National income, which enables people to purchase animal proteins, is regarded as a key determinant of adult heights [1] [2] . Japan and South Korea made rapid economic progress since the end of WW II, with S. Korea some two decades behind Japan due to the Korean War (1950-53) which devastated the country. Per capita GDP (in 2010 U.S. Dollars) in Japan increased from $8608 in 1960, to $25,489 in 1980, and eventually to $42,170 in 2000. That in S. Korea also increased steadily, but remained considerably behind Japan, at $944, $3700, and $15,104 over the corresponding period [3] . Accordingly, per capita daily caloric intake from animal products increased from 251 kcal in 1961 to 537 kcal in 1980 and 604 kcal in 2000 in Japan, whereas that in S. Korea also increased from 56 kcal, to 212 kcal, and eventually to 447 kcal over the same period [4] . As is shown in greater details in Table 2 and Table 3, Japan’s per capita intake of animal products was nearly twice as large as that in S. Korea in 1990, for example.

Based on national school health examinations conducted with similar methods both in Japan and S. Korea [5] [6] , school boys at age 17 - 18 years in Japan were 166 cm in mean height in the early 1960s, 2 - 3 cm taller than their Korean peers, 170 cm in the 1980s, 1 cm taller than in Korea, but ceased to grow taller in height around 1990. Their Korean pees kept growing taller in height, overtaking Japanese boys by 3 cm in the mid-2000s, as shown in greater detail in Table 1.

Intakes of animal proteins alone likely cannot explain the differences in child height development between the two countries over the past half century from 1960 to 2010. A genetic difference between Japanese and Korean population, however, is not easy to establish. The observed differences in child height development between Japan and S. Korea do not appear to be greater than those observed between different regions in the same country [7] [8] . Also, [9] “Growth status of Korean schoolchildren in Japan”, states that Korean children born and raised in Japan are very similar, in height and weight by age, to Japanese children, based on school health surveys conducted in Tokyo and Osaka in the end of the 1970s and found taller in height and heavier in weight than their counterparts in S. Korea at the same time.

Comprehensive surveys of daily nutritional intakes, by major food groups, both in terms of kcal/capita and grams/capita have been conducted since the end of WW II in Japan, whereas a national health and nutrition survey [21] was first conducted in 1998 in S. Korea, followed by the second one in 2001, and the third one in 2005. In comprehending trends and differences in food consumption between Japan and S. Korea since 1960 onward, official nutrition surveys cannot meet our needs for this paper. This is the reason why we relied on [4] for the basic information concerning changes and differences in food consumption between Japan and S. Korea over the past half century, as presented in the preceding section. Regrettably, however, we used national per capita net food supply (as proxy for consumption) for the entire population, not for the growing children, in particular.

Japan’s Nutrition Surveys [18] started to publish per capita food intakes by age groups in 1995 for the first time, while we may need the age-wide data for the period three decades up to 1995.

Japan’s Bureau of Statistics has conducted household income and expenditure surveys [22] of approximately 8000 households across the nation, with 1/6 of the subjects replaced each month every year since 1950. [22] publishes the survey results by goods and services, such as rice, --, beef, pork, ---, fresh fruit, coffee, --, gasoline, eating-out, including expenditures for school lunch, at sushi restaurants, etc. in major cities across the country and by income classes of households. Starting in 1971, [22] published expenditures on major goods and services

Sources: [4] . Note: *Derived by total domestic supply/population, provided in [20] .

(prices paid and quantities, in the case of goods) by age groups of household head (HH). In the case of foods, eating-out has been on the increase lately and thus [22] does not cover most of the actual consumption of selected food items. In the case of meat, for example, FIES is estimated to cover about half of total meat consumption [23] , 60% - 80% of fresh fruit [24] , and 50% - 60% of vegetables [25] .

Focusing just on at-home consumption of selected food products, individual consumption by age groups can be derived from [22] data classified by HH age groups, by means of the TMI model which explicitly incorporates family age composition by HH age groups [26] .

M. Blum states, “The central determinants of human stature is the protein-intensity of a nation’s diet. Populations consuming larger amounts of animal protein reach higher average height levels than countries with less animal protein consumption. However, a high consumption of animal proteins alone does not result in increasing body heights if the overall consumption of calories and other essential nutrients is insufficient” [2] , p. 21). The author is inclined to contend that this may apply to the comparative case of child height developments between Japan and S. Korea over the past half century since the early 1960s. Ishibashi, based on the comprehensive analyses of large samples of [22] panel data since the early 1980s, Japanese youth have been consuming more meats than the older adults [27] [28] . In Japan, vegetables are believed to regulate bowel movements and fruit is called mizikashi (jelly desert), implying fruit consumption has nothing to do with essential nutrients. The author, however, suspects that children in Japan consumed insufficient “essential nutrients” noted by M. Blum, due to the drastically reduced consumption of fruit and vegetables⁴ in the recent few decades.

[29] , Ministry of Agriculture drew public attention to the widespread tendencies of wakamono no kudamono-banare (steering away from fruit by the young), in the 1980s and the early 1990s by displaying household fresh fruit purchases classified by HH age groups divided simply by the number of persons contained in each group. [30] designed a quadratic programming model to derive individual at-home consumption of selected food products by age from FIES, classified by HH age groups, which was statistically refined by [26] .

Table 4 and Table 5 demonstrate that Japanese youth used to eat as much fruit and vegetables as older adults in the early 1970s but began to reduce their consumption of these products in the early 1980s, while the older adults kept constant their produce consumption at high levels: for example, nearly three times higher than young people’s consumption in the case of vegetables and more than five times in the case of fruit in 2000.

Sources: derived from [22] by the authors, using the TMI model. Notes: Estimated by 5 year age intervals first, which were simply averaged into 10 year intervals.

Sources: the same as Table 4. Notes: the same as Table 4.

At age 17 - 18 years, Japanese school boys were 2 - 3 cm taller in mean height in the 1960s through 1970s, barely 1 cm taller in the 1980s than their Korean peers and they ceased to grow any taller in and around 1990, whereas Korean boys kept steadily growing in height to overtake their Japanese peers by 3 cm in the mid-2000s and ceased to grow any taller since then.

After the end of WW II, Japan and South Korea made rapid and steady economic progress, with S. Korea some two decades behind Japan due to the Korean War (1950-53). As the economy grew, food consumption remarkably improved both in quantity and quality. Particularly, intake of animal-sourced products increased conspicuously in the two countries. Yet, animal product supply per person in Japan was considerably greater, as much as 30% higher, than S. Korea in the mid-1990s.

Increases in animal protein products alone cannot explain the differences in growth patterns of child height between the two countries. However, S. Koreans have been eating twice as many vegetables as Japanese on average and their per capita fruit consumption soared very rapidly since the mid-1970s, surpassing that of Japanese in the mid-1990s. Meanwhile, Japanese youth reduced their fruit and vegetable consumption from the mid-1970s on. This “steering away from fruit and vegetables” by Japanese youth could have contributed to the stagnation of child height growth since the early 1990s, and deserves scientific investigation.

The author is grateful to John Dyck, formerly an economist in Asian affairs at ERS, USDA, who advised to rearrange the structure of the article and thoroughly edited the manuscript. Thanks go to anonymous reviewers for considerate comments and careful proofs.

No research fund has been received from any sources.

The author declares no conflict of interest.

Mori, H. (2018) Secular Changes in Child Height in Japan and South Korea: Consumption of Animal Proteins and “Essential Nutrients”. Food and Nutrition Sciences, 9, 1458-1471. https://doi.org/10.4236/fns.2018.912106