Abstract
The globalization of food production and distribution has homogenized human dietary patterns irrespective of geography, but it is uncertain how far this homogenization has progressed. This study investigated the carbon and nitrogen isotope ratios in the scalp hair of 1305 contemporary Japanese and found values of −19.4 ± 0.6‰ and 9.4 ± 0.6‰ (mean ± SD), respectively. Within Japan, the inter-regional differences for both isotope ratios was less than 1‰, which indicates low dietary heterogeneity among prefectural divisions. The carbon and nitrogen isotope ratios of the hair showed a significant correlation with the results of questionnaires on self-reported dietary habits. The carbon isotope ratios from Japan were lower than those in samples from the USA but higher than those in samples from Europe. These differences stem from the varying dietary proportions of food products originally derived from C3 and C4 plants. The dietary variation of Japan is as small as those of Europe and USA and smaller than those of some Asian countries. These results indicate that dietary homogeneity has progressed in Japan, which may indicate the influence from the spread of the Western-style diet and food globalization, although dietary heterogeneity among countries is still preserved.
Highlights
The globalization of food production and distribution has homogenized human dietary patterns irrespective of geography, but it is uncertain how far this homogenization has progressed
Tofu and natto made from legumes exhibit lower carbon and nitrogen isotope ratios than animal products
The δ13C values of the hair samples were positively correlated with beef, marine fish, and eggs and negatively correlated with natto and tofu (R2 = 0.06, F = 8.23, P < 0.01 for δ13C). These results indicate that the individuals who frequently ate marine fish and beef showed higher carbon and nitrogen isotope ratios in hair, and the individuals who frequently ate tofu and natto showed lower carbon and nitrogen isotope ratios
Summary
The globalization of food production and distribution has homogenized human dietary patterns irrespective of geography, but it is uncertain how far this homogenization has progressed. These differences stem from the varying dietary proportions of food products originally derived from C3 and C4 plants. In accordance with the worldwide urbanization and westernization of lifestyles, the dietary patterns in developing countries have tended to change to a Western style[3] This is known as nutrition transition and is defined by the increased consumption of dietary products high in fats and sweeteners, a lower intake of cereals, and the insufficient consumption of vegetables and fruit[1,4]. Nitrogen isotope ratios of hair suggest the trophic level of food sources consumed by humans[21]. A global dataset of the isotope ratios in human hair samples was analyzed[41] to provide an isotopic perspective of dietary homogeneity around the world
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