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25 July 2023

Trends in Mean Energy and Nutrient Intakes in Japanese Children and Adolescents: The National Health and Nutrition Survey, 1995–2019

and
Department of Nutritional Epidemiology and Shokuiku, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition, Osaka 566-0002, Japan
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Author to whom correspondence should be addressed.
Nutrients2023, 15(15), 3297;https://doi.org/10.3390/nu15153297
This article belongs to the Special Issue Dietary and Nutritional Assessment in Children
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Abstract

This study aimed to describe the national trends in mean energy and nutrient intakes in Japanese children and adolescents from 1995 to 2019. We used data obtained from the National Health and Nutrition Survey and included 54,871 participants aged 1–19 years. The dietary intake was estimated using a 1-day, semi-weighed, household-based, dietary record. The trends of mean energy and nutrient intakes were analyzed using the Joinpoint Regression Program. A declining trend in the mean energy intake was observed in toddlers aged 1–6 years, school girls aged 7–14 years, and adolescent girls aged 15–19 years, while the mean energy intake from protein, fat, and carbohydrates changed little over time. The mean salt equivalent showed a decreasing trend in all age groups, although the 2019 mean values were above the tentative dietary goal for preventing lifestyle-related diseases, especially in adolescent boys. Declining trends in mean vitamin (vitamin A, vitamin B12, folate, vitamin D, and vitamin K) and mineral (calcium, iron, and copper) intakes were observed, while trends in the mean vitamin B6 and zinc intakes were unchanged since 2001. Continuous monitoring of dietary intake and further research are required to raise awareness of unhealthy diet habits and to improve the food environment for the healthy growth and development of children and adolescents.

1. Introduction

Dietary habits tend to change over time. Japanese adults have reported a decrease in total energy intake, energy intake from protein, and sodium intake, and an increase in energy intake from fat [1]. Moreover, higher-income groups have shown a trend toward a lower cereal intake in the past decade [2]. Children and adolescents who primarily share meals with their parents may also experience similar changes in dietary intake, but little is known about trends in nutrient intake in this age group. There is a high prevalence of stunted children younger than 5 years (7.1%, 2010) and a high percentage of underweight adolescents (19.8%, 2015) with increasing trends since the 1980s [3]. Therefore, assessing the intake status of essential nutrients for adequate child growth and development is important to determine countermeasures that will prevent child malnutrition.
In Japan, school lunches have been provided to children aged 6–14 years for approximately 70 years in accordance with the School Lunch Program Act. This act incorporates more than one third of the daily requirement for children with a moderate level of physical activity, as indicated in the Dietary Reference Intakes for Japanese (DRIs) [4,5]. Therefore, the nutrient intake of lunch meals in this age group should be stable. However, whether the daily intake, including other meals (breakfast and dinner), and the daily nutrient intake of preschool children and adolescents who do not receive school lunches, are adequate or insufficient over time remain unclear.
Monitoring the nutrient intake of children and adolescents is critical for assessing whether their nutritional requirements for growth and development are being met. The National Nutrition Survey (NNS), later renamed the National Health and Nutrition Survey (NHNS) in 2003, is an annual nationwide cross-sectional survey that has evaluated nutrient intakes for Japanese aged ≥1 year for longer than 70 years. Therefore, we aimed to describe the national trends in mean energy and nutrient intakes in children and adolescents from 1995 to 2019.

2. Materials and Methods

2.1. Study Participants

We used data from published survey reports from the NNS (1995–2002) and the NHNS (2003–2019) conducted by the Ministry of Health, Labour and Welfare of Japan [6]. The period of this study (1995–2019) was selected because the assessment of individual intake of nutrients and food groups began in 1995. Before this time, only household-based food consumption was assessed. The 2020 and 2021 NHNSs were canceled owing to the effect of the coronavirus disease 2019 pandemic. Therefore, the 2019 NHNS has the most recent data available. The study participants were selected using a stratified cluster sampling design across all 47 prefectures (Japanese equivalent to province). Residents aged ≥1 year in all households were selected from 300 census enumeration areas, except for the 2004, 2012, and 2016 surveys, which were conducted in 298 (2 areas in Niigata Prefecture were excluded owing to the Mid-Niigata Prefecture Earthquake), 475, and 462 areas, respectively. The method of cluster sampling in 2012 and 2016 differed from that in the other years, and weighing was performed to correct for differences between the number of households in each prefecture. Three prefectures (Iwate, Miyagi, and Fukushima) were excluded from the 2011 survey because of the Great East Japan earthquake, and one prefecture (Kumamoto) was excluded from the 2016 survey owing to the Kumamoto earthquake. The detailed methodology of the NNS and NHNS have been described elsewhere [7,8]. On the basis of official application procedures under Article 33 of the Statistics Act, we obtained approval for data use from the Ministry of Health, Labor, and Welfare. Ethical review and approval were waived for this study because only anonymized data were used.
Of the 1995–2019 survey participants, 54,871 (28,062 boys and 26,809 girls) who were aged 1–19 years were included in this analysis.

2.2. Dietary Assessment

Data on dietary intake were collected using a 1-day, semi-weighed, household-based, dietary record on a single day that was neither a Sunday nor a public holiday. The individuals who usually cook for the family recorded the names of food ingredients, weight, and the leftover amount of food for each child in the dietary record. When food weight was missing, trained dieticians estimated the food weight using an official food item booklet with standard portion sizes for frequently consumed dishes. To account for shared dishes within the household, the approximate proportions of each food were assigned to individual household members to estimate the individual food intake. School lunch recipes were collected from the educational board in charge in the case of local public schools and schools serving school lunches in the case of private schools. The individuals who usually cook for the family asked their children about the amount eaten at school lunch and recorded this information. During the survey, trained dietitians visited each household at least once a day to check the dietary record.
The nutrient intake was calculated using the Standard Tables of Food Composition in Japan (4th edition for the 1995–2000 survey; 5th edition for the 2001–2004 survey; 5th revised and enlarged edition for the 2005–2010 survey; 2010 edition for the 2011–2017 survey; 2015 edition for the 2018–2019 survey). Of the 38 energy and nutrient intakes observed in the NHNS [9], the following data on key nutrients for child growth and development based on the DRIs [10] and the American Academy of Pediatrics (AAP) statements [11] were examined in this study: energy, protein, total fat, saturated fat, cholesterol, carbohydrates, total dietary fiber, sodium, salt, energy from carbohydrates, energy from protein, energy from fat, vitamin A (retinol equivalent), thiamine, riboflavin, niacin equivalent, vitamin B6, vitamin B12, folate, pantothenic acid, vitamin C, vitamin E (alpha-tocopherol), vitamin K, potassium, calcium, magnesium, phosphorus, iron, zinc, and copper. Energy and major nutrient intakes have been reported since 1995, while the intake of some detailed nutrients, such as dietary fiber, began to be reported in 2001.

2.3. Statistical Analysis

The mean and standard deviation (SD) were calculated by sex, three age categories (1–6, 7–14, and 15–19 years), and the survey year. The trend analyses were performed using Stata Version 16.1 (StataCorp, College Station, TX, USA) and the Joinpoint Regression Program (Joinpoint Regression software, version 4.9.1.0; National Cancer Institute, Rockville, MD, USA) [12]. Joinpoint regression analysis uses statistical criteria to determine the minimum number of linear segments required to describe a trend and perform the annual percentage change (APC) for each segment. The Monte Carlo Permutation method was used to test if a change in the trend was statistically significant. Differences were considered statistically significant at p < 0.05.

3. Results

The trends in energy and nutrient intakes according to sex and age are shown in Table 1 (young boys aged 1–6 years), Table 2 (young girls aged 1–6 years), Table 3 (school boys aged 7–14 years), Table 4 (school girls aged 7–14 years), Table 5 (adolescent boys aged 15–19 years), and Table 6 (adolescent girls aged 15–19 years). The number of survey participants decreased over the years.
Table 1. Trends in energy and nutrient intakes in young boys aged 1–6 years in 1995–2019.
Table 2. Trends in energy and nutrient intakes in young girls aged 1–6 years in 1995–2019.
Table 3. Trends in energy and nutrient intakes in boys aged 7–14 years in 1995–2019.
Table 4. Trends in energy and nutrient intakes in girls aged 7–14 years in 1995–2019.
Table 5. Trends in energy and nutrient intakes in adolescent boys aged 15–19 years in 1995–2019.
Table 6. Trends in energy and nutrient intakes in adolescent girls aged 15–19 years in 1995–2019.
Joinpoint regression analyses showed a declining trend in the mean energy intake in toddlers aged 1–6 years (APC of −0.52 for boys and −0.68 for girls, p < 0.001), school girls aged 7–14 years (APC of −0.21, p < 0.001), and adolescent girls aged 15–19 years (APC of −0.37 [1995–2014]) (Figure 1). The latest mean energy intake in 2019 was almost within the estimated energy requirement in the 2020 DRIs, which was set at 900–1300, 1250–2900, and 1700–3150 kcal/day for 1–5, 6–14, and 15–19 years, respectively [10]. Additionally, the mean energy intake from protein, fat, and carbohydrates was within the tentative dietary goal for preventing lifestyle-related disease (DG) for energy intake from protein (13–20% energy), fat (20–30% energy), and carbohydrates (50–65% energy) in the 2020 DRIs, except for energy intake from fat in school and adolescent girls. Similarly, a decreasing trend in the mean protein intake was observed in toddlers aged 1–6 years (APC of −1.35 for boys [1995–2010] and APC of −1.53 for girls [1995–2009], p < 0.001) and school children aged 7–14 years (APC of −0.85 for boys [1995–2009] and −0.88 for girls [1995–2010], p < 0.001). However, adolescents aged 15–19 years showed a decreasing and then increasing trend in the mean protein intake (APC of −1.35 [1995–2008] and 0.64 [2008–2019] for boys, and APC of −0.94 [1995–2014] and 1.94 [2014–2019] for girls, p < 0.001) (Figure 2). A declining trend in the mean fat intake was observed in toddlers aged 1–6 years (APC of −0.58 for boys and −0.86 for girls, p < 0.001) and in school children aged 7–14 years (APC of −0.46 for boys [1995–2010] and −0.30 for girls, p < 0.001). However, the mean fat intake was unchanged in adolescents (Figure 3). A declining trend in the mean carbohydrate intake was found in toddlers aged 1–6 years (APC of −0.49 for boys and −0.57 for girls, p < 0.001) and in adolescent girls aged 15–19 years (APC of −0.32, p < 0.001) (Figure 4).
Figure 1. Trends in the proportion of energy intake according to sex and age categories. APC, annual percentage change. * p < 0.05.
Figure 2. Trends in the proportion of protein intake according to sex and age categories. APC, annual percentage change. * p < 0.05.
Figure 3. Trends in the proportion of fat intake according to sex and age categories. APC, annual percentage change. * p < 0.05.
Figure 4. Trends in the proportion of carbohydrate intake according to sex and age categories. APC, annual percentage change. * p < 0.05.
The intake of total dietary fiber has been reported since 2001. The intakes of saturated fat, sodium, and energy from protein in 2001 and 2004 were not described in the respective survey reports.
A decreasing trend in the mean salt equivalent was observed in toddlers aged 1–6 years (APC of −2.04 for boys [2007–2016] and APC of −1.61 for girls), school children aged 7–14 years (APC of −2.37 [1995–2004] and −0.72 [2004–2019] for boys, and APC of −2.49 [1995–2003] and −0.90 [2003–2019] for girls), and adolescents aged 15–19 years (APC of −2.08 [1995–2004] and −0.70 [2004–2019] for boys, and APC of −1.61 [1995–2014] for girls) (Figure 5). The latest mean salt equivalent in 2019 was above the DG in the 2020 DRIs (<3.0–3.5, 4.5–7.0, and 6.5–7.5 g/day for 1–5, 6–14, and 15–19 years, respectively).
Figure 5. Trends in the proportion of the salt equivalent according to sex and age categories. APC, annual percentage change. * p < 0.05.
The trends in mean vitamin and mineral intakes according to sex and age are shown in Table 7, Table 8, Table 9, Table 10, Table 11 and Table 12. Joinpoint regression analyses showed that all age groups showed a declining trend in the mean vitamin A intake, and the slope of the decrease was different after 2006 or 2007 (Figure 6). The 2019 mean vitamin A intake was almost within the estimated average requirement (EAR) in the 2020 DRIs (250–350, 300–550, and 450–650 μg retinol activity equivalents (RAE)/day for 1–5, 6–14, and 15–19 years, respectively). The trend in the mean vitamin B6 intake was unchanged over time. A declining trend in the mean vitamin B12 intake was observed, and the 2019 mean vitamin B12 intake was above the EAR in the 2020 DRIs (0.8–0.9, 1.1–2.0, and 2.0 μg/day for 1–5, 6–14, and 15–19 years, respectively). Similarly, the mean folate intake showed a decreasing trend in toddlers aged 1–6 years (APC of 1.54 for boys and 1.37 for girls [2001–2011], p < 0.001), school children aged 7–14 years (APC of 2.06 for boys [2001–2010] and 0.88 for girls, p < 0.001), and adolescents aged 15–19 years (APC of 0.53 for boys, p < 0.05 and 1.06 for girls [2001–2016], p < 0.001) (Figure 7). However, the 2019 mean folate intake was within or above the recommended dietary allowance (RDA) in the 2020 DRIs (90–110, 140–240, and 240 μg/day for 1–5, 6–14, and 15–19 years, respectively). The mean vitamin D intake showed a decreasing trend in toddler girls and adolescents, and the 2019 mean vitamin D intake was below the adequate intake in the 2020 DRIs, especially in adolescents (8.5–9.0 μg/d for 15–19 years). The mean vitamin K intake also showed a declining trend in toddlers, and the 2019 mean vitamin K intake was above the adequate intake in the 2020 DRIs (50–70, 80–170, and 150–160 μg/day for 1–5, 6–14, and 15–19 years, respectively).
Table 7. Trends in vitamin and mineral intakes in young boys aged 1–6 years in 1995–2019.
Table 8. Trends in vitamin and mineral intakes in young girls aged 1–6 years in 1995–2019.
Table 9. Trends in vitamin and mineral intakes in boys aged 7–14 years in 1995–2019.
Table 10. Trends in vitamin and mineral intakes in girls aged 7–14 years in 1995–2019.
Table 11. Trends in vitamin and mineral intakes in adolescent boys aged 15–19 years in 1995–2019.
Table 12. Trends in vitamin and mineral intakes in adolescent girls aged 15–19 years in 1995–2019.
Figure 6. Trends in the proportion of vitamin A intake according to sex and age categories. APC, annual percentage change. * p < 0.05. Prior to 2000, International Unit (IU) was used as the unit of vitamin A intake.
Figure 7. Trends in the proportion of folate intake according to sex and age categories. APC, annual percentage change. * p < 0.05.
The mean calcium intake showed a declining trend in toddlers aged 1–6 years (APC of 1.14 for boys and 1.37 for girls, p < 0.001), school girls aged 7–14 years (APC of 0.42, p < 0.001), and adolescents aged 15–19 years (APC of 1.06 for boys and 0.76 for girls, p < 0.001) (Figure 8). The 2019 mean calcium intake in young girls and adolescents was lower than the RDA in the 2020 DRIs (400–600, 550–1000, and 650–800 mg/day for 1–5, 6–14, and 15–19 years, respectively). All age groups showed a decreasing trend in the mean iron intake, with different slopes of a decrease in the three time periods (1995–1999, 1999–2002, and 2002–2019) (Figure 9). The 2019 mean iron intake was within the RDA in the 2020 DRIs (4.5–5.5, 5.5–10.0 (12.0 for menstruating), and 6.5–10.0 (10.5 for menstruating) mg/day for 1–5, 6–14, and 15–19 years, respectively), except for in young girls. The trend in the mean zinc intake was unchanged over time in toddlers and school girls, and the 2019 mean zinc intake was within or above the EAR in the 2020 DRIs (2–3, 3–9, and 7–10 mg/day for 1–5, 6–14, and 15–19 years, respectively). While the trend in the mean copper intake was slightly decreased in all age groups, the 2019 mean copper intake was above the EAR in the 2020 DRIs (0.2–0.3, 0.4–0.7, and 0.6–0.8 mg/day for 1–5, 6–14, and 15–19 years, respectively).
Figure 8. Trends in the proportion of calcium intake according to sex and age categories. APC, annual percentage change. * p < 0.05.
Figure 9. Trends in the proportion of iron intake according to sex and age categories. APC, annual percentage change. * p < 0.05.

4. Discussion

This study showed the trends in energy and nutrient intakes in Japanese children and adolescents for 25 years. The overall trend was a decrease in energy and nutrient intakes, although some nutrient intakes remained unchanged or increased by sex and age group.
The number of survey participants has decreased over the years. This may be linked to the declining trend in the number of live births in Japan, ranging from 1,187,064 in 1995 to 865,239 in 2019 [13]. Moreover, the household response rates are relatively low (63.5%, 2019) [6], although the response rate of individual children and adolescents is unknown. For more detailed analysis of nutrient intake by age group, it would be necessary to increase the response rate of households with children and adolescents in future surveys.
A declining trend in energy intake in boys (young group) and girls (all age groups) was observed in this study, which is consistent with adults [1], while the latest mean energy intake in 2019 was almost within the estimated energy requirement [10]. Moreover, we found that the mean energy intake from protein, fat, and carbohydrates changed little over time. The 2019 mean energy intakes were within the DG, except for the mean energy intake from fat in school and adolescent girls. A previous study showed that a higher household income was associated with higher energy from fat in adolescents [14]. This finding suggested that further study is required to determine the dietary fat source and the underlying factors that contribute to a high fat intake, especially in adolescents.
Although a decreasing trend in the mean salt equivalent in all age groups was observed in this study, the latest mean salt equivalent in 2019 was above the DG. Seasonings, such as soya sauce and soybean paste, account for approximately 70% of the dietary salt source [15]. Therefore, further salt-reduction measures need to be encouraged, especially in adolescent boys. These measures include expanding the options of low-sodium meals in school and university cafeterias, and by warning about salt consumption on food labels at on-campus stores.
Declining trends in mean vitamin A, vitamin B12, folate, and vitamin K intakes were observed, but none of the latest mean intakes in 2019 were deficient compared with the 2020 DRIs. However, the mean vitamin D intake decreased over time and was below the adequate intake, especially in adolescents. Because vitamin D deficiency can cause rickets and osteomalacia, high-risk adolescents may need to incorporate sunlight exposure and dietary modification with vitamin D supplements and vitamin D-fortified foods into their daily lives [16]. With regard to the decrease in vitamin A intake, it should be noted that prior to 2000, the International Unit (IU) was used as the unit of vitamin A intake.
A declining trend in the mean calcium intake was observed in all age groups, except for in school boys aged 7–14 years. Our finding that the mean calcium intake in young girls and adolescents was lower than the RDA is alarming. However, we observed trends in calcium intake from foods and did not consider calcium intake from breast milk or formula. Breast milk or formula may be able to compensate for this deficiency in calcium intake. Therefore, continued breastfeeding after the age of 1 year is recommended in Japan, in alignment with the World Health Organization’s recommendation to continue breastfeeding until the age of 2 years and older [17]. Further research is required to assess the overall calcium intake, including breast milk and formula, especially for 1–2-year-olds.
A decreasing trend in the mean iron intake was found in all age groups, and the 2019 mean iron intake was within the RDA, except for that in young girls. The revisions to the Standard Tables of Food Composition in Japan (4th edition for the 1995–2000 survey and 5th edition for the 2001–2004 survey) may have affected the changes in iron intake since 2001. The World Health Organization warns that the global prevalence of anemia in children aged 6–59 months was 39.8% in 2019 [18], although the actual status of iron deficiency anemia in young Japanese girls is unclear. Therefore, more public health attention is required regarding iron intake and the risks associated with iron deficiency in young girls.
This study has several limitations. First, dietary intake assessed by self-administered dietary records might not represent long-term habitual intake. Second, certain groups may have underreported their dietary intake, because the underreporting of energy intake in young children (1–5 years) and adolescents (15–19 years) and in children with obesity has previously been reported [19]. Third, although three age categories are insufficient because of children’s growth, nutrient intakes in the detailed age categories were unavailable in the survey reports from which the data were obtained. Fourth, while many nutrient intakes may have declining trends because the energy intake has decreased over the years, the survey reports do not disclose the values per 1000 kcal. Fifth, this study did not include nutrient intake from breast milk or formula in 1–2-year-olds. The National Nutrition Survey on Preschool Children showed that the percentage of children weaned by 12 months of age was 54.4% in 2005 and 34.7% in 2015 [20]. Sixth, children and adolescents with various illnesses requiring specific dietary regimens such as food allergies and diabetes could not be excluded from this study because the survey did not collect this information. Although these limitations should be noted when interpreting the results, this study showed the annual trends in mean energy and nutrient intakes using nationally representative data for Japanese children and adolescents over the last 25 years.

5. Conclusions

We found declining trends, with some exceptions, in energy and some nutrient intakes in Japanese children and adolescents from 1995 to 2019. Continuous monitoring of the dietary intake and further research are required to raise awareness of unhealthy diet habits and to improve the food environment for the healthy growth and development of children and adolescents.

Author Contributions

Conceptualization, C.S.; formal analysis, C.S.; writing—original draft preparation, C.S.; writing—review and editing, H.T. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported by a Grant-in-Aid for Young Scientists (Grant Number 21K13555) from the Japan Society for the Promotion of Science. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Institutional Review Board Statement

Ethical review and approval were waived for this study because only anonymized data were used.

Data Availability Statement

The data used in this study can be obtained from the survey reports of the Ministry of Health, Labor and Welfare (https://www.mhlw.go.jp/bunya/kenkou/kenkou_eiyou_chousa.html, accessed on 19 December 2022).

Conflicts of Interest

The authors declare no conflict of interest.

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