Prevalence and characterization of supplement use among healthy children and adolescents in an urban Japanese city

doi:10.4236/health.2011.33025

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Vol.3, No.3, 135-140 (2011) Health

doi:10.4236/health.2011.33025

Prevalence and characterization of supplement use

among healthy children and adolescents in an urban

Japanese city

Nagisa Mori, Masaru Kubota*, Shoko Hamada, Ayako Nagai

Department of Human Life and Environment, Nara Women’s University, Nara, Japan;

*Corresponding Author: masaru_kubota@chime.ocn.ne.jp

Received 2 January 2011; revised 20 February 2011, accepted 28 February 2011.

ABSTRACT

Although there a re numerous studies on the use

of supplements in children and adolescents

from western countries, only a small number of

studies have been conducted in Asian countrie s.

This study was planned to determine the use of

supplements and their association with life-

styles in healthy Japanese children and ado-

lescents. This is a community-based cross-sec-

tional study conducted i n a Jap anes e urban city,

Nara, in 2008. A total of 681 children and ado-

lescents aged between 3 and 17 years were en-

rolled. The parents were asked to complete a

questionnaire on the use of supplement s among

their children. Demographic information, health

and nutrition status of children as perceived by

parents, sleep duration, and a family history of

supplement use were also collected. A total of

20.4% of children and adolescents are presently

using (in the past one month) or have used (in

the p as t one y ear excluding the past one month)

supplements. The types of supplements most

commonly used were minerals, followed by vi-

tamins and blueberry extracts. Univariate analy-

sis indicated that supplement use was associ-

ated with older age, poor perception of health

status, shorter sleep duration, and a positive

family history of supplement use. Multiple lo-

gistic regression analysis showed that age and

a positive family history affected supplement

use. Given the approximately 20% of prevalence

of supplement use in Japanese children and

adolescents, there is a need for further research

to examine the supplements’ effectiveness and

safety.

Keywords: Supplement; Child; Adolescence;

Japan; Lifestyle

1. INTRODUCTION

The use of supplements is expanding rapidly because

of a growing worldwide awareness of health promotion

[1]. The actual prevalence of supplement use differs

greatly from country to country, presumably due to the

diversity of cultural, nutritional, and economic condi-

tions. A series of nationwide surveys in the United States

indicated that the rates of supplement use in adults aged

18 years or older ranged from 32 to 52% [2-5]. In Euro-

pean [6,7] and Asian [8,9] countries, the reported rates

were lower, i.e. approximately between 15 and 30%.

These reports have also identified the characteristics of

supplement users from cultural, economic, and nutri-

tional points of view. In contrast, little is known about

the prevalence of supplement use in children and ado-

lescents except in the United States, where as high as

approximately 30-50% of children and adolescents have

been reported to use supplements [10-13]. Small cohort

studies from Europe showed that the frequencies of sup-

plement use were 25.8% for German children and ado-

lescents [14], and 37-50% for Finnish children aged 2

and 3 years [15]. The only comprehensive report on sup-

plement use in children in Asian countries, as far as we

know, was the investigation carried out by the National

Institute of Health and Nutrition in Japan, which found

that 15% of preschool children used supplements [16].

However, this survey only targeted preschool children.

Therefore, the purpose of the present study is to deter-

mine the prevalence of supplement use in healthy Japa-

nese children and adolescents, and to consider the rela-

tionships between supplement use and demographic and

lifestyle factors.

2. MATERIALS AND METHODS

2.1. Study Design and Subjects

This study was done in Nara city from April to May in

2008. Nara is an urban city in Japan with a population of

N. Mori et al. / Health 3 (2011) 135-140

136

approximately 370,000. Among them, the approximate

population of children and adolescents aged between 3

and 17 years was 45,000. The request for participation in

the present study was first sent to several kindergartens

or schools nearby. After obtaining consent by the princi-

pal, enrolled kindergartens or schools were decided by

random selection. The questionnaire that we devised for

the present study was distributed to the parents of the

participants through their kindergartens or schools. The

parents were then asked to complete the questionnaire at

home. A “supplement” was defined as a preparation that

provides various kinds of food substances in the form of

either tablet, capsule, powder, liquid or jelly [17]. 975

questionnaires were distributed, and responses were ob-

tained from 736 parents (recovery rate: 75.5%). After

responses with incomplete answers or those involving

reported supplements that did not meet the definition

given above, such as the over-the-counter medicines,

were excluded, a total of 681 children and adolescents

aged between 3 and 17 years were available for analysis.

These included 142 preschool children (3-6 years), 125

students in the 4th grade (9-10 years) and 109 students in

the 6th grade of elementary school (11-12 years), and 180

students in the 3rd grade (14-15 years), and 125 in the 2nd

grade of senior high school (16-17 years). There were

326 males and 355 females. We obtained consent from

all parents beforehand to use their children’s data in our

study. This project was approved by the ethical and epi-

demiological committee at Nara Women’s University.

2.2. Questionnaire

First, it was asked whether the child was given any

type of supplement in the past one month (present use)

or the past one year excluding the past one month (past

use). Also, data on types of used supplements, and the

family history of supplement use were collected. Demo-

graphic features, parents’ perceptions of children’s health

status and balance of diet, and average sleep hours per

day in the past one month were requested.

2.3. Statistics

Difference in supplement use according to age was

examined by one-way analysis of variance (ANOVA).

After the present and past users were combined into total

users, the association of supplement use with demo-

graphic features and various lifestyle elements was

evaluated; the chi-square test was used to determine as-

sociations with sex and family history, and the Kruskal-

Wallis test was used for age, health status, balance of

diet, and sleep hours. Multiple logistic regression analy-

sis for prediction of children’s supplement use was per-

formed by including variables of age, gender, health

status, food status, sleep hours, and family history of

supplement use. In the analysis, age and sleep hours

were categorized as indicated in Table 2. A statistical

analysis was made using “StatMate III” (ATMS, Tokyo,

Japan). P values less than 0.05 were considered signifi-

cant.

3. RESULTS

3.1. Supplement Use

Table 1 indicates the numbers of samples and sup-

plement users in relation to the age of the participants. A

total of 139 children (20.4 %) had experience using sup-

plements, including 72 (10.6%) present users, and 67

(9.8%) past users. In addition, the prevalence of total

users tended to increase with an increase of age (p <

0.001). There was no gender difference between sup-

plement users and non-users.

3.2. Association of Supplement Use with

Demographic Features and Lifestyles

Univariate analysis indicated that supplement use was

associated with age, health status, sleep duration, and

family history. However, multiple logistic regression

analysis revealed that only age and family history of

supplement use were associated with supplement use

(Table 2).

3.3. Types of Used Supplements

The types of supplement most frequently used were

minerals including iron, calcium, and zinc 54 (37%),

followed by vitamins including multi-vitamins, vitamin

B and vitamin C 42 (29%), and blueberry extracts 23

(16%) (Figure 1). As far as side effects were concerned,

only one case with a rash after receiving blueberry ex-

tracts was reported.

Table 1. Numbers of subjects and supplement users.

Total

number Supplement

user

Age Present Past Total

4-6 yr 142 4 (2.8%) 7 (4.9%) 11 (7.7%)

9-10 yr 125 7 (5.6%) 10 (8.0%) 17 (13.6 %)

11-12 yr109 16 (14.7%) 4 (3.7%) 20 (18.3%)

14-15 yr180 27 (15.0%) 32 (17.8%) 59 (32.8%)

16-17 yr125 18 (14.4%) 14 (11.2%) 32 (25.6%)

Total 681 72 (10.6%) 67 (9.8%) 139 (20.4%)

N. Mori et al. / Health 3 (2011) 135-140

137

Table 2. Association between supplement use and demographic or lifestyle factors.

Supplement use

Number (-) (+) p value β coeffieint [95%CI]# p value

Total number (%) 681 542 (79.6) 139 (20.4)

Gender 0.78 0.29 [–0.12~0.72] 0.17

Male 326 (47.9)§ 258 (47.6) 68 (48.9)

Female 355 (52.1) 284 (52.4) 71 (51.1)

Age <0.001* 0.11 [0.03~0.19] <0.01

3-6 yr 141 (20.7) 133 (24.5) 8 (5.8)

9-10 yr 125 (18.4) 108 (19.9) 17 (12.2)

11-12 yr 109 (16.0) 88 (16.2) 21 (15.1)

14-15 yr 180 (26.4) 121 (22.3) 59 (42.4)

16-17 yr 126 (18.5) 92 (17.1) 34 (24.5)

Health status <0.01** 0.15 [–0.21~0.52] 0.41

Good 485 (71.2) 401 (74.0) 84 (60.4)

Moderate 169 (24.8) 119 (21.9) 50 (36.0)

Poor 27 (4.0) 22 (4.1) 5 (3.6)

Sleep duration <0.001** 0.28 [–0.61~0.04] 0.08

< 6 hrs/day 46 (6.8) 29 (5.4) 17 (12.2)

6 to < 7 hrs/day 216 (31.7) 154 (28.4) 62 (44.6)

7 to < 8 hrs/day 185 (27.2) 148 (27.3) 37 (26.6)

8 hrs/day ≤ 234 (34.3) 211 (38.9) 23 (16.6)

Balance of diet 0.11 0.35 [–0.03~0.72] 0.07

Good 334 (49.0) 275 (50.7) 59 (42.4)

Moderate 325 (47.7) 249 (45.9) 76 (54.7)

Poor 22 (3.3) 18 (3.4) 4 (2.9)

Family history of supplement use <0.001** 1.94 [1.46~2.42] <0.001

Negative 351 (51.5) 326 (60.1) 25 (18.0)

Positive 330 (48.5) 216 (39.9) 114 (82.0)

§ Numbers in parentheses indicate percentages. *Chi-square test. **Kruskal-Wallis test. # Logistic analysis.

4. DISCUSSION

Complementary and alternative medicine has become

popular throughout developed countries as the public’s

health awareness has increased [18]. Supplements be-

longing to the category of functional foods play a central

role in alternative and complementary medicine [18,19].

Although functional foods or supplements have not been

fully defined, these compounds are thought to benefi-

cially affect various functions in the body and to bring

about an improvement of health or well-being [19].

Therefore, the purposes of their use are twofold: 1) the

promotion or maintenance of health status, and 2) the

treatment of certain disorders related to shortages of

specific nutrients, especially in developing countries.

There have been numerous studies on the prevalence

of supplement use in healthy adult populations. The re-

sults of surveys differ depending upon the definition of

supplements, time of studies, and methods of surveys. In

addition, the regulation of health claims by official

N. Mori et al. / Health 3 (2011) 135-140

138

Figure 1. Types of supplements used in the present study. Mul-

tiple answers were allowed. Bars indicate the total number of

each supplement users. Minerals included multi-minerals, cal-

cium, iron and zinc. Vitamins included multi-vitamins, vitamin

A, vitamin D, and ascorbic acid.

organization should be taken into consideration. In Japan,

for example, supplement-type foods are not allowed to

present health claims except “food with nutrient function

claims”. In the United States, however, health claims are

well regulated by the Food and Drug Administration

through provisions of the Food, Drug, and Cosmetic Act.

Such difference may have an effect on the attitude of

supplement consumers [20]. In the United States, a se-

ries of National Health and Nutrition Examination Sur-

vey (NHANES) demonstrated that the prevalence of

supplement use in adults in the past two decades has

ranged from 32.4 to 52% [2,4,5]. There is a slight in-

creasing trend with time. In these reports, supplement

use was mainly investigated in adults aged 18 years and

over during the past one month. Surveys from other

countries have reported lower prevalence: 22% for men

and 33% for women in Sweden [7], 11% for men and

16.4% for women in Japan [8], and 21.8% for men and

32% for women in Korea [9]. Notably, these reports in-

volved older populations or different observation periods.

In spite of the difference in prevalence found among the

surveys, these surveys have postulated that similar

demographic or lifestyle factors can be used for predict-

ing supplement use. Female gender, older age, higher

education, higher income, and good self-reported health

were found to be associated with higher use of supple-

ments [2-9]. Association of positive lifestyle factors with

supplement use is regarded to reflect the characteristics

of supplement users [21].

An earlier study by Kovar in 1981 demonstrated that

36% of children aged less than 18 years used vitamin or

mineral supplements within the past two weeks [22].

Subsequent studies in the United States involving sub-

jects of almost the same age group have shown similar

prevalence rates of 31.8-34% [12,13]. These values were

not very different from those of European reports

[14,15]. In a recent Japanese study targeting preschool

children, the rate of supplement use was 15% [16].

Demographic or lifestyle factors associated with sup-

plement use in children were consistent with those in

adults. However, no gender difference was found in most

studies [12, 14-16]. In addition, a positive family history

of supplement use, especially supplement use by the

mother, had an influence on children’s use [10,16,23].

Our study is, as far as we know, the first cross- sec-

tional study involving children aged 3-17 years in an

Asian country. The overall prevalence of supplement use

was 20.4% which was slightly higher than that found in

the report by Sato et al. [16]. The difference is presuma-

bly due to the age of the subjects. Older age and a posi-

tive family history were associated with higher supple-

ment use. Notably, a good lifestyle and a balanced diet,

even if these were determined only according to the

parent’s perception, were found to be not associated with

supplement use. Types of supplements commonly used

in this study were minerals and vitamins. This finding is

consistent with previous studies in children and adoles-

cents [10-16]. Third-ranked supplement, blueberry ex-

tracts, is thought to be specific to Japan. The reason for

its wide use is presumably the expectation that it has an

effect on visual acuity as advertised through mass media

[24], since the percentage of myopia in students is high

in Japan [25]. Concerning adverse effects, Timbo et al

reported that 4% of supplement users experienced ad-

verse effects [26], but only one case was reported in this

study.

There are several weaknesses in the present study.

First, generalization of our results as the representative

of children and adolescents in Japan should be careful

because of the limited number of subjects. Second, the

parent’s ability to accurately differentiate various sup-

plements was quite uncertain. In order to minimize this

problem, a direct interview method should be introduced.

Finally, important information about home income and

parent’s education level was not included. We omitted

such questions because we were afraid that including

them would cause a decrease in the response rate [16]. In

spite of these weaknesses, we believe our present study

to be important for understanding the present status of

supplement use in children and adolescents, and in es-

tablishing future plans of supplement use. Majority of

supplement users expect to receive adequate information

about the supplements they are using, expect the partici-

pation of the authorities and the safety of supplement

[27]. For these purposes, the future involvement of pro-

fessionals such as doctors, dietitians, co-medical staffs,

nutrition representatives as advisers of supplement use is

necessary.

N. Mori et al. / Health 3 (2011) 135-140

139

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