Abstract
Aim
Tendency for taking dietary supplements is dramatically increasing. However, limited studies exist in this regard. We aimed to assess the frequency and determinants of dietary supplement use among a nationally-representative sample of Iranian children and adolescents.
Methods
This population-based cross-sectional study (the CASPIAN V) was conducted in students aged 7 to 18 years old in 2015. Multistage, stratified cluster sampling method was used to select participants from thirty provinces in Iran. Data regarding taking vitamin and mineral supplements were collected. Demographic information, anthropometric indices, physical activity, screen time and body image were also evaluated. Multivariate logistic regression model was used for analyses.
Results
The prevalence of dietary supplements use was 34.1% and the most popular dietary supplement was Iron (12.9%). Multivariate logistic regression showed that boys (0.84, 95%CI: 0.78, 0.91) and body image perception (OR: 0.84, 95%CI: 0.75, 0.94) used less dietary supplements compared to others. Children aged 11 to 14 years (OR: 1.15, 95%CI: 1.06, 1.26) and those with moderate family socioeconomic status (OR: 1.12, 95%CI: 1.007, 1.25) used more supplement compared to other groups. Moreover, those with higher paternal educational level (OR: 0.77, 95%CI: 0.64, 0.93) used less supplements. However, living area, family size, paternal occupation, children BMI, Intended weight loss, and body image by student did not indicate any significant association.
Conclusion
Our findings indicated that about one-third of Iranian children and adolescents used dietary supplements; iron supplements were the most frequent ones. Children aged 11 to 14 years, those with higher educated mothers and moderate family socioeconomic status used more supplements compared to others. However, boys, children with excess weight and those with high-educated parents used less supplements compared to others. More studies are needed to clarify the efficacy and safety of dietary supplements in different age groups in various societies.
Keywords: Predictors, Dietary supplement, Iron, Pediatrics
Introduction
Dietary supplements such as vitamins, minerals, and some medicinal herbs are examples of complementary and alternative medicine that their use as adjunct therapies and keeping health condition are gaining popularity [1]. Based on recent national surveys, the prevalence of both adults and children whom taking dietary supplement has increased over the past decade [2, 3]. Despite of beneficial effects of vitamins and minerals on health, their effects on the treatment of some specific diseases are often inconclusive [1, 4]. In addition, relatively little has been known regarding the characteristics of supplement users particularly among children.
A national health interview survey (NHIS) revealed that 37% of American children used dietary supplements and the most popular supplement was multivitamin mineral (≥84%). Based on this study, children with higher educated parents and higher social economic status were more likely to take supplements. Supplements were recommended for both prevention and treatment of illnesses [5]. Findings from the NHIS in 2007 found that about one in nine children (11.8%) used complementary therapy in the past 12 months. Children whose parents used complementary therapy were roughly five times more likely to take such therapies compared to other children [6]. Moreover, based on Reaves et al.,'s study, adolescents who used multiple vitamin supplements had more healthier lifestyle and dietary intake rather than nonusers [7]. The aforementioned studies mentioned that taking dietary supplements were associated with ethnicity, race, location, income, education level of families and environmental and cultural characteristics. Therefore, we cannot attribute the findings of different societies to each other. Obtaining sufficient information about the most common dietary supplement and the characteristics of users in any society can be helpful for political and health providers for any intervention in this regard. To the best of our knowledge, there is no national study on dietary supplements (vitamins & minerals) among Iranian children and adolescent. Accordingly, in the present study we aimed to assess the prevalence and determinants of dietary supplement use among a nationally-representative sample of Iranian children and adolescents.
Methods
Study population and sampling framework
In the present population-based cross-sectional study (the CASPIAN V), students aged 7 to 18 years old in primary and secondary schools in both urban and rural regions from thirty provinces in Iran were recruited in 2015. Children younger or older than this age range were not included. Stratified cluster sampling method was used to select participants. Sampling procedures were explained by details elsewhere [8]. Briefly, in each province, eligible participants stratified based on the place of residence (urban or rural) and the level of education (primary and secondary) as well as this equal number of boy and girl were selected considering the place of living and grade. To obtain the desired number of samples, stratified cluster sampling method was used in each province with equal cluster sizes (n = 10). They were stratified by age, sex and living area. In each province, 480 students were randomly chosen and totally, data from 14,400 students were collected at national level. Since 269 participants did not complete the questionnaires related to the purpose of this study, data analysis were performed on 14,131 children and adolescent.
For eligible students and their parents, the aim of the study and the procedures were explained. Characteristics of the study participants were asked by a team of health-care professionals at schools in a peaceful room, away from busy classrooms by a face-to-face interview using valid questioners. Anthropometric indices were also measured by trained researchers. For completing the questioners, at least one of the parents should be presented. They were informed that questionnaires are about basal characteristics, health status and health-related behaviors in their families. Furthermore, students were asked about taking any dietary supplement in one month prior to the study and their reasons.
Assessments
In the present study, two sets of questionnaires were designed for students and their parents. The student’s questionnaire was a translated form (in Persian) of the questionnaire obtained from the WHO-GSHS. Its validity and reliability were examined and confirmed earlier [8]. Cronbach’s alpha coefficient of the questionnaires was 0.97 and Pearson’s correlation coefficient of the test–retest phase was 0.94.
In the questionnaire, there were three questions related to taking supplements as follows: 1) do you take any dietary supplements such as vitamins and minerals?; 2) if yes, which supplement?, 3) how many times a week do you take supplements?
Socioeconomic status (SES)
SES score was estimated using parent’s education and occupation, home-ownership (yes, no), type of children’s school (public, private), and family assets (having personal computer, vehicle ownership). SES score calculated as a weighted average of the aforesaid parameters and then it was classified into low, medium and high.
Body image perception
In the questionnaire, there were some questions about body image. The questions regarding the student perception of his/her weight status (too thin, a little thin, appropriate weight, a little overweight, and very obese) and questions about tendency to lose weight were used to examine the students’ body image.
Screen time and physical activity
Total cumulative time spent for the screen time (ST) behaviors was calculated by asking and summing up the duration of watching TV and/or videos, working by computer, or computer games (hours/day). To estimate the level of physical activity, a validated questionnaire was used to collect data on physical activity outside the school in the previous week. Having sufficient physical activity was defined as daily minimum 30 min that led to sweating and considerable increases in heart rate or breathing.
Anthropometric measurements
Trained health-care experts measured weight and height of students using calibrated instruments with standard methods. Weight was measured while students wearing a light cloth with the precision of 0.1 kg. Height was measured without shoes to the nearest 0.1 cm. Body mass index (BMI) was calculated by dividing weight (kg) by the square meter of height.
Statistical analysis
Data were reported in Mean ± SD (quantitative variables) and frequency (qualitative variables). For comparing qualitative and quantitative variables among classifications, chi-square and ANOVA tests were used, respectively. To determine the association between dietary supplements and the characteristics of participants, univariate logistic regression model was used. In the multivariate logistic regression model, variables with p < 0.2 in crude logistic model were included and the association between dietary supplements and children’s characteristics were reported in odd ratio (OR) and 95% confidence intervals (95%CI). Due to the type of sampling (clustering sampling), survey analysis method was used for analyses. Stata 11.0 (Stata Corp, College Station, TX) was used for all analyses. P value <0.05 was considered statistically significant.
Results
As presented in Table 1, there were significant differences among all participants (considering age and sex classifications) except the category related to children aged 7–10 years regarding taking supplements. Frequency and type of dietary supplements considering socio-demographic characteristics are represented in Table 2. In total, the prevalence of dietary supplements use among children and adolescents were 34.1%.Although there were no significant differences between the frequency of urban and rural participants who used supplement (p = 0.23), differences among the types of dietary supplements considering living area (p = 0.04) were significant. Iron supplements were the most popular dietary supplements (12.9%) among multivitamins, B complex, vitamin D, and calcium supplements (Fig. 1). The second rank was dedicated to multivitamins (8.1%) which was followed by vitamin D supplement (2.9%). After considering age range, iron supplement was also remained in the first rank of frequent supplements. There were no differences in the frequency of supplements between boys and girls (p = 0.21). As presented in Tables 1 and 2, girls (p < 0.001) aged 11 to 14 years (p = 0.003), children with high educated parents (p = 0.02) and those with higher family SES (p = 0.001) used more dietary supplements compared to other groups. There were no differences in the frequency of subjects used supplements considering BMI, while the classifications of body image by both students (p = 0.006) and their parents (p = 0.002) showed significant differences in the frequency of taking supplements. Normal weight students based on body image of children (34.6%) and their parents (34.8%) used the most dietary supplements.
Table 1.
The frequency of taking dietary supplements in age and sex categories of participants
| Variable | Dietary supplement-use n (%) | Type n (%) |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| Age category (years) | Sex category | No | Yes | Multivitamin | B complex vitamins | Vitamin D | Calcium | Iron | Others |
| 7–10 | Girl |
1663 (67.5) |
801 (32.5) |
205 (25.6) |
64 (8.0) |
61 (7.6) |
44 (5.5) |
314 (39.2) |
113 (14.1) |
| Boy |
1588 (68.0) |
746 (32.0) |
179 (24.0) |
57 (7.6) |
70 (9.4) |
41 (5.5) |
286 (38.3) | 113 (15.1) | |
| Total |
3251 (67.8) |
1547 (32.2) |
384 (24.8) |
121 (7.8) | 131 (8.5) |
85 (5.5) |
600 (38.8) | 226 (14.6) | |
| P value٭ | 0.68 | 0.81 | |||||||
| 11–14 | Girl |
1733 (63.2) |
1007 (36.8) |
231 (22.9) |
83 (8.2) |
74 (7.3) |
75 (7.4) |
400 (39.7) |
144 (14.3) |
| Boy |
1874 (67.1) |
919 (32.9) |
264 (28.7) |
75 (8.2) |
66 (7.2) |
61 (6.6) |
330 (35.9) |
123 (13.4) |
|
| Total |
3607 (65.2) |
1926 (34.8) |
495 (25.7) |
158 (8.2) |
140 (7.3) |
136 (7.1) |
730 (37.9) |
267 (13.9) |
|
| ٭P value | 0.003 | 0.11 | |||||||
| 15–18 | Girl |
1119 (63.0) |
657 (37.0) |
142 (21.6) |
47 (7.2) |
84 (12.8) |
44 (6.7) |
274 (41.7) |
66 (10.0) |
| Boy |
1426 (70.5) |
598 (29.5) |
143 (23.9) |
43 (7.2) |
62 (10.4) |
30 (5.0) |
234 (39.1) |
86 (14.4) |
|
| Total |
2545 (67.0) |
1255 (33.0) |
285 (22.7) |
90 (7.2) |
146 (11.6) |
74 (5.9) |
508 (40.5) |
152 (12.1) |
|
| ٭P value | 0.0001 | 0.10 | |||||||
| Total | Girl |
4515 (64.7) |
2465 (35.3) |
578 (23.4) |
194 (7.9) |
219 (8.9) |
163 (6.6) |
988 (40.1) |
323 (13.1) |
| Boy |
4888 (68.4) |
2263 (31.6) |
586 (25.9) |
175 (7.7) |
198 (8.7) |
132 (5.8) |
850 (37.6) |
322 (14.2) |
|
| Total |
9403 (66.5) |
4728 (33.5) |
1164 (24.6) |
369 (7.8) |
417 (8.8) |
295 (6.2) |
1838 (38.9) |
645 (13.6) |
|
| ٭P value | 0.0001 | 0.21 | |||||||
| ٭Chi-square | |||||||||
Table 2.
Frequency and type of dietary supplements in Iranian children and adolescents according to sociodemographic variables: the CASPIAN-V study
| Variable | Dietary supplement-use n(%) | Type n (%) |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| Yes | No | Multivitamin | B complex vitamins | Vitamin D | Calcium | Iron | Others | ||
| Living area | Urban | 3406 (33.8) | 6683 (66.2) | 842 (24.7) | 258 (7.6) | 295 (8.7) | 201 (5.9) | 1366 (40.1) | 444 (13) |
| Rural | 1322 (32.7) | 2720 (67.3) | 322 (24.4) | 111 (8.4) | 122 (9.2) | 94 (7.1) | 472 (35.7) | 201 (15.2) | |
| P value٭ | 0.23 | 0.04 | |||||||
| Maternal educational level | illiterate | 766 (30.8) | 1719 (69.2) | 223 (29.1) | 38 (5) | 54 (7) | 66 (8.6) | 286 (37.3) | 99 (12.9) |
| diploma/unerdiploma | 3408 (33.9) | 6642 (66.1) | 786 (23.1) | 291 (8.5) | 316 (9.3) | 201 (5.9) | 1351 (39.6) | 463 (13.6) | |
| academic education | 542 (35.8) | 970 (64.2) | 151 (27.9) | 38 (7) | 46 (8.5) | 28 (5.2) | 200 (36.9) | 79 (14.6) | |
| P value | 0.002 | <0.001 | |||||||
| Paternal educational level | illiterate | 614 (35.7) | 1107 (64.3) | 181 (29.5) | 31 (5) | 37 (6) | 50 (8.1) | 250 (40.7) | 65 (10.6) |
| diploma/unerdiploma | 3335 (33.1) | 6735 (66.9) | 784 (23.5) | 278 (8.3) | 319 (9.6) | 202 (6.1) | 1299 (39) | 453 (13.6) | |
| academic education | 667 (35.5) | 1212 (64.5) | 170 (25.5) | 43 (6.4) | 58 (8.7) | 37 (5.5) | 253 (37.9) | 106 (15.9) | |
| P value | 0.02 | <0.001 | |||||||
| SES | low | 1411 (31.2) | 3110 (68.8) | 393 (27.9) | 105 (7.4) | 110 (7.8) | 92 (6.5) | 538 (38.1) | 173 (12.3) |
| moderate | 1541 (34.3) | 2954 (65.7) | 359 (23.3) | 114 (7.4) | 134 (8.7) | 88 (5.7) | 600 (38.9) | 246 (16) | |
| high | 1566 (34.8) | 2939 (65.2) | 364 (23.2) | 124 (7.9) | 154 (9.8) | 94 (6) | 653 (41.7) | 177 (11.3) | |
| P value | 0.001 | 0.001 | |||||||
| Family size | less than 4 | 2198 (33) | 4470 (67) | 492 (22.4) | 193 (8.8) | 224 (10.2) | 144 (6.6) | 806 (36.7) | 339 (15.4) |
| more than 5 | 2454 (33.7) | 4834 (66.3) | 652 (26.6) | 172 (7) | 193 (7.9) | 142 (5.8) | 998 (40.7) | 297 (12.1) | |
| P value | 0.37 | <0.001 | |||||||
| Family compusition | single parent | 246 (29.7) | 583 (70.3) | 46 (18.7) | 11 (4.5) | 32 (13) | 15 (6.1) | 99 (40.2) | 43 (17.5) |
| Two parents | 4462 (33.7) | 8776 (66.3) | 1111 (24.9) | 356 (8) | 386 (8.7) | 276 (6.2) | 1736 (38.9) | 597 (13.4) | |
| P value | 0.01 | 0.009 | |||||||
| Mother’s job | No paid | 4052 (32.9) | 8264 (67.1) | 1015 (25) | 302 (7.5) | 324 (8) | 250 (6.2) | 1598 (39.4) | 563 (13.9) |
| paid job | 667 (37.1) | 1130 (62.9) | 149 (22.3) | 67 (10) | 94 (14.1) | 44 (6.6) | 234 (35.1) | 79 (11.8) | |
| P value | <0.001 | <0.001 | |||||||
| Father’s job | No paid | 407 (32.8) | 835 (67.2) | 91 (22.4) | 37 (9.1) | 35 (8.6) | 19 (4.7) | 158 (38.8) | 67 (16.5) |
| paid job | 4301 (33.5) | 8521 (66.5) | 1069 (24.9) | 326 (7.6) | 382 (8.9) | 275 (6.4) | 1681 (39.1) | 568 (13.2) | |
| P value | 0.58 | 0.23 | |||||||
| children BMI | Underweight | 746 (33) | 1514 (67) | 188 (25.2) | 55 (7.4) | 58 (7.8) | 51 (6.8) | 292 (39.1) | 102 (13.7) |
| Normal weight | 2992 (33.9) | 5822 (66.1) | 727 (24.3) | 241 (8.1) | 266 (8.9) | 174 (5.8) | 1155 (38.6) | 429 (14.3) | |
| Excess weight | 1976 (67.6) | 946 (32.4) | 239 (25.3) | 69 (7.3) | 88 (9.3) | 69 (7.3) | 378 (40) | 103 (10.9) | |
| P value | 0.26 | 0.28 | |||||||
| children body image by students report | Underweight | 1331 (33.6) | 2627 (66.4) | 314 (23.6) | 106 (8) | 98 (7.4) | 102 (7.7) | 528 (39.7) | 183 (13.7) |
| Normal weight | 2068 (34.6) | 3903 (65.4) | 469 (22.7) | 200 (9.7) | 172 (8.3) | 118 (5.7) | 796 (38.5) | 313 (15.1) | |
| Excess weight | 1326 (31.6) | 2869 (68.4) | 381 (28.7) | 63 (4.3) | 147 (11.1) | 74 (5.6) | 514 (38.8) | 147 (11.1) | |
| P value | 0.006 | <0.001 | |||||||
| children body image by parents report | Underweight | 1674 (33) | 3393 (67) | 418 (25) | 128 (7.6) | 119 (7.1) | 99 (5.9) | 676 (40.4) | 234 (14) |
| Normal weight | 2353 (34.8) | 4412 (65.2) | 562 (23.9) | 190 (8.1) | 226 (9.6) | 145 (6.2) | 883 (37.5) | 347 (14.7) | |
| Excess weight | 670 (30.8) | 1506 (69.2) | 177 (26.4) | 47 (7) | 70 (10.4) | 49 (7.3) | 267 (39.9) | 60 (9) | |
| P value | 0.002 | 0.002 | |||||||
| Intended weight loss | No | 3919 (83.7) | 7850 (83.9) | 952 (82) | 336 (91.1) | 306 (74.3) | 260 (88.4) | 1479 (81.9) | 586 (91.3) |
| Yes | 764 (16.3) | 1505 (16.1) | 209 (18) | 33 (8.9) | 106 (25.7) | 34 (11.6) | 326 (18.1) | 56 (8.7) | |
| P value | 0.73 | <0.001 | |||||||
| Physical activity | Low | 2774 (59.2) | 5372 (57.7) | 674 (58.2) | 244 (66.8) | 207 (49.8) | 171 (58) | 1141 (62.7) | 337 (53) |
| High | 1915 (40.8) | 3938 (42.3) | 484 (41.8) | 121 (33.2) | 209 (50.2) | 124 (42) | 678 (37.3) | 299 (47) | |
| P value | 0.10 | <0.001 | |||||||
| Screen time | Low | 3923 (84.9) | 7607 (83.3) | 929 (83) | 321 (87.7) | 333 (80) | 237 (82.9) | 1575 (86.7) | 528 (85.4) |
| High | 698 (15.1) | 1522 (16.7) | 190 (17) | 45 (12.3) | 83 (20) | 49 (17.1) | 241 (13.3) | 90 (14.6) | |
| P value | 0.01 | 0.002 | |||||||
| ٭Chi-square | |||||||||
Fig. 1.
Prevalence of dietary supplement use in children and adolescents
The association of participants’ characteristics and the frequency of taking dietary supplements are shown in Table 3. There was also a positive association between family SES (OR: 1.17, 95%CI: 1.07, 1.28), maternal educational level (OR: 1.25, 95%CI: 1.09, 1.43), and maternal paid job (OR:1.20, 95%CI: 1.08, 1.33) with taking dietary supplements. However, inverse associations in boys (OR: 0.84; 95%CI: 0.79,0.90), students with two parents (OR: 0.83, 95%CI: 0.71, 0.96) and children who had higher screen time (OR: 0.88, 95%CI: 0.80, 0.98) were found with taking supplements. As indicated in Table 3, other parameters including living area, family size, paternal occupation, children BMI, Intended weight loss, and body image by student did not indicate any significant association.
Table 3.
Determinants of dietary supplements use in univariate logistic regression model: the CASPIAN-V study
| Variable | Dietary supplements use | |||
|---|---|---|---|---|
| Crude model | ||||
| OR | CI | P value | ||
| Sex | Girl | Reference | – | – |
| Boy | 0.84 | 0.79–0.9 | <0.001 | |
| Living area | Urban | Reference | – | – |
| Rural | 0.95 | 0.88–1.03 | 0.23 | |
| Age (year) | 7–10 | Reference | – | – |
| 11–14 | 1.12 | 1.034–1.21 | 0.006 | |
| 15–18 | 1.036 | 0.946–1.13 | 0.44 | |
| Family size (number) | ≤4 | Reference | – | – |
| >4 | 1.032 | 0.962–1.108 | 0.375 | |
| Maternal educational level | Illiterate | Reference | – | – |
| <=Diploma | 1.151 | 1.047–1.266 | 0.003 | |
| Academic education | 1.254 | 1.095–1.436 | 0.001 | |
| Paternal educational level | Illiterate | Reference | – | – |
| <=Diploma | 0.893 | 0.802–0.994 | 0.038 | |
| Academic education | 0.992 | 0.866–1.137 | 0.91 | |
| Maternal occupation status | No Paid job | Reference | – | – |
| Paid job | 1.204 | 1.086–1.334 | <0.001 | |
| Paternal occupation status | No Paid job | Reference | – | – |
| Paid job | 1.036 | 0.915–1.172 | 0.58 | |
| Family composition | single parent | single parent | single parent | single parent |
| Two parents | 0.830 | 0.712–0.967 | 0.017 | |
| Family SES | low | Reference | – | – |
| moderate | 1.150 | 1.053–1.256 | 0.002 | |
| high | 1.174 | 1.076–1.282 | <0.001 | |
| children BMI | Underweight | Reference | – | – |
| Normal weight | 1.043 | 0.945–1.151 | 0.401 | |
| Excess weight | 0.972 | 0.864–1.092 | 0.629 | |
| Intended weight loss | No | Reference | – | – |
| Yes | 1.017 | 0.925–1.118 | 0.731 | |
| children body image by students report | Underweight | Reference | – | – |
| Normal weight | 1.046 | 0.961–1.138 | 0.301 | |
| Excess weight | 0.912 | 0.831–1.001 | 0.052 | |
| children body image by parents report | Underweight | Reference | – | – |
| Normal weight | 1.081 | 1.001–1.168 | 0.048 | |
| Excess weight | 0.902 | 0.809–1.005 | 0.061 | |
| Physical activity | Low | Reference | – | – |
| High | 1.062 | 0.989–1.140 | 0.099 | |
| Screen time | Low | Reference | – | – |
| High | 0.889 | 0.807–0.980 | 0.018 | |
SES socioeconomic status
*In the adjusted model, all socioeconomic status variables and age are simultaneously in the model
Multivariate logistic regression showed that boys (0.84, 95%CI: 0.78, 0.91) and children with excess weight based on body image of their parents (OR: 0.84, 95%CI:0.75, 0.94) used less dietary supplements compared to other classifications (Table 4). Children aged 11 to 14 years old (OR: 1.15, 95%CI: 1.06, 1.26), and those with moderate family SES (OR: 1.12, 95%CI: 1.00, 1.25) used more supplement compared to other groups. We also found a positive association between maternal educational levels (OR: 1.41, 95%CI: 1.66, 1.71) and the frequency of using supplements, while there was a reverse link between paternal educational level (OR: 0.77, 95%CI: 0.64, 0.93) and using supplements by students.
Table 4.
Determinants of dietary supplements use in multivariate logistic regression model: the CASPIAN-V study
| Variable | Dietary supplements use | |||
|---|---|---|---|---|
| Adjusted model | ||||
| OR | CI | P value٭ | ||
| Sex | Girl | Reference | – | – |
| Boy | 0.847 | 0.786–0.912 | <0.001 | |
| Age | 7–10 | Reference | – | – |
| 11–14 | 1.159 | 1.062–1.265 | 0.001 | |
| 15–18 | 1.058 | 0.961–1.165 | 0.248 | |
| Maternal educational level | illiterate | Reference | – | – |
| diploma/underdiploma | 1.322 | 1.157–1.509 | <0.001 | |
| academic education | 1.412 | 1.166–1.710 | <0.001 | |
| Paternal educational level | illiterate | Reference | – | – |
| diploma/underdiploma | 0.733 | 0.637–0.843 | <0.001 | |
| academic education | 0.774 | 0.641–0.935 | 0.008 | |
| Family SES | low | Reference | – | – |
| moderate | 1.125 | 1.007–1.257 | 0.037 | |
| high | 1.133 | 1.0–1.283 | 0.051 | |
| children body image by students report | Underweight | Reference | – | – |
| Normal weight | 1.071 | 0.978–1.173 | 0.140 | |
| Excess weight | 0.952 | 0.863–1.051 | 0.333 | |
| children body image by parents report | Underweight | Reference | – | – |
| Normal weight | 1.046 | 0.964–1.136 | 0.277 | |
| Excess weight | 0.846 | 0.754–0.949 | 0.004 | |
| Screen time | Low | Reference | – | – |
| High | 0.904 | 0.816–1.002 | 0.054 | |
٭Multivariate logistic regression model, adjusted for variables with p < 0.2
Discussion
In the present national survey, dietary supplements use were reported in about one third of Iranian children and adolescents and iron supplements were the most popular dietary supplement (12.9%). Girls aged 11 to 14 years, those that had higher educated mothers (p = 0.02) and children with moderate family SES used more dietary supplements compared to other classifications. However, we found an inverse link between having two parents, greater screen time and the educational levels of students’ fathers with higher frequency of dietary supplements.
To the best of our knowledge, the present study is the first national survey in Asian countries which clarified the predictors of dietary supplement use. According to a systematic review, using food supplements among children varies between 5 to 26% among societies [9]. Dwyer et al., reported that 37% of children and adolescents used dietary supplements in the U.S [5]. Our findings (prevalence: 34.1%) were relatively similar to this study. Other previous studies on the prevalence of using dietary supplements in American children and adolescents also showed relatively similar frequencies [2, 10]. In addition, our findings were in line with Yoon et al.,'s study. They found that 34% of Korean children and adolescent used dietary supplements [11]. However, the frequency of dietary supplements in Japanese children were lower (16.4%) [12] than the aforementioned studies.
In our study, the most frequent supplement was Iron, while studies on American populations reported that multivitamin minerals were the most popular supplements [2, 5, 10, 13]. The differences may be due to differences in health policies, health insurance, nutrient deficiency, and different social and cultural conditions. In the present study, we did not examine dosages used among students, while in the study by Butte et al., it was reported that the use of multivitamins and minerals was at safe levels [4].
The present findings provide detailed information on the roles of individuals’ characteristics on using dietary supplements. Several parameters including sex, age range, family SES, family composition, screen time and educational levels influenced the using of supplements. After doing multivariate regression, we found that moderate levels of SES was only linked with using supplements, while there was no association with high family SES compared to low levels. In the previous studies, researchers reported different findings. They concluded that higher levels of SES can increase the frequency of using supplements [7, 14].
In the present study, girls used more supplements compared to boys especially when they were between 11 to 14 years. As the most frequent supplement was iron, it was expected that due to higher risk of anemia among Iranian girls in particular at puberty stage, the rate of taking supplements in girls were more than boys [15]. Moreover, children with high educated mother used more supplements compared to those with low educated ones. When the information of parents regarding health and nutrient requirements are sufficient, such results seems reasonable. The surprising finding is related to inverse association between the educational level of fathers and using supplements by their children. It is probable that fathers only encourage children to use supplements when they really have nutrient deficiency or suffer from an illness. It is notable that we did not ask the participants whether supplements were prescribed by doctors or not. The safety and the interactions of supplements with each other should be considered when using supplements; however, this issue is mostly ignored. Therefore, based on the characteristics found in our study, health providers are suggested to focus more on subjects with these properties and inform them about safety, suitable dosage and the interactions of supplements and the criteria for taking them. The American Academy of Pediatrics mentioned that micronutrient supplements may be advisable after considering some conditions in children who are chronically ill, but it did not recommend other supplements [16]. It is suggested that child health care practitioners be aware of supplements that their patients take and explain about safety and suitable use for them [5].
Most parents believe using supplements improve the growth of their children and prevent diseases. However, taking some supplements without prescribing by physicians and nutritionists may cause side effects, particularly in high dosage and in those with no nutrient deficiency. It can also interact with the absorption of other nutrients or medications that were prescribed by specialists. Accordingly, using effective educational strategies for parents, teachers and children can be helpful.
The present study has some limitations. First, the dosage of supplements and the reasons of intake were not asked. Second, it was not examined whether supplements had been prescribed by physicians or not. Third, no biochemical assessment on the levels of nutrient was performed. However, it seems to be the first national study on the determinants of using dietary supplements among children in Asian societies. It is a population-based study with representative sample that examined a vulnerable group of society. In addition, it provided detailed information about the pattern of using supplements and individuals properties which can be helpful for any national intervention in this regard.
Conclusion
Our findings indicated that about one-third of Iranian children and adolescents used dietary supplements and iron supplements were the most frequent supplement. Girls aged 11 to 14 years old with higher educated mothers and moderate family SES used more dietary supplements compared to other classifications. In addition, there were inverse links between having two parents, greater screen time and the educational levels of students’ fathers with the frequency of dietary supplements. However, more studies are needed to clarify the efficacy and safety of dietary supplements in different age groups in various societies.
Acknowledgements
The authors are thankful of the team working on this national project and all participants who cooperated with this study.
Data availability
The dataset supporting the conclusions of this article will not be shared publicly, to ensure participants’ privacy.
Compliance with ethical standards
Competing interests
The authors declare that they have no competing interests.
Ethics approval and consent to participate
The study was approved by the Research and Ethics Council of Isfahan University of Medical Sciences.
Footnotes
Publisher’s note
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Contributor Information
Mostafa Qorbani, Email: mqorbani1379@yahoo.com.
Mohammad Karim Shahrzad, Email: Mk_shahrzad@yahoo.com.
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Data Availability Statement
The dataset supporting the conclusions of this article will not be shared publicly, to ensure participants’ privacy.