Estimated Effects of Future Atmospheric [Formula: see text] Concentrations on Protein Intake and the Risk of Protein Deficiency by Country and Region

BACKGROUND: Crops grown under elevated atmospheric [Formula: see text] concentrations ([Formula: see text]) contain less protein. Crops particularly affected include rice and wheat, which are primary sources of dietary protein for many countries. OBJECTIVES: We aimed to estimate global and country-specific risks of protein deficiency attributable to anthropogenic [Formula: see text] emissions by 2050. METHODS: To model per capita protein intake in countries around the world under [Formula: see text] , we first established the effect size of [Formula: see text] on the protein concentration of edible portions of crops by performing a meta-analysis of published literature. We then estimated per-country protein intake under current and anticipated future [Formula: see text] using global food balance sheets (FBS). We modeled protein intake distributions within countries using Gini coefficients, and we estimated those at risk of deficiency from estimated average protein requirements (EAR) weighted by population age structure. RESULTS: Under [Formula: see text] , rice, wheat, barley, and potato protein contents decreased by 7.6%, 7.8%, 14.1%, and 6.4%, respectively. Consequently, 18 countries may lose [Formula: see text] of their dietary protein, including India (5.3%). By 2050, assuming today’s diets and levels of income inequality, an additional 1.6% or 148.4 million of the world’s population may be placed at risk of protein deficiency because of [Formula: see text]. In India, an additional 53 million people may become at risk. CONCLUSIONS: Anthropogenic [Formula: see text] emissions threaten the adequacy of protein intake worldwide. Elevated atmospheric [Formula: see text] may widen the disparity in protein intake within countries, with plant-based diets being the most vulnerable. https://doi.org/10.1289/EHP41