Crops becoming more calorific but less nutritious, study finds

More carbon dioxide in the environment is making food more calorific but less nutritious - and also potentially more toxic, a study has found.

- Senay Boztas

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."

While scientists have been looking at the effects of more CO₂ in the atmosphere on plants for a decade, their work has been difficult to compare. The new research established a baseline measurement derived from the observation that the gas appears to have a linear effect on growth, meaning that if the CO₂ level doubles, so does the effect on nutrients. This made it possible to compare almost 60,000 measurements across 32 nutrients and 43 crops, including rice, potatoes, tomatoes and wheat.