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... Sterre ter Haar, a lecturer at Leiden University in the Netherlands, and other researchers at the institution created a method to compare multiple studies on plants' responses to increased CO2 levels. The results, she said, were a shock: although crop yields increase, they become less nutrient-dense. While zinc levels in particular drop, lead levels increase.

"Seeing how dramatic some of the nutritional changes were, and how this differed across plants, was a big surprise," she told the Guardian. "We aren't seeing a simple dilution effect but rather a complete shift in the composition of our foods ... This also raises the question of whether we should adjust our diets in some way, or how we grow or produce our food." ...