There has been much controversy recently over the diet most natural to people. We will first consider the arguments of those who feel that human beings are not naturally suited for a diet that includes flesh and other animal products.
The French naturalist Baron Cuvier stated: "Fruits, roots, and the succulent parts of vegetables appear to be the natural food of man."  Geoffrey Hodson quoted the great Swedish naturalist Linnaeus as follows: "Man's structure, external and internal, compared with the of other animals, shows that fruit and succulent vegetables constitute his natural food."  The following comparisons support these statements: 
1. Our small and large intestines, like those of other primates, are four times longer than those of carnivores. Because of the long intestines, meat passes very slowly through the human digestive system; it takes about 4 days during which the disease-causing products of decaying meat are in constant contact with the digestive organs (vegetarian food takes only about 1 1/2 days). 
2. Our hands are similar to those of apes; they are meant for picking food such as vegetables, fruits, leaves, flowers, seeds, etc., and not for tearing flesh.
3. Our lower jaw, or mandible, can move both up and down and side to side, like the primates'; carnivores' jaws move only up and down.
4. Our saliva is alkaline like that of the higher species of apes; it contains ptyalin to digest carbohydrates. Carnivores' saliva is acidic.
5. Unlike carnivores, we do not have fangs for biting into flesh. Our so-called canine teeth are not truly canine like the dog's. We are not constituted to prey upon animals, rip apart their bodies, or bite into their flesh.
6. Although our gastric secretions are acidic like that of carnivores, their stomachs have four times as much acid; this strong acidic region is necessary to digest their high-protein flesh diet.
7. Carnivores have proportionally larger kidneys and livers than we have; they need these larger organs in order to handle the excessive nitrogenous waste of a flesh diet.
8. The carnivores' livers secrete a far greater amount of bile into the gut to deal with their high-fat meat diet.
Table I (below) indicates that people are closest in structure to animals that primarily eat fruits.
Structural Comparison of Humans to Animals
Meat eater Leaf-grass eater Fruit eater Human being Has claws No claws No claws No claws No pores on skin; perspires through tongue to cool body Perspires through milions of pores on skin Perspires through milions of pores on skin Perspires through milions of pores on skin Sharp, pointed front teeth to tear flesh No sharp, pointed front teeth No sharp, pointed front teeth No sharp, pointed front teeth Small salivary glands in the mouth (not needed to pre- digest grains and fruits Well-developed salivary glands needed to pre-digest grains amd fruits Well-developed salivary glands needed to pre-digest grains amd fruits Well-developed salivary glands needed to pre-digest grains amd fruits Acid saliva Alkaline saliva Alkaline saliva Alkaline saliva No flat, back molar teeth to grind food Flat, back molar teeth to grind food Flat, back molar teeth to grind food Flat, back molar teeth to grind food Much strong hydrochloric acid in stomach to digest tough animal muscle, bone, etc. Stomach acid 20 times weaker than meat eaters Stomach acid 20 times weaker than meat eaters Stomach acid 20 times weaker than meat eaters Intestinal tract only 3 times body length Intestinal tract 10 times body length Intestinal tract 10 times body length Intestinal tract 10 times body length
SOURCE: Barbara Parham, What's Wrong with Eating Meat?
Denver Colorado.,Ananda Marga Publications, 1979, pp. 10-11.
Reproduced with permission.
That our natural instinct is not toward flesh food is stated by R. H. Wheldon:
The gorge of a cat, for instance, will rise at the smell of a mouse or a piece of raw flesh, but not at the aroma of fruit. If a man can take delight in pouncing upon a bird, tear its still living body apart with his teeth, sucking the warm blood, one might infer that Nature had provided him with carnivorous instinct, but the very thought of doing such a thing makes him shudder. On the other hand, a bunch of luscious grapes makes his mouth water, and even in the absence of hunger, he will eat fruit to gratify taste.[5)]
Some scientists disagree with the above analysis.
They assert that people's natural diet is omnivorous, based on both flesh and vegetarian foods. They point to the many years that our ancestors have eaten meat and the fact that primates, the animals whose systems are closest to ours, have been observed to eat meat.
1. Certainly people have eaten meat for at least thousands of years. According to the Bible, after first giving people a vegetarian diet (Genesis 1:29), as a concession to human weakness, God gave people permission to eat meat in the time of Noah (Genesis 9:3). Just as an automobile will travel on a fuel which is not most suitable to it, people can live on a diet that is not ideal. The issue is not what people eat now and have eaten in the past, but the diet that is healthiest for people and is most consistent with our anatomy, physiology, and instincts. It should also be noted that a significant portion of people throughout history either ate no meat at all or ate it only on rare occasions. In addition, meat contains no essential nutrients that cannot be obtained from plant sources.
(2) With regard to primates eating meat, this issue has been hotly debated. Some species have never been observed to do so. Jane Goodall's studies of apes showed that meat eating incidents were extremely rare, and they were unusual and atypical of the species in general, occurring in un-chimplike surroundings. The staple diet of primates is vegetarian.
(A detailed analysis of this entire issue can be found in chapter 3, "The Aberrant Ape", in Food for a Future by Jon Wynne-Tyson (Thorsons, 1988).)
Even if people are naturally omnivorous, this means that we have a choice in our diet in terms of whether or not to eat meat. And it still leaves all the ethical arguments - compassion for animals, helping the hungry, protecting the environment - on the side of vegetarianism. Also, if we define our "natural" diet as that which is best for our health, there is abundant evidence that points to vegetarianism as our natural diet.
After a comprehensive analysis of this issue, a similar conclusion was reached by Sharon Bloyd-Pleshkin in her article, "In Search of Our Basic Diet". . On the question of whether or not people are omnivores, she quotes Dr. Neal Barnard, president of the Physicians Committee for Responsible Medicine: "That depends on what you mean by `omnivore`; Does it mean what you tend to eat? Or what diet you do best on?" So, as Ms. Bloyd-Pleshkin concludes, while human beings are capable of ingesting a wide range of foods, including meat, and while they have been eating meat for the past 2 million years, "modern research shows that we do best on a diet with little or no animal protein and fat." 
1. "Facts of Vegetarianism", North American Vegetarian Society pamphlet, (Box 72, Dolgeville, N. Y. 13329), p. 5.
3. M. M. Bhamgara, "Yoga and Diet", The Vegetarian Way, Proceedings of the 24th World Vegetarian Congress, Madras, India (1977), p. 137.
4. Barbara Parham, What`s Wrong With Eating Meat? (Denver, Colorado: Ananda Marga Publications, 1979), p. 23.
5. Dr. R. H. Wheldon, No Animal Food (New York: Heath Publishing Co.), p. 50, quoted by Nathaniel Altman, Eating for Life (Wheaton, Illinois: Theosophical Publishing House, 1977), p. 17.
6. Sharon Bloyd-Pleshkin, "In Search of Our basic Diet", Vegetarian Times, Issue 166, (June, 1991), pp. 46-55.
7. Ibid, p. 55.
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