Vegan advocates are excited to promote a vegan diet that:
- appears to be considerably healthier than the standard American diet
- doesn’t require us to exploit animals
- puts less of a burden on our environment
However are some going a little to far in their enthusiasm to spread the message to a larger audience?
Herbivore or Carnivore
Some vegan advocates have suggested that we are natural herbivores whilst meat eaters have argued that we are natural carnivores. These are false dichotomies – the truth is more complex.
Here are some arguments from the herbivores:
- Our intestines are designed for digesting plants not meat
- Meat eating is a recent development in human evolution that we haven’t adapted to
- Herbivores and plant eating primates like gorillas do fine just eating plants
And here are some counter arguments from the carnivores:
- Humans were made to eat animals
- Primitive man ate a diet primarily of meat
- Humans cannot survive without nutrients only found in meat
Let’s take a look at the facts behind these arguments.
Herbivores have long digestive systems optimized for breaking down cellulose whereas carnivores have short highly acidic digestives systems optimized for the quick processing and elimination of meat.
Our digestive system is indeed longer and considerably less acidic than those of carnivores, but it is also different than those of herbivores. Our digestive systems are shorter than those of herbivores, we do not ruminate like cows, we don’t regurgitate like rabbits and gorillas and we don’t have an extra large cecums like horses.
We have the intestines of an omnivore, a highly flexible digestive system that can deal with both plants and meat. However nothing in nature is black and white and in our case we don’t have the herbivores ability to break down foods with a high cellulose content and we don’t have the high acidity which allows carnivores to safely consume raw meat and carrion.
So we are biased towards more easily digestible plants, but we can consume higher cellulose foods and meat through cooking.
Archeological evidence shows that our ancestors have generally consumed some amount of animal products throughout our entire evolution. For most of that time meat consumption was probably very similar to our closest cousins the chimps at about 5% of calories.
About 35 thousand years ago Cro-Magnons managed to thrive in the cold climate of Europe through big game hunting. During this period and the coldest years of the Ice Age, meat consumption may have risen to as much as 50% of calories.
With the advent of agriculture in the Neolithic age meat consumption dropped back down to around 10% of calories.
And with the standard American diet we now consume about 69% of calories from animal sources.
The ability to eat plants when they were plentiful and eat meat during hard times has been a highly beneficial adaptation.
Herbivores, Primates and B12
Herbivores have specific adaptations which allow them to digest foods with a high cellulose content. They also have B12 rich bacteria in their gut which is absorbed through rumination and regurgitation. So whilst they clearly demonstrate that strong healthy animals can thrive on a 100% plant diet, they are not an ideal human comparison.
If we look at our closest cousins, the primates, we see that they have a number of mechanisms which allow them to get B12. Most monkeys including chimps eat meat. Those that do not eat meat have herbivore like digestive systems and also tend to consume B12 rich insects and bacteria along with the plants that they eat.
Gorilla’s, possibly the closest to vegan of the primates, regurgitate their food, eat insects and sometimes eat their own feces. Interestingly there have been some reports of wild animals kept in captivity and fed sterilized diets developing B12 deficiencies.
As for humans we are very efficient at utilizing and recycling B12 and we may even have as much as a 30 year reserve of B12. In the past bacterial contamination of our food with B12 rich strains of bacteria may have been sufficient to meet our B12 dietary needs even without animal sources.
The highly sterilized food sources of today may not provide us with a reliable source of B12. This last point is still somewhat controversial as most B12 deficiencies tend to present with confounding factors such as other dietary deficiencies or absorption problems. However most vegan coaches recommend some form of B12 supplementation just in case.
Shades of Grey
A lot of the arguments out there for or against a vegan diet tend to be black and white. As always the truth as always is more complex and what we need to focus on is the affect that modern food has on modern humans.
There is mounting evidence that the standard American diet with its high animal product and processed food content and low whole plant food content is harmful over the long run.
I choose a vegan diet, because it has been personally beneficial for me, it falls within the range of diets that are likely to be optimally healthy based on the current evidence available and because I find it easier and more enjoyable to eat a healthy vegan diet.
Are there other arguments for or against veganism that you have heard?