Lessons Learned from an Assessment of the Planetary Health Diet in Japan: Dietary and Supply Gaps, Self-Sufficiency, and Environmental Impacts

Achieving sustainable food systems that align with planetary and human health goals requires assessments of dietary patterns, supply structures, and environmental impacts. This study presents the first comprehensive evaluation of Japan’s food system, using the EAT-Lancet Healthy Reference Diet (EHRD) as a benchmark. First, this study developed an adjusted version of the EHRD for Japan, accounting for sex- and age-specific energy requirements, and calculated three sufficiency rates using the National Health and Nutrition Survey and the Food Balance Sheet in Japan: intake sufficiency rate (ISR), supply sufficiency rate (SSR), and food self-sufficiency rate (FSR). Second, the environmental impacts of transitioning to EHRD were evaluated using four environmental footprint models. Our analysis identifies a dual challenge of the current Japanese food system: traditional Japanese diet is known for its high consumption of plants, and yet there is a persistent deficit in the consumption and supply of recommended plant-based foods (e.g., legumes, fruits), alongside a severe oversupply and overconsumption of red meat sustained by imports. Results further show that shifting Japanese adults’ diets toward the EHRD would reduce CO2 emissions, water use, and relevant biodiversity impacts, while the direction and magnitude of change vary by food group. The findings also highlight telecoupling: given Japan’s heavy dependence on global supply chains, an EHRD transition would shift some environmental burdens abroad—potentially increasing impacts for under-consumed, import-dependent items (e.g., legumes, fruits, nuts) while alleviating pressures through reduced red meat consumption. Based on these findings, the study proposes three policy implications, including the development of a culturally acceptable dietary guideline, price interventions for recommended foods, and a reevaluation of the animal protein supply chain, including feed sustainability. Our results provide an evidence-based foundation for designing a unique path toward a healthier and more sustainable food system in Japan.