Debunking the paleo diet | Christina Warinner | TEDxOU

Debunking the paleo diet | Christina Warinner | TEDxOU


Translator: Kelly Burt
Reviewer: Laura Díaz Aguirre Thank you, it’s a pleasure to be here. I’m an archaeological scientist and I study the health
and dietary histories of ancient peoples using bone biochemistry and ancient DNA. I’m here because I want
to talk to you about the Paleo Diet. It’s one of America’s fastest growing
diet fads. The main idea behind it is that the key
to longevity and optimal health is to abandon
our modern agricultural diets, which make us ill, and move far back in time
to our Palaeolithic ancestors, more than 10,000 years ago,
and eat like them. Now, I’m really interested in this idea because it purports to put
archaeology in action, to take information we know about the past and use it in the present
to help us today. Now, this idea was really started
in the 1970s with this book, “The Stone Age Diet.” It’s diversified since then
into several variants, including the Paleo Diet,
the Primal Blueprint, the New Evolution Diet, and Neanderthin, and most of the language of these diets
makes references to anthropology, nutrition science,
and evolutionary medicine. The diet does seem
primarily targeted at men, so if you look at advertisements
and descriptions, they have virile, cavemen-like images, things like “live primal,”
lots of red meat. And basically, the idea behind it
can be broken down into four parts. One is that our agricultural diets today
make us chronically ill, that they are out of sync
with our biology. And two, that we need
to abandon these agricultural diets that started
during the agricultural period, and move back in time to the Palaeolithic and eat more like our ancestors
over 10,000 years ago. Third, that we know
what these diets were like, and what they were like was they had a lot
of meat, they were mainly meat based. That was supplemented with vegetables
and fruits and some nuts and oils, but it definitely did not contain
grains or legumes or dairy. And fourth, that if we
emulate this ancient diet, it will improve our health
and make us live longer. So what I want to talk to you about today
is that this version of the Paleo Diet that’s promoted in popular books,
on TV, on self-help websites and in the overwhelming majority of press
has no basis in archaeological reality. So, thank you! (Laughter) No, I’m not going to end there;
I will explain. So what I want to do
as an archaeologist is go through this, do a bit of myth-busting of some of these
foundational archaeological concepts upon which it’s based, and then I want to talk to you
about what we really do know from the archaeological record and from scientific studies
about what Palaeolithic people did eat. So, myth one is that humans
are evolved to eat meat and that Palaeolithic peoples
consumed large quantities of meat. Humans have no known
anatomical, physiological, or genetic adaptations
to meat consumption. Quite the opposite, we have
many adaptations to plant consumption. Take, for example, vitamin C. Carnivores can make their own vitamin C,
because vitamin C is found in plants. If you don’t eat plants,
you need to make it yourself. We can’t make it, we have
to consume it from plants. We have a longer digestive tract
than carnivores. That’s because our food
needs to stay in our bodies longer, so we have more time
to digest plant matter. We need more surface area,
we need more microbes. We have generalist dentition, so we have big molars that are there
to shred fibrous plant tissue. We do not have carnassials, which are the specialised teeth
that carnivores have to shred meat, and we do actually have
some genetic mutations in some populations that are adaptive to animal consumption,
but it’s to milk, not meat, and these arose in certain populations
during agricultural periods primarily in Europe and Africa. I call this “The Meat Myth.” The idea behind it
is that we should eat all this red meat, but that’s just really not true. The meats on this plate of meat here are from fattened cattle,
these are domestic animals. Anything a Palaeolithic
person would have eaten would have probably been very lean,
probably small, and they wouldn’t really
have eaten that much meat. Of course there’s also
bone marrow and organs, these would have been very important. We see evidence of harvesting
of bone marrow in faunal assembles where you see characteristic
cutting open of the bones, like you see here, for marrow extraction. Now sure, people did eat meat, and especially in the Arctic and areas with long periods
where plants were not available, they would have eaten a lot of meat. But people that lived
in more temperate or tropical regions would have had a very large
plant portion of their diet. So where does this Meat Myth come from? There’s really two places, and one is the inherent bias
in the archaeological record. Bone is 80% mineral by weight,
it’s going to preserve better and longer over thousands of years
than delicate plant remains. But the other issue comes
from some early bone biochemistry studies that were performed
on Neanderthals and early people. This bone biochemistry study is based on something called
nitrogen stable isotope analysis. It’s complicated, but I’m going
to try and break it down. The basic idea is that you are
what you eat, and so we – there’s nitrogen-15 and nitrogen-14,
heavy and light versions of nitrogen – and we consume this nitrogen in our food. But there’s one important difference, and that is, with each step
that you go up the trophic hierarchy, the amount of the heavier
isotope increases. So if you measure
the amount of heavy isotope in the bone, you can infer where that individual
was on a food chain. This is an example
of a generalized isotopic model. I’ve plotted where plants generally fall,
and above them are the herbivores, and then above them, the carnivores. But one of the problems is that not all
ecosystems conform to this model. There’s a lot of regional variability,
so if you don’t understand the region, you can come to erroneous conclusions.
I’ll give you some examples: we can take East Africa;
if we measure animals and ancient humans, in East Africa, we see
some very strange patterns. First of all, how can a human
be higher than a lion? Lions only eat other animals. And then,
how is this herbivore above a lion? Well, it turns out
that the food that you eat is not is not the only contributor
to these isotopic values. and that aridity can also have an impact. So what we’re likely seeing here
is differences in water access. So let’s move out of the savannah
and move into the tropical areas. Let’s look at the ancient Maya;
again we see something anomalous. We see the ancient Maya
lining up with jaguars. Now, we know the ancient Maya
had a diet heavily reliant on corn. So what’s happening here? We don’t exactly know,
but we think this may have to do with the way they performed agriculture
and how they fertilised their crops. Now let’s go to the Pleistocene. We see some
really interesting patterns here too. We see reindeer plotting very low,
in the range of plants. We see wolves plotting normally
where you would see herbivores, and we see mammoths
spanning all three levels, at once plants, herbivores and carnivores. So what we think is happening here is that in very cold climates,
animals eat unusual things. and in this case
what we think is happening is these mammoths
are eating lichens and bark and that’s giving them
very strange values. So if we now go to humans, ancient humans,
Palaeolithic humans, and Neanderthals, we see that they plot in the same
isotopic space as wolves and hyenas. Now that’s true, but as I’ve shown,
if you don’t have good control over the regional isotopic ecology,
you can come to an erroneous conclusion, and I think it’s premature to say this is very strong evidence
of meat consumption, given how very little we really know
about the Palaeolithic ecosystems. So, myth two is that Palaeolithic peoples
did not eat whole grains or legumes. Now, we have stone tool evidence
from at least 30,000 years ago – that’s 20,000 years
before the invention of agriculture – of people using stone tools that look like mortars and pestles
to grind up seeds and grain. More recently
we’ve been developing techniques where we can actually measure
this thing called “dental calculus.” It’s very interesting:
it’s fossilized dental plaque. We can go in the individual mouths
of people, pull out that plaque and recover microfossils
of plants and other remains. My team is working on developing
methods to extract DNA and proteins, and other research groups
are focussing on these microfossils like starch grains, pollen and phytoliths. Now, we’re still in early days here, but even with the limited
research we have, we can say that there is an abundance
of plant remains inside the dental calculus
of Paleolithic peoples. And these things include
grains, including barley. We’re finding barley inside
Neanderthal teeth, or inside the plaque. We also have legumes and tubers. So, myth three is that Paleo Diet foods,
in the fad diet, are what our Palaeolithic ancestors ate. That’s just not true. Every single food that’s pictured
in these advertisements are all domesticated foods,
products of farming, of agriculture. They’re from the Neolithic transition. Let’s give an example – bananas. Bananas are the ultimate farmer’s food. They can’t reproduce in the wild anymore. We’ve bred out their ability
to make seeds. So every banana you’ve ever eaten is a genetic clone of every other banana,
grown from cuttings. They’re definitely a farmer’s food. If you were to eat a wild banana,
it is so full of seeds that I bet many people in this room
wouldn’t even recognize it as edible. Let’s take salads, that seems
like a really great Paleo Diet food. Except that we’ve radically changed
the ingredients to suit our needs. So, wild lettuces contain
a great deal of latex, which is indigestible
and irritates our gastrointestinal system. It’s bitter, the leaves are tough. We’ve domesticated them
to be softer, to produce bigger leaves, to remove the latex and the bitterness, remove the spines that grow on the leaves and stems of wild varieties,
make them tastier for us. The tomato that’s shown here lacks the tomatine and solanine toxins
that are present in its wild relatives, which are all members
of the poisonous nightshade family. If we look at oil, it’s true that olive
oil is the only natural vegetable oil that can be harvested
without synthetic chemicals. Except, it still requires at least
rudimentary presses to remove it, something that no Palaeolithic person
would have ever built. This is a farmer’s food. This is a model diet I found on a website. It looks like a delicious
and nutritious breakfast, but a Palaeolithic person
wouldn’t have had access to it. First of all, the blueberries
are from New England, the avocados, from Mexico,
and the eggs, from China. (Laughter) This would have
never appeared on any Palaeolithic plate. And last, we have this problem of size. Domestic blueberries
are twice the size of wild blueberries. We’ve already talked
about bananas; you look at avocados. A wild avocado has maybe
a couple millimetres of fruit on it, and the same goes for wild olives. And of course chickens, chickens
are prolific producers. They lay eggs almost every single day. They’re predictable, large and abundant. If you’re trying to collect
wild eggs, they don’t lay year round, and they’re not as easy to find,
they’re typically small. But maybe you’re not convinced, so I’m going to give
just a couple more examples. This, you may all recognise as broccoli. Broccoli did not even exist
in the Palaeolithic period. What you see on the left
is wild broccoli – looks quite different. Now, wild broccoli is also:
wild cabbage, wild cauliflower, wild kale, wild kohlrabi and wild Brussels sprouts,
they’re all the same species. The only difference is they’re
different cultivars. We’ve selectively bred the same species to produce the kind of food
that we like best. These are human inventions. Broccoli, I think, is an interesting
example because it’s this weird thing. What even is broccoli? It’s such a strange looking vegetable. (Laughter) In case you don’t know, it’s flowers,
the flower of the plant. We’ve changed this wild plant into something that produces
so many dense flowers. It produces this odd,
stalk-like thing, but it is flowers. If you don’t believe me,
buy some broccoli at your grocery store, put it in a vase, like I did
on the right, and it will bloom. It makes a lovely, lovely bouquet. (Laughter) So let’s talk about carrots next. You all recognise the carrots
on the right, but wild carrot is what’s on the left. It contains falcarindiol and other
things that are natural pesticides. They’re bitter in flavour
and they taste really bad, and we’ve bred them out
and we’ve also expanded them made them much bigger, much sweeter,
and much more full of vitamins, because that’s what we want. Many of you may not know this, but almonds and apricots are extremely closely related
species of prune. The main difference is that
we’ve bred out the cyanide in almonds, so that we can eat the seed, and we have selected for bigger,
thicker fruits in apricots, because that’s what we want
to eat from that particular species. They’re very closely related and,
like carrots and broccoli, they are essentially human inventions. So let’s talk about some real Paleo diets. First of all, I need to clarify
that there is no one Paleo diet. There are many, many Paleo diets. People, when they spread out
across the world, colonised the continents, they ate local foods, and of course
they were extremely variable. So when we speak about Palaeolithic diets, it’s very important
to speak of them in the plural. Let’s take a closer look
at one in particular; we’re going to go 7,000 years
back in time to Oaxaca, Mexico, and right now you’re looking at the view
outside of the Guilá Naquitz rock shelter, one of the earliest sites in Mexico. This is a photograph
that I took in December, and people would have
been living here at this time, and what you are essentially
seeing right now is dinner. And this is a far cry from anything
that you would find on the Paleo Diet and anything you would find
in your modern supermarket. But, there was plenty of food here
for people to eat on a seasonal basis. So, September was high time
at Guilá Naquitz. This is when a lot of people
would have come in and occupied these rock shelters, and they would have eaten
the local resources. And if you notice,
this includes a lot of fruit, legumes, agaves,
that’s what we make tequila from today. Various nuts and beans and squashes
and wild game, predominantly rabbits. But by the time April came around, there was very little
edible food in this region so they would have moved on to other
places where food was more abundant. So if we take a step back and say, “Well, what can we really learn about the Palaeolithic diets
around the world?” There are some general
observations we can make. One is that they are regionally variable. People in the Arctic have
and will eat something different than people in the tropics. They have different resources. So people who live in places
with no plants tend to eat more animals, and people who live in places
where there are plants tend to eat more plants. They’re going to be seasonally variable, because plants seed and fruit
at different times, herds migrate and fish
spawn on a seasonal cycle. As these things happen, people have to move
from resource patch to resource patch, which means that there is periodic high
mobility, sometimes over long distances. Once again, it depends on the region. Food packets were generally small; if you go around collecting wild broccoli, you’ll have to collect an awful lot of it to be the equivalent
of its domesticated variety. The foods that you would have collected would have been
generally tough, woody and fibrous. You would eat meat, but you would
also eat the marrow and the organs of the animals you collect,
and they’d generally be very lean. Finally, the plants you’d eat would still contain a lot of toxins
at various levels, and phytochemicals, some of which
actually have very good health benefits. But it’s almost impossible
for us now to eat this sort of diet. Three billion people cannot eat
like foragers on this planet, we are too big. So, can we take lessons
from these Palaeolithic diets that we still can apply
to our lives today? And the answer is, ‘yes.’ I think there’s three main
lessons we can learn: First, there’s no one correct diet,
but diversity is the key. So, depending on where you live, you can eat very different things,
but you need diversity. We lack the ability to synthesise
many nutrients that we require for life, nutrients and vitamins, and we are required
to get them from our foods. Eating a diet that’s rich in species,
has high species diversity is very important. Now unfortunately in American diets today, the trend is going
in the opposite direction. If you go and you take a processed food
off a grocery store’s shelf, it doesn’t matter if it’s cake
batter, mayonnaise or coffee creamer, increasingly there is only three species
in almost everything we eat. We have corn, soy and wheat. That’s opposite direction
we need to be going. Second, we evolved to eat fresh foods,
in season, when they are ripe. That’s when they have their highest
nutritional content. But, of course, we have to also talk
about food storage and preservatives, because in large urban societies, you can’t always eat
everything fresh; food spoils. Some foods preserve naturally well;
these include things like seeds and nuts, and that’s why traditionally they’ve been
so important to agricultural populations. But we can preserve them in other ways,
through salting, through sugar, vinegar. We can pickle them, we can smoke them, we can dry them, we can add
artificial preservatives. What I find very interesting about this
is that these all work in the same way. They work by inhibiting bacterial growth. But we have to keep in mind that our gastrointestinal systems
are also full of bacteria, good bacteria that do
many good things for you: they digest your food,
regulate your immune system, promote mucosal function. If you eat foods full of preservatives, how does that affect your microbiome,
your good bacteria within you? And the answer is, ‘We really don’t know.’ And it’s something
we’re only starting to investigate. And third, we evolved to eat
whole foods in their complete package, with their fibre
and their roughage and everything. It turns out this is really important, that your foods are not just the sum
of the calories and the vitamins. But even the parts you can’t digest
are very important. The fibre that you eat regulates the speed at which
the food travels through your gut. It modulates metabolism,
it slows down the release of sugars, it has all sorts of functions, it feeds
the good bacteria that live in your gut. And increasingly we’re seeing
that low fibre diets are associated with microbial communities that cause things
like obesity and diabetes. What’s unfortunate also in the globalised
system of processed foods is that we’re losing these connections,
we’re losing the whole food, and we’re eating reconstituted,
concentrated foods, and we don’t get the benefits
of having, for example, the fibre and pectin in the fruit juice
because it’s been filtered out. We’re losing all of this balance. And, as an example
of how this thing gets so out of balance, we can eat so many more calories, so much more food in a very small package
without realising it, and that short-circuits our abilities to know when we’re full
and when we’ve had enough. So I have a question,
and my question is, I was wondering, Does anyone here know, if you take
a soda, let’s say a 34 ounce soda, which is increasingly becoming the normal
size, like this one, and you drink it – imagine that you’re back
in the Palaeolithic period, and you want to consume
the equivalent amount of sugar. How much sugar cane,
if you stumbled upon a sugar cane field, how much would you have to eat, how many feet of sugar cane
do you think you’d have to eat? I brought some sugar cane. How many feet of sugar cane do you think
you’d have to consume to reach that level? Any ideas? One… how many sticks do you
think you’d have to eat? They’re pretty big. Not quite 40 feet. You’d have to eat 8.5 feet of sugar cane
to reach that level. That’s an awful lot of sugar. There is no physical way
that a Palaeolithic person could have possibly eaten that much
sugar cane, even if they really wanted to, and now you can consume
it in about 20 minutes. So, by decoupling the whole food
from the nutrients inside of it, we trick our bodies
and we can override the mechanisms that we’ve evolved to signal
fullness and satiation. These are the three main lessons I think
we can learn from real Palaeolithic diets: there’s no one correct diet,
but dietary diversity is key, that we need to eat
fresh foods when possible and that we need to eat whole foods. So, anthropology and evolutionary medicine
have a lot to teach us about ourselves and new technologies
are opening up new windows into the past. But we still have a lot to learn from our Palaeolithic
and our Neolithic ancestors. Thank you. (Applause)