Relationship between Extent of Coffee Intake and Recognition of Its Effects and Ingredients

doi:10.4236/detection.2013.11001

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Detection, 2013, 1, 1-6

http://dx.doi.org/10.4236/detction.2013.11001 Published Online July 2013 (http://www.scirp.org/journal/detection)

Relationship between Extent of Coffee Intake and

Recognition of Its Effects and Ingredients*

Hiroki Sugiura1, Shinichi Demura1, Yoshinori Nagasawa2, Shunsuke Yamaji3, Tamotsu Kitabayashi4,

Shigeki Matsuda5, Takayoshi Yamada6, Ning Xu7

1Graduate School of Natural Science and Technology, Kanazawa University, Ishikawa, Japan; 2Department of Health and Sports

Sciences, Kyoto Pharmaceutical University, Kyoto, Japan; 3Faculty of Medical Sciences, University of Fukui, Fukui, Japan; 4Faculty

of Science Division 1, Tokyo University of Science, Tokyo, Japan; 5Junior College, Gifu Shotoku Gakuen University, Gifu, Japan;

6Faculty of Education and Regional Studies, University of Fukui, Fukui, Japan; 7Human and Socio-Environmental Studies, Kana-

zawa University, Ishikawa, Japan.

Email: [email protected]

Received June 12th, 2013; revised July 10th, 2013; accepted July 17th, 2013

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

This study examined the relationship between number of cups of coffee intake and recognition of the effects of coffee

intake and its ingredients in young males and females. The subjects included 624 young people (ages 15 - 24; 359 males,

265 females), who drank coffee habitually. They were classified into three groups on the basis of the number of cups of

coffee consumed per day: “one cup,” “two cups,” and “over three cups.” In males, about 25% of the “over three cups”

group expected “resolution of stress” from coffee, and this percentage was higher than that in the other groups. In fe-

males, about 18% of the same group had similar expectations; however, no significant group difference was found

among the three groups. Few persons expected protective effects of diabetes mellitus and cancer in both genders (about

5% answer rate). About 20% of males and 18% of females in the “over three cups” group recognized the “laxative

property” of coffee intake, and a significant group difference was found only in males. Even in the “one cup” group,

over 77% knew that “caffeine” is an ingredient of coffee; however, few persons (under 15%) knew “poly-phenol,”

which has protective effects of diabetes mellitus and cancer. In addition, no significant group difference was found in

both genders. In conclusion, regardless of the coffee intake cup-number in both genders, recognition of the effects of

coffee intake was low in both males and females and the recognition of effects differs by the intake cup-number in

males. Only few persons knew the other ingredients in coffee apart from “caffeine.”

Keywords: Coffee; Number of Cups of Intake; Expectation; Recognition

1. Introduction

Coffee is a luxury drink that is drunk by people all over

the world. It includes ingredients such as caffeine and

poly-phenol [1]. The former has effects such as allevia-

tion of stress and fatigue and central excitation [2], and

the latter has effects that reduce risks such as diabetes,

liver cirrhosis, colorectal cancer, and death [1]. On the

other hand, caffeine also has negative effects such as

diuretic and laxative properties [3,4]. Periodic coffee

intake is an effective precaution against lifestyle-related

diseases and it may be important that people recognize

the positive and negative effects of coffee intake on the

body, and drink it.

Freedman et al., Hildebrand et al., and Kuchinke and

Lux examined the effects on the body of differences in

number of cups of coffee consumed per day, and re-

ported that higher intake can be expected to produce

positive effects [5-7]. Findings on coffee intake have

been reported by many papers [8-14], including the

above reports, and have also been discussed in the media

and magazines. Habitual coffee drinkers are more likely

to recognize the effects of coffee intake and its ingredi-

ents. In addition, people who drink more coffee may

know more about coffee.

According to a survey by the All Japan Coffee Asso-

ciation in 2010 [15], coffee consumption tends to be

lower in people under 24 years old than in people over 25

years old. As stated above, because positive health effects

are expected from coffee intake, habitual coffee intake by

young people may be regarded as a useful preventive

*Research funds were not provided by any institution.

Relationship between Extent of Coffee Intake and Recognition of Its Effects and Ingredients

measure against lifestyle-related diseases. This study

examines the effects of differences in coffee intake on

physical health and recognition of coffee ingredients by

young males and females.

2. Method

2.1. Participants

A survey was administered to 1919 young people, living

in the Akita, Kanagawa, Tokyo, Ishikawa, Fukui, Gifu,

and Kyoto Prefectures in Japan (Number of responses:

1712). After examining the survey results (missing an-

swers, different answers toward the same question, etc.),

data of 132 people were excluded. The data of 1580 peo-

ple (age: 19.2 ± 1.3 years) were judged to be adequate

(males: n = 717, females: n = 863). A total of 624 young

people (19.3 ± 1.5 years, ages 15 - 24, 359 males and 265

females), who drank coffee habitually, were asked to

participate and they were classified into three groups on

the basis of the number of cups of coffee consumed per

day on average: “one cup”, “two cups”, and “over three

cups”. In addition, 50.1% of males and 38.8% of females

drank more than one cup of coffee per day, this being

significantly higher in males. Table 1 shows the daily

number of cups of coffee drunk by males and females.

The present experimental protocol was approved by the

Ethics Committee on Human Experimentation of Faculty

of Human Science, Kanazawa University (Ref. No.

2012-10).

2.2. Survey

Many studies have reported the effects of coffee intake,

but the effect of the amount of coffee consumed per day

on differences in knowledge and recognition about coffee

intake has not been examined. The following survey was

administered to young people to examine the above

problem. The survey items were created with reference to

questionnaires from previous studies [5-7,16]: “coffee

ingestion”, “number of cups of coffee consumed per day”,

“recognition of effects of coffee on health”, “recognition

of negative effects of coffee on the body”, and “ingredi-

ents in coffee”. Participants answered “number of cups of

coffee consumed per day” on the basis of a photograph

of a general coffee cup shown in the questionnaire (Fig-

ure 1). Participants responded to questions regarding

“recognition of health and negative effects of coffee on

the body” with a “Yes” or “No”, and questions of “in-

gredients in coffee” with a free description.

2.3. Statistical Analysis

Differences in responses to each question were examined

by a chi-squared frequency test (χ2 test). As with a corre-

lation coefficient, the percentage is also affected by sam-

Figure 1. One cup of coffee as defined in this study.

ple size. However, the effect of this problem is judged to

be low, because a large sample (about 500) was used in

this study. The significance level in this study was set at

p < 0.05, which was adjusted using the Bonferroni me-

thod.

3. Results

Table 1 shows the frequency and rate of coffee intake

(number of cups), by males and females. There were sig-

nificant differences in coffee intake rates in both genders,

in the following order: “one cup group (males: 60.2%,

females: 67.2%)”, “two cups group (males: 27.9%, fe-

males: 22.6%)”, and “over three cups group (males:

12.0%, females: 10.2%)”. Few people of either gender

(about 12%) drank more than three cups of coffee per

day. Sex differences were not significant in any group

(Table 2).

Table 3 shows the frequency and rate of expectations

of positive physical effects of coffee intake and test re-

sults for differences according to number of cups of cof-

fee drunk and gender. In males, a significant difference

was found on the item “stress reduction” with a higher

rate in the group who drank over three cups than in the

other two groups (one cup: 6.9%, two cups: 7.0%, over

three cups: 25.6%). In addition, all people who did not

endorse “not expect positive effects” in the “over three

cups group” expected “stress reduction”. In females, non-

significant differences were found on all items. In both

genders, rates of endorsement of “no expectation” were

over 70% (74.4% - 90.0%) in all groups.

Table 4 shows the frequency and rate of recognition of

the negative physical effects of coffee intake and test

results for differences according to number of cups of

coffee drunk and gender. In males, a significant differ-

ence was found in the item “produce loose stools”, with

higher endorsement in the “over three cups” group than

in the other two groups (one cup: 8.3%, two cups: 10.0%,

over three cups: 20.9%). However, the rates of endorse-

ment were low (under 21%) in all groups. In females, no

significant differences were found on any item. In addi-

tion, the endorsement rate was medium for the items

“stomach problems (20.8% - 51.9%)” and “close to a

restroom (32.9% - 51.2%)” in both genders, but was low

for the other items (0% - 18.5%).

Table 5 shows the frequency and rate of recognition of

the ingredients in coffee, and test results for differences

according to number of cups of coffee drunk and gender.

In both genders, non-significant differences were found

Relationship between Extent of Coffee Intake and Recognition of Its Effects and Ingredients

Table 1. Group difference in coffee intake (number of cups per day) according to gender.

One cup (A) Two cups (B) Over three cups (C)

n % n % n % χ2 p Post-hoc

Male (n = 359) 216 (60.2%) 100 (27.9%)43 (12.0%)129.9* 0.00 C < B < A

Female (n = 265) 178 (67.2%) 60 (22.6%)27 (10.2%)83.6* 0.00 C < B < A

Note: *p < 0.05.

Table 2. Coffee consumption by gender.

One cup Two cups Over three cups

n % n % n %

χ2 p

Male (n = 359) 216 (60.2%) 100 (27.9%) 43 (12.0%)

Female (n = 265) 178 (67.2%) 60 (22.6%) 27 (10.2%) 3.24 0.20

Table 3. Relationship between coffee intake and recognition of positive effects according to gender.

One cup (A) Two cups (B) Over three cups (C)

n % n % n % χ2 p Post-hoc

1. Not expectant 191 (88.4%)90 (90.0%) 32 (74.4%) 7.28 0.03

2. Diabetes mellitus prevention 2 (0.9%) 2 (2.0%) 1 (2.3%) 0.88 0.64

3. Cancer prevention 2 (0.9%) 1 (1.0%) 2 (4.7%) 3.78 0.15

4. Diet 3 (1.4%) 3 (3.0%) 3 (7.0%) 4.72 0.09

5. Metabolic syndrome prevention 2 (0.9%) 2 (2.0%) 2 (4.7%) 3.12 0.21

Male

6. Resolution of stress 15 (6.9%) 7 (7.0%) 11 (25.6%) 15.7* 0.000 A, B < C

1. Not expectant 148 (83.1%)50 (83.3%) 21 (77.8%) 0.50 0.78

2. Diabetes mellitus prevention 1 (0.6%) 0 (0%) 1 (3.7%) 3.68 0.16

3. Cancer prevention 6 (3.4%) 2 (3.3%) 1 (3.7%) 0.01 1.00

4. Diet 3 (1.7%) 2 (3.3%) 3 (11.1%) 7.14 0.03

5. Metabolic syndrome prevention 1 (0.6%) 0 (0%) 1 (3.7%) 3.68 0.16

Female

6. Resolution of stress 16 (9.0%) 3 (5.0%) 5 (18.5%) 4.14 0.13

Note: Male: One cup (n = 216), Two cups (n = 100), Over three cups (n = 43); Female: One cup (n = 178), Two cups (n = 60), Over three cups (n = 27); *p <

0.05/6 = 0.008.

Table 4. Relationship between coffee intake and recognition of negative effects according to gender.

One cup (A) Two cups (B) Over three cups (C)

n % n % n %

χ2 p Post-hoc

1. Unknown 103 (47.7%)36 (36.0%)13 (30.2%)6.76 0.03

2. Stomach problems 45 (20.8%)25 (25.0%)27 (50.0%)5.36 0.07

3. Close to a restroom 71 (32.9%)43 (43.0%)22 (51.2%)6.64 0.04

4. Creates loose stools 18 (8.3%)10 (10.0%)9 (20.9%)10.0* 0.007 A, B < C

5. Dehydration 8 (3.7%)3 (3.0%) 4 (9.3%)3.29 0.19

6. Trembling hands 9 (4.2%) 2 (2.0%)2 (4.7%)1.07 0.59

Male

7. Getting palpitations 12 (5.6%)4 (4.0%)3 (7.0%)0.61 0.74

1. Unknown 70 (39.3%) 22 (36.7%)7 (25.9%)1.82 0.40

2. Stomach problems 48 (27.0%)13 (21.7%)14 (51.9%)8.84 0.012

3. Close to a restroom 67 (37.6%)27 (45.0%)13 (48.1%)1.76 0.41

4. Creates loose stools 18 (10.1%)6 (10.0%)5 (18.5%)1.77 0.41

5. Dehydration 6 (3.4%)3 (5.0%) 2 (7.4%)1.10 0.58

6. Trembling hands 4 (2.2%)0 (0%) 2 (7.4%)4.62 0.10

Female

7. Getting palpitations 1 (0.6%) 1 (1.7%) 1 (3.7%)2.27 0.32

Note: Male: One cup (n = 216), Two cups (n = 100), Over three cups (n = 43); Female: One cup (n = 178), Two cups (n = 60), Over three cups (n = 27); *p <

0.05/6 = 0.008.

Relationship between Extent of Coffee Intake and Recognition of Its Effects and Ingredients

Table 5. Relationship betwee n coffe e intake and recognition of the ingredients of coffee according to gender.

One cup Two cups Over three cups

n % n % n %

χ2 p

1. Caffeine 179 (82.9%) 91 (91.0%) 39 (90.7%) 4.64 0.10

Male 2. Polyphenol 7 (3.2%) 9 (9.0%) 4 (9.3%) 5.60 0.06

1. Caffeine 137 (77.0%) 52 (86.7%) 25 (92.6%) 5.43 0.07

Female 2. Polyphenol 9 (5.1%) 2 (3.3%) 4 (14.8%) 4.97 0.08

Note: Male: One cup (n = 216), Two cups (n = 100), Over three cups (n = 43); Female: One cup (n = 178), Two cups (n = 60), Over three cups (n = 27).

for all ingredients. Recognition rates were high (77.0% -

92.6%) for “caffeine”, but low (3.2% - 14.8%) for “poly-

phenol” in all groups.

4. Discussion

Among 1580 young people (males: n = 717, females: n =

863), 39.5% (n = 624) habitually drank coffee. In addi-

tion, coffee intake was significantly higher in males

(50.1%, n = 359) than in females (30.7%, n = 265). Posi-

tive effects of coffee intake on the body have been dis-

cussed in the media and magazines. Freedman et al.,

Hildebrand et al., and Kuchinke and Lux examined the

effects on the body of the number of cups of coffee con-

sumed daily and reported that drinking more coffee can

be expected to produce positive effects [5-7]. People who

drink coffee habitually may know the effects of coffee

intake and its ingredients. This study examined the ef-

fects of differences in the extent of daily coffee intake on

knowledge of the effects of caffeine on physical health

and recognition of coffee ingredients by young males and

females.

The results showed that 50.1% of young males and

30.7% of young females drank coffee almost every day.

In addition, the proportions of the sample decreased sig-

nificantly in both genders in the following order: “one

cup group”, “two cups group”, and “over three cups

group”. In both genders, about 60% of coffee drinkers

drank one cup of coffee daily and about 12% of them

drank more than three cups, the latter group representing

about 5% (male: 6.0%, female: 3.1%) of all participants

(n = 1580). Inoue et al. investigated consumption of

Japanese tea, tea (red tea) and coffee, and reported that

Japanese tea is drunk the most in Japan [17]. Hence, it is

inferred that even young people drink Japanese tea in

preference to coffee.

Although it was clarified that most people (74.4% -

90.0%) of both genders, in all groups, did not expect

positive effects of coffee on health, about 25% of males

who drank more than three cups expected “stress reduc-

tion”, more than in the other two groups. Ratliff-Crain

and Kane reported that people with stress have higher

intake of caffeine [18]. Kuchinke and Lux reported that

the ability to judge positive words was enhanced by caf-

feine intake that included around three cups of coffee [7].

Mohr et al. reported that caffeine alleviates effect of

stress [2]. However, it is inferred that while some males

who drink over three cups expect the effect, overall such

persons are very few.

Hildebrand et al. reported that drinking more than four

cups of coffee per day reduces the risk of oral cancer by

50% [6]. However, the present results showed that very

few people expected cancer prevention (under 4.7%).

Young people may be very unconcerned about cancer

prevention. Freedman et al. reported that people who

drink more than three cups of coffee per day have a 10%

lower death rate than people who do not drink coffee [5].

Drinking coffee habitually as a luxury may contribute to

health promotion. It may be desirable for more young

people to recognize the effects of coffee on physical

health.

In both genders, about 40% (25.9% - 47.7%) of people

in all groups were unaware of the negative effects of

coffee intake. Brown et al. reported that coffee has laxa-

tive properties [3]. Males who felt that coffee “creates

loose stools” were more prevalent in the “over three

cups” group than in the other two groups. However, in

females, differences in coffee intake were unrelated to

recognition of this effect, and recognition overall was

low (about 18%). Because females get constipated more

easily than males, the laxative effect of coffee becomes

known when they want to make “loose stool” [19]. In

addition, many people did not know about the possibility

of “stomach problems”, “close to a restroom”, “dehydra-

tion”, “trembling hand”, “getting palpitations”, etc., from

coffee intake. It is inferred that these effects of coffee

intake differ between people and many healthy young

people experience few of them.

The results of the free description of coffee ingredients

showed that about 80% of people in both genders knew

that coffee includes “caffeine”. Effects such as “an alert-

ing influence” and “alleviate fatigue” are expected from

caffeine intake [2], and this information has been widely

publicized through the media. Hence, it is considered that

most people who drink coffee recognize caffeine. On the

other hand, polyphenol, the other major constituent after

caffeine, was little known (under 15%). Few people of

Relationship between Extent of Coffee Intake and Recognition of Its Effects and Ingredients 5

either gender may be aware of ingredients other than

“caffeine,” irrespective of the extent of their coffee in-

take. It has been reported that polyphenol has effects that

reduce risks such as diabetes, liver cirrhosis, colorectal

cancer, and death [1]. It will be necessary to get young

people to recognize these effects.

From the present results, even if people drink large

amounts of coffee, it may not be always be the case that

they have high expectations and recognition of positive

effects of coffee on the body. In any case, it may be im-

portant that people recognize the positive physical effects

of coffee intake, and drink it.

5. Conclusion

Irrespective of gender, coffee intake has little relation-

ship to expectations and recognition of the effects of

coffee on the body. Young males who drink a large

amount of coffee tend to recognize “resolution of stress”

and “creates loose stools”, but overall recognition rates

are low.

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