Understanding Greens in the Human Diet: Learning from Chimpanzees!

Besides fruits, leafy greens play a key role in the natural human diet as a source of minerals and proteins. Greens contain all the minerals that we need: magnesium, potassium, iron, phosphorus, calcium, sulfur, boron, copper, zinc, selenium, manganese, boron, molybdenum, and iodine in seaweeds from marine environments and are a source of protein.

However, not all greens we eat today are equally beneficial for our species, and some should even be limited as they contain high levels of anti-nutrients, heavy metals or are too hard to digest, which is why we need to know what we are doing not to mess this up!

In this article, we will elaborate on what types of green foods we have adapted to eat and what types of green functional foods and herbs are a powerful add to our everyday greens!

For quick readers:

In our species’ diet, tender, young leaves, like succulent lettuce, young leaves, microgreens, and sprouts, should make up a substantial part. Additionally, mineral-rich supplements from greens, like powdered tree leaves and seaweeds could be an interesting nutritional and herbal addition. Greens that are high in anti-nutrients or tannins or do not taste good on their own, are not really part of the natural human diet and should be limited, especially in smoothies.

Learning from chimpanzees!

What types of greens are best for humans? This question is not that easy to answer, and I am just starting to dive in. To understand which types of green foods are the best ones for our species, we can look at our closest living relatives, the chimpanzees. Leaves play an important role in the diet of apes and other primates as a source of protein and minerals. Besides nutritional sources, many greens are used as herbs for self-medication by primates, indicating that the use of functional greens is part of a natural diet.

Besides learning from chimpanzees and from the traditions of people living in the tropics! And it did not surprise me that the favorite leaves eaten by chimpanzees are also some of the most miraculous herbal extracts used by people! But let’s dive in:

Apes are frugivores, not herbivores!

Most animals eat green plant matter. Even obligate carnivores do! All frugivorous apes and primates consume a substantial amount of green plant foods, especially leaves. Some lesser primates are categorized as folivores because the main part of their diet is leaves, while apes are highly frugivorous with fruits as their main source of energy and nutrition.

As frugivores, humans have not evolved to extract nutrients effectively from cellulose-rich greens and many raw leafy greens are hard to digest. In contrast, herbivores have a specialized digestive system to get the nutrients they need from green plant matter – for example, ruminants like cows and goats, but also non-ruminant animals like gorillas. Additionally, many leaves contain harsh (or even toxic) plant compounds, some of which serve the purpose of chemical self-defense against plant-eating animals.

Herbivores have a higher tolerance for these compounds than frugivores. Herbivores are actually mastering greens as an energy source: They are specialized in digesting a large amount of green matter and extract energy from cellulose with fermenting bacteria (i.e.,Fibrobacter succinogenes, Ruminococcus flavefaciens, and Ruminococcus albus). Their microbiome also produces phytase enzyme that helps overcome the anti-nutrient effects of phytates.

In contrast, frugivorous apes, which includes humans, are not specialized for large amounts of greens but are within a range of ca. 5-20% of the diet. An average chimpanzee’s diet consists of around 70% tropical fruits and figs, 24% other plant-based foods (flowers, nuts, leaves, sprouts, seeds, barks, tubers), 6% animal-based (of which 4 % are insects, and 1-2 % are meat).

Greens in the chimpanzee diet

Chimpanzees consume leaves, buds, or young shoots with a preference for young leaves or types of leaves with low tannin content (Takemoto, 2003). Even during food scarcity, they avoid tannin-rich leaves. When we compare these preferences to humans, we can see that they are the same: Bitter or hard leafy greens, like dark lettuce or kale, are naturally not appealing to us without dressing or processing like steaming, just on their own.

“Young leaves from tropical trees are far more nutritious than I realized. In fact, the young tips have the same profile of essential amino acids as meat, although in lower concentrations,” said Milton. She said that leaf protein is perfectly good and clearly satisfies all the protein needs of the monkeys” (source)

Just like apes, humans are naturally most attracted to succulent, slightly sweet, tender greens. However, we do not live in our natural habitat like apes do – with consequences on our food availability!

Greens in the human diet

What types of greens are suitable for humans? To answer this question I apply what we can learn from chimpanzees and from the traditions of people living in the tropics! Why the tropics? Because humans are a tropical species. Humans have evolved in tropical forests, as newer anthropological research suggests.

Our evolutionary foods are tropical fruits, greens, and nuts!

No wonder most wild tropical fruits are edible and are a superior food source to fruits from temperate climates! It, thus, comes as no surprise that the favorite tropical tree leaves eaten by chimpanzees are also some of the most miraculous herbal extracts used by people!

“Many fruits and unconventional foods are available in the tropics and represent valuable minerals sources. Green leaves appear as outstanding mineral sources, especially in calcium and iron, followed by nuts.”

Leterme et al. 2006

Today we eat mostly cultivated greens:

Humans have migrated from our natural habitat – the tropics – to other biomes and survived without our original food sources. Our ancestors ate new types of foods exposing them to new plant biochemistry – which is often not really suitable, nor sufficient as food source. The new environment made them adopt a survival diet, mainly consisting of meat, until they mastered agriculture and the cultivation of plant foods.

In cold climates, we require manipulating and cultivating foods that we can eat and tolerate well. For this reason, humans have reduced the load of anti-nutrients and harsh plant components by selectively cultivating them into safely edible varieties. The same goes for fruits: we have tropical fruits, and we have selectively bred, cultivated fruits from colder climates.

As a consequence we now find two types of green food sources we should consider: Evolutionary greens and cultivated greens. Both types of greens have a place in the natural human diet today, as we just can do the best with what we have!

1. Evolutionary greens

Greens foods are no exception to the “tropical origin” reality! In fact, tropical plants contain not only the most powerful plant components, but they are also the ones that the human body has adapted to process in the course of evolution. To get the most benefits but also the least harmful (greatest tolerance), we must look at our evolutionary greens – and might learn from chimpanzees:

Chimpanzees spend a substantial part of their time foraging for fruits in the trees and also consume the leaves of the trees they are foraging. In general, they eat the leaves and fruits of a high number of different wild and cultivated plant species. They eat tender, young leaves!

For example, in Bossou, chimpanzees consume the fruits and leaves of wild tropical trees and cultivated trees, which are also used by local people:

• Fig tree leaves (Ficus exasperata); humans use leaf extract for pain relief and others. Read more here.
• Monkey fruit tree leaves (also known as giant yellow mulberry, Myrianthus arboreus); humans use the young leaves as food and other parts as medicine. Read more here.
• Corkwood tree leaves (Musanga cecropioides); human use the leaves as “popular medicine, especially to treat a range of feminine complaints” Read more here.
• Papaya leaves: papaya leaf tea is well-known in ethnobotanical uses. Read an overview here.
• Okra leaves; Okra leaves are a common food source for humans. Read more here.
• Avocado leaves; Avocado leaves can be used as a food source and have ethnobotanical uses. Read more here.

(sources: www.greencorridor.info, Takemoto, 2003, Hockings et al., 2009)

There are thousands of beneficial tropical leaves in the tropics, which are also a food source for primates. The food choice of our closest relatives strongly depends on temporal and spatial availability. Some chimpanzee populations have also been found to eat seaweeds, if available. Chimpanzees get their minerals from various sources, like soil, insects or barks. In a sense they have found ways to supplement their diet and even self-medicate with herbs.

If we do not consume any of those greens, as chimpanzees do, we miss out on many anti-parasitic and anti-inflammatory bioactive components, which have been proven highly beneficial for humans! Therefore, integrating a few of them as herbs, nutritional supplements or medicine could be a great idea! The most known nutritional supplement is probably moringa green powder and various seaweed supplements, like sea moss, kelp, or calcium-rich red algae.

2. Cultivated greens

We have cultivated the greens in colder climates, which best please our taste buds and are non-toxic. We can get a good amount of nutrients from those greens! The key question to choosing our greens is: What would we eat instinctually? What tastes decent even without dressing?

We need to rely on our natural instincts here:

While greens provide nutrients, they also produce powerful secondary plant metabolites, which serve different purposes. A principal purpose is chemical self-defense against whoever eats them (see the list of anti-nutrients above)! We can taste some of these compounds and are instinctively repelled – for example, by bitterness or also by hard-to-chew matter in contrast to tender and succulent leaves, shoots, and buds. Wild edible young sprouts, leaves, and buds in your environment that taste good, are a good addition to your greens.

Here are a few types of green that are very suitable for humans:

Here are a few that are not really human food sources and can contain high levels of anti-nutrients or toxins. Adding those regularly or in too much quantity into your salads or smoothies can lead to overexposure to unwanted plant toxins and can upset your stomach! Examples:

Would you bite into a raw kale and eat it up entirely? Most of us would not! Crispy young tender lettuce leaves, which taste even slightly sweetish are what we naturally feel appealed to eat – alongside sweet fruit. However, it might be challenging to eat the amount we naturally would, or get the amount of minerals from the tender lettuce and greens listed above.

How to do greens right

What types of greens should we eat? In our species’ diet, tender, young leaves, like succulent lettuce, young leaves, microgreens, and sprouts, should make up a substantial part. Additionally, mineral-rich supplements from greens like powdered tree leaves, seaweeds, and powdered wild fruits is helpful to up our mineral intake – while trying to imitate our natural food patterns without easy access to the foods that we need. Greens that are high in anti-nutrients or tannins or do not taste good on their own, are not really part of the natural human diet and should be limited, especially in smoothies.

How much greens do we need? It depends on what other types of food we eat. If we look into nature, chimpanzees eat a large amount of young leaves from trees, but if they can, they go after ripe fruits (fruit availability varies). Fruits also contain all the minerals that greens do, but in lower concentrations, as fruits also provide a lot of liquid. Tropical fruits, wild fruits, contain much more nutrients and minerals than modern, cultivated ones, which is why we should consider natural supplements, like functional foods.

Here are three ways to increase our greens in a healthy way:

1. Juicing greens

Juicing tender greens with fruits helps us eat more greens. Greens and fruits are a natural combination, which might be the reason we love the taste!

2. Combining greens and fruits in salads

Fruit-enriched salads based on leafy greens have become an integral part of plant-based diets for a reason:

3. Taking green supplements

Due to the limited access to our evolutionary green food sources, we might consider herbal extracts from tropical greens to get additional benefits from greens, like the powerful antiparasitic, antioxidant, and polyphenolic components that we have evolved to consume! We can use tropical herbs as functional foods and reap the health benefits of their unique bioactive molecules and nutrients.

• The most famous example is moringa green powder.
• Some nutritional supplements are made from tropical leaf extract: Guava leaf extract for zinc or curry leaf extract for iron are available.
• Other supplements to consider are algae: Green algae, red calcium algae, sea moss, kelp with iodine, etc. As with all supplements, quality is key.
• Teas are also an easy-to-find addition, like guava leaf tea, papaya leaf tea, or mango leaf tea, which are known for their benefits to people living in the tropics.

Read more about greens in the natural human diet here.

If you like to read more on species-specific foods in the human diet, visit our food group overview.

References

1. Yoshimura, H., Hirata, S. and Kinoshita, K. (2021) ‘Plant‐eating carnivores: Multispecies analysis on factors influencing the frequency of plant occurrence in obligate carnivores’, Ecology and Evolution, 11(16), pp. 10968–10983. doi:10.1002/ece3.7885. 
2. Kaczmarek, B. (2020) ‘Tannic acid with antiviral and antibacterial activity as a promising component of biomaterials—a Minireview’, Materials, 13(14), p. 3224. doi:10.3390/ma13143224. 
3. Leterme, P. et al. (2006) “Mineral content of tropical fruits and unconventional foods of the Andes and the Rain Forest of Colombia,” Food Chemistry, 95(4), pp. 644–652. Available at: https://doi.org/10.1016/j.foodchem.2005.02.003.
4. Milton, K. (1999) ‘A hypothesis to explain the role of meat-eating in human evolution’, Evolutionary Anthropology: Issues, News, and Reviews, 8(1), pp. 11–21. doi:10.1002/(sici)1520-6505(1999)8:1<11::aid-evan6>3.0.co;2-m. 
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15. Kaczmarek, B. (2020) ‘Tannic acid with antiviral and antibacterial activity as a promising component of biomaterials—a Minireview’, Materials, 13(14), p. 3224. doi:10.3390/ma13143224. 
16. Takemoto, H. Phytochemical Determination for Leaf Food Choice by Wild Chimpanzees in Guinea, Bossou. J Chem Ecol 29, 2551–2573 (2003). https://doi.org/10.1023/A:1026366119705 
17. Hoglund, S. (2020) How and why to Rotate Your Greens for smoothies: Blender Babes, Blender Babes – Healthy Smoothie Recipes | Blendtec vs Vitamix Reviews. Available at: https://www.blenderbabes.com/articles/food/green-smoothies-alkaloid-buildup-why-its-important-to-rotate-your-greens/ (Accessed: 30 October 2023). 
18. S. Sayago-Ayerdi, D. L. García-Martínez, A. C. Ramírez-Castillo, H. R. Ramírez-Concepción, M. Viuda-Martos, Tropical fruits and their co-products as bioactive compounds and their health effects: A Review. Foods. 10, 1952 (2021)
19. Leterme, P. et al. (2006) “Mineral content of tropical fruits and unconventional foods of the Andes and the Rain Forest of Colombia,” Food Chemistry, 95(4), pp. 644–652. Available at: https://doi.org/10.1016/j.foodchem.2005.02.003.
20. Orwa C, A Mutua, Kindt R , Jamnadass R, S Anthony. 2009 Agroforestree Database: A tree reference and selection guide version 4.0 (http://www.worldagroforestry.org/sites/treedbs/treedatabases.asp)
21. Author unknown (No date) Musanga cecropioides. Useful tropical plants Available at: https://tropical.theferns.info/viewtropical.php?id=Musanga%2Bcecropioides (Accessed: 30 October 2023). 
22. Hill, A. (2020) 7 emerging benefits and uses of Papaya Leaf, Healthline. Available at: https://www.healthline.com/nutrition/papaya-leaf#2.-May-promote-balanced-blood-sugar (Accessed: 30 October 2023). 
23. Okra leaves Information, Recipes and Facts. Specialty Produce. Available at: https://specialtyproduce.com/produce/Okra_Leaves_8953.php (Accessed: 30 October 2023). 
24. Abotsi WM, Woode E, Ainooson GK, Amo-Barimah AK, Boakye-Gyasi E. Antiarthritic and antioxidant effects of the leaf extract of Ficus exasperata P. Beauv. (Moraceae). Pharmacognosy Res. 2010 Mar;2(2):89-97. doi: 10.4103/0974-8490.62958. PMID: 21808547; PMCID: PMC3140113.