2023 Volume 34 Issue 1 Pages 1-9
This article has been retracted from Biomedical Research on Trace Elements 34 (1): 1-9, 2023.
本誌、Vol. 34, No. 1（2023 年発行）p. 1-9 に掲載された本短報は撤回されました。
Minerals play an important role in the human body[1]. Iron is an essential element for humans. Iron deficiency causes anemia in infants[2] and adolescents[3]. Zinc is also an essential element that catalyzes more than 300 enzymes[1]. It is necessary for growth and development and plays an important role in wound healing and sense of taste and smell[4]. Compared with iron, the need for zinc appears to be underestimated because physical symptoms are not fully recognized in daily life, especially among adolescents[5]. Additionally, few studies have objectively evaluated feelings about lifestyle and trace elements. Based on the Practice Guideline for Zinc Deficiency of the Japanese Society of Clinical Nutrition[6], asymptomatic zinc deficiency was defined as serum zinc concentration of 60–80 μg/dL and symptomatic zinc deficiency as serum zinc concentration <60 μg/dL. The correlation between serum zinc concentration and physical symptoms is not fully understood. Ohguri et al. reported that adult women who exercise every day have higher serum zinc concentrations than those who do not exercise[7].
Thus, this study aimed to examine the effect of zinc as a trace material in adolescent girls in junior high and high schools by surveying the students’ daily habits and simultaneously taking blood examination data for two years.
Participants
Healthy female school students aged 12–18 years were recruited from a school in Tokyo, Japan, from 2020 to 2021. Students’ examination and survey data were obtained consecutively for two years.
This study was approved by the Ethics Committee of Juntendo University Nerima Hospital (Approval no. N20-0013). Written informed consent was obtained from the students before participation.
The school conducts annual health checkups, including physical and blood examinations. Body height and weight from physical examination data were used to calculate the body mass index (BMI) and standard deviations (SD). Standard height and weight were defined based on the 2000 Statistical Report[8]. Blood samples were obtained in a nonfasting state. The menstrual period was not considered. Blood cell count, general biochemical items, and serum iron and zinc concentrations were measured (Table 1). Abnormal values of iron and zinc were defined based on the literature[6, 9].
Examination summary.
| Average | Minimum | Maximum | Standard deviation | |
|---|---|---|---|---|
| Physical examination (n = 153 examinations) | ||||
| Age, year | 15.6 | 12.1 | 17.9 | 1.435 |
| Height, cm | 159.0 | 142.2 | 175.4 | 5.982 |
| Weight, kg | 52.5 | 36.1 | 75.3 | 6.790 |
| BMI | 20.8 | 15.7 | 30.6 | 2.428 |
| Height SD | 0.40 | −1.81 | 3.49 | 1.096 |
| Weight SD | 0.13 | −1.89 | 2.93 | 0.830 |
| Laboratory data (n = 153 tests) | ||||
| Hb (g/dL) [11.6–14.9] | 13.6 | 8.7 | 15.9 | 1.177 |
| RBC (×104/µL) [390–510] | 465 | 392 | 541 | 31.67 |
| AST (IU/L) [12.0–29.5] | 19.6 | 11 | 37 | 5.207 |
| ALT (IU/L) [9.0–30.5] | 12.7 | 5 | 56 | 6.408 |
| Total cholesterol (mg/dL) [125–230] | 187.5 | 125 | 301 | 28.50 |
| Fe (µg/dL) [22–177] | 101.3 | 17 | 273 | 40.45 |
| Zn (µ g/dL) [85–117] | 84.1 | 58 | 118 | 12.05 |
SD stands for the standard deviation of Japanese standard body proportion in 2000. The values in brackets indicate the normal range in the adolescent female population[10,11].
A questionnaire was distributed to the participants. The questionnaire contained items on exercise type, exercise frequency, and daily habits (Tables 2 and 3). The items are multiple choice items, and participants can provide other responses freely for extra choices. For exercise habits, if students answered ≥2 sports activities, the toughest sports activity was chosen. For example, volleyball was chosen if the answers were walking and volleyball. Some students returned the form for two consecutive years. For daily living activities, the answer choices were negative, neutral, and positive. We treated negative and neutral answer for negative answer and positive answer for positive for t-test evaluation. Only the questionnaire in the first year was used because it was unclear which answer should be used if the responses were different across the 2 years.
A minimal sample size of 50 with 10 and 0.95 for sample differentiation and power (1-β error probability), respectively, was assumed. The quantitative characteristics of the individuals were compared using a t-test or chi-square test. For repeated students, a paired t-test was applied. Logistic analysis was performed to obtain the Receiver Operating Characteristic (ROC) curve. Statistical analysis was performed using JMP for Windows version 14.3.0 (SAS Institute Inc., Cary, NC, USA).
A total of 102 female students were enrolled in the study, accounting for 41.5% of the total number of students in the studied school. Additionally, 51 students were examined twice. Table 1 shows the results of the physical and laboratory examinations. The participants appear to have no obvious differences in body states compared with normal Japanese populations because the SD is close to 1.0. The descriptive statistics values of the blood parameters (Table 1) are within the normal variance. No significant correlations were observed across physical examination and laboratory data. The SD of serum iron concentration was the highest in our analyses, as described in a previous study[12].
The iron and zinc serum concentrations are shown in Table 2. The cutoff value for iron was 48 µg/dL[6]. The cutoff value for zinc was 60–79 and <60 µg/dL for asymptomatic and symptomatic zinc deficiency, respectively. In our cohort, the rates of iron, asymptomatic zinc, and symptomatic zinc deficiencies were 7.8, 47.6, and 1.2%, respectively. The correlation between iron and zinc serum concentrations from 153 examinations is shown in Fig. 1. No significant correlation was observed between iron and zinc serum concentrations. Exercise habits were evaluated simultaneously including the type of sports and strength. There was no correlation with any blood examination results.
The results of the questionnaire survey of students’ exercise habits are shown in Table 3. The answers included sports activities inside the school (i.e., club membership) and outside the school. The number of students with volleyball and dance habits was greater than that of students with other exercise habits, which indicated that these clubs have many members. Exercise intensity was the highest with volleyball. One student did not respond to the actual sports activity.
The results regarding daily habits are shown in Fig. 2. Questions related to zinc or iron deficiency was selected as described in the literature[1, 3]. The items “Feel vitality” and “Feel anemia” focused on iron deficiency. Other items targeted zinc deficiency. The distribution of responses varied across the questions. No significant differences were observed between the survey results regarding habits and exercises.
The correlation between daily habits and laboratory data is shown in Table 4 and Fig. 3. As for zinc deficiency, no statistical significant difference was observed between normal students and those with asymptomatic zinc deficiency (Fig. 3a). One student had symptomatic zinc deficiency (serum zinc concentration was 58 µg/dL). The student reported having rough skin and experiencing prolonged skin injury healing.
The correlation between serum iron concentration and exercise strength is shown in Fig. 3b. A significant difference was observed between the group without exercise and the group performing extreme exercises. The serum iron concentration in the nonexercise group was lower than that in the extreme exercise group. In contrast, no correlation was observed in the type of sports activity (data not shown). In the nonexercise group, 14 (43.8%) students answered that they did no activity, 4 (12.5%) did yoga, and 3 (9.4%) had walking habits. In the extreme exercise group, 18 (90.0%) students played volleyball.
The ROC curve of each element is shown in Fig. 4. The area under the curve (AUC) was not significant in each element.
The results of blood examinations in two consecutive years were evaluated. However, no significant difference was observed between the results (data not shown).
Prevalence of iron and zinc deficiency.
| Fe | ||||
|---|---|---|---|---|
| Normal | Deficiency | Total | ||
| Zn | Normal | 86 | 7 | 93 |
| Asymptomatic deficiency | 54 | 5 | 59 | |
| Symptomatic deficiency | 1 | 0 | 1 | |
| Total | 141 | 12 | 153 | |
Iron deficiency was less than 48 µg/dL. Asymptomatic zinc deficiency was 60–79 µg/dL. Symptomatic zinc deficiency was less than 60 µg/dL.
Survey responses for exercise habits.
| None | Normal | Extremely | Total | |
|---|---|---|---|---|
| Walking | 3 | 4 | 0 | 7 |
| Running | 0 | 2 | 0 | 2 |
| Skating | 0 | 2 | 1 | 3 |
| Dance | 4 | 5 | 1 | 10 |
| Tennis | 1 | 1 | 0 | 2 |
| Basketball | 0 | 2 | 0 | 2 |
| Badminton | 3 | 1 | 0 | 4 |
| Volleyball | 1 | 6 | 17 | 24 |
| Yoga | 4 | 3 | 0 | 7 |
| Roller skating | 0 | 1 | 0 | 1 |
| Kendo | 0 | 3 | 0 | 3 |
| Swimming | 1 | 0 | 0 | 1 |
| Skipping | 1 | 0 | 0 | 1 |
| Others | 0 | 1 | 0 | 1 |
| None | 14 | 0 | 0 | 14 |
Correlation between serum iron and zinc concentrations in 153 blood examinations. No significant correlation was observed.
Results of the survey on daily living activities.
Survey response for daily living combined with laboratory data.
| (a) Zinc deficiency | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Not agree | Neutral | Agree | |||||||
| Nor | Asy | Sym | Nor | Asy | Sym | Nor | Asy | Sym | |
| Like spicy foods | 14 | 14 | 0 | 9 | 9 | 1 | 18 | 16 | 0 |
| Have rough skin | 16 | 11 | 0 | 12 | 10 | 0 | 13 | 18 | 1 |
| Prolong skin injury healing | 24 | 12 | 0 | 9 | 18 | 0 | 8 | 9 | 1 |
| Growth during puberty | 9 | 4 | 0 | 7 | 7 | 1 | 25 | 28 | 0 |
| Good appetite | 3 | 3 | 0 | 3 | 4 | 0 | 35 | 32 | 1 |
| Catch a cold frequently | 26 | 24 | 0 | 11 | 11 | 1 | 4 | 4 | 0 |
| Feel vitality | 3 | 2 | 1 | 13 | 4 | 0 | 25 | 33 | 0 |
| Feel anemia | 24 | 27 | 0 | 8 | 5 | 0 | 9 | 7 | 1 |
| (b) Iron deficiency | ||||||
|---|---|---|---|---|---|---|
| Not agree | Neutral | Agree | ||||
| Nor | Def | Nor | Def | Nor | Def | |
| Feel vitality | 5 | 1 | 15 | 2 | 55 | 3 |
| Feel anemia | 49 | 2 | 12 | 1 | 14 | 3 |
Numbers in each cell represent subject counts. Nor: normal. Asy: asymptomatic zinc deficiency. Sym: symptomatic zinc deficiency. Def: iron deficiency.
(a) Univariate analysis of zinc concentration and skin-related symptoms. Horizontal axis shows counts of each individual’s positive answer for rough skin and prolong skin healing. No significant correlation was observed (p = 0.1489). The horizontal line shows the average of the whole data (81.2 µg/dL).
(b) Univariate analysis of iron concentration and exercise habits. Asterisk (*) indicates a significant difference with p = 0.0313. The horizontal line shows the average of the whole data, 97.4 µg/dL.
(a) Receiver Operating Characteristic (ROC) curve of zinc concentration and rough skin.
(b) The ROC of iron concentration and exercise habits. The numbers in the legend show the area under the curve (AUC).
This study demonstrated that clinical zinc deficiency may influence adolescent students’ perception of skin problems. Additionally, asymptomatic zinc deficiency results in various outcomes from the viewpoint of students’ subjective thinking.
First, the prevalence of zinc deficiency was higher than that of iron deficiency. Atasoy et al. reported a zinc deficiency of 10.9% and an iron deficiency of 6.0%[13]. The prevalence of zinc deficiency varies (7%–37%)[13-17]. It depends on the cutoff value of serum zinc concentration (50–75 μg/dL) and cohort population. In this study, the prevalence of symptomatic zinc deficiency was 1.2%, which is lower than that of the published data. The difference might be due to both population and cutoff differences.
Regarding exercise activities (Table 3), the strength of the sports activity appears to depend on the response to the sports items. For instance, volleyball was commonly selected as an extreme exercise, which may reflect club participation. Since these responses are subjective, they are not related to laboratory data or physical examination results. The proportion of each analysis did not show any trends.
The results of the survey shown in Fig. 2 show that it contained positive (good appetite and feeling vitality), negative (rough skin, chronic skin injury, frequent infection, and anemia), and neutral (growth spurt and taste) items. For positive questions, many students answered “agree.”
Comparing the relationship between the questionnaire and blood examination data, no correlation was observed except for exercise strength and iron concentration (Fig. 3b). The study results showed a significant difference in serum iron concentration across exercise intensities. In contrast, no significant difference was observed in serum hemoglobin levels. Iron serum concentration varies drastically within the day. Statland et al. reported a variation of up to 12.9%[18]. The SD of serum iron concentrations in each group were 33.6 µg/dL and 42.1 µg/dL for the nonexercise and extreme exercise groups, respectively. The mean values for the nonexercise and extreme exercise groups were 87.3 µg/dL and 109.5 µg/dL, respectively. This statistical value is similar to reported values[19].
Sandström et al. reported that the prevalence of iron deficiency in the athlete group was lower than that in the nonathlete group among female adolescents[20]. This might be the result of good iron intake and low menstrual bleeding.
In this cohort, one student had symptomatic zinc deficiency. She answered positive for findings of rough skin and prolonged skin healing. Although the number of subjects is too small for statistical evaluation, symptomatic zinc deficiency may affect physical symptoms. No statistical tendency was observed for the correlation between asymptomatic zinc deficiency and students’ perceptions. Zinc and its related zinc-finger proteins play a role of regulation of apoptosis, folding, and assembly of protein and lipid binding that stabilizes skin homeostatis[21]. Considering such physiological mechanisms, zinc deficiency is suspected to affect the participants’ perceptions. There are other factors that may affect serum zinc concentration, such as a decrease due to zinc absorption inhibition in small intestine caused by some types of food consumed at the same time. Calcium and milk are some examples of such foods[22]. Physical or mental stress state also affects serum zinc concentrations[6, 23]. Also, we tried to reveal the cutoff values of iron and zinc, to detect subjective symptoms (Fig. 4). The AUC of these elements was low. This might be caused by the high tolerance of elements’ blood concentration[6].
The inquiry form of the current study did not enquire regarding oral supplement habits. Therefore, we were not able to assess the correlation between zinc deficiency and oral intake. There are several reports regarding insufficient oral zinc intake that causes disorders. Mossad et al. reported that oral zinc intake reduced the duration of experiencing common cold symptoms in a randomized controlled trial[24]. Kobayashi et al. reported that 12%－13% of junior high school and high school students consumed oral mineral supplements. Moreover, 32.3% of eczema patients consumed vitamin or mineral supplement. It is greater than healthy group in their study[25].
This study has several limitations. First, this study might have selection bias because the study population was female students, which may affect iron concentration by menstrual discharge, and the students were from a single institute. Second, participants were not asked about oral supplementation intake. Even if the sample size estimation was sufficient, oral intake might affect the results.
In conclusion, serum zinc concentration may affect adolescent female students’ perceptions of skin disorders. A higher serum zinc concentration may improve the quality of life of female students by preventing skin problems. Serum iron concentration was higher in the extreme exercise group than that in the nonexercise group. Iron should be taken appropriately with high precautions to prevent iron deficiency.
This work was partially supported by Nobelpharma Co., Ltd.
N.Y. designed the study, collected and analyzed the data, and wrote the manuscript. C.K. performed clinical evaluations and reviewed the manuscript. S.N., Y.O., and T.S. supervised the study and revised the manuscript. All authors have read and approved the final manuscript.
Supplemental document: an inquiry form.
