If you have looked into the natural concept of a biologically-appropriate diet – the diet of the human species – you may ask yourself: What am I really eating? Would I eat it straight from nature by simply using my instincts? And, thus, is it actually human food?
Those seemingly basic questions turn out to be more important than we thought in human nutrition! After all, simplicity is the ultimate sophistication! Here we explore “food groups” by their biological role to answer some of it and to elaborate if humans are naturally adapted to eat a type of food.
Most “foods” we eat in modern society are not really human foods, but survival foods that have their origins in culture not “nature”: in order to survive in cold or dry climates humans have adopted a cooked omnivorous diet which enabled us to turn non-edible matter into edible foods. However, as biological frugivorous primates, those survival foods are not optimal for humans and can stress and overburden the body, especially in bigger quantities and over time.
Rediscovering the natural human diet
How can we know which foods are biologically appropriate for humans? These are approaches we can use and combine:
- Instincts in nature: only what is edible and tasty in nature (raw and unaltered) is real human food. Animals in nature know what to eat and what not. We humans do too, but we do not live in our original natural habitat, the tropical forest with abundant fruits. Instead, we make otherwise inedible and unpalatable foods edible – by cooking.
- Learning from chimpanzees: we can compare the diet of closely related species and their biological adaptations to diet. In our case those are the chimpanzees – our frugivorous cousins! In the wild, their diet is around 70% ripe tropical fruits. 24% other plant-based foods, such as flowers, nuts, leaves, seeds, barks, and tubers. 6% animal-based (eggs, insects, and meat). Insects account for 4% and meat for 1-2% (more details here) – and everything raw.
- What am I actually eating? Studying the ecological and nutritional properties of foods (like here) can give us valuable information on their suitability as food.
But let’s dive into what food groups exist and how suitable they really are for humans:
Food suitability overview
- Fruits and vegetable-fruits: Sweet, ripe tropical fruits are the healthiest food for humans and should make up the biggest part of the human diet. Edible temperate fruits and veggie-fruits are more acidic and watery – or starchy (i.e., pumpkins) – and are a valuable add to the human diet, especially when living outside the tropics, in temperate climate. They should only be eaten ripe. We should be aware of nightshades (tomatoes, bell peppers, eggplants etc.), which contain a certain level of toxins (Sharma & Mishra, 2021). Also, do not use pumpkins, cucumbers, and other veggie-fruits when they taste slightly bitter (read more on vegetable fruits here).
- Nuts: Nuts are part of a frugivorous diet. Try to get them in raw quality and preferably tropical ones. Do not make them more than 10-20 % of your diet.
- Greens and seaweed: tender greens, sprouts and watery salads are optimal for humans. Those type of greens we enjoy even without dressing and feel instinctually appealed. Cellulose-rich greens like kale or darker greens are not really suitable for our digestion, nor naturally appealing as foods. Phytochemical-rich aromatic leaves can be used as medicine, not necessarily foods.
- Root vegetables: Root vegetables are a fallback food for frugivores. Because they do contain sugars and slight sweetness, too. Root vegetables can be integrated into a human diet, especially in colder areas. Potatoes are nightshades that are not naturally edible and are toxic raw.
- Grains and legumes: Grains and legumes are not part of a biologically suitable diet. They need to be cooked in order to be digestible or even lose their toxicity. Even cooked grains were introduced very recently into our diet after agriculture started. Grains are excellent staple foods for humans that do not spoil quickly, but for health, they are problematic.
- Mushrooms: Edible fresh mushrooms can be eaten raw. However, they are not a frugivore’s first choice in larger quantities!
- Meat, Fish, and other animals: Meat and insects are part of the frugivorous diet of most chimpanzees – but only to a small amount and raw. Human instincts do not find those foods appealing! However, they were originally survival (fallback) foods to survive in cold climates.
- Eggs: Eggs are also part of the frugivorous diet of chimpanzees. It seems that raw eggs are less off-putting for us than raw meat. Still, they are not really appealing – unless maybe we are really starving!
- Dairy: Dairy is not a natural human food. It is highly nutritious baby food but not optimal for adults. We have not consumed another species’ milk before migrating to colder climates and domesticating animals. Which is why we are not well-adapted to dairy. However, because it was such an important survival food, some minor adaptations have occurred! Dairy could be used as a functional food if you live in a cold climate where our tropical species’ diet is hard to apply in a complete way – however, in small amounts and raw quality.
- Isolates and Extracts: Isolates, such as sugars and fats/oils, are not part of the human diet. Added sugar is easier on the body than fats, as frugivores are adapted to metabolize bigger amounts of simple sugars. Natural sugars can sometimes be used to mix into fruit smoothies when we do not have enough ripe sweet tropical fruits at hand. In this case, we can use “natural” sugars like coconut-flower sugar or dates (not isolates).
- Meat and Dairy Alternatives: Most of those products are damaging to the human body and contain inflammatory added plant oils. Only homemade nut-milk could pass as appropriate human food.
- Highly Processed “Foods” and Artificial Additives: They are not natural human foods and the human body is not adapted to process such products.
Below, each food group is discussed in-depth!
Aren’t humans omnivores?
Humans are frugivorous omnivores, anatomically and physiologically, as we are able to digest plant-based foods and animal-based foods. However, we are very similar to the highly frugivorous chimpanzees and share their adaptations to a high-fruit diet. Humans have become “cultural omnivores”, because cooked animal foods have allowed them to survive outside tropical forests. However, humans are still “biological frugivores”.
If you are new to this, visit this overview about frugivores here!
Preferred foods vs. fallback foods
In nature, there is not an abundance of all foods during the whole year. Therefore, animals have preferred foods and fallback foods, which are in time of scarcity for their survival. This topic matters in terms of species-appropriate foods, as we can try to evaluate, which foods are optimal and which foods are second choice.
What about cooked foods?
Humans do not have biological adaptation to cooked diets other than a slightly higher tolerance to the toxins of cooked foods. However, for survival in colder climates, when tropical fruits and foods lack, we need to integrate some cooked foods in the long run (not all though). Read more here.
Cooked foods are survival foods in colder climates, because only tropical forests can sustain larger frugivores with raw foods.
Nutritional deficiencies and supplements
To understand natural human nutrition, we must gain awareness that our species-appropriate foods contain all nutrients in amounts and proportions that we have evolved to absorb, metabolize and eliminate them. Only when we have pre-damaged our body’s systems to the extent that we cannot do so anymore, can we experience deficiencies on our species-appropriate diet. Or, if we get suboptimal foods (i.e. due to living outside our natural habitat or low food quality due to environmental factors and agriculture) which is the case for most of us! That is why we need to consider supplementing.
Visit also our guide and article on the frugivore diet and supplementing:
Food groups on a species-appropriate diet:
1. Fruits
Fruits are the most important food group in the diet of frugivorous primates!
Especially tropical fruits are optimal for human nutrition and health, because as tropicals primates we have evolved with tropicals fruits as food source and are adapted to its nutrition and also its phytochemicals.
Because humans are adapted to a high-fruits diet, we have lost our innate ability to produce vitamin C. This gene loss is typical for high-fruit species, unlike most mammals, which are able synthesize vitamin C. Therefore, humans have to take in a lot of vitamin C from external sources: fruits should make up around 70% of our diet!
Not all fruits of all plants are edible for humans; in fact, there are many toxic fruits! Those fruits have not co-evolved as a human food source!
What are fruits botanically?
Botanically, fruits are the seed-containing fleshy parts of a plant that develop from a flower. Fruits are unique as a food source because of the symbiotic relationship between plant and fruits consumer:
Fruits are also the plant part that attracts and rewards seed-dispersing animals. Many flowering and fruit-bearing plants depend on animals to disperse their seeds (unlike i.e., wind-dispersed species).
Therefore they attract the animal with its colorful and smelling fruits to be consumed and have its seed dispersed. The animal has the reward of energy- and nutrient-rich fruit flesh.
The more nutritious and tasty fruits are, plus the less toxic fruits are to their consumer, the more successful the plant is in reproducing!
Nutrition
Fruits are the nutritional reward for the animal and contain energetic nutrition, simple sweet sugars, water-soluble vitamins, macro minerals (i.e., potassium), and trace minerals like boron, silica, and even low levels of protein and lipids (fat). Fruits are made up of living cells, which always contain all nutrients! They also contain fiber and a lot of naturally purified water.
Anti-nutrients
Because fruits are “intended” to be eaten by the plant, they are not protected with potent phytochemicals to keep consumers off – unlike all other parts of the plant. Some exceptions are fruits that have not evolved with primates but rather as food source for birds. However, some of those fruits have been bread to become edible.
What type of fruits is the healthiest?
- Edible tropical fruits are ideal for humans: tropical fruits are mostly sweet and optimal for primates, including humans. Remember that we are originally tropical species and thus have evolved with tropical fruits. This matters, in terms of a successful fruit-diet, because tropical fruits have another nutritional profile than temperate fruits and also have less toxicity. This is reflected by the fact that most wild tropical fruits are edible for us, but most temperate fruits in their wild form are not!
- Temperate fruits are a good addition: temperate fruits are mostly acidic and were bread to be more suitable for human taste and consumption. They are a good addition to a fruit diet, but cannot replace tropical fruits. Those include apples, pears, plums, berries, apricots and the like.
- Some non-sweet “veggie”-fruits are suitable, and some not: i.e., cucumber, tomato, bell peppers, and pumpkins. They resulted from extensive breeding and originated in colder areas and thus have not evolved as primate foods. Moreover, some can be inflammatory because they still have some secondary plant compounds that can be toxic to humans, especially nightshades like tomatoes, bell peppers, and eggplants. This is why some people can have a sensitive reaction to those fruits, and some are not suitable for raw consumption. Read more on vegetable fruits here.
Acidic temperate or subtropical fruits often contain smaller seeds, as they originally evolved with birds that disperse their tiny seeds (swallowing).
2. Nuts
Nuts are the only type of seeds that are part of a frugivorous, species-appropriate diet. Like with fruits, especially tropical nuts are optimal for humans. Nuts, however, should not make up a greater part of the diet than 10 – 20 % because of their anti-nutrients.
What are nuts botanically?
Nuts are actually seeds, mainly from trees (as opposed to grains, which are seeds from grasses). () Nuts are like seeds of fruits, but the plant structures around the seed is not edible – unlike edible fruit flesh – but hard and shell-like. Thus nuts do not have a symbiotic relationship with its consumer (unlike fruits) which has an effect on the content of off-putting plant components!
The coconut is a nut, which is eaten by many frugivorous monkeys. The seed of the coconut is the white water-holding flesh. The mesocarp is wooden-like and inedible.
Nutrition
Nuts contain fats and fat-soluble vitamins, but also proteins and trace minerals, like iron, zinc, selenium, and chromium. Nuts are made up of living cells, which always contain all macronutrients! Besides being everyday food, nuts can be used as functional foods, i.e., for selenium supplementation with Brazil Nuts.
Anti-nutrients
Because nuts are not “intended” to be eaten, they are protected with potent phytochemicals to keep consumers off. If we eat nuts that have evolved as a food source for primates, we likely have evolved a high tolerance for the plant-protective compounds.
3. Green vegetables and Seaweed
Tender greens and leafy greens are part of a natural frugivorous diet.
However, unlike folivores (specialized leaf-eaters) or herbivores (green plant-eaters), we are not strongly attracted to cellulose-rich foods (darker leaves/greens) in nature. Nor are we equipped to effectively digest them, or process huge amounts of the secondary plant metabolites (see below).
What are green plant parts botanically?
Greens are the leaves and non-woody stems or branches of a plant. Green parts of a plant grow above the soil surface: The green-colored pigments capture sunlight for the plant’s sugar (energy) production – photosynthesis. The sugars are then transported throughout the plant, stored in the roots, or brought to the fruits to attract fruit-eating animals. The green parts are, therefore, the power generator of plants and ultimately provide all energy for animal life.
Note: fruit-veggies like cucumber, squashes, tomatoes etc. are often categorized as vegetables, because they are not sweet. But they are the fruit of the plant. In contrast, vegetables are all other parts of the plant than fruits. Therefore, here in this biological approach, veggie-fruits are in the fruits section, not the vegetable section (see above)!
Nutrition
Green plant parts contain chlorophyll and, therefore, a lot of magnesium, as well as other minerals and vitamins. Remember, leaves and all plant parts contain living cells that – by nature – must contain all components of a living cell: carbs, lipids, proteins, and vitamins. Similarly to fruits, greens also contain fiber and purified water.
In watery young light-green leaves, the minerals are more bioavailable. Unlike herbivores, we are not adapted to extracting all of our nutrients from greens. Herbivores have complex digestive systems and microorganisms to digest.
Seaweeds are leafy plants from the sea. They contain other nutrients and minerals than greens that grow on land. Iodine is the key nutrient in seaweed that is important for human health – and can be a cause of concern when not living close to the iodine-rich sea.
Anti-Nutrients
The plant protects green parts against being eaten, which is why most green plant parts contain phenolic defense compounds (Chowdhary et al., 2021). Those potent chemicals can be used as medicine. However, they should not be eaten in large amounts by frugivores (herbivores are better adapted to those compounds). Naturally, our taste buds indicate what is palatable and what is not. For example, bitter taste is off-putting, as it signals toxicity – bitter taste makes animals avoid eating something!
We should only eat as much of the green parts of plants as we could eat in their “natural state” – following our instincts. Lettuce with salad dressing or kale in a smoothie, for example: Would you eat as much lettuce or kale as is – without seasoning and mixed with fruit? Because the seasoning or the fruit covers the natural taste and prevents our body from sending the “right” signals. Crazily mixed smoothies are not necessarily the best option.
What makes a leafy green salad actually appealing are the veggie-fruits. What makes greens tasty is the fruits and/or the dressing (sugar, oil, salt).
4. Root Vegetables
Root vegetables are not frugivores’ first choice, but they can be fallback food. Roots can substitute the carbs from sweet fruits in form of complex carbs (not-sweet, though).
However, as frugivores, we prefer picking sweet fruits from trees to digging for roots because our hands are more suitable for foraging for fruits than digging.
Cooking makes the complex carbs (starches) better available, similar to fruits. As a special cas, potatoes are from the toxic nightshade plant family and are toxic raw, and thus are not suitable as food for humans.
What are roots botanically?
Root vegetables are root parts of a plant and grow within the soil. Roots are made for inorganic mineral, water and nitrogen uptake from the soil. Nitrogen builds the basis of protein production!
Some plants store a bulk of energy in the form of starches (complex sugar) in their roots. Those are the ones we tend to eat as food plants. However, not all root vegetables are starchy, but also contain glucose (simple sugar, sweetish). They are similar in this way to fruit-vegetables. The only difference is that the root is produced as a store for the plant and not – like the fruit – for the consumer. Root and stem vegetables can be consumed in any amount, but only eat as much as you would eat in their “natural state.” Example of celery juice: Would you eat so much celery just like that?
Nutrition
Roots contain energetic nutrition in the form of complex carbs and simple carbs, but also minerals and water-soluble minerals.
Besides starchy roots, we have watery roots with more simple (sweet) carbs that are edible in their raw state.
Anti-Nutrition
All modern root vegetables are the result of extensive breeding and cultivation. As a result, most natural roots have potent phytochemicals (as self-defense of the plant) and are not palatable. This is why many plant roots are used in phytomedicine but in small quantities, not as a food source.
5. Grains, Legumes, Pseudo-grains, Seeds
Grains (seeds of grasses) and legumes (seeds of leguminous plants) are not suitable foods for humans and are difficult to digest even after cooking. Some substances in legumes are so toxic that they are still toxic to humans, even after soaking, boiling, or sprouting. They are only suitable foods for highly specialized grain-eaters (granivores), but not for a species that is naturally not adapted to those compounds.
What are grains, legumes botanically?
Seeds, grains and pseudo-grains contain the embryos (and thus the potential progeny) of the according plant. The embryos are chemically protected from being eaten by the plant – which means the plant tries to put off animals by producing toxins.
Symbiosis results in low plant toxicity: Seeds in fruits for frugivores have another function: seeds usually pass the digestive tract unharmed (or even benefit from this process) and thus do not serve nutrition but instead are dispersed via defecation (Corlett, 2017). In contrast, grain-eating animals (granivores like birds, rodents, and insects) digest the grains, destroying the plant’s progeny. These two different evolutionary relationship types (symbiosis vs. preying) result in low vs. high toxicity because the plant’s protection is through toxic chemicals.
Nutrients
Grains and legumes contain a good amount of carbs and proteins. Those nutrients are only safely accessible for frugivores through cooking. Cooked complex carbs are the fallback substitute for the simple carbs in fruits.
Anti-Nutrients
Seeds are the embryos of the plant, the next generation, which is especially well-protected from predators with often toxic substances (a type of natural pesticide). These are so-called “anti-nutrients” because they interfere with digestion, and the nutrients are no longer well absorbed (read here more about legume toxicity).
The explanation of seed toxicity is easy to understand: the protection of the next generation is crucial to a species’ survival. Thus those plants that have the right genes to effectively avoid being eaten, will bring effective natural pesticide into the seed. Good for them, not good for us, as we are not adapted to those toxins like granivores (seed-eaters)
In countries where many legumes are eaten, the insidious poisoning “lathyrism” caused by certain legumes is also known. This shows that these plant parts stress the body due to the protective toxins.
Grains are the seeds of grasses, which in nature are the food source of granivores like insects or rodents. Examples are rice, wheat, or even corn.
Because of the compounds in grains and legumes, many people experience an improvement in their health simply by avoiding grains and their products, such as pasta, bread, and dough, but also legumes, such as beans, lentils and peanuts (see list here).
6. Mushrooms
Bonobos (chimpanzees) have been found to eat mushrooms in the wild. Humans are able to eat many types of mushrooms raw. Edible fresh mushrooms can be eaten raw. However, they are not a frugivore’s first choice in larger quantities:
Fungi are a distinct biological group. They are difficult to digest and not very appealing to us in their natural state. Nor do they taste really good in larger quantities without being seasoned, salted, cooked, roasted, or the like. Most wild mushrooms are very poisonous. Only some cultivated mushrooms can be eaten raw. However, mushrooms are well suited for the switch from meat to vegetables.
7. Meat, Fish, Insects and Seafood
Meat and insects are a part of the (frugivorous) diet of chimpanzees in the wild – but it makes up a very small amount and raw. Some individuals highly likely do not eat meat at all (read more here)! Moreover, human instincts do not find those foods appealing, but they may be considered survival foods.
Humans have no hunting instincts (nor anatomical hunting traits) and would not consume raw, bloody meat like carnivores. However, for survival, humans cooked meat to make it palatable and safe to eat. For this reason, meat is not a preferred (optimal) food but a survival food.
We are not adapted to metabolize as much protein like a carnivorous species. Even small amounts of animal-based foods quickly exceed the amount of protein that is safe for the kidneys!
Learning intuition from children: During the holidays, my 7-year-old daughter and her friend saw fishermen pull a small shark ashore to kill it. They fell away crying in terror and mourned for him all day. Zero hunting instinct! Unlike a baby lion or cat, which have inborn instincts to hunt and eat raw meat.
8. Eggs
Eggs are also part of the frugivorous diet of chimpanzees. It seems that raw eggs are less off-putting for humans than raw meat. Still, they are not really appealing – unless maybe we are really starving!
There is also the issue of widespread allergy against egg proteins. A problem that is linked to the application of modern egg-produced medications…
9. Dairy
Milk and eggs are products of animals that contain everything to nourish the growing offspring. Milk was and is a practical survival food in many regions outside the tropics. However, it is not optimal for our digestive anatomy and physiology. Modern milk is also often heavily processed, i.e. heated and also contaminated by medicines (from animal husbandry) which are administered to the animals. Additives are then added to dairy products.
If dairy products and/or eggs are still consumed, then it is essential to pay attention to the quality (Demeter, organic, if possible raw for dairy products). In some cases dairy can be used as a functional foods, especially when living in a cold climate, where the foods of a raw frugivorous diet are difficult to access.
10. Isolates
Generally, we don’t need extra added isolated fat to complete our foods. However, isolates and extracts can be used in a functional purpose, for deficiency or medical use, such as herbs or nutrients.
11. Meat and Dairy Alternatives
Most of those products are unhealthy and full of added plant oils. Only homemade nut-milk can pass to be appropriate in the human diet. Plant-based alternatives for dairy and meat are mostly made from grains, nuts, soy and and legumes like beans, lentils, and chickpeas (see above) with additives that enable the “right” consistency. They are really far-away from being natural foods, thus they are to be avoided.
12. Highly Processed “Foods” and Artificial Additives
Processed foods such as packaged products like french fries, biscuits, mayonnaise, frozen pizza, ice cream, chewing gum, and the like are to be avoided and are clearly not natural foods – or foods at all. The ingredients are often isolated substances that are “mixed” together to make them palatable to us. In addition, there are often synthetic additives and stabilizers, which are to be avoided completely.
However, if such products are still consumed (or someone you know consumes them), buying organic quality can make a big difference: many (of the most harmful) additives are not allowed in organic products.
Conclusion
There are no standard answer for everyone, because we live in different regions and have different levels of health. Some can transition fast into a high-fruits diet, while other cannot (yet) digest fruits, due to pre-damage.
This is not reductionistic science but rather the bigger picture and ecological patterns that have been out of the picture in nutrition for too long!
By learning more about our foods’ properties, we can make informed decision, what is natural and healthy in our diet.
For more information on how to adopt a high-fruit diet, check out our guide here:
Go to How to do the Frugivore Diet
References
- D. Sharma, S. Mishra, An acute toxicity in human health of raw and cooked vegetable in tomato and spinach. Food Science and Nutrition. 6, 1–6 (2020), doi:10.24966/fsn-1076/100075. (link)
- Quick-start guide to nuts and seeds. Harvard Health (2021) (available at https://www.health.harvard.edu/nutrition/quick-start-guide-to-nuts-and-seeds). (link)
- L. Streit, What is cellulose and is it safe to eat? Healthline (2021) (available at https://www.healthline.com/nutrition/cellulose-fiber). (link)
- V. Chowdhary, S. Alooparampil, R. V. Pandya, J. G. Tank, Physiological function of phenolic compounds in plant defense system. Phenolic Compounds – Chemistry, Synthesis, Diversity, Non-Conventional Industrial, Pharmaceutical and Therapeutic Applications (2022), doi:10.5772/intechopen.101131. (link)
- Y. P. Gupta, Anti-nutritional and toxic factors in food legumes: A Review. Plant Foods for Human Nutrition. 37, 201–228 (1987), doi:10.1007/bf01091786. (link)
- R. T. Corlett, Frugivory and seed dispersal by vertebrates in tropical and Subtropical Asia: An update. Global Ecology and Conservation. 11, 1–22 (2017), doi:10.1016/j.gecco.2017.04.007. (link)
- Jeremy, 10 surprising reasons to avoid eating legumes. Paleo Flourish (2020) (available at https://paleoflourish.com/paleo-why-legumes-are-bad). (link)
- Monkey food. Ascopolyporus – fungus case study (available at https://www.anbg.gov.au/fungi/case-studies/monkey-food.html). (link)
