Secular Changes in Relative Height of Children in Japan, South Korea and Taiwan: Is “Genetics” the Key Determinant?

At age 20 years, Korean men were recorded as being 2 cm taller than Japanese but 3 cm shorter than Taiwanese in the beginning of last century [1], when Korea and Taiwan were under Japan’s colonization. These differences could have been attributed mostly to genetics. At the turn of the century, Japan’s economy was the richest and Taiwan was 60% greater than S. Korea in per capita consumption of animal products. Yet Korean males were slightly, by 1-2 cm taller than their Taiwanese peers in height. Genetics was no longer a strong explanation of relative height. Following Blum [2], a high consumption of animal proteins does not result in increasing body height if overall consumption of calories and other essential nutrients is insufficient. This paper tries to identify what essential nutrients may have been insufficient in Japanese and Taiwanese food consumption, particularly among growing children.

ese youth were a few cm taller than their Korean peers a century ago *2 under Japan's colonization. According to National Nutrition Surveys [14] by Japanese government, through Ministry of Health and Welfare, men in their 40s in 1949-51 were 159 cm tall and men in their 50s were 158 cm, respectively, in Japan, implying that Japanese men in their 20s in the 1920-30s were slightly shorter than 160 cm, i.e., 1 to 2 cm shorter than their Korean peers at that time.
Korean youth were reported to be 161-2 cm in mean height in the 1920-30s, although the surveys were not nation-wide and limited in sample size [15]. It seems plausible that Koreans were 1-3 cm taller in mean height than Japanese in the pre-war era.
In the post-war period, Japanese men at age 20 years in 1960 and 1980, cohorts born in 1940 and 1960, respectively, are reported to be 162. 6 and 165.7 cm tall in the data provided by [1] cited above, as compared to 165.1 and 169.6 cm for school boys at age 17-18 years in the corresponding years, as reported in School Health Surveys, based on nationwide samples by Japanese government Ministry of Education [16]. Steckel states, "Stature is a net measure that captures the supply of inputs to health" [17][18][19]. The author, a food economist, has been tackling the differences in growth patterns of child height in Japan and S. Korea covering the past half century, mainly from the perspective of "supply of inputs to health", predominantly food consumption.

Data
Japanese government, through Ministry of Health and Welfare has been conducting the National Nutrition Surveys [14], over the entire nation every year, beginning shortly after the end of WW II.
The mean height and weight of survey subjects are reported by age groups, 1 to 25 years disaggregated by one-year interval, and age groups, 26-29, 30-39, ---, 60-69, 70~ years. For its part, South Korean government initiated a wide-scale, extensive health and nutrition survey, KNHANES [20], in 1998, followed by the 2 nd one in 2001, and the 3 rd one in 2005 *3 . In addition, Japanese government, through Ministry of Education has been conducting the Scholl Health Examination Surveys [16] since the start of the last century, in which the mean height of school children from elementary school 1 st graders (6 years+ *4 ) to senior high school 3 rd graders(17years+ *4 ) is reported. Likewise, S. Korean government, through Department of Education, has been conducting the similar school health surveys since 1960 [21]. However, these school surveys in neither country cover the ages from 1 to 5 and 18 to 20 years but are based on large nationwide samples. It is widely held in the profession that the first years of life, "1000 days", are crucial in determining future adult height [22][23][24].
Therefore, school health surveys in both countries have some limitations, which should be kept in mind. Mean height of those in high school in the earlier period of our survey, the 1960s in particular, may not represent the same age groups in the entire population, because the rate of enrollment in senior high school was 58% in 1960, as compared to 92% in 1975 in Japan, whereas the corresponding rate was as low as 20.3% in 1970 but sharply rose to 79.4% in 1990 in S. Korea and 43.2% in 1976 and 72.9% in 1991, respectively in Taiwan [7]. compiles changes in mean height of boys from elementary school 1 st graders to high school 3 rd graders in Japan, S. Korea and Taiwan from 1960 to 2010 by 5-year intervals. The data are based on the school health surveys mentioned above. In order to smooth the annual fluctuations *5 in the original data (available to the author), simple 3 year moving averages are provided in Table 1( e.g., 1970 = average (1969:1971)). Despite the statistical likelihood that mean height of high school students in S.
Korea and Taiwan as well in the earlier years of our investigation, specifically the 1960s and 1970s, could be slightly greater than the national averages then, Japanese school boys at age 17 years were 2-3 cm taller than their S. Korean and Taiwanese peers in the 1960s through the 1970s. It is estimated that the Taiwanese male high school students were slightly taller in mean height than their Korean peers in the 1960s through the 1980s, (refer to Table 1).  The composition of these calories matters as well. Per capita daily supply of calories from animal products has increased appre-  In the capacity of food economist, with no biological/medical background, the author will focus on food supply, as one of the key components of "inputs to health" [17], in the subsequent sections, to try to answer even partially the above questions.    Table 4 provides changes in per capita consumption (=purchases) of fresh fruit by age groups by 10 year intervals, of individual family members from 1971 *10 to 2010, esti-mated by the author, using the TMI model [40]. A reserved concern on "steering away from fruit by Japanese youth" raised by the White Paper on Agriculture, 25 years ago has come true on unexpectedly extensive scales since then. It is clearly demonstrated that children in Japan, on per capita basis, consumed nearly the same amount of fresh fruit, some 40 kg at home as adults in their middle age in the early 1970s but reduced their consumption to 20 kg in the mid-* 10 The author discovered only recently that 1971 annual report, FIES, contains household purchase data classified by HH age groups, exactly in the same format as annual reports for 1979 and onwards.

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1980s and further down to 5 kg in the early 2000s. In contrast, those in their 50s and 60s increased their fresh fruit consumption, on per capita basis, from 40-50 kg to 60 kg and kept their consumption at the high level over the corresponding period. As of 2010, at-home per capita consumption of fresh fruit by children and young adults was nearly one 10 th that of those in their 60s and 70s in Japan. Table 5 provides changes in per capita at-home consumption of fresh vegetables, including fresh potatoes by age groups of family members, estimated by the author. Although not to the extent of fresh fruit, per capita consumption of fresh vegetables by Japanese youth has declined considerably, as compared to that in their 50s and 60s over the period from the mid-1970s to the early 2000s.  Table 8 [42]. Sources: derived from FIES by the author, using the TMI model. Notes: Estimated by 5 year age intervals first, which were simply averaged into 10 year intervals. Sources: derived from FIES by the author, using the TMI model. Notes: meat includes ham and other processed meats; estimated by 5-year age intervals first and simply averaged into 10year intervals. Sources: derived from FIES by the author, using the TMI model. Notes: meat includes ham and other processed meats; estimated by 5-year age intervals first and simply averaged into 10 year intervals.
It looks certain that South Korean youth have not steered away from vegetables and fruit in their daily food consumption, unlike their Japanese peers in the 1980s through the early 2000s. The au-thor has not obtained detailed data on food consumption, particularly by age groups in Taiwan, to his regret.

Conclusions
Should one eat more, with physical activities kept unchanged, one will get bigger. If children before maturity eat more, with or without more physical activities, they tend to grow bigger, either in height or weight, or in both. Especially, if they eat more animal sourced foods, particularly milk, they will grow taller in height.
There is little question about this [43][44][45]. After the mid-1950s, when Japan's economy had recovered to its pre-war level, Japanese began to eat more foods, in terms of total caloric intakes, and better foods, i.e., more animal sourced foods and fruit, in particular.
Japanese youth in their early 20s, who spent their early years of childhood in starvation during the war and soon after the war period, grew taller in height than those who were born before the war with reasonable amount of food supply but spent their late childhood during the severe food shortage period [46]. The same thing happened in S. Korea, which was under Japan's colonization until the end of WW II and whose economy was devastated by the Korean War, 1950-53, but began to grow very rapidly after the early or mid-1960s.
Taiwan, which was under Japan's colonization, like Korea, began to grow economically some 10 years earlier than S. Korea. In the late 1990s, Taiwanese youth were nearly the same in height as S. Koreans, at 171-72 cm, and both 0.5-1 cm taller than their Japanese peers. Taiwanese youth ceased to grow any taller since then, whereas S. Korean youth kept growing further in height to overtake their Taiwanese peers by 2 cm and their Japanese peers by 3 cm in the mid-2000s. With respect to per capita GDP, Taiwan was considerably richer, and Japan was substantially richer than S. Korea at that time. With respect to per capita caloric supply from animal products, meat, fish and milk in the 1980s and 1990s, Taiwan and Japan were similar and consumed as much as at least 40% more than S. Korea. As mentioned earlier, at age 20 years, young men in Taiwan (Table 3). Consumption of animal proteins is highly effective in explaining incre-ments in child height in South Korea alone but does not seem to be highly successful in identifying differences in child height development between the three countries, Japan and S. Korea with Taiwan added where data are available. Japan has steadily decreased per capita consumption of fruit since the mid-1970s, whereas S. Korea rapidly increased it, to exceed Japan by 30% in 2000. The author provided his own estimates of radical tendencies of "steering away from fresh fruit" among Japanese youth since the mid-1970s.
Taiwan, however, exceeded Japan in respect of per capita supply (=consumption) of fruit in 1980 and consumed twice as much fruit as Japan and 60% more fruit than S. Korea in 2000.
On the other hand, per capita supply of vegetables in Taiwan has been nearly the same as that in Japan, but nearly one half that in S. Korea since 1980 and this applies to the case of per capita consumption of cereals, e.g., per capita consumption of cereals in Tai

Appendix: Brief Notes on Data Sources
Stature Take the case of Japan. National Nutrition Survey [14] conducted every year since soon after the end of WW II, carries data on mean height of males and females by age groups, 1 to 25 years by one-year age interval, 26-29, 30-39, --60-69, 70-. School Health Examination Surveys [16] conducted every year on all schools over the country report mean height of children, both sexes, from 1 st graders in elementary school to 3 rd graders in high school. The size of survey subjects, by each age group from 1 to 25 years old, by NNS, is limited as compared to SHES. This may be the reason why annual data classified by age everyone year are not stable, as compared with SHES, as shown in Appendix Figure A. When analyzing chang-es over time and differences between countries in mean height in the order of 1 to 2 cm, SHES seems to excel NNS.

Consumption
Appendix  Table   A). Both in Japan and South Korea, family income and expenditure surveys, based on monthly diary type surveys have been done, which cover ever increasing eating out, in such categories as school lunch expenditures, expenditure in sushi-restaurants.
Food balance sheets provide annual per capita supply, not consumption, by major food products from very early years in most countries and FAO provides food balance sheets for Japan, South Korea, and Taiwan every year since 1961 to 2013. Supply is not the same as consumption but could be taken as a proxy for consumption.

Acknowledgment
The author is deeply grateful to Dr. Howard Elliot, former Deputy Director General, ISNAR, The Hague, for valuable and affirmative comments and thorough editing of the manuscript. The author is also dearly appreciative to Dr. Kelly Olds, Professor at National Taiwan University, who collected official stature data on school children in Taiwan since the beginning of the 1960s for this project.

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