Climate change risks of micronutrient deficiency will become severe in high-vulnerability development pathways and in the absence of societal adaptation, leading to hundreds of millions of additional people lacking key nutrients for atmospheric CO2 levels above 500 ppm  . For example, concentration of many micronutrients  can decrease by 5-10% under atmospheric CO2 concentrations of 690 ppm . The decline in zinc content is projected to lead to an additional 150-220 million people affected by zinc deficiency with increases in existing deficiencies in more than 1 billion people . Similarly, decrease in protein and micronutrient content in rice due to a higher CO2 concentration  can lead to 600 million people with rice as a staple at risk of micronutrient deficiency by 2050 . Additionally, the impact on protein content of increased CO2 concentration  can lead an additional 150 million people with protein deficiency by 2050  in comparison with the scenario without increased CO2 concentration .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report