There is a scientific consensus that our high consumption of animal products, especially meat, is bad for our health and the environment. The studies are abundant (see here and here). Almost no-one is denying that our consumption of animal products is too high and that we should reduce our meat consumption. Too much is never good. But the question people often ask is: where is the optimum level? Is the best diet for our health and the environment a vegan diet? Or is a diet with some animal products better?
It is obviously true that animal products contain essential food nutrients for human health, such as proteins, minerals and vitamins. It is also obviously true that the animal manure produced in livestock farming contains essential fertilizer nutrients for agriculture, such as nitrogen and phosphorus. And it is obviously true that animals can eat things that we do not want to eat or cannot digest, such as our food residues or grass, and turn these things in nutrients that we can use. Animal agriculture can be considered as an upcycling of our food waste. Does this mean that some level of livestock production and animal consumption is necessary for an optimal human and environmental health?
At the current level of animal consumption, we eat more than enough essential nutrients, so the harmful substances such as saturated fats, pathogens and carcinogens become dominant. And at our current level of animal agriculture, animals not only eat our food waste and grass, but they also eat lots of feed crops produced on cropland that can be used to grow things humans can directly eat. Most of this feed crop is turned into inedible animal manure. This is a kind of food waste, a downcycling of nutrients. Furthermore, at our current level, animal agriculture produces more than enough manure, resulting in overfertilization. Hence, the more animal products we consume, the higher our negative environmental and health impacts.
The negative health and environmental impacts are functions of the amount of animal products consumed. Simplifying matters, we can draw a J-shaped curve to represent this negative health or environmental impact. Our current situation is on the far right of the curve, where the harm or negative impact is high and there is a sharp increase in negative impact if we move further to the right. The vegan situation is on the far left. The question is: where is the minimum of this J-curve? What level of animal consumption minimizes the negative health or environmental impact? This minimum level is the one that optimizes our health or minimizes our environmental footprint.
In the past, the optimal level of animal consumption was probably higher than zero. Farmers needed animal manure because synthetic fertilizers were absent. Consumers needed meat because other, plant-based or vegan sources of essential nutrients were lacking. And grassland and food residues could not be used for anything, except for animal agriculture.
But at this moment the situation is less clear. There is an abundance of vegan sources of essential nutrients, wrapped in healthy fibers and phytonutrients instead of unhealthy saturated fats and carcinogens. We have other options to utilize our food residues: they can be used as bio-energy, turned into fertilizer or be upcycled using new food technologies. New farming techniques such as synthetic fertilizers and green manure allow farmers to have highly productive croplands without the need for animal manure. And the near future is even more promising. New agricultural technologies allow us to keep soils fertile in a more sustainable way than with animal manure. New food technologies allow us to process inedible resources such as grass or crop residues into new delicious healthy animal-free foods. Food technologists are developing clean meat, milk and eggs without animals, and they may be able to make those products healthier than their animal counterparts by increasing the healthy and decreasing the unhealthy substances.
Technological developments result in a downward shift of our J-shaped curve, because these technologies reduce negative impacts. But also the minimum of the J-shape is shifting to the left. The J-shape becomes more like a forward slash shape (/). Eventually, the minimum level will be at zero consumption of animal products.
The logic behind this is straightforward: animal farming doesn’t allow much room for maneuver for technological improvements. It is very difficult to breed animals that grow muscle tissue that only contains healthy substances and avoids e.g. the saturated fats. It is very difficult to breed animals that produce different kinds of animal manure with different nutrient compositions, optimized for all types of agricultural crops. It is very difficult to breed animals that can eat all kinds of inedible food residues. It is very difficult to breed animals that can more efficiently turn crops into tasty food products without energy waste (crop calories turned into heat by an animal’s metabolism) and nutrient waste (crop nutrients turned into manure by an animal’s digestive system). On the other hand, new food and agricultural technologies have much more room for improvements without the need for animals in the system.
At a more general, abstract description, this is an example of a regression to the mean or regression to zero. If food and agricultural technologies develop, the minimum level can shift to the left or the right, but which of those two is more likely? When a new technology is developed, it can sometimes enhance an existing technology. For example, new crop breeding technologies allowed for the development of new herbicide tolerant crops, which promoted the use of some herbicides, an existing technology. However, new technologies can also replace existing technologies. For example, genetic manipulation allowed for the development of mold and insect resistant crops, decreasing the use of fungicides and insecticides. In most cases, new technologies replace existing technologies. The existing technologies lose their relative benefits. Of all the technologies ever invented, most became obsolete. Hence, the average benefit of a technology is zero. The same goes for technologies that have animals in the system. Cars made horse carts obsolete. Tractors made draft horses obsolete. Synthetic insulin made animal-sourced insulin obsolete. Kerosene made whale oil obsolete. The same goes for food: there are way more food production technologies possible that do not have animals in their systems, so it is more likely that one of those animal-free technologies is better for our health and the environment, making the animal-dependent technology obsolete.
Conclusion: if a vegan diet is not already the most healthy and environmentally friendly diet, it soon will be.