But today’s agricultural system relies on a suite of crops that researchers have spent decades fine-tuning for specific niches. It isn’t clear that the country could easily grow a new set of crops that would make up for the lost nutrition from meat for the entire population. (Many individuals, of course, already opt against eating meat for ethical, religious or other reasons.)

“We don’t make that assumption,” Dr. White said. “We kind of ask the inverse question: Given the food that’s available, how do we feed people?”

Christian Peters, an associate professor at the Friedman School of Nutrition Science and Policy at Tufts University, said much of the country’s current agricultural output was used to feed animals. “There is a large amount of what we call co-products that come out of the food production system,” he said. “We have these things that we would otherwise turn into a waste, and we use them to raise animals.”

In addition, grazing cows are able to wrest calories from grasslands that are not suitable for growing food for humans.

Cows are also a source of fertilizer, Dr. White said. Her analysis looked at livestock manure that is used as fertilizer and assumed that it would have to be replaced with synthetic fertilizers, which are often made from natural gas. The main component of natural gas is methane, the same gas that makes cows so problematic in the first place.