A balanced staple food structure effectively curbs the environmental impact and counters the nutrient losses from elevated CO2

The projected rise in atmospheric CO2 levels to 550 ppm by mid-century may reduce protein, iron, and zinc levels in certain cereal crops by 3–17 %. In China, staple foods provide nearly 50 % of total energy and 40 % of essential nutrients, and their cultivation exacerbates environmental stress; adjusting staple food consumption may bring environmental and health benefits. Using China Health and Nutrition Survey (CHNS) data, this study compared current staple food consumption (SBAU) to an optimized balanced diet scenario with the consumption of whole grains and legumes replaces excessive refined grains. Findings reveal that SBAU falls short of recommended nutrient intake (RNI), while the optimized scenario offsets the nutritional impact of the elevated CO2, exceeding 95 % of the RNI for zinc and iron from staple food. Additionally, transition to the optimized scenario also reduces greenhouse gas emissions and blue water consumption by 7 % and 39 %, respectively.