We examined the cross-sectional and longitudinal associations between the TJDS and seven environmental indicators using Poore et al.’s supplemental data [29]. The association between the TJDS and environmental indicators was similar in 2010, 2015, and 2020. The longitudinal analysis showed the same trends for the five environmental indicators as the cross-sectional analysis. The TJDS was negatively associated with land use, GHG2007, GHG2013, Acidifying, and Water use in cross-sectional and longitudinal analyses. While Eutrophying (cross-sectional, n. s.; longitudinal, negative) and Freshwater (cross-sectional, positive longitudinal, n.s.) had different results in the cross-sectional and longitudinal analyses. These results suggest that the negative associations between TJDS and Land use, GHG, Acidifying, and Water use are not incidental but permanent.

This is the first study to examine the relationship between Japanese-style diet and eight of the 17 SDGs on a longitudinal and global scale. Using the original GHG database, Sugimoto et al. [5] reported that the top contributor to GHGs was meat, followed by fish and seafood. Oita et al. [7] examined the changes in the nitrogen footprint (NF) of the Japanese diet from 1961 to 2011 using FAOSTAT. They reported that the protein intake in 1975 was the closest to the protein recommendation and reported a lower NF than that in 2011. The protein intake percentage from meat increased from 3 to 15%, while that from rice decreased from 45 to 28% during this period in Japan. However, we did not find any studies examining the relationship between Japanese-type diets and environmental indicators in other countries, including Japan. Nelson et al. [4] reported that plant-based foods, such as dietary guideline-related diets, Mediterranean-style diets, the Dietary Approaches to Stop Hypertension diet, and other sustainable diet scenarios, were lower in total energy and had less impact on environmental indicators such as GHG and land use than animal-based foods from 23 articles extracted through a systematic review. Other systematic reviews have reported similar results [39]. The relationship between the TJDS and the seven environmental indicators we used were consistent with that reported in a previous report, indicating that the Japanese diet is likely to have a small environmental impact on a global scale in Land use GHG, Acidifying, and Water use not only TJDS is useful for health. The Japanese diet is also consumed worldwide [10] and is considered to be internationalized. The results suggest that the Japanese diet is also a healthy dietary option. For Asian countries where rice is the staple food among cereals, it is a significant finding that a rice-based diet was found to be negatively associated with several environmental indicators.

The problem with the Japanese diet regarding its environmental impact is that rice cultivation requires a large amount of freshwater [40, 41]. Our cross-sectional results also show a positive correlation between the TJDS and Freshwater use. Islam et al. [42] reported that more than half of the world’s population consumes rice; however, rice production systems are the largest anthropogenic wetlands. Several agronomic strategies have been proposed to improve water-use efficiency and reduce GHG emissions. They concluded that improved water management and timely coordination of N fertiliser with crop demand could reduce water use and N loss via N2O and CH4 emissions. Our longitudinal analysis, including the interaction between the TJDS and year, showed that the association between the TJDS and freshwater was reversed in 2018, and although not significant, the higher the TJDS, the less freshwater (data not presented). These results may explain why the Freshwater and　Eutrophying　analyses differed between the cross-sectional and longitudinal analyses in our study.

Our data also showed that even countries with very similar TJDS scores have different residuals for environmental indicators. Although the scores were similar, the food supply that made up the scores differed greatly, which may have contributed to the variation in the magnitude of the effects of the environmental indicators.

In addition, the mean scores of TJDS were − 0.4 in 2010 and − 0.1 in 2020; however, our analysis showed no period change in scores between 2010 and 2020. Economic development and changes in eating habits have been reported to alter environmental impact [7, 29, 40,41,42]. In our data, we compared China, India, and Japan. GHG2013 in 2010 was 11.4 kg CO2 eq in China, 2.8 kg CO2 eq in India, and 5.9 kg CO2 eq in Japan, a global total of 871.2 kg CO2 eq; in 2020, it was 13.0 kg CO2 eq in China, 3.3 kg CO2 eq in India, and 6.1 kg CO2 eq in Japan, a global total of 918.0 kg CO2 eq, the same was true for GHG2007. Similarly, Land use and Acidifying were increasing, with global totals of 1535.7 m2 (in 2010), 1587.7 m2 (in 2020), 5671.2 g SO2 eq (in 2010), 6049.9 g SO2 eq (in 2020), respectively. Eutrophying and Freshwater trends vary by country; however, the total was increasing. Aleksandrowicz et al. reported that in India, where malnutrition is still prevalent, the spread of healthier diets could result in a slight increase in the environmental footprint of the food system over the current situation. However, an even larger increase is expected if the diets consumed by the wealthiest people become widespread [43]. Natori et al. [44] examined the possibility of using the Satoyama Index, which was developed with a focus on biodiversity and tested in Japan for socio-ecological production landscape mapping on a global scale. It can be used globally to identify landscapes resulting from complex interactions between people and nature, with statistical significance. International comparisons using the same indicators may create an environment where environmentally friendly agricultural technologies can be provided. Japanese-style agriculture will also be helpful in achieving SDGs.

The SDGs must be achieved not only from the production and distribution aspects but also from the consumer aspect. From the consumer perspective, obesity prevention and food loss reduction are major issues that can be addressed to achieve the SDGs [40, 45]. However, using the TJDS and environmental indicators of Poore et al., we were able to show that a traditional Japanese-style diet was environmentally friendly. Some have reported a disconnect between current public health and SDGs studies [40]. Although the SDGs are diverse, Poore et al. pointed out that environmental impacts need to be judged comprehensively and that it is necessary to study all aspects of food production, distribution, and retail to consumers and create measures starting with items that are easy to address. This study may also help in this regard.

The strength of this study is that we examined the relationship between Japanese-style diets and multiple environmental indicators on a global scale and longitudinally considering the environmental impacts from production to consumers. Agricultural producers and consumers in each country can compare the seven environmental indicators internationally and choose the indicators most likely to help them achieve SDGs.

Conversely, a limitation of this study is whether these environmental indicators reflect changes in environmental impacts over the past decade. This study used large amounts of open data and their systematic reviews to create seven environmental indicators. The data were centred on 2010, and the external data related to 2009-11 [29]. Poore et al’s efforts the data collected for the review were biased, and some areas were inferred and supplemented with outside information. Moreover, foods in the FAOSTAT that were included from Poore et al.’s supplement data in this paper do not cover all food items in the FAOSTAT.

Despite a few problems, no other environmental indicators similar to this one was found.

Another limitation is that this was an ecological study. In the future, we would like to examine whether these environmental indicators can be used to explain the relationship between an individual’s diet and environmental factors using cohort data or other methods.

In conclusion, TJDS is an indicator of the association between Japanese diet and health events [16, 25,26,27,28]. In addition, TJDS was negatively related to land use, GHG emissions, Acidifying emissions, and stress-weighted Water use. Japanese style diet could contribute to the SDGs on a global scale.