 ± 2.5

58.9 ± 11.6

67.9 ± 9.2

49.8 ± 4.6

Results are expressed as mean ± standard deviation. BMI, body mass index.

Table 2. Result of the blood chemistry test.
Test item

Unit

Measured value

Reference range

FBG

mg /dL

83.6 ± 4.9

99

IRI

μU/mL

5.3 ± 1.5

-

HDL-C

mg/dL

61.3 ± 13.8

40

HbA1c
Total cholesterol
LDL-C
TG

AST

ALT
γ - GT%

5.1 ± 0.2

mg/dL

181.5 ± 24.3

mg/dL

103.6 ± 19.8

mg/dL
U/ L
U/ L
U/ L

5.5

-

60 - 11975.4 ± 62.6

30 - 149

15.8 ± 18.4

30

17.8 ± 5.8

17.3 ± 9.3

3050Results are expressed as mean ± standard deviation, n = 16, FBG, fasting blood glucose; IRI, immunoreactive insulin; HDL,
high-density lipoprotein; LDL, low-density lipoprotein; TG, triglyceride; AST, aspartate transaminase; ALT, alaninetransaminase; γ - GT, γ -glutamyltransferase.

_ 119 _

Effect of Yokan Intake on Postprandial Blood Glucose

exercise, and sleep should be maintained in the same
quantity and quality as prior to participation in the study.
The initiation of new health foods, supplements, etc. will
be prohibited. Other activities that may affect the results ofthe study are prohibited. On the day before and the day ofthe examination, the following items were instructed to beobserved. Excessive exercise is prohibited during the pre-test
and the day before the test. Sleep at least 6 hours on the day
before the examination. Alcohol consumption is prohibitedfrom the day before until the end of the examination on theday. Avoid fatty foods for dinner and drink nothing but water
after 10 : 00 p.m. on the day before the pre-test and the day ofthe exam. Exercise and any physical activity that may cause
sweating is prohibited until the end of the examination on
the day of the examination. For women, the examination will
not be conducted during menstrual periods. During the test,
the subject should remain in a sitting position and should not
use the telephone, sleep, engage in excessive brain activity(e.g., texting, computers), or engage in physical activity. Afterintake of the test foods, the subjects should fast until the endof the study.
Subjects affixed the Libre Pro sensor to themselveson the lateral upper arm at least 2 days prior to the test. No
restrictions were placed on bathing, swimming, or exercise
during the period of wearing the Libre Pro Sensor. The test
was conducted at 10:00 a.m. The test food was consumed
in a 10-min period. The subjects then watched a video in asitting position, allowing them to remain relaxed until 12:00,
when the test ended.
The test food was ingested after chewing each mouthfulat least 30 times before swallowing. Blood glucose readings
were collected before (1st time), 15 min (2nd time), 30 min(3rd time), 45 min (4th time), 60 min (5th time), 90 min (6thtime), and 120 min (7th time) after ingesting the test food.

Test foods
Nutritional components of the test foods used in thisstudy were calculated using the values labeled on each food,and the carbohydrate intake per serving was standardized
to 50 g (Table 3 ). Commercially available packaged rice,sprinkle, Yokan products, and sugar water were used inthis study. Packaged rice was "Sato no Gohan, Niigata
Koshihikari 150 g" (Sato Shokuhin Kogyo, Niigata, Japan).
The sprinkle was "Noritama" (Marumiya Shokuhin Kogyo,
Suginami-ku, Tokyo, Japan). Three types of Yokan products
were used: Small Yokan: Yoru no Ume, Sora no Tabi,

Omokage (Toraya, Minato-ku, Tokyo). Granulated sugar(Mitsui Sugar, Chuo-ku, Tokyo) was used as the sugar.
Wilkinson Soda Water (Asahi Soft Drinks, Sumida-ku,
Tokyo) was used as the soda water. The test foods were A ~ E,
and the intake amounts were as follows.
A (reference food): 150 g packaged rice + 2.5 g sprinkles(total carbohydrate: 50 g)
B (test food): 71 g small Yokan "Yoru no Ume"
(total carbohydrate: 50 g)
C (test food): 73 g small Yokan "Sora no Tabi"(total carbohydrate: 50 g)
D (test food): 73 g small Yokan "Omokage"(total carbohydrate: 50 g)
E (test food): Sugar water (50 g sugar dissolved in 150 mL
water containing approximately 10 % carbonated water)(total carbohydrate content: 50 g)
All A ~ E test foods were ingested within 10 min after
the start of the test.

Selection of subjects for safety analysis
The subjects for the safety analysis were those who had
consumed the test food at least once.

Selection of subjects for efficacy analysis
The subjects for the efficacy analysis were those whocompleted the prescribed study schedule and reviewed all
study details, excluding those who met the exclusion criteria
for analysis as described below. Persons whose conduct wasconspicuously found to undermine the reliability of the test
results. Subjects who were found after the start of study tohave met the exclusion criteria or were unable to comply withthe restrictions.

Statistical analysis
The safety evaluation and analysis of the study were
performed on the safety analysis subjects, and adverse eventsand side effects were evaluated by tabulating the symptoms,
severity, and frequency of adverse events and side effects.
Efficacy analysis of the test results was performed onthe "subjects for the efficacy analysis". The value obtainedby subtracting the blood glucose level over time after
consumption of the test food from the blood glucose level

Table 3. Nutrition facts of test food.
Test foodServing unit(g)

Energy(kcal)

Protein
(g)

Fat
(g)

Carbohydrate(g)

Sodium chloride
amount (g)

A

152.5

220

3. 5

0.6

50

0.23

B

71

210

3

0

50

0

C

73

215

3

0

50

0.03

D

73

213

3

0

50

0

E

50

194

0

0

50

0

A, rice 150 g + sprinkle 2.5 g; B, small Yokan Yoru no Ume; C, small Yokan Sora no Tabi; D, small Yokan Omokage; E, sugar water 150 mL.

_ 12 0 _Glycative Stress Research

before consumption of the test food (first time; 0 min value)
was the blood glucose change value (Δ blood glucose; ΔBG),
and the maximum blood glucose change value up to 120 min
after the test started was the maximum blood glucose change
value (ΔCmax; maximum blood glucose concentration). The
area under curve of the elevated blood glucose (incremental
area under curve; iAUC) was calculated according to theunified protocol of the Japanese Association for the Study of
GI 19). Statistical analysis was performed using the software
BellCurve for Excel (Shakai Joho Service, Shinjuku-ku,
Tokyo). Blood glucose values were expressed as mean ±standard error (SE). For cross-group comparisons of study
results, after multiple testing using the Bonferroni method,a two-tailed test with a risk rate of less than 5 % (p < 0.05)
indicated a significant difference, and a two-tailed test witha risk rate of 0.05 ≤ p < 0.1 indicated a significant trend.

Evaluation of efficacy
Since no subjects met the exclusion criteria for analysis,
all 16 study participants were included in the efficacy analysis.

Efficacy analysis
Overall analysis

The subjects' blood glucose levels before consumptionof each test food ranged from 83.8 ~ 91.9 mg/dL, reaching
their highest level 45 min after the start of the study and thendeclining ( Table 4 ). The changes in blood glucose (ΔBG)
after consumption of test food A were all higher at 90 min(p < 0.001) and 120 min (p < 0.001) compared to B, C, andD, and lower at 30 min (p = 0.032) and 45 min (p = 0.053)
compared to E and higher at 90 min (p = 0.002) and 120 min(p < 0.001) and higher at 90 min (p = 0.002) and 120 min(p < 0.001, Fig. 1 ). ΔBG after intake of B was lower than E
after 45 min (p = 0.032). ΔBG after intake of C tended to belower than E after 45 min (p = 0.086). No differences wereobserved in ΔBG at other measurement times after intake of
B, C, and D.
The iAUCs of the test foods were higher in the order
A > E > B > C > D and significantly lower in B (p = 0.018),
C (p = 0.008) and D (p = 0.004) compared to A (Fig. 2-a).
There was a trend toward lower iAUCs for D compared to E
(p = 0.094).
The ΔCmax of the test foods were higher in the orderof E > D > A > B and C ( Fig. 2-b ). The ΔCmax of B (p =0.064) and C (p = 0.062) tended to be lower than that of E.

Ethical standards
This study was conducted in compliance with the
Declaration of Helsinki (as amended by the 2013 WMA
Fortaleza Assembly) and the Ethical Guidelines for
Medical Research Involving Human Subjects (notified
by the Ministry of Education, Culture, Sports, Scienceand Technology and the Ministry of Health, Labor andWelfare). The study was conducted after the subjects were
fully informed of the study details in advance, and after
they expressed their willingness to participate in the study
and voluntarily submitted a consent form. This study was
conducted under the deliberation and approval of the Ethics
Review Committee on "Research on Human Subjects" of the
Glycation and Stress Research Society (GSE #2021013). In
addition, this study was conducted by registering with the
public database set up by the University Medical Institutionsof National Universities (UMIN # 000045927).

Subclass analysis
In the subclass analysis, all 16 subjects were divided
into the top 8 highest (high group) and the bottom 8 lowest(low group) based on the iAUC at the intake of test foodA, the reference diet, to examine differences in iAUC and
ΔCmax after intake of test foods (B, C, D, E) (Fig. 3 ). The
iAUC and ΔCmax were 1.75-fold (p < 0.001) and 1.47-fold(p = 0.0046) higher in the high group than in the low group,
respectively, when test food A was consumed. The iAUCof the high value group was 1.74 -fold (p = 0.02) higher inResults

Safety assessment
No adverse events were reported in this study (data notshown).

Table 4. Blood glucose level fluctuation after test food intake.
Time (min)

A

B

C

D

E

0

85.6 ± 3.0 (5.8)

83.8 ± 1.8 (3.5)

91.9 ± 2.6 (5.0)

88.3 ± 2.1 (4.1)

83.8 ± 2.5 (4.9)

15

98.5 ± 3.2 (6.2)

102.1 ± 3.4 (6.6)

112.9 ± 3.6 (7.0)

103.4 ± 3.0 (5.9)

105.2 ± 4.2 (8.3)

30

126.4 ± 3.8 (7.5)

130.9 ± 4.7 (9.2)

142.8 ± 4.6 (9.1)

131.7 ± 4.3 (8.4)

140.7 ± 5.4 (10.6)

45

139.8 ± 5.1 (10.0)

136.9 ± 4.7 (9.1)

147.1 ± 5.4 (10.7)

143.8 ± 4.9 (9.7)

154.4 ± 5.0 (9.8)

60

133.1 ± 6.0 (11.7)

122.9 ± 5.4 (10.6)

130.4 ± 6.2 (12.2)

132.4 ± 7.3 (14.2)

137.3 ± 5.3 (10.4)

90

125.0 ± 4.9 (9.6)

99.5 ± 5.0 (9.7)

103.8 ± 4.2 (8.3)

99.7 ± 5.4 (10.5)

102.4 ± 3.9 (7.6)

120

125.0 ± 4.5 (8.9)

89.3 ± 4.9 (9.5)

91.0 ± 3.3 (6.4)

87.2 ± 4.0 ( 7.8)

88.1 ± 4.8 (9.4)

Results are expressed as mean ± standard error (95 % CI), n = 16, A-E; details of the test food are shown in Table 3.

_ 121 _

Effect of Yokan Intake on Postprandial Blood Glucose

80
70

†

60

*

BG (mg/dL)

50
40
30

*
*

20
10

0

0

15

30

45

60

-10

75

90

D

E

105

120

135

Time (min)A

B

C

Fig. 1. Fluctuation of the ΔBG level at the time of test food intake.

Results are expressed as mean ± standard error, n = 16, †p < 0.1, * p < 0.05 vs standard food (A), Bonferroni test, A ~ E ;details of the test food are shown in Table 3.

Fig 1.
b)

a)

*

†

80
70

4000

Cmax (mg/dL)

iAUC (mg/dL · min)

5000

†

†

3000
2000
1000

60
50
40
30
20
10

0

A

B

C

D

0

E

Test food

A

B

C

D

E

Test foodFig. 2. The amount of iAUC and ΔCmax after test food intake.

Fig2. b) ΔCmax. Results are expressed as mean ± standard error, n = 16. † p < 0.1, * p < 0.05, Bonferroni test. ΔCmax,a) iAUC,

maximum blood glucose change; iAUC, incremental area under the curve of blood glucose change. A ~ E ; details of the test
food are shown in Table 3.

(a)

(b)
_ 122 _Glycative Stress Research

b)

a)

100

*

6000

*

Cmax (mg/dL)

iAUC (mg/dL · min)

8000

*

4000
2000
0

*

80
60
40
20

A

B

C

D

0

E

A

Test food

B

C

D

E

Test foodFig. 3. Subclass analysis of iAUC and ΔCmax after test food intake.

a) iAUC,Fig
3. b) ΔCmax. , higher group (n = 8); , lower group (n = 8), Results are expressed as mean ± standard error, * p < 0.05,
Bonferroni test. ΔCmax, maximum blood glucose change; iAUC, incremental area under the curve of blood glucose change. A ~ E ;b)a)details of the test food are shown in Table 3.

B and 1.69-fold (p = 0.003) higher in C than in the low
value group, but no difference was observed in D and E. The
ΔCmax of B, C, D, and E did not differ between the highand low groups.

Discussion

Blood glucose changes after Yokan intake

In this study, the amount of carbohydrate in the test
foods was uniformly set at 50 g. Test foods B, C, and D are
Yokan, which are processed with sugar, beans such as azuki
beans and agar as main ingredients. Compared to the intake
of sugar water (E) alone, B showed lower ΔBG (p = 0.032)
and ΔCmax (p = 0.064) after 45 min, C showed lower ΔBG(p = 0.086) and ΔCmax (p = 0.062) after 45 min, and D
showed a lower iAUC (p = 0.094).
In a study in which rice was cooked with 1.7 ~ 2.5 %agar added to rice, the agar inhibited thermal changes in therice and glucose formation in the digestive tract, resulting
in suppression of postprandial hyperglycemia 20). Combined
intake of rice and 50 % xanthan gum solution suppressed
postprandial hyperglycemia by prolonging the residence timeof the rice in the stomach through food mass formation andby inhibiting digestion through sol (colloid) formation of riceand xanthan gum 21). Furthermore, flavonoids 22) and catechinglycosides 23) contained in azuki beans extract have beenreported to inhibit α-glucosidase. From these results, it waspresumed that the low ΔBG of B, C, and D was caused by
the azuki beans and agar contained in Yokan.
The ΔBG of A (rice) decreased more slowly than thatof the other test foods after 60 min. The main carbohydrates
in A are rice-derived starch, B, C, and D are sugar and azuki
bean-derived starch, and E is sugar. Factors that influence
the postprandial hyperglycemia include the gastric emptying
time of ingested carbohydrates, the rate of digestion andabsorption in the small intestine, and the promotion of insulin
secretion by incretin 24). The difference in ΔBG after intake

of A may involve differences in digestion and absorptionof starch and sugar in rice. In our previous study 5), thesuppression of elevated blood glucose levels after intakeof bread containing heat-moisture-treated high-amylose
corn starch (HMT-HAS) was more pronounced in businessworkers (mean age: 36.9 ± 9.3 years, n = 19) than in university
students (22.6 ± 1.3 years, n = 13). The differences in the age
and insulin resistance of the subjects were presumed to befactors in the blood glucose level differences.
The results of the subclass analysis in this study showedthat differences between the high and low iAUC groups in A
(rice) were observed only in B and C, while not in D and E.
Test foods B, C, and D are Yokan, and their main ingredientsare the same. Azuki bean paste obtained by cooking azuki
beans changes the structure and function of starch andprotein during the heating process and storage 25). Therefore,food processing and cooking methods may also play a role inblood glucose changes after food intake.

GI of test foods
The GI is the potential ability of a carbohydrate-richfood or meal to raise postprandial blood glucose elevationand is an index developed to evaluate the quality ofphysiological functions of carbohydrates 6). The GI value iscalculated by using rice or glucose as the reference food.
When glucose is used as the reference food, 70 or
higher is defined as high GI, 69 ~ 56 as medium GI, and55 or lower as low GI. In addition, when rice is used as thereference diet, foods that are 83 or higher, multiplied by 1.2
times the definition of the GI value category, are consideredhigh GI foods, foods between 82 and 65 are considered
medium GI foods, and foods 64 or lower are considered
low GI foods 26). The iAUCs obtained from the results ofthis study were calculated based on the protocol (unified
method)19) recommended by the Japanese Association of thestudy of GI, with the GI of test food A (rice) as 100. The
GI were 72.1 for B, 69.8 for C, 68.0 for D, and 90.9 for E_ 123 _

Effect of Yokan Intake on Postprandial Blood Glucose(Fig. 2-a). Therefore, in terms of GI, E was estimated to be ahigh GI food, and B, C, and D were estimated to be medium
GI foods. The average GI value of the diet consumed by
Japanese women (when glucose is used as the referencediet) is 67 27). Therefore, the effect of carbohydrates on the
Yokan intake (B, C, and D) in terms of GI was considered
to approximate that off common foods. In contrast, Yokan is
not a staple food but a luxury food. Thus, it is not expected
to lower GI as a composite food consisting of a staple food,main dish, and a side dish. It is common practice to consume
Yokan and wagashi together with tea or matcha tea. Catechininduced α-amylase and α-glucosidase inhibitory effects havebeen observed in tea 28, 29). Therefore, the GI of Yokan in
the general eating habits of Japanese is expected to be evenlower.

Effects of Yokan intake on glycative stress
Glycative stress is also increased by postprandial
hyperglycemia, oxidative stress, and mental stress 1).
Generally, sweetened confectionery is considered a food that
increases glycative stress because of its high sugar content
and its tendency to cause a postprandial glucose elevation.
In this study, in which the amount of carbohydrate wasstandardized to 50g, the iAUC (D) or ΔCmax (B, C) of Yokan
was lower than that of sugar water. The inhibitory effect of
Yokan on glycative stress is presumed to be due not only tothe inhibitory effect of agar, a raw material, on elevated blood
glucose 20), but also to the effect of components contained inazuki beans. Azuki beans contain 15 flavonoids 30) and havebeen shown to have antioxidant effects 31) and α-amylase andα-glucosidase inhibitory effects 22, 23). The red azuki beanpaste obtained by cooking azuki beans contains 70 different
aroma components 32), and maltol is presumed to be involved
as a characteristic sweet aroma component 33). The aroma

component of azuki bean paste is involved in imparting a
sense of deliciousness satisfaction in food intake 33). Yokan
has also been developed as a space food, not only for its
long-term shelf life and suitability as a food with reduced
dispersibility when ingested, but also for its function as amental stress-relieving food for astronauts 34). Based on thesefindings, Yokan intake was considered to be a functional
food with a smaller influence on glycative stress than rice orsugar water when consumed in appropriate amounts.

Research limitations
The subjects of this study were healthy 20 ~ 30 year-old
men and women. The effects of Yokan on blood glucose withage and on food intake after intake such as a snack have notbeen verified. These effects need to be further verified in the
future.

Conclusion
The results of the examination of blood glucose changes
after yokan intake indicate that Yokan may be a functional
food with a smaller effect on glycative stress than rice orsugar intake, if consumed in appropriate amounts.

Conflict of interest declaration
This research received support from Toraya Confectionery
Co. Ltd. (Minato-ku, Tokyo, Japan).

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