The nutritional density, including protein content, micronutrients and B-vitamins, of wheat, rice, barley and other important food crops is negatively affected by higher CO2 concentrations  . Projections indicate negative impacts on human nutrition by rising CO2 concentrations by mid- to late-century . Staple crops are projected to have protein and mineral concentrations decreased by 5-15% and B vitamins up to 30% when the concentrations of CO2 double above pre- industrial levels . Without changes in diets and accounting for nutrient declines in staple crops, a projected additional 175 million people could be zinc deficient and an additional 122 million people could become protein deficient . Weyant et al.  projected that CO2-related reductions in crop zinc and iron levels could result in 125.8 million DALYs lost globally, with Southeast Asian and sub-Saharan African countries most affected. Zhu et al.  estimated 600 million people at risk from reductions in the protein, micronutrient and B-vitamin content of widely grown rice cultivars in Southeast Asia.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report