The researchers mapped global patterns of crop production and allocation of maize, wheat and rice in China, Brazil, India and the United States to calculate the amount of human-consumable calories. Combined, the countries represent nearly half of total cropland area and global calorie production.

“Looking at alternate diet scenarios, if we shift all crops from current uses to direct human consumption, we could feed an additional 4 billion people,” said the study’s lead author, Emily Cassidy, a researcher at the University of Minnesota’s Global Landscapes Initiative.

The Food and Agriculture Organization of the United Nations estimates that demand for meat and dairy will increase by 68 percent for meat and 57 percent for dairy by 2030.