Our Diet is Already Plant-Based

Humanity's existential crisis is insufficient animal source food

This is the final post developed from my presentation “Human Flourishing: Integrated Livestock Cropping Systems’ Goal” which I delivered as part of the IV International Symposium on Integrated Cropping-livestock Systems, November 7, 2023 in Bento Gonçalves, Brazil. Links to installments one, two, three, four and five.

Animal source foods are irreplaceable sources of many essential nutrients in addition to indispensable amino acids, but today’s public dietary advice and food system conversations typically oversimplify the topic of protein in human nutrition. This oversimplification leads to misunderstandings. Please watch my recent Low Carb Down Under Sydney presentation "Ruminating on Protein“

for my discussion on how these misunderstandings have resulted in poor public health, flawed dietary advice, misguided food policies, and mistaken environmental assessments.

Humanity’s diet is already plant-based.

(FAO, 2020)¹

Time won’t permit me to go into great detail here, so I’ll briefly look at energy and protein in humanity’s food supply.

We hear that we should adopt a “plant-based” diet for health and environmental reasons. It’s clear that for some this means a plant-only or vegan diet. The reality is that humanity’s food supply is already plant-based.

Recent FAOstat data shows that the majority of fat, calories, and protein already come from plant source foods. A perspective informed by metabolic health would at least entertain the notion that this could be a significant causal factor in the global pandemic of metabolic illnesses..

(FAO, 2020)

Let’s just focus on the energy supply, expressed as kilocalories per person per day. Of course there are variations between global regions. And if we examined the countries within a given region, there would be great differences. And, of course, there would be significant variations within any given country. But notice that none of these regions cross the 30% of calories from animal source food line. Keep that figure in mind.

Here’s an interesting point. When I made these bars, what color did I use for plant-source protein or energy? Green, of course! And red, of course, for animal-source protein or energy. But would those colors accurately represent the food groups in humanity’s food supply?

(FAO, 2020)

These data show that the leading source of energy in humanity’s food supply is wheat and products. The second leading energy source is rice and products. The third is sugar. The fourth is maize and products.

None of these are a green color.

All of them are poor sources of nutrition.

Milk is the first animal source of energy in humanity’s food supply. It’s not red.

This is just one example of how the way we think of things can influence conversations about our food systems. Perhaps this is another way for us to build bridges with audiences that are not in agriculture.

(FAO, 2020)

Given the importance of wheat as a source of energy, it shouldn’t come as a surprise that it is also the largest source of protein in humanity's food supply. Just over three-tenths of humanity's protein supply is provided by wheat and rice and their derivatives. We must remember, however, that this is a low-quality protein, deficient in usable lysine. Approximately 40% of humanity's global protein supply already comes from plant-based (source) foods.

A critical point: In these figures "protein" is presented on an equvilant mass basis, as if proteins of plant and animal origins have the same nutritional value. Of course they don't.

When cereals and other plant source foods are processed, lysine becomes less available. This is particularly important given the prevalence of ultra-processed foods in many diets.

The protein quality of meat products, which is already high, can be increased by processing. For example, when we cure pork belly to make bacon, or when we turn meat trimmings into salami and other processed meats, or when we dry meat to produce jerky. These are essential components of food systems and environmental considerations that are often overlooked.

(Moughan, 2021)²

In 2021 Prof. Moughan published work looking at the protein supplies of the poorest countries and territories. These stacked bars each represent a location with the plant-source protein on the bottom and the animal-source protein on the top. The black line represents the estimated average daily protein requirement.

When looking at these data, some have said that it’s only those few very poorest locations that don’t have sufficient protein. But there are two significant errors with this interpretation.

(Moughan, 2021)

First, it fails to account for the differences in the quality of the dietary protein.  Protein utilization is determined by the amino acid that's present in the least amount relative to its requirement. Remember Liebig's barrel, discussed earlier? Lysine is the amino acid that’s globally limiting. When this is accounted for, none of the food supplies of these regions are sufficient. Metrics matter, as Moughan states in the title.

The second error is that the average daily “requirement” is based upon the Recommended Daily Allowance (RDA) of 0.8g/kg bodyweight. This is typically treated as a target when it’s a minimum. Research findings suggest that intakes of 1.2 to 1.6 would be better targets, depending upon the stage of life.³ These issues have not been accounted for in projections of future protein demand.

They also impact estimations of environmental impacts. Moughan demonstrated that when the calculations shift from yield of crude protein to yield of utilizable lysine it dramatically shifts comparisons of plant- and animal-source protein in terms of greenhouse gas emissions, water and land use.

(DGAC, 2015)⁴

This is not just a problem of the low-income countries. This is NHANES data from the United States, published in 2015. While there are limitations to these data, it's the best available. In this graph, the center is zero. Bars extending to the right indicate dietary intakes above the RDA, while bars extending to the left indicate intakes below.

These data indicated that 40% of Americans weren't getting enough protein, while most females over the age of eight weren't getting enough. Please note that this is counting all protein sources as if they're equivalent and is also using the 0.8 grams per kilogram RDA.

Remarkably enough, many look at this data and they say that protein is not a nutrient of concern or that we are eating too much. These positions cannot be called evidence-based!

Animal source foods - the foundation of a balanced diet

(Cordain et al., 2000; Nordhagen et al., 2020; Vieux et al., 2022)

Instead of describing animal source foods as merely part of a balanced diet let's call them the foundation of a balanced diet! Prioritize your protein at every meal (and don't fear the animal fats that naturally accompany animal source proteins).

Remember when I pointed out that none of the global regions crossed the 30% of calories from animal source food line? Work published in 2000 by Cordain and colleagues⁵ looked at the diets of populations of hunter-gatherers that could still be accessed at the time of their work. They found a range of calories from animal source food in those diets ranged from 30 to 100% of calories coming from animal source foods. The mean was approximately 70% of calories. In 2020 Nordhagen and colleagues⁶ published evidence of rapidly-increasing, multiple micro nutrient deficiencies in populations when less than 30% of calories are supplied by animal-source food in that population’s food supply. In 2022 Vieux and colleagues⁷ published evidence suggesting that when less than half of dietary protein is coming from animal-source foods other nutrient deficiencies are increasingly likely.

Animal-source foods don't merely provide essential amino acids. They provide all the essential nutrients not provided by plant-source foods. Even those nutrients provided by plant-source foods are better utilized when provided via animal-source foods. One fifth of humanity is iron deficient.⁸ Quoting Adele Hite - 

“Iron is under-consumed by adolescent and premenopausal females, including women who are pregnant. Meat foods in the protein group provide heme iron, which is more bioavailable than non-heme plant-derived iron. Heme iron is especially important for young children and women who are pregnant.”

Animal-source foods do not contain the anti-nutrient compounds that interfere with absorption. For example, the more plant material in the diet, the lower the digestibility of the diet’s protein (Moughan, 2021).

In closing, let me repeat. Humankind faces many problems as we look toward the mid-century world. Climate change is one of them, but it is not our only problem. The word "existential" is overused in public and policy discussions. But when one understands that the current global pandemic of chronic diseases is primarily a manifestation of malnutrition, it seems an appropriate word to use.

Humanity requires a diet of higher nutritional quality than is currently being provided to it. There are many factors that contribute to this reality, and they differ across the high-, middle-, and low-income countries. Nevertheless, the preponderance of the highest-quality scientific evidence available from the broadest range of scientific disciplines strongly suggests that the greatest harm related to animal source food consumption is from not having enough.

Integrated Cropping-Livestock Systems will be an essential component in the effort to improve the productivity and efficiency of global ruminant animal agriculture systems. This improvement will be essential in the effort to provide humanity with the higher-quality diet required. Your research and demonstration efforts are, therefore, essential to the goal of increasing human flourishing throughout the world.

I am so encouraged that the human component was added to the Integrated Cropping-Livestock Systems Symposium. Thank you for this opportunity to be a part of this vital event. I welcome opportunities to exchange ideas and collaborate with members of this community. Please don’t hesitate to contact me.

Thank you for your interest and attention. I’m grateful for the oportunity to participate in this event. My sincere thanks to the organizing committee and all my colleagues present!

1. FAO, 2020. FAOSTAT statistical database. Food and Agriculture Organization of the United Nations.

2. Moughan, P.J., 2021. Population protein intakes and food sustainability indices: The metrics matter. Global Food Security. 29, 100548. https://doi.org/10.1016/j.gfs.2021.100548.

3. Elango, R., 2023. Protein Requirements in Humans: A Need for Reassessment. The Journal of Nutrition. 153(12), 3355-3356. https://doi.org/10.1016/j.tjnut.2023.10.018.

Phillips, S.M., Chevalier, S., Leidy, H.J., 2016. Protein “requirements” beyond the RDA: implications for optimizing health. Appl. Physiol. Nutr. Metab. 41(5), 565-572. https://doi.org/10.1139/apnm-2015-0550.

4. DGAC, 2015. Scientific Report of the 2015 Dietary Guidelines Advisory Committee. . Washington, DC.

5. Cordain, L., Miller, J.B., Eaton, S.B., Mann, N., Holt, S.H.A., Speth, J.D., 2000. Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter-gatherer diets. The American Journal of Clinical Nutrition. 71(3), 682-692. https://doi.org/10.1093/ajcn/71.3.682.

6. Nordhagen, S., Beal, T., Haddad, L., 2020. GAIN Discussion Paper Series 5 - The role of animal-source foods in healthy, sustainable, and equitable food systems. https://doi.org/10.36072/dp.5

7. Vieux, F., Rémond, D., Peyraud, J.-L., Darmon, N., 2022. Approximately Half of Total Protein Intake by Adults Must be Animal-Based to Meet Nonprotein, Nutrient-Based Recommendations, With Variations Due to Age and Sex. The Journal of Nutrition. 152(11), 2514-2525. https://doi.org/10.1093/jn/nxac150.

8. Hirosawa, T., Hayashi, A., Harada, Y., Shimizu, T., 2022. The Clinical and Biological Manifestations in Women with Iron Deficiency Without Anemia Compared to Iron Deficiency Anemia in a General Internal Medicine Setting: A Retrospective Cohort Study. International Journal of General Medicine. Volume 15, 6765-6773. https://doi.org/10.2147/ijgm.s376405.