Have you ever noticed our human eyesight is perfect at finding colorful fruit? Have you ever thought about how fruit smells so good to us that we make perfumes out of their scent? These observations may lead you to ask if humans are frugivores (animals that prefer a diet of fruit). But everyone says we’re omnivores, right?
Humans today are categorized as omnivores and not frugivores. However, we likely evolved from tree-dwelling frugivores, and the healthiest populations on Earth eat plant-centered diets. The ideal diet for human thriving seems to be mostly plant-based, but it’s unclear if fruit should be the focus.
In this post, I’ll cover this question from three different angles:
- What diet does our anatomy and physiology suggest? Do we have the body of an herbivore, omnivore, frugivore, or what? (Skip to this section.)
- What diet does our evolutionary history suggest? What did our early hominid ancestors eat? And what do our primate cousins eat today? (Skip to this section.)
- What diet leads to the best human health in practice? Are most fruitarians healthy? Which diet has been shown to lead to the best longevity? (Skip to this section.)
But first, let’s cover some terminology!
Omnivore vs Frugivore
There’s no point in writing thousands of words about whether humans are frugivores or omnivores if we’re not clear what we mean by the terms we’re using. So, some definitions:
- Omnivore: An animal that eats plant and animal matter. There are nuances within this category: We can speak of omnivory in behavioral or physiological terms. It’s not just what you do eat but also what your body is capable of deriving energy from. Omnivore also does not imply 50% plants, 50% animals. (Many of our primate relatives are categorized as omnivores but eat around 95% plants.)
- Frugivore: An herbivore or omnivore whose preferred food type is fruit. Frugivores typically consume other food groups, too: Seeds, roots, leaves, and maybe insects or other animal sources of protein. But the biggest single chunk of the diet is fruit. (Chimps are frugivores, eating about 48% fruit.)
Notice this important detail: Many animals that are frugivores are also omnivores, technically. The terms are not actually mutually exclusive. “Omnivore” refers to the scope of the diet, while “frugivore” refers to the emphasis of the diet.
Something else to recognize: There’s a basic, definitional sense in which humans are undeniably omnivores. We’re clearly capable of deriving energy from plants and animals, and across our species, most humans do eat both.
However, that’s not really the point when people debate whether humans are herbivores, omnivores, carnivores, or frugivores. What we’re really asking is this: What is the human body truly adapted to eat? What diet do we most thrive on?
And that will be the focus of this post. Let’s start with what diet our anatomy suggests.
Frugivore Anatomy and Physiology
You may have seen charts or memes that place pictures of human teeth or intestines side-by-side with carnivores, omnivores, and herbivores, making arguments about which category we belong in.
When these images are shared by meat-eaters, they typically emphasize the canine teeth in humans. When posted by vegans or vegetarians, they may emphasize the molars or small mouth opening.
In truth, our anatomy is obviously going to resemble that of other primates the most, since we are most closely related to them. And yes, these primates—chimps, bonobos, etc—are mostly frugivores.
But let’s dig a bit deeper into our human anatomy and the diet it suggests, beyond the superficial details.
Frugivore Digestive System?
The digestive tract is the most obvious part of the body to examine to determine the diet we were made to eat.
Teeth, Jaw, and Mouth
Food enters here first, and there’s already a lot we can observe:
- Teeth: What are human teeth designed to eat? Many people point to our canines as evidence we’re designed to eat meat. But this is a weak argument, as our canines are much smaller than those of true omnivores like dogs. Also, keep in mind: Many herbivores and frugivores (like gorillas and the male musk deer) have big canines despite not eating much (if any) meat. Below I’ll cover more about the fossilized teeth of early humans and what they suggest about their diet.
- Jaw: Our jaw hinges and moves more like an herbivore’s, including side-to-side movement for grinding plant matter, along with a lack of shearing action by having our molars directly on top of one another.
- Tongue: Our tongue lacks the protein receptors and fat receptors that omnivores and carnivores typically have. These receptors make raw, unseasoned meats more appealing to true omnivores. Humans today must cook and season meats with plants and salt to find it appetizing.
- Size of mouth opening: Our small mouth opening (relative to overall head/body size) also puts us in the same category as other herbivores and frugivores. It’s a mouth that simply does not seem to be designed to catch animals or gulp down big hunks of meat.
- Salivary Enzymes: We have ptyalin in our saliva, which is a type of amylase, anenzymeused to digest starches—but omnivores and carnivores don’t have this in their saliva. Interestingly, humans have much more amylase than chimps or bonobos, suggesting we’ve evolved further toward starch digestion since diverging from them evolutionarily. (source)
So far, humans look more like herbivores or frugivores than true omnivores… But let’s continue.
Intestines and Acidity/Alkalinity
Moving inside the abdomen now:
- Intestine length: Human intestines are about 10-12x the length of our trunk, which puts us in line with the herbivores. Omnivore and carnivore intestines are much shorter, typically about 3-6x of trunk length.
- Intestine shape: Our intestines have more pockets, pouches, and ribbing where plant matter will catch, sit, and slowly digest. This is opposed to carnivore and omnivore intestines, which are more smooth.
- Digestion Time: As an effect of the shape and length of our intestines, the time it takes for us to digest food is much shorter than true omnivores or carnivores. Here, too, we fit in with the frugivores and other herbivores.
- Relationship with Fiber: Although we are clearly not ruminant herbivores like cows who actually feed on cellulose, we do require plant fiber to stimulate peristalsis (the churning movement in our GI tract). Carnivores and omnivores do not require fiber in this way.
- pH Levels: The stomachs of carnivores and omnivores are very acidic, around a pH of 1. This helps them to dissolve bone, feathers, claws, and other such features of their prey. Herbivore stomach pH is around 4 or 5—and that’s where we are, too. Our saliva is also more alkaline, like an herbivore, and so is our urine.
- Urine: There’s another key indicator besides the pH levels in our urine, and it’s this: Carnivores and omnivores have very concentrated urine. Meanwhile, human urine concentration tends to be more in the range of herbivore levels, much lower.
Frugivore Anatomy: Beyond the Digestive System
Even on the outside of our bodies, we have several distinct characteristics we can observe as similar to those of other frugivores:
- Eyesight: We have trichromatic vision (blue, yellow, red). Dogs and other meat-eaters typically don’t see color, or not as vividly. And our color vision, shared with other primates, served a purpose evolutionarily—it allowed us to identify fruits and other colorful plant foods.
- Sense of Smell: Humans are attracted to fruity scents, and we often choose fruit scents as perfumes. Dead animals typically smell bad to us—but this may actually reflect an adaptation to scavenging in our past. The fact that decaying corpses smell bad to us may have helped us only choose the fresh corpses when scavenging meat.
- Hands: We don’t have claws to help us catch or cut open prey. Of course, we’ve been able to fashion tools that let us catch, cut, and kill, but these tools aren’t built into our bodies, as they are for omnivores like bears. Some people argue our hands were specifically designed for grabbing fruit—but I don’t know if I’d go that far. Our hands are useful for many things that would’ve been evolutionarily advantageous, not just grabbing fruit specifically.
Frugivore Psychology and Behavior
Beyond our anatomy, how do we think and act in comparison with herbivores, omnivores, and carnivores?
- Repulsion From Killing and Raw Meat: When you see raw, uncooked meat, does it look appetizing to you? And do you like to watch animals die? Most of us would say “no” to these things. In fact, slaughterhouse workers often suffer from PTSD from repeatedly killing animals all day. The fact is that we’re not naturally drawn to killing animals or their uncooked, unflavored corpses in the same way that we’re naturally drawn to the appearance and aroma of fruit.
- How We Drink Water: This one’s kind of strange—but it’s a simple consequence of the mouth shape details noted above. Have you noticed that carnivores typically drink water by lapping it up? And in contrast, we drink water by sipping it up. If you look across many different species, you’ll see a pattern: It’s the herbivores who sip water like we do.
- Amount of Sleep: Carnivores typically sleep most of the day, with short periods of activity for hunting. Herbivores tend to need less sleep. Some herbivores, like horses, only sleep for ~2 hours a day. Our sleep times are a bit lower than most other omnivores, suggesting yet again, more kinship with the herbivores.
So again, it’s no surprise that in most of these measures, we’re most similar to the chimps, bonobos, and other primates, who are frugivores.
But the fact that our anatomy and physiology still look and function mostly like that of an herbivore (or frugivorous omnivore) is still worth noting, independent of our actual history and lineage.
Our species has clearly shown an ability to survive on many different diets throughout history—but, for the most part, it seems we’re still carrying around the bodily equipment of a frugivore.
The History and Evolution of the Human Diet
To get a better picture of our species-specific diet, we can also look at historical and evolutionary evidence.
To do this, let’s first look at the diets of our closest living relatives today, the other primates. Then, let’s look at the evidence for what our early human ancestors ate.
Our Closest Primate Relatives
If we look at chimpanzees and bonobos, with whom we share the most genetic material, they are frugivores, indeed. Bonobos have a diet of 57% fruit, and chimps have a diet of 48% fruit. (source, source)
Orangutans are even more frugivorous, with 61% of their diet coming from fruit, but we are less closely related to them. (source)
It should be noted: These figures still leave plenty of room for other dietary components, too: Leaves, seeds, nuts, honey, termites, buds, and other foods. But fruit is #1.
It’s also interesting to note: Chimpanzees do hunt, but not as a mainstay of their diet—meat is less than 2% of what they eat (source). Meanwhile, bonobos do not hunt, but they will sometimes eat meat opportunistically.
What Did Humans First Eat? Were Early Hominids Frugivores?
If we go back to our Australopithecus ancestors who lived a few million years back, their diets are certainly believed to have been plant-based. But there’s debate about which foods were dominant. (source)
Since many of our ancestors likely lived on the plains of Africa, some may have relied more on grasses, root vegetables, nuts, and seeds compared to tree-dwelling species that came before them. But there’s still evidence of fruit consumption by our bipedal ancestors. (source, source)
In fact, some research does point to a possibility that all species before Homo erectus were frugivores. A famous 1979 NY Times article broke that news from Dr. Alan Walker’s research, which was based on studying hominid teeth with an electron microscope.
There’s a lot more research that’s been done on many of these early human ancestors. Unfortunately, I’m not an expert who can guide you through all of it or settle any disputes. If you’re really trying to go deep with this issue, you’d want to start by looking at these species:
- Australopithecus afarensis (~3 million years ago)
- Homo habilis (the first to make tools, ~2 million years ago)
- Homo erectus (bigger brains, lived until ~100,000 years ago)
- Homo neanderthalensis (lived until ~40,000 years ago)
The Evolution Toward Starch and Meat
So the general picture of our ancestor’s diets seems to be that we likely came from a tree-dwelling frugivore species, as did the other primates—but our diet has also changed a lot based on our environment since then.
Part of what changed was not just our geographical environment but our ability to use tools. With Homo habilis (~2 million years ago), we see the use of stone tools.
Stone tools made it easier to eat meat, as well as starch like hard tubers. Even before the use of fire for cooking, these foods could be prepared by “slicing, pounding, or flaking.” (source)
It’s possible that these changes in our diet were part of what allowed our species to evolve into the animals we are today. Starch and meat are more calorie-dense than fruits or leaves—they likely fueled our nomadic spread across the planet.
Meat-eating in our ancestors likely began with scavenging. But there are now fossil records of early hominids (most likely Homo habilis) hunting for meat ~2 million years ago (source). So at least some meat has been part of the human diet for a long time.
With Homo erectus (just after Homo habilis), we see evidence of group hunting to kill even large mammals like elephants, along with fire for cooking. In Homo erectus, Dr. Walker’s research did finally show evidence of an “omnivorous” diet, not a frugivorous one.
There Is No Single “Ancestral Diet”
When you take all the above evidence into account, the overall picture is that there isn’t one “ancestral diet” to our species. We’ve evolved throughout many times, living in many places on the globe.
This was a point emphasized by Peter Unger, a professor of paleoecology writing in Scientific American: Our ancestors all ate different diets based on the region in which they lived.
Depending on the time of year, too, different plants are in bloom and different game is present. The flexibility of our diet has been one of its most characteristic features.
As Dr. Ungar writes, “What was the ancestral human diet? The question itself makes no sense.” There wasn’t just one.
Even between Australopithecus species living in Eastern Africa vs South Africa, diet is believed to have differed greatly. And then as Homo sapiens, we started traveling all over the planet!
If you go far back enough, yes, we likely evolved from frugivores, like the other primates. But how useful is that statement, really? If you go even further back, we also evolved from sea-dwelling animals! So there’s a limit to saying we should eat our ancestor’s diets.
And we shouldn’t assume our ancestors necessarily had the best diet from a health perspective. To reproduce, they only needed to live a couple of decades. They probably didn’t live long enough to get heart disease from a bad diet. So we don’t necessarily know if their diet was optimal for longevity and disease prevention.
The real question is what diet actually works best for us in practice, today.
In another blog post, I’ve written all about human civilizations that have eaten plant-based to one degree or another. From India to Japan, from Buddhism to specific Christian groups, there’s a lot of interesting history to uncover.
But to assess how well we’re fitted to a plant-based diet—and specifically fruit—we should perhaps look at the nutritional science on fruit-based diets directly.
So let’s cover that now!
Is It Healthy to Eat Mostly Fruit?
When humans choose to eat a diet of mostly fruit, we usually call that a fruitarian diet.
Usually, in practice, this is a raw vegan diet containing no animal products or cooked foods. Usually, it contains fruits and vegetables, with most calories coming from fruit.
Probably the most popular kind of fruitarian diet is described in Dr. Douglas Graham’s book 80/10/10 (Amazon link). The title of the book is a reference to the macronutrient ratio: 80% carbs, 10% fat, 10% protein.
A fruitarian diet is sometimes also called a high-carb low-fat (HCLF) vegan diet. However, “HCLF vegan” is actually a broader term that can also include starch-based diets which are much lower in fruit. (I have a full post about HCLF veganism here.)
So let’s look at whether fruitarian diets tend to work well for humans in practice.
Benefits of High-Fruit Diets
In 2012, the Global Burden of Disease Study determined that the #1 dietary risk factor in the world was not eating enough fruit. The study estimated that nearly 5 million people per year die from not eating enough fruit.
This suggests that fruit may be very important to our diet, indeed! But can we eat too much fruit? A lot of people are concerned about the sugar in fruit.
One study found that in overweight patients with type-2 diabetes, there was no benefit to restricting fruit intake. That’s pretty remarkable considering that diabetics are (understandably) often told to limit sugars.
Fruit comes naturally packaged with components like fiber and polyphenols that actually seem to offset the potentially harmful impacts of sugar. Studies have found that if you add berries to a sugary meal, it actually decreases the blood-sugar spike following that meal.
But still. This is not evidence that fruit should be the majority of your diet. What does the research say about people eating a lot of fruit?
Well, I couldn’t find a lot of great, peer-reviewed research on long-term fruitarians.
This study put test subjects on a diet of 20 pieces of fruit per day, along with loads of vegetables, too, for two weeks. All health changes observed were positive, including a significant reduction in LDL (bad) cholesterol.
So again, it looks good, but that’s only two weeks. What about anecdotal evidence?
Fruitarian Success Stories
Certainly, there are stories of high-fruit diets going very well for specific people. Ultramarathon runner Michael Arnstein was interviewed on CNN about his fruitarian diet. He gives a glowing review, saying at one point, “It’s almost made me superhuman.”
But how much of this success can be attributed to the exercise side of his lifestyle? In another video, Arnstein talks about how, at the time, he was running 15 to 30 miles per day. Seriously. He says he just runs to work each day instead of driving.
Many other high-profile fruitarians are also fitness enthusiasts, often accomplishing great feats in cycling, running, yoga, or other bodyweight sports. It seems to work wonders for some.
One of my favorite raw vegans online is John Kohler from Ok Raw. He’s been living a 99.9% raw diet for over 15 years, with a lot of fruit, and he seems to be doing well and loving it. He explains the differences between his raw diet and others’ in this video.
But not everyone has a glowing review of high-fruit diets.
Potential Downsides of High-Fruit Diets
When Ashton Kutcher was preparing to play Steve Jobs in the 2013 biopic Jobs, he adopted a fruitarian diet for a month. (Jobs himself was a fruitarian for a while.) But at the end of the month, Ashton was in the hospital with pancreatitis! What went wrong?
According to the articles I read, it’s not actually known what caused Ashton’s pancreas problems exactly. But he’s not the only one who’s done poorly on a restrictively high-fruit diet.
Kate Flowers is a vegan YouTuber who followed a fruitarian diet for 3 years and since then, has clearly stated that she regrets it.
She said her hair started falling out on a fruitarian diet. She also said that when she attended Woodstock Fruit Festival—an annual fruitarian festival in upstate New York—many of the attendees looked skinny to an extreme degree. They just didn’t look healthy.
There are also many negative testimonials you can find if you just search online for something like “HCLF vegan weight gain.” Many people who wanted to lose weight on a fruit-heavy diet have actually gained weight.
Below are some of the biggest nutritional drawbacks of long-term high-fruit diets as they’re commonly practiced.
Low in Protein
There are no high-protein fruits. This means a fruitarian diet is potentially even lower in protein than most vegan diets.
It may be the case that humans don’t require as much protein as mainstream nutritional advice often suggests—but we do need enough. And if you want to build muscle, you especially need it.
Frugivorous animals like chimps do eat some other food groups besides fruit, such as seeds, roots, and leaves. And these other foods contain a bit more protein, so they can help assist.
Likewise, fruitarians tend to eat greens and maybe even some nuts and seeds. But still, are you getting enough protein for optimal performance and health? I’m not sure. You’re likely bound to have somewhat low muscle mass on a fruitarian diet.
Andrew Perlot, a raw food athlete who eats mostly fruit, eventually chose to start eating sprouted lentils as a way to combat this relative lack of protein in his own raw diet. So that’s one solution.
Low in Essential Fats
We need a certain amount of healthy fats in our diet. There are a few high-fat fruits, like avocado and durian… But you can’t get much of the prized omega-3 fat from fruit.
For significant amounts of omega-3 fats, we need to go to fish or algae—or at least to specific seeds and nuts that contain alpha-linolenic acid (ALA), a precursor of the omega-3 that our body uses.
Personally, I recommend all vegans (fruitarian or not) supplement with omega-3 from algae. Then you don’t need to worry about your body’s inefficient conversion of ALA to DHA/EPA. Here’s a blog post about the multivitamin I personally take to cover my omega-3.
But some of the more fanatical high-carb low-fat (HCLF) vegans will even warn against taking an omega-3 supplement. I personally think this is horrible advice.
This is what personally led me to move away from a high-fruit diet.
Fruits contain simple sugars, and while fruit is much healthier than processed sugar, it can still cause issues in high quantities.
For me specifically, I noticed that eating high-sugar fruits like bananas and dates worsens my acne.
It’s widely acknowledged that processed sugar is bad for acne—but most people don’t realize fruit can cause the same problems.
I’ve heard from multiple other high-carb vegans that all the bananas exacerbated their acne, too.
If you struggle with acne, you really need to read my big post on how to clear acne as a vegan. It took me years of studying and experimenting on myself to learn what I share in that post. It’s a lot more than just “don’t eat sugar.”
Anyway, too much fruit may also be a problem for diabetics—although that’s a point of some debate.
Since many factors can impact our insulin sensitivity, we won’t all handle the sugars from a fruit meal equally well. How we each handle high-sugar fruits may depend on our genetics as well as our diet and lifestyle leading up to that point.
If someone put a gun to my head and made me eat fruitarian (for some weird reason), I would likely eat a lot of avocado, berries, and greens. Beyond that, I’d focus on juicer fruits—not the densest, sugariest ones.
What are the effects of a high-fruit diet on dental health? Can all the sugars and acid from fruit give you cavities? Apparently, yes—but you may be able to mitigate that with the right steps.
Aside from all the sugar and acid, fruitarian diets also tend to be low in calcium and other nutrients that work with it, such as vitamin D, K2, and magnesium. So if you’re going high-fruit, stay mindful of these nutrients!
One simple tip for lessening dental erosion from acidic fruit is to rinse your mouth with water after the meal. I always try to do this after eating citrus fruits, especially.
Another simple tip is to avoid dried fruits when possible. Not only are they higher-glycemic foods, but they also tend to get stuck in your teeth more, leading to potential cavities.
What Do the Longest-Living Populations in the World Eat?
When it comes to determining the healthiest diet for humans, I often think of the Blue Zones. Blue Zones are specific populations in the world that have the most centenarians, and a longer life expectancy in general.
People living in Blue Zones tend to eat a plant-focused diet. Meat is only eaten about 5 times per month on average, and the servings are about the size of a deck of cards. (source)
But what kind of plants are they focusing on? Is fruit central in any of these longest-living populations? Here’s how much fruit each population eats:
- Loma Linda, California: 27% fruit
- Ikaria, Greece: 16% fruit
- Nicoya, Cost Rica: 9% fruit
- Sardinia, Italy: 1% fruit
- Okinawa, Japan: >1% fruit
So, not super high in fruit—some of them eat almost no fruit, percentage-wise, and they still live far longer than average. What foods do these populations eat the most of? Here’s the biggest piece of the pie for each:
- Loma Linda, California: 33% vegetables
- Ikaria, Greece: 37% vegetables
- Nicoya, Cost Rica: 26% whole grains
- Sardinia, Italy: 47% whole grains
- Okinawa, Japan: 67% sweet potatoes
So they’re all centered on plant foods—not meat. But the most fruit-centered is the Adventists in Loma Linda, California, and they’re still only at 27% fruit. Find the full diet breakdowns here.
Species Specific Diet: Omnivore vs Herbivore
There’s more evidence showing that humans tend to do best on a broadly plant-focused diet, too:
- Only herbivores get atherosclerosis on a meat-based diet. Dogs, lions, and tigers can be given excess saturated fat and cholesterol from meat, and it doesn’t cause them to get clogged arteries (source). But for us, meat does cause atherosclerosis over time—same as for other herbivores.
- A plant-based diet can reverse heart disease. Heart diseases is the #1 cause of death in America. A plant-based diet is the only diet ever shown to reverse heart disease in the majority of patients when combined with other healthy lifestyle changes.
- Only vegans have LDL cholesterol levels in the ideal range. In one study, omnivores averaged an LDL cholesterol of 123 mg/dl, whereas vegans averaged 69 mg/dl. The ideal has been noted to be between 50 and 70 mg/dl.
- Only vegans have an average BMI in the “healthy” range. On average, omnivores are overweight. On average, even pescatarians and lacto-ovo vegetarians are a bit overweight. Only vegans fall into the “healthy” body mass index range. (source)
Are Humans Frugivores? Or Some Other Kind of Herbivores?
Personally, I’m more convinced by the evidence for plant-based diets more broadly, compared to the evidence for a high-fruit diet specifically.
Despite occasional glowing fruitarian success stories, I see many examples of people struggling with fruitarian diets: Acne, weight gain (or unhealthy weight loss), hair loss, cavities, low muscle mass, and possible pancreas issues.
I could be wrong, but I think it’s fair to say a fruitarian diet is not the best overall diet for the majority of people today.
At the same time, I find strong evidence that a broadly plant-based (herbivorous) diet does lead to human thriving. It’s led to the longest-lived populations, heart disease reversal, ideal BMI, ideal LDL cholesterol levels, and more benefits I didn’t even cover here.
So, Are Humans Meant to Eat Mostly Fruit?
I would sum up the story like this:
- Humans inherited the bodily equipment of a frugivorous omnivore from our primate relatives.
- We still have mostly the same digestive system as our frugivore cousins.
- Humans have shown remarkable dietary flexibility throughout evolutionary history—we can live on many diets.
- In practice, humans today seem to get the best results on a mostly plant-based diet.
- There’s more evidence showing peak health on a high-starch or high-vegetable diet than high-fruit specifically.
It makes sense that our ideal diet would be at least somewhat similar to our primate cousins’, which is mostly (but not strictly) herbivorous. But there’s also good evidence we’ve adapted to a higher starch consumption compared to other primates.
Some people seem to do very well on a high-fruit diet, but there are also significant risks when focused narrowly on fruit long-term, and it doesn’t go well for everyone. Ultimately, I wouldn’t really call us frugivores—but we do bear a lot of resemblance to them, and we probably come from frugivore ancestors.
Two More Recommendations for Your Vegan Journey
1. This is the best vegan multivitamin I’ve found in 13 years of being vegan. It has vitamin B12, vitamin D, omega-3—and nothing else. Translation: It only has the nutrients vegans are actually low in. Read my full review of Future Kind’s multivitamin here (with 10% discount).
2. This is the best vegan starter kit I know of. It’s a bundle of 9 beautiful e-books that help you transition to a healthy plant-based diet—the right way. The advice is spot-on, and it has print-outs and checklists that make it easy to implement. Read my full review of Nutriciously here.