抄録
The Japanese diet is known for its ideal balance of the three macronutrients, namely protein, fat, and carbohydrates. Dietary statistics indicate that over time, in Japan, these macronutrient ratios have been maintained since the mid-1970s in close agreement with favorable macronutrient ratio intake standards, set by the Japanese Ministry of Health, Labour and Welfare. The ideal ratio is principally achieved by reducing carbohydrates, while increasing fats. However, in recent years, this macronutrient ratio appears to depart from ideal ranges, due to over-westernization of the Japanese diet. To investigate the extent of this phenomenon, we analyzed a time series data set for ingested nutrition by using cointegration techniques to identify long-run, stable relationships among the three macronutrients, between 1956 and 2015. Next, we set a restriction on the cointegrating vectors, representing ideal macronutrient ratio standards. This restriction was used as the null hypothesis that the detected long-run relationships among the three macronutrients were favorable, compared to the idealized macronutrient intake standard. We run the likelihood ratio tests for the full sample and sub-samples, by recursively increasing the number of observations obtained since 1978. Our results reject the null hypothesis, at the conventional level of significance, for the full sample and almost all sub-samples. These outcomes indicate that although the Japanese diet between the late 1980s and early 2000s were the closest to the ideal macronutrient ratios of proteins, fats, and carbohydrates, it is diverging since that time from these favorable ratios.
