Malnutrition is worsening, affecting every country and over 3 billion people. There is evidence that rising CO₂ levels will not only indirectly increase malnutrition through climate change effects, but also directly through a downshift in the plant ionome, reducing nutritional quality and increasing hidden hunger. Attempts to calculate the human health impact have been conducted with limited statistical power on a small group of nutrients. The impact on different age-sex groups, countries, and nutrients is still largely unknown. This research aims to fill this gap, creating a meta-analysis of the most data (5,809 entries), crops (43), and elements (31 plus phytate) of any study to date, resolving a methodological gap for disharmonious data and applying this to the GENuS model of global nutritional supply in 2011 for eight nutrients (calcium, copper, iron, magnesium, phosphorus, potassium, protein, and zinc) to see which countries will be able to provide enough nutrients for their citizens in a 550 ppm world compared to at 350 ppm.
Bootstrapping reveals a distinct 5% to 12% systemic downshift in the plant ionome. Both C3 and C4 plants respond, disproving the hypothesis that C4 plants are mostly unaffected by CO₂ rise and supporting the idea that the CO₂ saturation point is not directly linked to mineral uptake.  Elements have a differential response, suggesting that the carbon dilution theory is an inappropriate explanation. Zinc, protein, and iron have the largest decreases, and zinc in chickpeas decreases the most (40%) of all groups. Grains (wheat and rice) and soybeans are the hardest hit crops, decreasing in nutritional value up to 12%.
The total nutrient supply decreases by 2.3% to 6.4%, increasing the malnourishment and obesity double burden. Countries will no longer provide enough nutrients from food solely due to changes in the plant ionome, impacting every country. Half of the world will develop new deficiencies. The strongest predictor of resiliency to nutritional changes from CO2 rise is diet diversity. Exacerbating global inequality, the impact will be particularly pronounced in African and Asian countries, and among women aged 25-29 compared to men of the same age group and children aged 0-4 years. Changing plant stoichiometry will have dramatic global implications for hidden hunger, worsening or introducing deficiencies, especially in iron, phosphorus, potassium, and zinc.