Mineral malnutrition stemming from undiversified plant-based diets is a top global challenge. In C₃ plants (e.g., rice, wheat), elevated concentrations of atmospheric carbon dioxide (eCO₂) reduce protein and nitrogen concentrations, and can increase the total non-structural carbohydrates (TNC; mainly starch, sugars). However, contradictory findings have obscured the effect of eCO₂ on the ionome—the mineral and trace-element composition—of plants. Consequently, CO₂-induced shifts in plant quality have been ignored in the estimation of the impact of global change on humans. This study shows that eCO₂ reduces the overall mineral concentrations (−8%, 95% confidence interval: −9.1 to −6.9, p<0.00001) and increases TNC:minerals > carbon:minerals in C₃ plants. The meta-analysis of 7761 observations, including 2264 observations at state of the art FACE centers, covers 130 species/cultivars. The attained statistical power reveals that the shift is systemic and global. Its potential to exacerbate the prevalence of ‘hidden hunger’ and obesity is discussed.

DOI: http://dx.doi.org/10.7554/eLife.02245.001