The moral high ground of food just shifted a little bit.

Using biophysical simulation models to compare 10 eating patterns, researchers found that eating fewer animal products will increase the number of people that can be supported by existing farmland. But as it turns out, eliminating animal products altogether isn’t the best way to maximize sustainable land use. Their work was published in Elementa, a journal on the science of the anthropocene.

The researchers considered the vegan diet, two vegetarian diets (one that includes dairy, the other dairy and eggs), four omnivorous diets (with varying degrees of vegetarian influence), one low in fats and sugars, and one akin to the modern American dietary pattern.

Based on their models, the vegan diet would feed fewer people than two of the vegetarian and two of the four omnivorous diets studied. The bottom line: Going cold turkey on animal-based products may not actually be the most sustainable long choice for humanity in the long term.

…the vegan diet wastes available land that could otherwise be used to feed more people.

Of course, this is not an argument to embrace a meaty diet. The study says striving for plant-based diets (with a little bit of meat on the side, at most) is the way towards environmental efficiency (in other words, using land more sustainably to produce more food).

The average US consumer today requires more than 2.5 acres (over two football fields) of land each year to sustain his or her current diet. That number decreases dramatically as you reduce meat consumption and add in more vegetables. Three of the vegetarian diets examined in the study would use less than 0.5 acres of land per person each yea, freeing up more land to feed more people.

So why not go whole-hog vegan?

When applied to an entire global population, the vegan diet wastes available land that could otherwise feed more people. That’s because we use different kinds of land to produce different types of food, and not all diets exploit these land types equally.

Grazing land is often unsuitable for growing crops, but great for feeding food animals such as cattle.

is often unsuitable for growing crops, but great for feeding food animals such as cattle. Perennial cropland supports crops that are alive year-round and are harvested multiple times before dying, including a lot of the grain and hay used to feed livestock.

supports crops that are alive year-round and are harvested multiple times before dying, including a lot of the grain and hay used to feed livestock. Cultivated cropland is where you typically find vegetables, fruits and nuts.

The five diets that contained the most meat used all available crop and animal grazing land. The five diets using the least amount of meat—or none at all—varied in land use. But the vegan diet stood out because it was the only diet that used no perennial cropland at all, and, as a result, would waste the chance to produce a lot of food.

The omnivorous diets on the chart below reflect four patterns, each with more or less vegetarian influence. The smaller the percentages reflect less animal products in that diet.

Throwing a bone to vegans

Of course, these findings were from a single study, and determining what people should eat to maximize both sustainability and health is a tricky business. Economists, biologists, nutritionists, and environmentalists have all undertaken studies to find a definitive answer, but that remains elusive as there are many variables along the food chain—to say nothing of how our bodies interact with foods differently.

And then there’s the issue of philosophy. A lot of vegans aren’t in the business of avoiding animal products for the sake of land sustainability. Many would prefer to just leave animal husbandry out of food altogether.

Correction: An earlier version of this story was published with the headline, “Being vegan isn’t as environmentally friendly as you think.” The headline and descriptions of sustainability were changed to more accurately reflect the research described in the story, which focuses on using land efficiently to feed more people, not protecting the environment.