Some people are vegetarians because they were raised that way. Some are vegetarians because they just don't like meat. (Mrs. Fraggle falls into that category.) But these days, quite a few people have converted to vegetarianism because they just don't like the idea of killing other creatures just to eat them, when it is possible to put together a nutritionally satisfactory diet with no animal flesh.
Vegan diets are more difficult to put together because the protein from milk and eggs is the mainstay of many vegetarian diets; protein from plant sources is difficult to balance, especially without eating other parts of the plant that are not necessarily healthy in large doses. But I find the vegan philosophy difficult to relate to. Everyone on this planet has a job to do, and if the job of a cow is to give milk and the job of a chicken is to lay eggs, why is that any worse than the jobs we do, so long as they're treated well. (Which, admittedly, these days, they aren't. But let's solve that problem.)
COULD YOU QUOTE RELIABLE SOURCES WHETHER IN FAVOR OR AGAINST THE FOLLOWING CLAIMS?
Probably not, since this is not my field of expertise. But some of this stuff qualifies as "extraordinary claims" so by the Rule of Laplace it had better be supported by extraordinary evidence before the responsibility falls on us to disprove it.
1. The physiology of human stomach can't be clasified as omnivore, it secretes hydrochloric acid, while carnivorous animals secretes ammoniacal salts (alkaline).
Balderdash. Our first bipedal ancestors 7 million years ago were herbivores, but before long they learned to make tools out of flint and they began eating meat. First it was meat those blades could scrape off the bones left by predators, but then they learned how to use blades and spears to hunt. The enormous increase in the protein in their diet allowed their brains to quadruple in size, eventually leading to our species about 200,000 years ago. At that point humans were
obligate carnivores. We could not live without the concentrated protein in meat. Sure, grains and legumes have plenty of protein, but our digestive systems can't extract it from the tough protective tissue unless it's cooked, and the technology of controlled fire had just barely been invented.
Meat remained our primary sustenance until the Agricultural Revolution, a mere 12 thousand years ago. This is only a few hundred generation for a species like ours with such a long maturity cycle, and a few hundred generations is not long enough for a major mutation like adaptation to a new food source.
[Although about half the human population adapted to be able to digest milk about ten thousand years ago, an ability most mammals lose when they're weaned, as well as many people in regions were dairy farming was not introduced until recently.] We are still cavemen and we still need meat. With agriculture we learned to use cooked wheat, corn, rice and other grains, as well as soy and other kinds of beans. But we didn't understand that
that is not a complete diet despite the protein content. By the era of the Roman Empire, when the population was so large that most people didn't have access to meat and had to subsist on bread, the average lifespan of an adult who had survived childhood was about 23 years. Everyone except the aristocrats simply died of malnutrion: insufficient vitamins and minerals.
Today we know about vitamins and minerals so we can prepare a nutritious, balanced diet out of plant sources. Yet there are still plenty of people whose metabolism rejects that food. Look at all the people who are allergic to wheat, soybeans or peanuts--three of the most common sources of plant protein!
So if someone tells you that our stomachs are not well-adapted to a combination diet of meat (or milk and eggs) with vegetables, demand that he show you the science behind that claim. There isn't any!
2. Meat releases a toxic substance called putrescine.
A lot of things are toxic if you brew up a concentrated batch of it and drink it. Statements like that are usually telltales of dishonest arguing. Surely you've seen the commercials in which "Concentrated stomach acid burned a hole through this napkin!!!"
Beef takes up to 3 days to digest completely.
We have a relatively long digestive tract. Most things take a while to digest completely. The reason fiber is recommended in our diet is that it makes the food bulkier so it passes through more quickly. But our digestive tract is nothing compared to a cow or any of the
ruminants. Their food is passed back and forth between several different stomach chambers where symbiotic bacteria break it down and convert it into starch and protein, which are digestible by mammals. Even the other species of apes--gorillas, chimpanzees, orangutans and gibbons--are grazers and they too have much longer intestines than ours. Since we began eating meat our intestines became shorter, but they're still very long compared to, say, a dog. Dogs completely digest their food and pass out the waste in a few hours. This is because they eat meat, dairy products, and cooked food, which are easy to digest. Give a dog a raw carrot and it will come out as a raw carrot.
3. Can we trust 100% in the transparency of meat producers? antibiotics, hormones, and fattening agents applied to animals could cause us illnesses in the long term.
Well sure. But this is not an indictment of a carnivorous diet. It is an indictment of the meat industry. There is quite a grass-roots movement against these practices, so you younger people will probably live to see them discontinued. What I want to see discontinued is the "factory farming" that crams the poor creatures into a space too small to even turn around, much less exercise. Just because I like to eat meat doesn't mean I want the animals to suffer. California recently passed a voter initiative requiring larger quarters for livestock. The rest of the country always follows our examples eventually.
4. Some essential aminoacids exist only in animal sources.
This is dead wrong. However, no one kind of plant contains
all of the essential amino acids. Grains have one subset, and nuts and seeds have the other. You have to eat a balance of grains and nuts or seeds to get a complete diet. Legumes have an even smaller subset. It is not difficult to put together a vegan diet with all the essential amino acids. The problem is with the vitamins and minerals.
Meat contains exactly the right ratio of amino acids because
our bodies are meat and that's what we need.
5. In the Louis Kuhne's book The New Science of Healing (1899) he claims vegetarian physicians did an experiment of raising many healthier vegetarian generations.
Health is the result of many factors, not just diet. Presumably these physicians also did other things for the children that improved their health.
Remember: Correlation does not imply causation.
Which reasons would consider a pure rationalist for being a vegetarian?
What's a "pure" rationalist? A carnivore's diet is very resource-intensive and with today's population it would be difficult to produce enough meat for the now poverty-stricken people in Africa and other benighted regions to become carnivores like us Americans. However, grazing land for dairy cattle produces ten times as much food per acre as grazing land for beef cattle. So it wouldn't be hard to provide an ovo-lacto-vegetarian diet for the whole planet. That would be perfectly healthy. And even an avowed carnivore like me could be arm-wrestled into adopting it, whereas I'd deport anybody who tried to make me eat a vegan diet.
