Additional evidence of our herbivorous nature is also found in the length of our intestines. Carnivores have short intestinal tracts and colons that allow meat to pass through it relatively quickly, before it has a chance to rot and cause illness. Humans, on the other hand, have intestinal tracts that are much longer than carnivores. Like other herbivores, longer intestines allow the body more time to break down fiber and absorb the nutrients from a plant-based diet.
It is dangerous and holds many health risks to eat meat with a long intestinal tract. The bacteria in meat have extra time to multiply during the long trip through the digestive system, and meat actually begins to rot and putrify while it makes its way through the intestines. Many studies have also shown that meat can cause colon cancer in humans.
Analysing our anatomy clearly indicates the fact that the human body is built to run on a vegetarian diet. Humans have none of the obvious anatomical characteristics that either carnivores or even natural omnivores have.
As a comparison, here is a chart that shows the typical anatomical features of carnivores, omnivores, herbivores, and humans. Notice how close the human physical characteristics match those of herbivores.
Carnivores swallow their food whole, relying on their high acidic stomach juices to do most of the digestive work. The stomach acid of carnivores not only breaks down the flesh, it also kills the dangerous bacteria that would otherwise sicken or kill the meat-eater.
The chart below shows how weak our stomach acid is in comparison to carnivores. Strong acids are not needed to digest pre-chewed fruits and vegetables. Compare the stomach acidity of carnivores and herbivores, it is quite clear that humans fall into the herbivore category. Although we can cook meat to kill some of the bacteria and make it easier to chew, it's clear that humans, unlike all natural carnivores, are not designed to easily digest meat.
Herbivores rely on their vitamin C sources purley from their diets alone, whereas carnivores make it internally. Humans do not make their own vitamin C and rely solely on diet, just as the herbivore does.
Natural carnivores eat meat raw; humans cook meat to disguise the taste of raw flesh. Why would we have to do this if we were naturally meant to eat meat?
When carnivores chew, their jaws move up and down only. This enables them to tear chunks of flesh from their prey and swallow it whole. Humans and other herbivores can move their jaws up and down AND from side to side, this movement allows the herbivore to grind up fruit and vegetables with their back teeth. Humans have flat back molars just as other herbivores do, which allows for the grinding of fibrous plant foods. Carnivores do not have these flat molars. If humans had been meant to eat meat, they would have the sharp teeth and claws of carnivores. Instead, their jaw structure, flat molars, and lack of claws indicate that they are best suited for a plant-based diet.
Herbivores produce a certain amount of digestive enzymes capable of breaking down a plant based diet. However, due to the fact that most humans consume meat in their diet, additional enzymes are required for digestion. Enzymes not only play a part in digestion, but are also involved in our immune system. This also indicates a reason for the increase in cancer as our meat eating increases. (see enzymes).
Human, Carnivore, Omnivore and Herbivore Comparison Chart
Carnivore -----------Shearing; minimal side-to-side motion
Omnivore -----------Shearing; minimal side-to-side motion
Herbivore -----------No shear; side-to-side, front-to-back
Human --------------No shear; side-to-side, front-to-back
Carnivore -----------Short and pointed
Omnivore -----------Short and pointed
Herbivore -----------Broad, flattened, and square-shaped
Human --------------Broad, flattened, and square-shaped
Carnivore -----------None; swallows food whole
Omnivore -----------Swallows food whole and/or simple crushing
Herbivore -----------Excessive chewing necessary
Human --------------Excessive chewing necessary
Carnivore ----------Around, or less than pH of 1 with food in stomach
Omnivore -----------Around, or less than pH of 1 with food in stomach
Herbivore -----------pH of 4 to 5 with food in stomach
Human --------------pH of 4 to 5 with food in stomach
Length of Small Intestine
Carnivore ------------3 to 6 times body length
Omnivore ------------4 to 6 times body length
Herbivore ------------10 to more than 12 times body length
Human ---------------10 to 11 times body length
Carnivore ------------Sharp claws
Omnivore ------------Sharp claws
Herbivore ------------Flattened nails or blunt hooves
Human ---------------Flattened nails
Maintaining a vegetarian diet greatly reduces your risk of cancer by ensure intestinal health and helping to boost the immune system in prevention and helping to overcoming cancer. Meat eating can also contribute to an increased population of internal parasites (see Human parasites).