Most fruits are delicious, satisfying and beneficial. They are the best non-violent food. (List of fruits).

When many years ago I started researching each type of plant food, one after another, I discovered for myself, that fruits are the least dangerous source of energy and building material for our bodies in general. (We assume we don't need to explain in this topic why eating animal food is inhumane and disadvantageous). I personally do not believe in ideal food, because it is a matter of adaptation and trade off, but fruits are certainly on the very top of my preference list, I choose them almost always over anything else for various reasons.

I found many strange details about elements in green and root vegetables - not all of them are slightly poisonous (as saponins in potatoes, for example), but many can impair assimilation of other vital nutrients. Cruciferous vegetables (like broccoli, cabbage, kale, cauliflower) may interfere with thyroid function. Collard greens are among  foods that contain measurable amounts of oxalates. When oxalates become too concentrated in body fluids, they can crystallize and cause health problems (e.g. kidney stones). And so on. (See more in Toxins in Raw Food).

Actually, there is a quite logical possible explanation to it: green vegetables are vital organs of plans, and plants naturally protect themselves from being eaten. Some of them create only fruit as intended food for other organisms (mainly to spread the seeds inside of the fruit), and they are certainly try to make them more attractive for end-consumers :) The latter - frugivores - adapt to fruit too. Herbivores have very complex digestive system, not similar to ours, to deal with grasses. When both the fruit-producing plant and the frugivore species benefit by fruit-eating behavior their interaction is called a mutualism.

Why fruit only?

Frugivores

Frugivores - species whose diet consists primarily of fruits. Mammals and bird species represent the majority of seed dispersing species. Most primates are predominantly frugivores, hence they eat raw plant matter (fruit). Humans are primates and it could be better for them to nurture themselves this way due to specificity of the gut morphology and other digestive processes. 

David J. Chivers, C. M. Hladik , Morphology of the gastrointestinal tract in primates: comparisons with other mammals in relation to diet, Abstract:

The frugivorous group are mostly primates: 50 of the 78 mammalian species, and 117 of the 180 individuals included in this analysis are primates.

C. M. Hladik and P. Pasquet, The human adaptations to meat eating:

Gut measurements of primate species do not support the contention that human digestive tract is specialized for meat-eating, especially when taking into account allometric factors and their variations between folivores, frugivores and meat-eaters. The dietary status of the human species is that of an unspecialised frugivore, having a flexible diet that includes seeds and meat (omnivorous diet). Some formerly adaptive traits (e.g. the “thrifty genotype”) could have resulted from selective pressure during transitory variations of feeding behaviour linked to environmental constraints existing in the past.

Trichromacy (three colors vision) provides an important advantage for fruit eating species - it can be a valuable aid in determining when fruit is ripe. The enhanced red vision allows to better distinguish between fruit and foliage.

Dr. Alan Walker, an anthropologist of John Hopkins University in Maryland, NY Times, May 1979:

“Preliminary studies of fossil teeth have led to the startling suggestion that our early human ancestors (Australopithecus) were not predominantly meat-eaters or even eaters of seeds, shoots, leaves or grasses, nor were they omnivorous. Instead they appear to have subsisted chiefly on a diet of fruit. Every tooth examined from the hominids of the 12 million year period leading up to Homo Erectus appeared to be that of a fruit-eater.”

Its simple, easy, good for the environment and makes you feel good

Cos they resemble us; both in inner essence and physical.

Does anybody have any info on why greens are not a good food for us?  I haven't been eating greens for the last 2 months and feel amazing and have experienced no problems but last time I did this (a 4 to 5 month period) a couple months into this I started getting chest pains whenever I ate which persisted until I reintroduced greens into my diet.  I do not like greens and really have to force myself to eat them, so would prefer to give them a miss.  Any info you have would be greatly appreciated!

Cheers,

Stephen

This question about adding some greens is still open for me, and probably should stay open for most of us, because there is simply not enough data to be conclusive on this point, in my opinion. I eat greens very seldom and very little, and I have not noticed any substantial favorable reactions of my body on them.

It is known that many greens are rich of micro elements, like spinach of iron, for example. But the value of those elements for us in their interaction with enzymes only, and they are not very well absorbed from these vegetables anyway. Another example: calcium, it is not highly bioavailable from those sources. (There is something more to say, I'll get to it later).

Why not

Herbert M. Shelton in The Hygienic System, Volume II, Orthotrophy, Page 223:

As there are no pure frugivores, all frugivores eating freely of green leaves and other parts of plants, man may, also, without violating his constitutional nature, partake of green plants. These parts of plants possess certain advantages, in which fruits are deficient. Actual tests have shown that the addition of green vegetables to the fruit and nut diet improves the diet.

William Esser:

Fruits and nuts are the perfect foods for man, but in the civilized areas of the world it is virtually an impossibility to obtain a sufficiently rounded upply for perfect nutrition and health. Therefore it is necessary to supplement them with vegetables. It will be found that vegetables are delicious and succulent.

Thanks Lena, it's good to know I'm not the only one who is on the fence on this issue.  Think I'm just going to go without until I get a desire to eat them.  So much nicer just eating mono meals of fruit!

quote " Herbivores have very complex digestive system, not similar to ours, to deal with grasses."

I have found a way of eating that I like and it digests well. I have a "double shot" (2 oz) of wheat grass juice with an orange juice chaser for breakfast and then eat whole fresh fruit for the rest of the day.

I'm just going to go without until I get a desire to eat them

This is exactly my approach too! I have noticed when I eat greens I have immediate thirst after it - I don't think it is a sign of their best suitability for my body... And another thing: this year I ate cabbage several times, and after that my body had a specific smell (of the vegetable) - I am not used to it and don't like it much, but my main concern is whether my organism tries to lead out some ingredients of this food with all possible means. The same happens to me after eating even smallest amount of onions and - surprisingly - large doses of Caribbean papaya (only this sort).

a "double shot" (2 oz) of wheat grass juice

That could be a reasonable middle-way for many people.

I think I am just too lazy for that, and I don't like sprouts: I tried many of them once or twice and disliked the taste of most of them, and was strongly dis-appealed by the smell of some. I assume, it can have something to do with microorganisms breeding on them, and some of those can be toxic as far as I know. I had no such problems with soaked seeds though, maybe just a little. 

Another related citation:

David J. Chivers, C. M. Hladik, Morphology of the gastrointestinal tract in primates: comparisons with other mammals in relation to diet, Abstract:
Three categories of dietary adaptation are recognized - faunivory, frugivory, and folivory - according to the distinctive structural and biochemical features of animal matter, fruit, and leaves respectively, and the predominance of only one in the diets of most species. Mammals subsisting mainly on animal matter have a simple stomach and colon and a long small intestine, whereas folivorous species have a complex stomach and/or an enlarged caecum and colon; mammals eating mostly fruit have an intermediate morphology, according to the nature of the fruit and their tendency to supplement this diet with either animal matter or leaves.

The frugivorous group are mostly primates: 50 of the 78 mammalian species, and 117 of the 180 individuals included in this analysis are primates. Coefficients of gut differentiation, the ratio of stomach and large intestine to small intestine (by area, weight, and volume), are low in faunivores and high in folivores; the continuous spread of coefficients reflects the different degrees of adaptation to these two dietary extremes.

Interspecific comparisons are developed by allowing for allometric factors. In faunivores, in which fermentation is minimal, the volume of stomach and large intestine is related to actual body size, whereas these chambers are more voluminous in larger frugivores and mid-gut fermenting folivores; fore-gut fermenters show a marked decrease in capacity with increasing body size. Surface areas for absorption are related to metabolic body size, directly so in frugivores; area for absorption is relatively less in larger faunivores and more in large folivores, especially those with large stomachs. Indices of gut specialization are derived from these regressions by nonlinear transformation, with references to the main functional features of capacity for fermentation and surface area for absorption.

Fruit only experiments

Jim Sloman (mayyoubehappy.com), Are We Fruit Eaters?, Living Nutrition v.17, 2005:
In T.C. Fry's booklet, How to Determine Your Natural Dietetic Character, he reported a very interesting experiment that was done in South Africa by Prof. B. Meyer of the University of Pretoria. The results were published in the South Africa Medical Journal of February 20, 1971. Prof. Meyer set out to prove that humans could not live on a diet of fruit alone. The experiment lasted six months. The control group would continue on a "normal" diet. The experimental group, under controlled conditions, ate only fresh raw fruit and nuts (which are also botanically classified as fruit). What happened?

At the end of six months, the various diseases of those in the control group had gotten worse. Meanwhile, those in the experimental group, who (it was assumed) would be wasting away, had instead become virtually disease-free! Dr. Meyer conducted various tests of their health, and could find no deficiencies of protein or vitamin B12 or anything else. In fact, everyone was in superb health.

But the professor was in for another surprise. The participants in the experimental group refused to give up the diet! He had supposed that they'd be anxious to return to "normal" foods, but they insisted that nothing would tear them away from this diet, and that they actually felt better and more vital and alive than they had in their youth.

An earlier 1971 study by Meyer tested a 45 year old teacher who claimed she had eaten only fruits for the past 12 years, who was found to be in "excellent health". In a further trial in the study, body weights of overweight subjects showed a tendency to "level off" at the "'theoretically ideal' weight".

Weight

Essie Honaball, of South Africa, writes in her book I Live On Fruit that she had a rare wasting disease. After seeing every medical practitioner possible, she happened to run into a man named Cornelius de Villiers-Dreyer, who was 76 years old at the time. Cornelius was one of the great fruitarians and life-educators. He had been living on fruits and nuts for most of his life, and Essie was astonished by his mental and physical vitality. Even though she was in a very wasted condition, he counseled her to begin a fruitarian diet. Out of sheer desperation, she agreed. What happened? She wasted away even more! She said that at a certain point she looked like the inmate of a concentration camp. But then, on the very same diet, she noticed suddenly that she was gaining weight. After she was through with detoxing, her body naturally returned to a normal weight, where she remained from then on.

Protein

By calories, fruit provides an average of about 5% protein. This happens to be the same as mother's milk. And mother's milk is our (intended) sustenance at a time when we're growing most rapidly and need protein the most. Moreover, the protein in fruit is predigested, since it comes in the form of free amino acids which don't need to be broken down in the body. Further, the protein in fresh fruit is uncooked, which means that it's more bioavailable and usable by the body, so that we need less of it in this form.

Disease protection

Reuters, 2007:

Just three servings a month of raw broccoli or cabbage can reduce the risk of bladder cancer by as much as 40 percent, researchers reported this week. Other studies show that dark-colored berries can reduce the risk of cancer too - adding more evidence to a growing body of research that shows fruits and vegetables, especially richly colored varieties, can reduce the risk of cancer.

Elio Riboli and Teresa Norat, Epidemiologic evidence of the protective effect of fruit and vegetables on cancer risk, American Journal of Clinical Nutrition, 2003:

The overall relative risk estimates from cohort studies suggest a protective effect of both fruit and vegetables for most cancer sites considered, but the risk reduction is significant only for cancers of the lung and bladder and only for fruit.

Hey I studied at the University of Pretoria here in South Africa!!!! Now I feel all proud :)

I would feel proud too :)

Here is a separate topic for toxins in raw food: http://fruitarians.net/forum/topic/Toxins-in-Raw-Food.htm

Nutritionists' advise

Americans ate an average of 100.42 pounds of fresh fruit each in 1997, and 100.21 pounds in 2007.

This flat trend worries nutritionists, who recommend that adults and children consume at least two servings of fruits and three servings of vegetables daily. CDC reports that this advice is ignored: Less than one third of adults meet the current guidelines. Even more concerning, among high school students surveyed, only about 1 in 3 ate the recommended number of fruits, and less than 1 in 5 ate the recommended vegetable amounts (CDC 2009).

The health benefits of a diet rich in fruits and vegetables outweigh the risks of pesticide exposure. Overall, eating conventionally grown produce is far better than not eating fruits and vegetables at all. But EWG’s Shopper’s Guide can help reduce exposures to pesticides as much as possible for people wisely seeking to eat more fresh fruits and vegetables.

Longivity

Inuit Greenlanders, who historically have had limited access to fruits and vegetables, have the worst longevity statistics in North America. Research from the past and present shows that they die on the average about 10 years younger and have a higher rate of cancer than the overall Canadian population.

Similar statistics are available for the high meat-consuming Maasai in Kenya. They eat a diet high in wild hunted meats and have the worst life expectancy in the modern world. Life expectancy is 46.5 years for men and 48.4 years for women (World Almanac, 2002). It gets worse in Tanzania, where the average male is expected to live just 43.85 years. Adult mortality figures on the Kenyan Maasai show that they have a 50% chance of dying before the age of 59.2.  African researchers report that, historically, Maasai rarely lived beyond age 60.

Victoria Boutenko explains that greens are hardly digestible and why kids don't like them: