There are many ways to slice and dice diets which humans can eat. After all, our species is omnivorous. In stark contrast to really specialized animals like cows, spiders and koalas, humans can seemingly survive on almost anything. But is there an optimal nutritional strategy?
TL;DR: Humans can eat exclusively plants, a mix of plants and animals, or even exclusively animals.
Plants versus animals is one very basic way of categorizing our food. Most people have never thought deeply about this. Most of us know about veganism, which means eating only plants. But is that a healthy long term strategy? What about the opposite, eating only animals (carnivorous) ? Much fewer people have ever considered that as a permanent way of eating. Is that possible, let alone healthy? Or is a combination of plants and animals the best choice? If so, how much of what?
Vegan (100% Plant-Based)
There are, to my knowledge, no human societies who have survived, let alone thrived on a purely plant-based diet for generations. There seem to be many people, even athletes, who thrive on a plant-based diet in our modern times. But it seems like this takes a lot of effort to get right, in particular there are some essential nutrients that need to be supplemented, for example vitamin B12 and DHA (a long chain n-3 fatty acid).
Carnivorous (100% Meat-Based)
There are some societies who are reported to have survived on a nearly 100% animal based diet for generations, like the Maasai (spelling varies) in Africa and the Inuit in the Arctic. But their health is a disputed issue. Advocates for plant-based diets claim that they were in bad health, with poor bone structure and atherosclerosis. Meat proponents claim the opposite. In modern times, there are many case reports of people thriving on a 100% meat based diet. No supplements seem to be necessary, but there is no clear consensus. There are nutrients which are in very low supply on this diet – vitamin C being the example that is most often used. But research suggests that the body demands less of the vitamin when only meat is consumed, and fresh meat does in fact contain small amounts of vitamin C.
The “Balanced” Diet (Plants and Meat)
This is of course what the overwhelming majority on the planet eats. It is also not a very meaningful distinction. Even more so than for the other two approaches, it depends on which plants and which animals we eat, and in which quantities, and how we eat them – do we apply less processing, more processing, cooking/raw, meal timing and so on.
The takeaway message here is that especially in the modern world, all three approaches can be implemented. I think this is important to remember, as most people are at most aware of two of them.