⦁ Introduction In ten years after the end of WWII, Japan’s economy recovered to the prewar level and achieved fast and steady progress toward the 1990s. People, the young in particular learned to eat animal prod- ucts and the teens grew in height nearly 10 cm by the early-1990s and plateaued in stature after that. South Korea was two decades behind Japan in economic development due to the Korean War (1950-53) and then has achieved uninterrupted progress to parallel with Japan in respect of living standard by the turn of the century. Teens in Korea caught up with their Japanese peers in height in the mid-1990s and overtook them by 3 cm in the mid-2000s and then plateaued in height. With respect to per capita caloric supply from animal products, Japan was 546 kcal, 147 kcal greater than Korea in the mid-1990s. In the mid-2000s, when Korean teens overtook Japanese peers, Japan was still 82 kcal greater than Korea (Table 1). There is probably nothing odd about this. Both may have de- pleted their reserve gene potential for height (Kopcyzinsky, 2016) [1]. Japan and South Korea have the same school system, with 6 grades of primary school (6.5 years old for 1st grade), 3 grades of middle school (12.5 years old for 1st grade) and 3 grades of high school (15.5 years old for 1st grade), all of which start in early spring. Their Ministry/Department of Education conducts nation- wide School Health Surveys (stature and health conditions, such as eyesight) in the first month of school year and publishes the survey statistics on the internet/printed report [2;3]. In human biology, the importance of “first years of life”, or “first 1,000 days” is stressed for determining future adult height (A. Deaton; T. Cole; Prentice -et al.) [4;5;6]. School Health Surveys do not cover the first 5 years. In this short communication, the author attempts to analyze the growth patterns of male students from 1st grade of middle school (12.5 years old) to final grade of high school (17.5 years old) in South Korea in comparison with Japan from the mid-1980s to the most recent year, as published data available, Before undertaking actual analyses, the author would like to re- mind the audience of the key concept of growth, a longitudinal phenomenon: one does not grow from 6 years of age to 17 years of age cross-sectionally, or instantaneously in the same year. To construct growth chart, age 6 in 1990 is to be connected to age 7 in 1991, age 12 in 1996, , and age 17 in 2001, in turn.
⦁ Changes in Growth Patterns and Inputs to Health over Time With respect to the mean height of males in the Northeast Asia, they tend to cease growing taller after the age of 17, in contrast to Caucasians in northern Europe who seem to grow another 1 or 2 cm taller toward their 20th in age. Young adults in the Nether- lands, Sweden, and most neighboring counties grow above 180 cm in mean height in recent years, whereas the early teens, 12 or 13 years of age are reported about the same or not appreciably taller in mean height than their Korean peers in the early 2000s (Holmgren, Anton, 2019; Mori, 2021) [7;8]. It looks as though Korean male adolescents should grow appreciably less or slower in mean height than their European peers. With no background in anthropology, however, the author suspects that it might be plausible for Korean teens to attain the mean height level, prevalent currently in Eu- rope, should they eat the more properly, if not substantially more milk*1. *1 Nearly 80% of the Asian populations are reported to lack lac- tose, after infancy. Due to the availability of official data on mean height by age and per capita food supply/consumption formatted in the same fashion, the author will provide secular changes in growth patterns in terms mean height in cm from 12 years of age (in 1980) to 17 years of age (in 1985) over the subsequent 30 years in South Korea, and Japan as a control (Figure 1). In the same fashion, mean height growth in cm from 6 years of age (in 1979) to 12 years of age (in 1985) over the same period will be provided as a reference. Figure 1: Teens in Korea grew approximately 2 cm greater or faster than their Japanese peers over the period from the early 1980s to the early 2000s but they began to decline gradually but distinctly in growth speed in the early 1990s, whereas Japanese peers keep falling only moderately and levelled off in the early 2000s. As a result, Korean teens are nearly 3 cm less or lower than Japanese peers in growth speed in the end of the survey period, the 2010s, despite the Korean high school seniors still keeping 3.0 cm lead in mean height above their Japanese peers decline. Through Figure 1. Korean boys both in primary school (6 to 12*2) and jun- ior and senior high school (12 to 17) have proved a couple of cm less or slower in height growth than their Japanese peers toward the end of the survey period. *2 First month of junior high school 1st grade≒end month of primary school 6th grade. Children in South Korea and Japan have proved variously differ- ent so much in respect of height growth patterns over the recent decades of survey period, which can not to be attributed to ethnic- ity. Stature is a net measure that captures not only the supply of inputs to health but demands on those inputs (R. J. Steckel, 1995) [9]. Empirically, increases in supply of animal products played a crucial role in increasing population’s height. Increases in animal protein alone, however, cannot result in taller height (Table 1), un- less supply of overall food calories and essential nutrients are suf- ficient (Blum, 2013) [10]. The author, based on cohort analyses of consumption of various food products in the past two decades, is fully aware that individual food consumption varies significantly by age/generation at the same time in the same nation [11]. (Ta- ble 2) clearly demonstrates that the newer generations, currently young in age, consume very little fruit in Japan. Korea has long been known for Kimchi. The author and his associates have dis- covered that the younger generations in South Korea have turned away from vegetables(≒Kimchi) in recent decades (Table 3). In respect of per capita consumption, available from Food Balance Sheets, FAOSTAT, United Nations [12], and Food Balance Sheets, Department of Agriculture, individual governments [13;14], secu- lar changes in individual consumption by age groups, preferably infants through adolescents, cannot be identified. Korea National Health and Nutrition Examination Survey, which provides indi- vidual food intakes by age groups was conducted in 1998 for the first time, followed by the 2nd one in 2001 and the 3rd one in 2005 [15]. Secular changes in individual food intakes: “inputs to health” need to be identified by major segments of childhood, if not every year of age, to comprehend changes in growth patterns of human height, particularly in developing societies or coun- tries where cohort effects are dominant. Individual at-home con- sumption of various food products, Tables 2-3 were derived from Household Income and Expenditure Surveys [16] classified by age groups of household head by the author. With the technical helps of Inaba, Kawaguchi, and M. Tanaka, the author developed robust econometric models to derive per capita at-home consumption of various food products by individual household members by age from household expenditure surveys (Mori and Inaba, 1997; Tana- ka, Mori and Inaba, 2004; etc.) [17;18]. Individual consumption of fresh fruit by age groups in Japan, 1971~2010, was derived from Family Income and Expenditure Surveys [19] and individual expenditures of vegetables, including Kimchi, by age groups in South Korea, 1990~2019, was derived from Household Income and Expenditure Surveys. Children in Japan started to steer away from fruit in the mid-1970s and are estimated to eat less than one- tenth of fruit consumed by the older adults in 2010 (Table 2). Chil- dren in Korea started to turn away from vegetables(≒Kimchi) in the early 1990s and are estimated to eat one-tenth of vegetables consumed by the older adults in the end of the 2010s (Table 3). (Table 4) demonstrates that children in Korea increased at-home consumption of meats (in terms of real expenditure) nearly 30% over the same period. Considering the older people prefer beef to pork, the more expensive cuts, children in Korea are surmised to eat nearly the same amount of meat as the older consumers.
⦁ Conclusion Sources: Household Income and Expenditure Surveys, classifued by age group of househod head. Estimated by the author by means of TMI model. 7. Anton H. Nordic populations are still growing taller—secular When the economy develops, population’s living standards im- prove and “inputs to health” would be enhanced, resulting in big- ger stature (taller height). The Korean economy has kept devel- oping without serious hazards currently at a par with the Japan’s economy. Teens in Korea overtook Japanese peers in height by 3 cm in the mid-2000s and plateaued since then. Have they simply depleted their gene potential in height? When examined in respect of growth pattern from 1st grade of junior high school to 3rd grade of high school, with Japan’s case as a control, over the past 4 dec- ades, Korean teens have proved highly unstable in growth, nearly 3 cm faster than their Japanese peers in the early 1980s and in the mid-1990s, and then nearly 3 cm slower than the latter in the 2010s. Similar rise and fall in growth speed are observed in the case of growth from 1st grade of primary school to 1st grade of junior school, before and after the early-2000s, leaving intuitive anticipation that Korean teens could keep growing in comparable magnitude as European teens from now. For this anticipation come true, we are expected to discover why growth speed from 12 to 17 in age has kept declining constantly from the early 1990 to the end of the 2010s in South Korea (Figure 1).
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Mori H. Why Korean Teens Started Declining in Height Growth in The Midst of Economic Prosperity: Despite Increasing Supply of Animal Protein?. Annals of Clinical and Medical Case Reports 2022