What If The US Went Vegan Overnight? Part 1: Nutrition

Earlier this month, a paper written by Robin R. White and Mary Beth Hall, entitled “Nutritional and greenhouse gas impacts of removing animals from US agriculture” appeared in the Proceedings of the National Academy of Sciences of the USA (PNAS).  The study has already inspired plenty of panic. You have probably seen the headlines already. Quartz reported in apocalyptic overtones that “If The Entire US Went Vegan, It’d be a Public Health Disaster.” Quartz (and other news outlets) seem to have extrapolated their headlines from the authors’ conclusion that, “compared with systems with animals, diets formulated for the US population in the plants-only systems had greater excess of dietary energy and resulted in a greater number of deficiencies in essential nutrients.” But is that actually true? If the US went vegan overnight, would it be a nutritional disaster? And what assumptions were the authors making that led them to this conclusion?

Would going vegan overnight lead to nutritional deficiency?

The most inflammatory finding is the authors’ contention that a “plant-only” system will produce excess dietary energy (which they argue is a bad thing), and that this “plant’s only system” will “result[] in a greater number of deficiencies in essential nutrients.” Where are the authors getting this from?

White and Hall make a number of deeply problematic  and wildly unrealistic assumptions regarding agriculture.

The nutritional data provided in the paper is on domestically grown food with zero nutritional supplementation. In scenarios that include imports, there is no attempt made to use those imports to fill nutritional gaps.

I personally choose to overlook the fact that the study’s authors claim no conflict of interest, but some may find it interesting that authors Robin R. White and Mary Beth Hall represent the Department of Animal and Poultry Science at Virginia Tech and the US Dairy Forage Research Center, US Department of Agriculture, respectively. However, I think that it will become clear on closer examination that the obfuscatory nature of the study and its conclusions cast some doubt as to whether or not the authors are cherry picking their data. 

More Food Calories Produced in a System without Animals

According to White and Hall’s calculations, an agricultural system without animals produced 23% more calories than required by the US population. Most of us would tend to think of this as a good thing: excess of anything beyond what a nation can use provides surplus to be sold overseas.

However, using the closed loop assumptions of the study, the authors worry that an abundance of calories will cause obesity:

Given the obesity rate in the United States (33), increased consumption of food energy is not desirable. Despite the production of a greater quantity of food in the plants-only system, the actual diets produced from the foods result in a greater number of deficient nutrients and an excess of energy.

Of course, this is patently ridiculous from an economic perspective.  If the US suddenly produced 23% more food than required, they would simply export cereal grains and legumes and import other nutritious foods to fill in the gaps.

At least the authors confess as much out later in the study:

The changes in…values among scenarios suggests that consideration of specific nutrient needs and international nutrient/food routing is essential to determine the balance of agriculture needed to feed the global population.

In other words, it would make a lot more sense to sell excess crops you don’t need, and buy the ones you do. In case this rather obvious finding seems critical to the report, the scientists didn’t think so. Instead, they based their entire thesis on a scenario where food imports are not guided by the type of “international nutrient/food routing” that seems so promising.

What about Nutrients?

The research also only considered food sources of nutrients, and supplements were not taken into account. So clearly, B12 was a problem.

Nevertheless, the study examined a very small subset of nutrients to determine the nutritional adequacy of each of these scenarios. The study looked at Calcium, Vitamin A, Vitamin D, Vitamin B12, Vitamin E, Vitamin K, Choline, EPA & DHA and Arachidonic acid.

daily diet composition, CO2e emissions, intake, cost, and nutrient adequacy robin white mary beth hall

Comparison of the daily diet composition, CO2e emissions, intake, cost, and nutrient adequacy of the current US diet compared with a series of optimized diets with and without (modeled) animal-derived foods.


Why do levels of calcium appear so low in the “no animal” scenario? Rather than attempting to convert grazing land and land used for feed production to other purposes (so that adequate amounts of fruit and vegetables could be grown), the authors chose a scenario where feed grains (mainly corn, wheat and soy) were simply fed to people, as opposed to livestock. In the scenario imagined by the authors of this study, almost all newly available land is likewise devoted to grain production.

Interestingly, when you look at the top figure, you’ll notice that current ACTUAL consumption of calcium is almost identical to the amount of calcium in the “no-animal” example. So, while the authors would like us to believe that calcium consumption is inadequate compared to the current scenario, there’s less than a ten percent difference.

Some Nutrients are Higher/Similar in Both Scenarios

I should start by pointing out that Vitamins E, K and Choline are all relatively similar in both the plant-based and animal agriculture scenarios (E and K are actually higher in the “animal-free” scenario).

B12 and D Numbers Are Not Surprising: Supplements Needed

Of course, the only way to supply sufficient B12 on a vegan diet is through supplementation, which is easily accomplished with fortified foods. However, since (somewhat unrealistically) the study supposed zero supplementation, B12 shows as zero in the animal free scenario.

Of course, if you live in a place that received sufficient sunshine, you probably get plenty of vitamin D all year. But if you’re like me and live at a higher latitude, or simply spend less time outdoors, vitamin D supplementation is a necessity. Plant-based vitamin D supplements are affordable and easy to find. But since they are not permitted by the structure of this study, it’s easy to say that a plant-based diet is “deficient.”

The Arachadonic Acid Deception

The Arachidonic acid component is one of the most confusing aspects of this study. Arachidonic acid is not an essential fatty acid. It is synthesized in the body as long as there is sufficient consumption of linoleic acid, which is prevalent in American diets since it is found in almost every vegetable oil, including Safflower, Canola, and Soybean oils. High levels are associated with disease and it makes zero sense why it is being listed as if it were a key concern in plant-based diets (it’s not). I delved into the supplementary appendix for the article and discovered they had done a search for arachadonic acid content of plant foods, and finding none, marked it as zero. This is either the result of profound ignorance of the metabolic pathways for producing this nutrient, or deliberate deception. The only mammals that lack the metabolic pathway for synthesizing arachadonic acid are obligate carnivores, such as cats.


The EPA and DHA numbers are likewise misleading. Without animal agriculture, White and Hall assume an EPA and DHA intake of precisely zero.

But while pure EPA and DHA are found in Fish, they can also be converted in the human body from ALA (which is how the fish get it in the first place – either from eating ALA and DHA-containing algae, or from eating other fish that eat algae). And while vegans often do not get enough of these fatty acids (due to insufficient intake of nuts, seeds, flaxseed, algae and other sources of ALA), it can definitely be done easily, and at a relatively low cost (three ounces of walnuts – high in ALA – will convert to as much DHA and EPA as a serving of fish). Even paleo diet guru and licensed acupuncturist Chris Kresser admits it’s possible to enough DHA and EPA on a vegan diet (though he recommends DHA supplements). And so does Dr. Andrew Weil.

So, while a diet heavily dominated by grain (such as the one designed by White and Hall) may contain inadequate levels of ALA (and thus EPA and DHA) the number could never be zero. This is yet another example of inaccurate dietary analysis in the study.


In short, a vegan diet can safely and easily be supplemented to make up for any deficiency in B12 or vitamin D. The authors’ assumptions about arachidonic acid betray either profound ignorance of nutritional science, or a desire to mislead. Vitamin A and Calcium could easily be increased in the diet by trading excess grain for foods with better nutritional profiles (or simply focusing on more strategic crop growth). With generosity, I will assume that the bizarre nature of the author’s assumptions are for simplicity’s sake, but the results are misleading and potentially dangerous if they dissuade people from pursuing a plant-based diet without any factual basis. In a world threatened by overpopulation and climate change, a diet that promises to produce 23% calories on the same amount of land, with no change aside from removing animals, cannot be ignored.

Please join me Saturday for part two of my discussion of this paper, where I’ll be examining the authors’ claims regarding greenhouse gas emissions.

What do you think? Join the conversation!

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