Rising Atmospheric CO₂ Lowers Concentrations of Plant Carotenoids Essential to Human Health: A Meta-Analysis

Plant and human tissues (e.g., leaves, retina) share the need for carotenoids to protect against light-induced and other oxidative stresses. While plants synthesize carotenoids de novo, humans must obtain them primarily through plant-based foods. In plants, elevated levels of atmospheric carbon dioxide (eCO₂) decrease the concentrations of essential minerals, including magnesium and zinc (essential for brain and eye health), but the overall effect of globally rising CO₂ levels on carotenoids is unknown. Here, investigation is sought on how eCO₂ affects carotenoids in plants. A meta-analysis of 1026 experimental observations from 37 studies shows that eCO₂ decreases plant carotenoid concentrations by 15% (95% CI: −26% to −6%). The meta-analysis of available gene expression data for Arabidopsis thaliana points to a potential CO₂-induced downregulation of carotenoid biosynthesis (Log2 fold-change −13%, 95% CI: −17% to −9%). Some other stoichiometric and biochemical mechanisms related to CO₂-induced changes in carotenoids are also highlighted. While overall eCO₂ decreases carotenoid concentrations, individual CO₂ studies report variable responses, including increases in carotenoid levels, especially in abiotically stressed plants. The initial assessment raises a novel question about the potential effects of rising CO₂ on human health through its global effect on plant carotenoids.