Directly affecting plants, increased concentrations of CO2 worsen the nutritional quality of food by decreasing protein and mineral concentrations from 5–15%, and B vitamins by up to 30%. Higher CO2 concentrations increase photosynthesis in some plants (for example wheat, rice, potatoes, and barley), which can increase crop yields. But those increases come at the cost of lower nutritional quality as plants accumulate more carbohydrates and less minerals (eg, iron and zinc) which can negatively affect human nutrition. Calcium and magnesium also decrease in plants exposed to higher CO2 concentrations. And cattle have been increasingly protein-stressed, probably decreasing weight gain. Undernutrition is expected to be the greatest health risk of increasing CO2.
www.thelancet.com/journals/lanplh/article/PIIS2542-5196(19)30108-1/fulltext