This article and the next two endeavor to establish all the particulars of human dietetic character.
The information is originally written by T,C.Fry in The Life Science Health System and Dr. Douglas N. Graham in his book “The 80/10/10 Diet” .

Human Anatomy, Physiology and Psychology Evidence Our Dietary Nature

How does one determine the correct food for any given creature? Let us suppose that you were given a baby animal and you had no idea what it was or what it was supposed to eat. Perhaps it was a gift from a foreign land. How would you know what to fee it?
The answer is relatively simple. All you would have to do is offer the creature different types of foods in their whole, natural state. That which it was designed for, it would eat. It would likely ignore all the other items, not even considering them as food.
The same technique would work with a human child. Put the child in a room with a lamb and a banana. Sit back and watch to see which he plays with and which he eats. We can be fairly sure of the outcome. Try again with fats versus fruits by offering a choice of (natural, raw, unsalted) nuts, seeds, avocados, or olives on the one hand and any fresh sweet fruit on the other. Again, we can safely predict that the child will choose the sweet fruit.
What would you eat in nature? Despite the gross perversion of our instincts, they are still alive and well and will reassert should we be relegated back to nature. Therefore, this quest is to ascertain what we would eat in nature. Our instinctive foods, the foods which helped to develop us to our magnificence, necessarily contain all that we need to thrive on.
Our premises to determine our dietary nature are: that Mother nature, i.e., the sum of all factors and influences under which we lived in nature, served us correctly to start with, inasmuch as we thrived an attained our high station in its midst; that what was right for us then is still right for us in view that we’re still structurally and physiologically the same as we were during most of our sojourn as humans in nature; that we can still, within our modern context, supply ourselves with naturel foods substantially and significantly; and that we can also observe, meaningfully, the other requisites of life in our modern context.

Are We Carnivorous?

Today’s “nutritionists” are subservient to the “basic four” food concepts. While this concept may look good on paper, it is a disaster in practice, because most of America’s health problems stem largely from its observance. According to these nutritionists, we do not have any fixed dietary as have most animals in nature. Rather, humans are considered to be some sort of omnivorous creature above all the laws of nature. Many assert we have definite carnivorous leanings. Quite a few nutrition experts have termed our incisor teeth “fangs,” in defense of the erroneous position that humans are meat eaters.
Humans are well-equipped in all their anatomical features to gather fruits, but most unsuited to capture animals and rend them. Fangs and pointed teeth that penetrate and kill, rip and tear are a feature of all carnivores except birds.
Let’s put this matter of human carnivorism on a personal level. Can you picture yourself quietly stalking a rabbit and pouncing upon it? If it should slip away, can you picture yourself exploding with a blinding burst of speed that may be 30 to 50 miles per hour for the short distance needed to overtake your prey? Can you picture yourself catching the rabbit in your mouth, and then sinking your fangs deeply into its vitals, crushing and killing it? Can you picture yourself ripping the animal to shreds and swallowing it in bloody bits and chunks without thorough mastication? Can you savor the animal’s blood, guts, bones and organs? If you cannot carry out this practice with gusto and delight, you are not of a meat-eating disposition.
For instance, picture a three year old child in a playpen. Into the pen we place a rabbit and an apple. Will the child be hostile to the rabbit, kill and eat it and play with the apple? Or will the child eat the apple, and befriend and play with the rabbit?
You must admit that we are not anatomically equipped as carnivores. You must also admit that the idea of attacking, killing and rending animals on the spot does not appeal to humans psychologically—we are not natural killers. What most of us do not realize is that we are not only psychologically but also physiologically unsuited to utilizing meat as a food.
When a natural carnivore swallows hunks of carrion unchewed, the flesh is digested in the stomach of the carnivore with ease and facility. Should we swallow large hunks of flesh without chewing, we’d digest very little of it before putrefaction set in. This putrefactive material would cause us many problems until it could be expelled from the intestinal tract. Why does a carnivore so readily digest something we can handle almost not at all?
Flesh is a proteinaceous food that is digested in an acid medium. Humans, relative to carnivores, secrete a very weak hydrochloric acid and little of the protein-splitting enzyme, pepsin. Carnivorous animals have a concentration of these flesh-digesting media 1100% greater than humans! Should a lion swallow your hand whole he would quite readily digest it. Should a human do the same thing, I leave to your imagination what would happen. Digestion is among the things that wouldn’t happen!
There are hundreds of anatomical features that we humans have which place us among frugivorous animals. We are anatomically fruit eaters. Not everyone will admit our lack of claws and fangs and possession of gentle sensitive hands suits us for fruit gathering rather than animal catching. They fail to see that our likeness to fruit-eating creatures places us in the fruit-eating camp. Most people fancy that we’re in no animal camp at all—we’re humans, gods of a special sort not heir to the principle that apply to animals. They consider us to be not animals at all—just humans!
Let’s return to our consideration of humans as meat-eaters. Natural meat eaters have built-in equipment with which to apprehend, capture, kill and rend their quarry. Claws and fangs are very much a part of a carnivore’s equipment. Let’s consider the human mouth. We couldn’t catch an animal in our mouth or dispatch it that way if we tried. Two witnessed dogs catch other animals many times by charging them and snapping their powerful jaws on them at a vital spot. I’ve seen these dogs sink their fangs deep into the throat of animals must larger than themselves and inflict fatal wounds. A human could not grab an animal in its mouth as does a dog, coyote, wolf or cat. Even biting a live animal with our teeth and mouth opened to the fullest would not permit for the insertion of any animal other than very small ones. And, if the animal was alive, we might have more damage inflicted upon us than we could inflict except with the brute strength of our hands and arms. On the contrary, the human mouth is excellent for biting into fruits or the insertion of fruits and chewing. Obviously we are adapted for eating small items.
The anatomical features that distinguish humans from carnivores such as cats, dogs, eagles, jackals and other carnivorous animals are many. There are few features wherein we are alike. Humans are also very dissimilar to omnivorous animals such as hogs, bears, and the like. Almost everything about these animals is different from humans.
Keep in mind that our mental disposition matches our anatomical and physiological disposition. What we admire naturally (as contrary to acquired perversions) is in accord with our dietary. Our aesthetic standards attribute beauty to fruit trees, and fruit but not to dying and bleeding animals. We savor fruit and are repulsed by blood. We do not savor grass or insects.
One of the most telling facts is rather simple. About 5% of the flesh volume of all animals consists of waste materials that are normally eliminated by the kidneys—uric acid, a precursor to urine. Uric acid is a poison to humans, not only because it is a toxic waste product but because it is non-metabolizable.
All carnivorous animals secrete the enzyme uricase. Uricase breaks down uric acid so that it can be eliminated quite readily. Unfortunately, humans absorb uric acid when meat is eaten. The uric acid stimulates the body like caffeine or other drugs until the body neutralizes it by drawing upon alkaline reserves, especially calcium. In the absence of such reserves, the body draws upon bones and teeth.
What happens to the calcium urate crystals that are formed as a result of this neutralization? For the most part, the body excretes them. Inasmuch as they’re in the circulating media of blood and lymph, the body does not eliminate them with dispatch, especially in view of the enormity of the eliminative tasks of most people. Hence the body “buries” the crystals “under the rug,” that is, it shunts them aside to areas in which they do the least physiological harm. The body has a tendency to concentrate neutralized uric acid as calcium urates in the joints, lower back and the feet. These deposits lead to arthritis, bursitis, lower back pains, gout, rheumatism, etc. Once an arthritic sufferer recognizes this bodily process as the cause of his suffering, he is usually quite willing to give up meat-eating. Fasting will, in most cases, enable the body to slowly autolyze these deposits and return to normal. A proper diet will not cause such a condition in the first place nor after correction has been realized.

Are We Herbivores?

There are about twenty million people in this country who call themselves “vegetarians.” Most vegetarians fuel their bodies with what is called vegetarian fare. That is, they fancy themselves as a class of herbivores or plant eaters. We Life Scientists contend that we are not ruminants or herbivores.
We are also very dissimilar anatomically to grass-eaters. We all know we are not grass-eaters. We reject the idea of eating grass and weeds, the natural dietary of cattle and other herbivora. It’s completely contrary to our nature to do so.
Our natural foods must necessarily appeal to ALL our relevant senses. It follows that our natural foods must delight our eyes, be of a fragrance that tantalizes our olfactory senses, and be of such titillating quality to the taste buds as to be ambrosia. Eating should always be a gustatory delight.
Which would you prefer? The aromatic sweet flesh of a properly ripened pineapple or a head of broccoli? Would you rather have a delectable sun-ripened peach or a few raw collard greens? Would you prefer a stalk of celery or a bunch of purple concord grapes? Which entices you the most, a colorful juicy orange or spinach greens? Does a head of cabbage attract you as much as a properly ripened, brilliantly yellow and brown speckled banana? Which lures your eye most for beauty, a large red delicious apple or a freshly dug carrot? Does a basket of brussels sprouts turn your head as much as a basket of strawberries? Is the heavenly delicacy of a Cornice pear matched by anything you’ve ever eaten from the lettuce family?
If you’ve ever eaten a cherimoya, mango, mangosteen, soursop, sapodilla, fig, date, watermelon, cantaloup, honeydew or other mouthwatering delights, you know well their joys. Can you compare the eating of any single vegetable in its raw state to eating any of these heady delights? Can you not see that, in order for a food to be a natural item of human dietary, we must be capable of relishing that food eaten by itself in the raw state?
Not only must the food be a gourmet experience in its living state but our fill of it must furnish us with most if not all our nutrient needs. This is a most vital consideration.
Can you name a single vegetable that you’d ravish, as a full meal of itself in its raw state? Almost any vegetable that you can name fails in the first prerequisite of a food: it must furnish us amply of our fuel requirements. Almost every vegetable you name does not furnish us with any significant amount of caloric values. All green leaves, regardless of their calorie rating, yield us no net increase in calories. The energy of digestion and assimilation often exceed the calories obtained therefrom. Most of the calories of vegetables are bound in indigestible cellulose. Ruminants with four stomachs, true herbivores, can digest cellulose and thereby obtain fuel and nutrient values. We humans become as thin as a rail if we try to sustain ourselves on vegetable fare.
The potato, a tuber, is regarded as a vegetable. If eaten raw, it cannot be relished. Moreover, its starches cannot be utilized for two reasons. First, most of its food values are inaccessible to us because they are encapsulated in cellulose membranes. Secondly, those values which are freed quickly exhaust our supply of the starch-splitting enzyme, ptyalin (salivary amylase).
Cereal gains, which are popularly regarded as vegetables even though they are not, have the same drawbacks in digestion as does the potato. Grains occur in an edible state but a day or two in their cycles. Otherwise they’re inedible except upon heavy soaking or sprouting. Even when soaked or sprouted, every grain is deficient in one or several aspects of its nutrient complement. Most also offer digestive problems. The gluten of wheat, for instance, is indigestible. We simply don’t possess the enzymes to break it down. Wheat protein is bound as gluten. Further, most grains contain phytic acid, which we cannot handle. They bind calcium and thus rob us of that mineral salt.
An examination of every vegetable reveals it, when it stands on its own, as unsuited for human sustenance in some significant aspect or other. Fruit, on the other hand, supplies us amply with all our needs including proteins, mineral salts, vitamins, fuel and other vital food components, known and unknown.
We can relish fruits in their raw ripe state without any special preparation beyond pitting and/or peeling. I know of very few vegetables that would even begin to furnish our needs amply that we can make a meal of, even if we did relish them. Turnips, rutabagas, kohlrabi, fresh sweet corn, sprouted legumes and fresh sweet peas (where starch has not set) would be some of the near exceptions.
Without cookery and condiments most vegetables are unappealing. We must jazz up their lack of taste appeal with stimulating herbs or unwholesome flavorings, fats, seasonings, etc. We must deceive our senses in order to consume vegetables. Condiments and cooking are very destructive to our health.
Most vegetarians eat fruits, even a preponderance of fruits, yet call themselves vegetarians. Many vegetarians consume fish, milk and dairy products and eggs and still fancy themselves vegetarians. Of course these products are not even vegetables. Vegetables are plants. But the seeds of plants, the legumes, the grains, certain fruits such as cucumbers, squash, pumpkins, tomatoes, eggplants and peppers are regarded as vegetables though technically they are not.
Not all fruits meet the proper criteria as food for humans. Nuts and avocados are suitable as food but we could not sustain ourselves on them whereas we can sustain ourselves indefinitely on grapes, bananas, oranges, figs, dates and many other fruits. We’d never make it on fruits such as cucumbers, tomatoes, eggplants, peppers and squash any more so than we can make it on cabbage or celery.
A good indication of what our natural foods are can be determined by the natural preferences of a child that has been fed nothing but its mother’s milk. Does it like cereals or bananas’? Apples or cabbage? What will a child go for if let to choose its own food? In my experience such a child always has chosen fruits. When served vegetables, my child found them a chore to eat, though he ate them to some extent.
We have considered vegetables and fruits based on aesthetic appeal and fuel requirements. There are other touchstones for consideration which we shall now explore. Humans are classed as frugivora or frugivores or fruit eaters because of their anatomy, their primate character, their digestive faculties, their psychological disposition and their background in nature. Research has shown that we had an arboreal past—that we were once tree dwellers. At that time we depended upon the products of tree, and later upon the fruits of stalk and vine, for our sustenance.
For example, Dr. Alan Walker, an anthropologist of Johns Hopkins University in Maryland, has done research that shows that humans were once exclusively fruit eaters. By careful examination of fossil teeth and fossilized remains of humans with the aid of electron microscopes and other sophisticated tools, Dr. Walker and other researchers are absolutely certain that our ancestors, up to a point in relatively recent history, were total fruitarians.
These findings complement other findings and verify the consistent scientific classification of humans as frugivora.
Creatures that live in accord with their biological heritage do not develop disease. They live out their normal life spans and die natural deaths. Humans have by and large strayed from their natural dietary and for that reason suffer disease and early death. Humans who undertake to live on their natural dietary and observe other modalities of healthful living also live unto a ripe old age and die a natural death. Although it is a rarity, people who touch base with life’s requisites have lived well past 100. In Hunza such a lifespan is a rule rather than the exception, even though their dietary is far from ideal.
Green leaves and stalks contain a greater concentration of vitamins, minerals and other nutrients than fruits. But they also contain, in most cases, compounds we cannot handle well. Lettuce contains minute amounts of a poison called lactucarium, which is a soporific. It is contained in a milk-like substance, just as in the poppy. Large amounts of lactucarium can be gathered and converted to substances resembling opium and heroin.
Celery has bitter properties in the leaves which make them repulsive to the normal palate. Anything that disagrees with our taste buds has, ipso facto, been rejected at that point. That is not to say, on the other side of the ledger, that a pleasant taste is the sole criteria by which to select foods, even with foods as they occur in nature, our taste is the surest guide we have if our taste buds are unperverted.
I deeply believe that we can add certain vegetables to our diet in small quantities with some benefit, most notably lettuce and celery. Their wealth of vitamins and mineral salts as well as their high quality protein amply supplement and insure adequacy of a fruitarian diet. Our bodies handle small amounts of such vegetable fare rather efficiently and without protest. In conjunction with a vegetable meal certain fruits can also be added, especially bell peppers, tomatoes and avocados. Secondarily we can add nuts on occasion or seeds such as pumpkin, sesame id sunflower. These seeds have the same dietetic character as nuts even though humans probably never ate them in nature.
It is well to always keep in mind that we are not naturally herbivores, graminivores, carnivores, insectivores or omnivores. Neither are we oil, protein or starch eaters except incidentally. Our protein needs are met amply from fruits but the occasional addition of nuts, seeds and greens insures dietary protein adequacy. However, we do not handle concentrated foods containing oil, proteins and arches with any great degree of efficiency. They are best eaten infrequently, perhaps two or three times weekly as Proteins require about 70% as much energy to digest and assimilate as they furnish whereas sweet fruits are so efficiently handled that the body is able to utilize over 90% of their caloric energy after deducting energies expended in ingestion and assimilation. Moreover, proteins are not used for energy as long as carbohydrates and fats are available.
That to which we are physiologically adapted is also most effectively and efficiently utilized. Vegetables, I repeat, yield us no calories as a rule though we do obtain from them a plethora of nutrients. Even so, fresh ripe raw fruits furnish us amply of our needs including proteins, vitamins and mineral salts. Even our very small need for essential fatty acids is well met by fruits. When we meet our requirements, that’s enough. Enough is all we need. Oversubscription can be like overloading a truck or a mule—it is very taxing and damaging.
Though vegetables are not natural to our dietary I must reiterate this observation: Not all vegetables are bad in our diet for they are consonant with our needs. On the same order, not all fruits are good for us. Many fruits are poisonous. Some, though not poisonous, are not handled well, such as oily fruits like Brazil nuts and pecans, high protein and fat content nuts and seeds such as almonds and sunflower, and starchy fruits such as pumpkins and chestnuts.
No natural food in the world rivals fruits for exquisiteness and wholesomeness. Inasmuch as tables of composition of foods show fruits replete with our needs, and inasmuch as we can more efficiently make use of the nutrients of fruits than any vegetable, legume or grain, we can safely confine ourselves to completely fruitarian fare with great benefit.
While the condition and quality of fruits available in our marketplaces are lamentable, the same goes for everything else sold as foods! So we are still better off with fruits. Some fine quality fruits can be obtained and we should concentrate upon those. Dried fruits have considerable goodness too. We should complement our fruit meals with some dried fruits, especially if we’re in need of high caloric intake.

Are We Milk Drinkers?

America’s dairy industry has no intention of letting Americans become weaned. We are to remain sucklings all our life.
One of the most telling arguments against milk drinking is to elucidate the realities of milk-drinking. Consider the following statements. Milk would be much fresher and more wholesome if taken directly from the teat of the cow as it is done in nature by calves.
Should anyone argue seriously that milk is the one perfect food you can agree with them that this is true—for a calf. Then you might inquire if their bodies secrete rennin and lactase. These enzymes respectively break down the casein of milk, the calcium/protein component and lactose, the milk sugar. Humans normally cease to secrete these enzymes at about age three, and thereafter can no longer handle milk. It’s no accident that our number one “allergy” is milk. The body properly objects to substances it cannot use for food.
Yes, milk may be the one most perfect food but that does us no good if we can’t digest and use it. Further, when our bacterial flora decompose it, fermenting part and putrefying part, the by-products of decomposition will cause many problems we didn’t bargain for.

Are We Grain Eaters?

Grains are grass seeds. The grains of today are rather tall, but they’re huge compared to the seeds from which they’re developed. Grains have been cultivated and eaten humans for only about 8,000 years.
In nature we did not eat grains or grass seeds. We did not develop any gathering or digestive equipment for grains. Natural grain eaters must be able to efficiently gather, grind and digest grains. Humans fail on all counts. Our teeth handle grains poorly. In fact, humans refuse to chew tasteless and hard grains. Even so, humans, not being starch eaters, cannot digest more than a handful of grains, if that much. True starch eaters secrete a plethora of starch-splitting enzymes in copious amounts. Humans secrete one starch-splitting enzyme, salivary amylase (ptyalin) which is quickly exhausted. After a mouthful or two of starch, the eater palls and stops.
Nope, we’re not grain eaters. The way we do eat grains by mechanical gathering, refining, cooking, etc. makes them palatable but more pathogenic.

THE CARNIVORA	THE OMNIVORA	THE HERBIVORA	THE ANTHROPOID APES	MAN
Zonary placenta	Placenta non-acciduate	Placenta non-deciduate	Discoidal placenta	Discoidal placenta
Four Footed	Four Footed	Four footed	Two hands and two feet	Two hands and two feet
Have claws	Have hoofs	Have hoofs (cloven)	Flat nails	Flat nails
Go on all fours	Go on all fours	Go on all fours	Walks upright	Walks upright
Have tails	Have tails	Have tails	Without tails	Without tails
Eyes look sideways	Eyes look sideways	Eyes look sideways	Eyes look forward	Eyes look forward
Skin without pores	Skin with pores	Skin with pores (save with pachyderms as the elephant	Millions of pores	Millions of pores
Slightly developed incisor teeth	Very well-developed incisor teeth		Well-developed incisor teeth	Well-developed incisor teeth
Pointed molar teeth	Molar teeth in folds		Blunt molar teeth	Blunt molar teeth
*Dental formula 5 to 8.1.6.1.5 to 8 5 to 8.1.6.1.5 to 8	Dental formula 8.1.2 to 3.1.8 8.1.2 to 3.1.8	Dental formula 6.0.0.0.6 6.1.6.1.6	Dental formula 5.1.4.1.5. 5.1.4.1.5.	Dental formula 5.1.4.1.5 5.1.4.1.5
Small salivary glands	Well-developed salivary glands	Well-developed salivary glands	Well-developed salivary glands	Well-developed salivary glands
Acid reaction of saliva and urine	Saliva and urine acid	Alkaline reaction, saliva and urine	Alkaline reaction, saliva and urine	Alkaline reaction of saliva and urine
Rasping tongue	Smooth tongue	Smooth tongue	Smooth tongue	Smooth tongue
Teats on abdomen	Teats on abdomen	Teats on abdomen	Miammary glands on breast	Mammary glands on breast
Stomach simple and roundish	Stomach simple and roundish large cul-de-sac	A stomach in three compartments (in camel and some ruminents four)	Stomach with duodenum (as second stomach)	Stomach with duodenum (as second stomach)
Intestinal canal 3 times length of the body	Intestinal canal 10 times length of the body	Length of intestinal canal varies according to species, but is usually 10 times longer than body	Intestinal canal 12 times length of the body	Intestinal canal 12 times length-of the body
Colon Smooth	Intestinal canal smooth and convoluted	Intestinal canal smooth and convoluted	Colon convoluted	Colon convoluted
Lives on flesh	Lives on flesh, carrion and plants	Lives on grass, herbs and plants	Lives on fruit and nuts	Lives on fruit and nuts

*The figures in the center represent the number of incisors upon each side

Physiological Criteria Foods Must Meet

Every creature in nature has become adapted to securing and nourishing itself on particular foods. All natural equipment and faculties dispose to this specialization. Humans are not exceptions to this rule. Because we have developed tools using our capabilities and can supply ourselves with an abundance of anything on earth as food does not in any way alter our physiological adaptations and specializations.
Every creature has basic nutritive requirements. Our biology books detail these rather impartially and correctly for animals. But the books and teachings that concern human nutrition do not deal impartially with the subject. Our educational establishment is the captive of our mammoth industrial complex. This means they prostitute their teachings to cater to the needs of those whose grants support them. Thus, human nutrition as taught in our society is dictated, not by physiological faculties and needs, but by the wishes of those food industries that stand to gain from the miseducation that panders to their products.

Food Adaptations of Various Species

The food specializations of various species are categorized by general designation. Some of these categories are as follows:

Herbivores (grass and vegetable eaters such as cattle, sheep, goats, deer, horses, rabbits, etc.)
Graminivores (animals that subsist on grains—birds primarily)
Insectivores (bats, birds and creatures that subsist on insects)
Frugivores (fruit-eating animals—primates and anthropoids, humans, orangutans, apes, monkeys, etc.)
Carnivores (animals that live on the flesh, bone, offal, etc. of other animals—cats, dogs, lions, tigers, wolves, buzzards, hawks, eagles, jackals, etc.)
Omnivores (animals such as swine (pigs, hogs) that live off a mixed diet of fruits, vegetables, grains, flesh, offal, etc.)

Range of Food Processing Capabilities

Humans are endowed with certain natural capacities and limitations in the acquisition, processing and utilization of foods. Human development (which endowed us with our faculties and capabilities) specialized and restricted our equipment and capabilities for food gathering and processing to certain foods just as in the case of other animals. The faculties of most creatures are developed so as to make disposition of surpluses or to survive scarcities. Surpluses are either stored as reserves or are excreted. Redundancies beyond needs and ability to readily excrete founder humans and other animals that are so unwise as to overeat.
In ascertaining the criteria that a food must have to satisfy human needs, we must be cognizant of the capacities and capabilities of the organism as well as the properties of the food.

Food Adaptations of Humans

Humans are classified as frugivores because they have the equipment to harvest and efficiently process only a class of foods called fruits. Humans are not alone in this class. For millions of years humans subsisted solely, exclusively and only on fruits. That is the way it was expressed by Dr. Alan Walker of Johns Hopkins University, an anthropologist who conducted extensive research into the dietary background of humans. Even though humans have eaten foods outside their dietary adaptations off and on for perhaps hundreds of thousands of years and have eaten some cooked foods for tens of thousands of years, there has been no physiological change that would justify straying from our natural dietary.

The Physiological Determinants Of The Optimum Diet

A wealth of information exists about the physiology of food digestion and absorption. Unfortunately, the science of nutrition has often depended upon “rat experiments” and artificially induced deficiencies, rather than upon the true needs of humans, to determine dietary requirements.
A more reasonable approach to determining the true dietary nature of humans is to study human anatomy and physiology. By studying human physiological nature, certain characteristics of the proper diet can be deduced that are in accordance with the inherent nature and anatomical makeup of humankind. This approach does not depend upon contrived experiments, nor is it already biased by what the majority of people believe a traditional diet should be. Instead, human physical capabilities and predispositions are the chief factors in determining true dietary needs.

Food Appropriation

The diet of most animals is largely determined by their food-gathering equipment. The long neck of the giraffe enables him to feed upon the foliage of trees. The teeth and claws of the lion are its means of killing and rending animals for its meals. The eagle’s eyesight and power of flight make this creature a formidable predator of ground rodents.
So, it is salient to ask, how are you physiologically equipped to obtain your food? You have no sharp claws for tearing, no pointed teeth for slashing, nor are your eyes or sense of smell very well developed for hunting. You cannot run fast enough to chase down your prey nor can you naturally swoop through the sky or dive deep into the ocean.
You do have a marvelous set of fingers with an oposable thumb and limbs for reaching and climbing. Actually your food-gathering capabilities are very similar to the chimpanzee’s!
Only man can plant and harvest. He can peel oranges and bananas and pick berries and grapes. He can climb the trees for fruits or gather the vegetables from the ground. Of all the creatures on the earth, man is most ideal for being a gardener and caretaker of the plants and trees.
Man’s hands set him apart from the other animals in his food-gathering capabilities. Man appropriates his food by picking fruits from trees or by planting vegetables. It is the hands of man that are used to obtain his food, and the most natural things for such a being to eat are those foods that can be gathered and harvested—the fruits, vegetables and nuts of the earth.

The Mastication of Food

Man’s teeth are not curved or sharpened like those of the wolf or tiger, nor are they wide and flat like those of the grass-and-grain-eating animals. Instead, they are shaped most similar to the fruit-eating monkey’s.
The saliva in man’s mouth has a different acidity entirely than that of the meat-eating animals; it is much less acidic. Nor is man’s saliva as efficacious in digesting starches as is the saliva of grain-and-tuber-eating animals.
Man’s mouth is actually best suited for eating succulent vegetables and fruits.

The Stomach

If a dog swallows a bone and it proceeds to its stomach, it will be completely dissolved by the dog’s strong gastric juices. Carnivores may safely gulp hunks of meat whole because of the high acidity of the juices in their stomachs.
Humans have choked to death on similar chunks of meat. It is interesting to note that almost all of the fatal chokings on food have involved pieces of meat (vegetarians, beware: peanut butter is a close second on fatal food chokings).
Unlike the grass-and-grain-eaters (such as cattle), man’s stomach cannot process large amounts of cellulose. He cannot regurgitate and re-chew his food as does the cow, for example.
Nor can man’s stomach digest a mixture of all different types of food. Each food requires its own special set of digestive conditions in the stomach. Notice too that little or no starch digestion occurs in the stomach, and that fat digestion is a lengthy process that is only successful for small amounts of unheated fats.
Obviously, anything in the world can be put into the stomach, and probably has. However, the physiology of the stomach is such that only foods in compatible combinations can be effectively digested.

The Intestines

The length of man’s intestines is much longer than that. of the carnivore’s. This is because meat tends to putrefy rather quickly in the intestines and must be expelled quickly. Man’s lengthy intestinal tract cannot handle low-fiber foods such as meat quickly. Consequently, such foods decrease the motility of the intestines and fermentation results, along with eventual constipation.
Cancer of the lower intestines occurs only among populations of meat-eaters. It is virtually unheard of when a diet high in natural fiber (raw fruits and vegetables) is adopted.
Constipation also disappears on a high-fiber diet. Fruit-and-vegetable-eating animals maintain excellent tonality of the intestines and usually experience a natural bowel movement after each feeding.

The Optimum Diet

Let’s review the physiology of digestion so that we may determine the optimum human diet. First, it is obvious that man is built to be a gardener and harvester of fruits, vegetables and nuts. He does not possess the physical apparatus that the carnivorous animals have. Second, the teeth, saliva and digestive enzymes of man point to a diet consisting mainly of fruits and non-starchy, vegetables.
Third, the length of the small intestine is too long to handle putrefying meat and is too short for grasses and grains. Humans should eat a high fiber, high-moisture diet to insure health of the small and large intestines.
From these observations, it is evident that the optimum articles of diet for man are fresh fruits and succulent vegetables. Strictly speaking, based upon man’s digestive physiology, the following raw foodstuffs make up the optimum diet, listed in order of preference:

Fresh fruits;
Succulent fruit-like vegetables;
Leafy greens and sprouts;
Non-starchy vegetables; and
Nuts and seeds.

The following foods, while not optimum, can be handled by man’s digestive physiology in small amounts when properly combined:

Starchy vegetables;
Grains and
Legumes.

The next foods, while sometimes eaten on a vegetarian, diet, are not well adopted to man’s physiology and place an undue strain on the organism:

Free oils; and
Dairy products.

These foods are definitely disruptive of man’s health and are not compatible with his physiology:

Meat;
Eggs;
Refined starches and sugars;
Salt, herbs, spices, etc.;
All processed, preserved and artificial foods; and
Cooked foods.

The person desiring optimum health should eat exclusively from the first list of foods. These foods are most compatible with human physiology. Within this category, foods should be eaten in moderate amounts and in proper combinations.
The ultimate diet that is most conducive to human physiology and that promotes the highest level of health is the mono-fruit diet; that is, the eating of a single variety of fruit for each meal.

Gemma’s comments

As we will see in the next article, I don’t agree with T.C.Fry position about nuts and seeds. As Dr. David Klein says, nuts and seeds are not our best food.
I don't agree with the clasification of adequacy of foods. I would rather say that:

Optimum diet: