Japanese food economist says decreasing fruit consumption may have stopped adult height in Japan since the 1990s
By Kang Hyun-kyung
Korean teens were shorter than Japanese in the 1960s, yet from the 1990s this has changed. Koreans have outgrown Japanese and are now taller than the latter.
How could that have happened?
Hiroshi Mori, professor emeritus at the Sensu University of Japan, has been wrestling with adult height in Korea and Japan.
He gave it some rigorous thought over the past couple of years after reading a newspaper article, of which the implications he said were "eye-opening."
"Koreans were shorter than the Japanese in the 1960s, and the two people were almost the same in the 1970s and 80s. But Koreans have outgrown Japanese since the 1990s," Mori said.
The food economist was intrigued by the data, among other facts mentioned in the article, that average Korean teens' heights have continued to grow until the mid-2000s, whereas Japanese stopped growing from the 1990s.
The average male Korean teen is 3 centimeters taller than Japanese and the average Korean girl is 2.5 centimeters taller, making Koreans the tallest in East Asia.
"The article said Korean senior high school boys ceased to grow any taller in mean height in the mid-2000s at 173.7 centimeters," Mori said. "This came as a surprise to me because I knew freshman students at Senshu University stopped growing in height in the early 1990s when I was still teaching there. I was also surprised that senior high school boys in Japan were 170.8 cm in the same year and did not change a bit afterwards, and they are 3 cm shorter than their Korean peers."
Mori, 90, wondered what prompted Korean teens to overtake Japanese in height. This never left his mind because he believed Japanese teens have no good reason to lag behind Koreans in terms of height. Japanese consume more meat than Koreans. Japanese also drink more milk than Koreans do. Meat and milk are some of the main sources of protein, which is said to be deeply associated with height. Koreans eat more grains than Japanese do, but few studies find any correlation between grain consumption and height.
According to molecular biologist Chao-Qiang Lai at Tufts University, about 60 percent to 80 percent of the difference in height between individuals is determined by genetic factors while the remaining 20 to 40 percent can be attributed to environmental factors, mainly nutrition.
After some extensive comparative research on the topic, Mori found something interesting in food consumption patterns of the two countries.
Fruit and vegetable consumption in Japan has decreased, whereas Koreans eat more fruit and vegetables, leading him to wonder if this has something to do with the reversed height trends between the two countries.
"Children in Japan began to eat less fruit and vegetables from the early 1980s," he said, calling it "kumamono-banare" (young Japanese' consumption of fruit is in decline).
In Japan, per capita consumption of vegetables has remained almost the same at 120 kilograms per year since World War II.
On the contrary, fruit and vegetable consumption in Korea has soared during the same time period, tripling in size. Koreans consumed an average 82.3 kilograms of vegetables a year in 1965 but their consumption rose to 197.9 kilograms in the 1980s and further increased to 235.7 kilograms in 2000.
"I'm not contending that fruit and vegetables should be key determinants of a child's height. But I suspect Japanese teens' significantly lower consumption of fruit and vegetables might have a negative impact on bone mineral accrual," he said.
His remarks indicate nutrition _ one of two key determinants to human height along with genetics_ was downplayed for some reason and thus needs due attention.
Mori cited the empirical studies of the residents of Mikkabi-cho, Shizuoka, which is home to quality mandarins, when considering the possible impacts of fruit and vegetable consumption on children's height. Conducted by the National Fruit Tree Science Institute of Japan in collaboration with the Hamanatsu University School of Medicine, the research team found high intakes of fruit, particularly mandarins, was positively associated with bone mineral accrual and density in post-menopausal women.
Mori teamed up with British scholar Tim Cole of the University College London's Department of Policy and Practice for an article "Fifty Years of Child Health and Weight in Japan and South Korea," which was published in the American Journal of Human Biology last year.
The Japanese food economist also shared his findings with Korean professors and students during a seminar held at Gangwon University in early June.
Lee Byung-oh, a faculty member of Agricultural and Resource Development at Gangwon University who arranged the seminar, said Mori's research findings are "very interesting."
"As a food economist, professor Mori tried to find nutritional factors that caused the traits of adult height that occurred over the past decades," he said.
Lee said Mori's findings make sense. "His findings are convincing in that nutrition plays a role in determining human height. You can see there is a nutritional impact on adult height when you compare South and North Koreans. In general North Koreans are shorter than South Koreans and insufficient food intake in the North is attributable to the height disparity," he said.
Lee, however, said height is the result of a combination of various factors, noting nutrition is just one of them. "Personally I was convinced genetic factors also played a part," he said. Mentioning old Koreans' derogatory labeling of Japanese as "Oei-nom" or shorter men, he said such a labeling reflects that even in the old days when South Korea was poor, South Koreans were taller than Japanese.
"Thus I was not surprised that today Koreans in general are taller than Japanese. There seems to be some ethnic characteristics that also play a role in determining height, but there're no empirical studies that can back it up," he said.
Lee said inaccurate data also makes it difficult to confirm Mori's research findings.
Unlike Japan where per capita consumption of vegetable, fruit, milk and meat for teens is available, Korea has no such detailed data. "We only have data that shows per capita consumption of those food items for Koreans of all age groups. This makes it difficult to compare consumption of fruit and vegetables between Korean and Japanese teens," he said.
Japan's National Center for Global Health and Medicine attributes the ceased growth of Japanese teens since the 1990s to an increase of low-birth-weight babies. According to WHO, infants of 2.5 kilograms or less at birth are considered to have a low birth weight. The figure was 5.1 percent in 1975 but it rose to 9.6 percent in 2013, according to Japan's Ministry of Health, Labor and Welfare.
By Kang Hyun-kyung
Korean teens were shorter than Japanese in the 1960s, yet from the 1990s this has changed. Koreans have outgrown Japanese and are now taller than the latter.
How could that have happened?
Hiroshi Mori, professor emeritus at the Sensu University of Japan, has been wrestling with adult height in Korea and Japan.
He gave it some rigorous thought over the past couple of years after reading a newspaper article, of which the implications he said were "eye-opening."
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"Koreans were shorter than the Japanese in the 1960s, and the two people were almost the same in the 1970s and 80s. But Koreans have outgrown Japanese since the 1990s," Mori said.
The food economist was intrigued by the data, among other facts mentioned in the article, that average Korean teens' heights have continued to grow until the mid-2000s, whereas Japanese stopped growing from the 1990s.
The average male Korean teen is 3 centimeters taller than Japanese and the average Korean girl is 2.5 centimeters taller, making Koreans the tallest in East Asia.
"The article said Korean senior high school boys ceased to grow any taller in mean height in the mid-2000s at 173.7 centimeters," Mori said. "This came as a surprise to me because I knew freshman students at Senshu University stopped growing in height in the early 1990s when I was still teaching there. I was also surprised that senior high school boys in Japan were 170.8 cm in the same year and did not change a bit afterwards, and they are 3 cm shorter than their Korean peers."
Mori, 90, wondered what prompted Korean teens to overtake Japanese in height. This never left his mind because he believed Japanese teens have no good reason to lag behind Koreans in terms of height. Japanese consume more meat than Koreans. Japanese also drink more milk than Koreans do. Meat and milk are some of the main sources of protein, which is said to be deeply associated with height. Koreans eat more grains than Japanese do, but few studies find any correlation between grain consumption and height.
According to molecular biologist Chao-Qiang Lai at Tufts University, about 60 percent to 80 percent of the difference in height between individuals is determined by genetic factors while the remaining 20 to 40 percent can be attributed to environmental factors, mainly nutrition.
After some extensive comparative research on the topic, Mori found something interesting in food consumption patterns of the two countries.
Fruit and vegetable consumption in Japan has decreased, whereas Koreans eat more fruit and vegetables, leading him to wonder if this has something to do with the reversed height trends between the two countries.
"Children in Japan began to eat less fruit and vegetables from the early 1980s," he said, calling it "kumamono-banare" (young Japanese' consumption of fruit is in decline).
In Japan, per capita consumption of vegetables has remained almost the same at 120 kilograms per year since World War II.
On the contrary, fruit and vegetable consumption in Korea has soared during the same time period, tripling in size. Koreans consumed an average 82.3 kilograms of vegetables a year in 1965 but their consumption rose to 197.9 kilograms in the 1980s and further increased to 235.7 kilograms in 2000.
"I'm not contending that fruit and vegetables should be key determinants of a child's height. But I suspect Japanese teens' significantly lower consumption of fruit and vegetables might have a negative impact on bone mineral accrual," he said.
His remarks indicate nutrition _ one of two key determinants to human height along with genetics_ was downplayed for some reason and thus needs due attention.
Mori cited the empirical studies of the residents of Mikkabi-cho, Shizuoka, which is home to quality mandarins, when considering the possible impacts of fruit and vegetable consumption on children's height. Conducted by the National Fruit Tree Science Institute of Japan in collaboration with the Hamanatsu University School of Medicine, the research team found high intakes of fruit, particularly mandarins, was positively associated with bone mineral accrual and density in post-menopausal women.
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| Hiroshi Mori, professor emeritus of Sensu University of Japan / Courtesy of Hiroshi Mori |
Mori teamed up with British scholar Tim Cole of the University College London's Department of Policy and Practice for an article "Fifty Years of Child Health and Weight in Japan and South Korea," which was published in the American Journal of Human Biology last year.
The Japanese food economist also shared his findings with Korean professors and students during a seminar held at Gangwon University in early June.
Lee Byung-oh, a faculty member of Agricultural and Resource Development at Gangwon University who arranged the seminar, said Mori's research findings are "very interesting."
"As a food economist, professor Mori tried to find nutritional factors that caused the traits of adult height that occurred over the past decades," he said.
Lee said Mori's findings make sense. "His findings are convincing in that nutrition plays a role in determining human height. You can see there is a nutritional impact on adult height when you compare South and North Koreans. In general North Koreans are shorter than South Koreans and insufficient food intake in the North is attributable to the height disparity," he said.
Lee, however, said height is the result of a combination of various factors, noting nutrition is just one of them. "Personally I was convinced genetic factors also played a part," he said. Mentioning old Koreans' derogatory labeling of Japanese as "Oei-nom" or shorter men, he said such a labeling reflects that even in the old days when South Korea was poor, South Koreans were taller than Japanese.
"Thus I was not surprised that today Koreans in general are taller than Japanese. There seems to be some ethnic characteristics that also play a role in determining height, but there're no empirical studies that can back it up," he said.
Lee said inaccurate data also makes it difficult to confirm Mori's research findings.
Unlike Japan where per capita consumption of vegetable, fruit, milk and meat for teens is available, Korea has no such detailed data. "We only have data that shows per capita consumption of those food items for Koreans of all age groups. This makes it difficult to compare consumption of fruit and vegetables between Korean and Japanese teens," he said.
Japan's National Center for Global Health and Medicine attributes the ceased growth of Japanese teens since the 1990s to an increase of low-birth-weight babies. According to WHO, infants of 2.5 kilograms or less at birth are considered to have a low birth weight. The figure was 5.1 percent in 1975 but it rose to 9.6 percent in 2013, according to Japan's Ministry of Health, Labor and Welfare.
