One study speculates that if the U.S. went vegan, it would have dire consequences. Is it accurate, or a lesson in reading scientific literature critically?

Research studies are not always what they seem, and it’s a good practice to dig deeper into the numbers and draw your own conclusions. Sometimes, studies that seem to support our values and strategies have flaws that we should be aware of before we use those numbers. On the other hand, sometimes studies that seem negative for animal advocacy can be analyzed and and we can arrive at other conclusions.

At first glance, this study seems to spell bad news for a plant-based diet: after simulating the disappearance of all animal agriculture, researchers find that U.S. greenhouse gas emissions are reduced by 2.6%, though we would increase our deficiency of certain essential nutrients and produce an excess of food. This is a common refrain for anti-vegan advocates: there may be some modest benefits, but it’s an unsustainable system at a large scale. When looking at this study, however, there are several issues that may suggest otherwise beg a second look, starting with the fact that both authors have a background in animal and dairy science. However, that alone is not enough to discount their findings – we have to look at their methods.

The average vegan has an increased rate of consumption of fruits and vegetables compared to an omnivore, as well as a lower rate of consumption of refined grains.[1] So, if the entire country adopted a vegan diet, we would expect an increased demand for fruits and vegetables. The authors, however, replace virtually all animal products with grains. The simulated omnivorous diet is 25% grains, 15% vegetables, 5% fruit, and 48% animal products, with a small amount of legumes and sugars. The simulated vegan diet, however, is 85% grain, with only 9% vegetables and 5% fruits. So despite real-world vegans’ increasing demand for fruits and vegetables, the authors’ simulated diets actually decrease the consumption of these foods. Why?

The authors’ model assumes that the U.S. agricultural system would continue to produce the same crops that it currently does. This, despite the fact that the vast majority of corn and soy – our two biggest crops – are not intended for human consumption. Corn is primarily used for biofuels and animal feed. The corn that is consumed by humans is often in the form of high-fructose corn syrup.[2] Meanwhile, U.S. soybeans are mostly used for oil or for animal feed. The rest is used for human consumption, or for various industrial purposes like lubricants and hydraulic fluid.[3] Despite this, the authors argue that since current demand for vegetables and fruits is high, the farmers currently producing soy and corn must be unable or unwilling to grow anything else. They say that if it were viable for farmers to be producing more fruits and vegetables in the current system, they would. This is not necessarily true in the United States.

Corn, wheat, and soy are heavily subsidized by the U.S. government, while most fruits and vegetables are not. This makes them much safer crops to grow, as a drop in demand or a bad harvest will not necessarily bankrupt the farm.[4] Given the choice between a risky income source and a stable one, most farmers choose stability. This is especially true for grains, as the animal agriculture system itself functions as a risk-reducer. If a farm’s grain yield is unsuitable for human consumption, it is often turned into animal feed and sold at low prices. If grain farmers no longer had subsidies to rely on and could no longer sell their low-quality surplus to meat and dairy producers, their industry would become much more risky. Risk inspires both prudence and innovation. Reducing or removing subsidies forces farmers to improve their practices and follow the market. This is the norm in every other industry: meet demand and exceed your competitors. If demand shifted towards more vegetables, fruits, and legumes, farmers would be forced to adjust accordingly, and the best farmers would come out on top.

The authors argue, problematically, that it would be impossible to feed the country a nutritionally adequate diet without meat and dairy. According to them, many vitamins and minerals would be missing, including A, B12, D, E, K, and calcium. To anyone with a basic understanding of nutrition, this is unsurprising; of course a diet composed mostly of corn and soy would be inadequate. However, all of these nutrients (besides B12 and D) are found in high numbers in plant foods.

A single sweet potato has 400% of your daily vitamin A, 2oz of sunflower seeds has 130% of your vitamin E, a 1/2 cup of kale has over 100% of your vitamin K, and a 1/2 cup of tofu has the same amount of calcium as a cup of whole milk. Vitamins B12 and D are easily supplemented, either through standalone supplements or fortified foods. Omega-3s are also rare in plant foods, but can be found in high quantities in algae oil, which is often sold as a supplement and can be used to fortify drinks or foods.

Clearly, the plant kingdom is not lacking in foods that produce these nutrients, but the authors argue that we simply would be unable to produce these foods in a great enough quantity to satisfy everyone’s needs. This is based on the assumption that we would be growing the same crops in similar quantities that we do now, which is not supported by actual data regarding vegan consumption patterns, nor the laws of economics.

This is primarily a lesson in good science literacy. We are often tempted to take science at face value and ignore the fact that scientists are fallible like the rest of us. In this instance, two scientists with vested interests in the animal agriculture system ran a study that seemingly affirms the necessity of meat and dairy. Upon closer inspection, the authors appear to have designed the study with a particular conclusion in mind, similar to two petroleum engineering professors running a study showing how solar power is not a feasible energy source. While we shouldn’t rule their findings out simply because of the scientists’ backgrounds, we should approach them with a critical eye.

Likewise, we shouldn’t be afraid to approach studies from “the vegan side” with the same level of critique. The point isn’t to promote vegan science per se, but rather to keep all sides honest, and to evaluate the methods and results of any study critically. When we have good data, we can make better choices grounded in reality, and we’re all better for it.

[1] Patterns Of Food Consumption Among Vegetarians And Nonvegetarians. Journal of Nutrition, 112(10).

[2] It’s Time to Rethink America’s Corn System. Scientific American.

[3] Uses Of Soybeans. NC Soybean Producers Association.

[4] Farm Bill: Why Don’t Taxpayers Subsidize The Foods That Are Better For Us? Washington Post.