Speaker 1: Hey, welcome to Science Stuff production of iHeartRadio. I'm Hora
Speaker 1: Cham and today we are answering the question why can
Speaker 1: dogs eat chocolate? Will a Hershey's kiss be the kiss
Speaker 1: of death for your pooch? Or will a roller bar
Speaker 1: make your dog roll over into the grave? How toxic
Speaker 1: is chocolate to dogs? Why is it toxic? And when
Speaker 1: do dogs evolve this intolerance. We'll talk to a couple
Speaker 1: of veterinary toxicologists and to one dog geneticis to get
Speaker 1: to the nougat center of this question. So come along
Speaker 1: as we answer the question why can dogs eat chocolate?
Speaker 1: I promise the answer won't be rough.
Speaker 2: Hi.
Speaker 1: Everyone, you've probably heard that eating chocolate is bad for dogs. People,
Speaker 1: it seems, can eat a lot of chocolate and chocoholics,
Speaker 1: I'm looking at you, but it seems to be dangerous
Speaker 1: or even potentially deadly for dogs. Now, most people seem
Speaker 1: to think that's because chocolate has a chemical in it
Speaker 1: that is uniquely toxic for dogs, but that is perfectly
Speaker 1: safe for humans. But as we'll learn today, that's not
Speaker 1: really true. First, we'll talk about how serious it is
Speaker 1: if a dog eats chocolate. Then we'll talk about what
Speaker 1: chocolate does to dogs, and in the last segment, we'll
Speaker 1: ask an evolutionary biologist to tell us when scientists think
Speaker 1: this sensitivity evolved in dogs and spoiler alert, it may
Speaker 1: be some humans's fault. Okay, the first topic is how
Speaker 1: serious is it if a dog eats chocolate? So the
Speaker 1: first thing I did was call an emergency hotline, not
Speaker 1: because my dog had eaten chocolate, but to talk to
Speaker 1: one of their experts. So here's my chat with doctor
Speaker 1: Renee Schmidt. Thank you for calling Pet Poison Helpline, a
Speaker 1: twenty four to seven animal poison control center.
Speaker 3: If you are a pet owner, please press one.
Speaker 2: Well, thank you doctor Schmidt for joining us.
Speaker 4: Yeah, thank you so much for having me. I'm doctor
Speaker 4: Rene Schmid with Pet Poison Helpline. I'm the director of
Speaker 4: Veterinary Medicine and senior veterinary toxicologist, so I help educate
Speaker 4: pet owners as well as venary professionals on anything toxin related,
Speaker 4: as well as working with our staff internally.
Speaker 2: Amazing.
Speaker 1: Can you tell us about Pet Poison Hotline.
Speaker 4: We are a twenty four to seven animal poison control
Speaker 4: center and so pet parents as well as veterinary professionals
Speaker 4: can call us, and if an animal has been exposed
Speaker 4: to something that may be toxic, we can assess it
Speaker 4: to determine if the exposure is going to be a
Speaker 4: concern for that animal or not. While the vast majority
Speaker 4: of calls we receive are end dogs and cats, so
Speaker 4: we can help with any species of animal and with
Speaker 4: anything that they get into. So we had a sloth
Speaker 4: that's got into a cleaning chemical. We had a goose
Speaker 4: not too long ago that got into marijuana. You name it,
Speaker 4: and we've probably gotten a call on it. And we're
Speaker 4: staff twenty four hours a day.
Speaker 1: And you said you're all over the country, so we.
Speaker 4: Take calls all over the country and really all over
Speaker 4: the world. So the vast majority of our calls are
Speaker 4: from the United States and Canada. We also take calls
Speaker 4: from the Caribbean and Hong Kong and other countries throughout
Speaker 4: the world.
Speaker 1: Oh my goodness, And how do you cover twenty four hours?
Speaker 1: Are you just constantly on calls.
Speaker 4: Yeah, so we're a busy place. It's amazing how many
Speaker 4: animals get into things that they couldn't. We have employees
Speaker 4: who have ships throughout the day and evenings so that
Speaker 4: we always have veterinarians and technicians who are on and
Speaker 4: ready to take calls at any time.
Speaker 1: How often do you get calls about dogs eating chocolate?
Speaker 4: It's our number one call, It's our most common call.
Speaker 4: I've been here for twelve years, we've been in business
Speaker 4: for twenty one years, and it's been our number one
Speaker 4: toxin every year since we've been keeping track. We always
Speaker 4: look back the year prior to see what was our
Speaker 4: top toxins, and chocolate always I always say it takes
Speaker 4: the cake. It's always number one. You know, if you
Speaker 4: think about it, so many households have chocolate in them.
Speaker 4: Maybe we're cooking with it, we're buying it in different
Speaker 4: products or candy and chocolate itself, or maybe it's in
Speaker 4: brownies and cookies for the holidays, we're gifting it, and
Speaker 4: so maybe it's under the tree, or it's sitting out
Speaker 4: at parties and you know, activities and social events. So
Speaker 4: it's something that is really a commonplace in so many
Speaker 4: households that it smells good, it tastes good, so dogs
Speaker 4: are naturally kind of drawn to it.
Speaker 2: You say it takes the chocolate cake.
Speaker 4: Yes, that's right, it takes the chocolate cake, for sure.
Speaker 1: So, yeah, there are a lot of dogs out there
Speaker 1: eating chocolate. Another animal poison control center would run by
Speaker 1: the American Society for the Prevention of Cruelty to Animals
Speaker 1: or ASBCA, reported that they receive about seventy six calls
Speaker 1: a day of dogs eating chocolate, which translates to about
Speaker 1: twenty seven thousand, seven hundred and forty cases a year. Next,
Speaker 1: I ask sector SMIT, what happens if a dog eats chocolate?
Speaker 1: What are some of the symptoms dogs might exhibit if
Speaker 1: they eat it.
Speaker 4: Yeah, so symptoms are similar to over simulation. So they
Speaker 4: might be a little bit restless, they might be pacing,
Speaker 4: panting that maybe agitate a little bit. They can have
Speaker 4: a high heart rate, They can have a high blood
Speaker 4: pressure depending on how much they ingest. They can have
Speaker 4: heart abnormalities in rhythm abnormalities. Vomiting is certainly a common one,
Speaker 4: as well as maybe some loose stool, and in some
Speaker 4: cases it may not even be a toxic amount that
Speaker 4: they get into. The can have a risk for pincreatitis,
Speaker 4: which is just that inflammation of the pancreas when they
Speaker 4: get a high fat meal, and because of the richness
Speaker 4: of the chocolate, product itself, it could be enough to
Speaker 4: cause that to flare up. So thinking about our dogs
Speaker 4: that are more sensitive to pincreatitis, So the miniature Schnauzers
Speaker 4: and Yorky's some of those breeds, that may be something
Speaker 4: we have to be even more concerned about, even if
Speaker 4: they didn't get into enough to cause a toxic concern.
Speaker 1: Oh wait, it's also the fat content.
Speaker 4: Yeah, sure can be. So it depends on the amount
Speaker 4: that they get into. Dogs can tolerate a hershey kiss,
Speaker 4: but who wants to stop it just one? And so
Speaker 4: it's you know, when they get into that large handful
Speaker 4: or the bag, that can definitely be more problematic and
Speaker 4: cause that flare up.
Speaker 1: Now would you see that immediately or is that more
Speaker 1: of a long term concern.
Speaker 4: So stomach sign so vomiting and diarrhea and loose stool,
Speaker 4: that's something that we can see within a few hours,
Speaker 4: the true and a development of pancreatitis might actually be
Speaker 4: seen maybe later on twelve to twenty four hours or
Speaker 4: even a day or so later.
Speaker 2: That's right.
Speaker 1: Eating chocolate can be serious for dogs. It can cause
Speaker 1: heart problems, high blood pressure, it can affect the nervous
Speaker 1: system and even cause seizures. According to the Cornell College
Speaker 1: of Veterinary Medicine, drinking as little as half a cup
Speaker 1: of chocolate milk can be deadly for an average chihuahua,
Speaker 1: But according to doctor Schmid, not every call they get
Speaker 1: is life threatening. You said it's your number one call.
Speaker 1: I guess how would you break down those calls? Are
Speaker 1: most of them pretty serious? Are some of them like, oh,
Speaker 1: they ate a kiss or a small bar and they're
Speaker 1: probably okay? How would you break that down?
Speaker 4: That's a great question, And I would say that it's
Speaker 4: really fairly evenly spread out to being not really an issue. Fortunately,
Speaker 4: so many pet parents understand that chocolate is concerning to
Speaker 4: their pet and they shouldn't get into it. So I
Speaker 4: would say that it's a really pretty fairly evenly spread
Speaker 4: between a mild or low concern. Maybe they just ingested
Speaker 4: one chocolate chip cookie, and it's a labrador, it's a large,
Speaker 4: free dog, and so probably not going to be a
Speaker 4: big issue. But then we get this past Halloween, we
Speaker 4: had a dog that ingested over six and a half
Speaker 4: pounds of chocolate in one setting.
Speaker 1: Oh my goodness, how did that dog get into six
Speaker 1: pounds of chocolate? Was it they just had a chocolate factory,
Speaker 1: or they had.
Speaker 4: Their Halloween A family had their Halloween candy out because
Speaker 4: it was Halloween Day or the day before, and it
Speaker 4: was in an area that the dog was able to
Speaker 4: get to and the owners weren't home at the time,
Speaker 4: and he helped himself.
Speaker 1: Well, it just opened up all the wrappers and everything.
Speaker 4: He ingested a lot of the rappers. A lot of
Speaker 4: the rappers were ingested and chewed him and kind of
Speaker 4: broke them open.
Speaker 1: And yeah, oh my goodness, yep, dogs love chocolate. Don't
Speaker 1: even eat the wrappers, all right. This made me curious
Speaker 1: if doctor Schmid ever gets calls about other animals getting
Speaker 1: poisoned by chocolate. You mentioned other animals. Do you get
Speaker 1: calls about other animals like cats? And what are some
Speaker 1: unusual animals that you've had calls about chocolate?
Speaker 2: So we do.
Speaker 4: We get calls on every species, and the vast majority
Speaker 4: of the calls we receive are going to be dogs
Speaker 4: and then cats, And it makes sense because they're around
Speaker 4: humans more. They just have more access to the things
Speaker 4: in the household. We certainly get calls from chocolate on
Speaker 4: other species of animals to you know, usually something like
Speaker 4: a rabbit or a ferret, or maybe a chinchilla.
Speaker 1: That's incredible. It's a little bit ironic that you would
Speaker 1: have a bunny getting poison patrol call about chocolate.
Speaker 4: Yeah right, Hopefully that rabbit didn't eat any of the
Speaker 4: chocolate bunny at easter.
Speaker 1: So chocolate effect other animals too, including cats and rabbits.
Speaker 1: And if you search the scientific literature, you'll find reports
Speaker 1: of chocolate poisoning in cows, bears, and even coyotes. So
Speaker 1: what's going on here? What is it about chocolate that
Speaker 1: makes it so harmful to so many animals except apparently humans.
Speaker 1: When we come back, we'll talk to another expert on
Speaker 1: what it means for something to be toxic and how
Speaker 1: that affects what your pet can eat.
Speaker 2: Stay with us, we'll be right back. Welcome back. Okay.
Speaker 1: We learned that dogs definitely like chocolate, but that it's
Speaker 1: not good for them. We also learned that it's not
Speaker 1: good for other animals like cats and rabbits and even bears,
Speaker 1: and yet people seem to be fine with it. In fact,
Speaker 1: some of us eat it a lot. So what's going on?
Speaker 2: To answer this?
Speaker 1: I reached out to doctor Bob Poppingaate, a professor of
Speaker 1: veterinary toxicology at the University of California at Davis who
Speaker 1: runs the toxicology lab at the California Animal Health and
Speaker 1: Food Safety Laboratory. He was just a few days from retiring,
Speaker 1: but he took the time to talk to me. So
Speaker 1: here's my conversation with doctor Bob Poppingate. Well, thank you
Speaker 1: doctor popping Gate for joining us.
Speaker 3: Pleasure to be here.
Speaker 1: So today we're trying to answer the question of why
Speaker 1: dogs can't eat chocolate, and I thought maybe we would
Speaker 1: start by taking a step back, giving people a general
Speaker 1: idea of what it means for something to be toxic
Speaker 1: to an animal or to us.
Speaker 3: Well, pretty much anything is toxic. Key is how much
Speaker 3: is actually ingested. One of the tenants is that dose
Speaker 3: makes the poison, So it's all about the inherent toxicity
Speaker 3: of a compound, and also how much is actually ingested
Speaker 3: by a dog or a person or a child, whatever.
Speaker 3: Some things are more toxic inherently. If you ingest enough water,
Speaker 3: that can be toxic.
Speaker 1: Okay, According to doctor Popingay, there are two variables here,
Speaker 1: how inherently toxic something is, In other words, how bad
Speaker 1: it is for you and how much of it you eat.
Speaker 1: For example, cyanide is bad for you even if you
Speaker 1: only eat a little of it, But water, which is
Speaker 1: normally good for you, can also be deadly if you
Speaker 1: drink enough of it. Here's how doctor Popingay explains it.
Speaker 1: What do you mean by everything can be toxic?
Speaker 3: Well, it gets back to the inherent toxicity of a compound. So,
Speaker 3: you know, there are certain vitamins that are required. We
Speaker 3: ingest a certain amount of vitamin E or vitamin D
Speaker 3: per day, but in excessive doses of vitamin E can
Speaker 3: cause adverse effects. So it just depends on the individual compound.
Speaker 3: But in sufficient doses, anything can be toxic to our bodies.
Speaker 1: Now, what makes something more inherently toxic than others?
Speaker 3: You know, it gets back to sort of the unique
Speaker 3: characteristic of a compound and our ability to handle that compound.
Speaker 1: These things do they generally interfere with how the body works.
Speaker 1: Are these things burning a hole in my stomach or well.
Speaker 3: There's a lot of different ways that a given chemical
Speaker 3: can cause toxicity or adverse effects. You know, it can
Speaker 3: affect our enzyme systems, it can affect neurotransmission, the neurotransmitters
Speaker 3: that are released by our nervous system. It can block
Speaker 3: certain body signals. It can damage cell membranes through what's
Speaker 3: called oxidative damage, some things like corrosives. It's going to
Speaker 3: cause damage to the mucosa, the upper gi track. So
Speaker 3: a lot of different ways that chemicals can cause adverse effects.
Speaker 1: Well, it seems that almost America, we can eat anything,
Speaker 1: all right, So something can be toxic for lots of reasons.
Speaker 1: There are almost endless ways in which chemicals can mess
Speaker 1: with the signals in our bodies or directly damaged cells
Speaker 1: or membranes. So now the question is what makes chocolate.
Speaker 1: So then specifically for dogs, how bad is chocolate for dogs?
Speaker 3: Well, that is very common intoxication in dogs. It's one
Speaker 3: of the top things that veterians have to deal with.
Speaker 3: But dogs can tolerate a certain amount of chocolate. The
Speaker 3: chemicals in chocolate that cause problems, they're related and they're
Speaker 3: called methyl xanthines. One is called theobromine, the other's caffeine.
Speaker 3: So people are probably more familiar with caffeine, which is
Speaker 3: also in chocolate, so we have both. People are less
Speaker 3: familiar with the theobromine, which is related to caffeine has
Speaker 3: the same effects, but the theobromine is at higher concentrations
Speaker 3: in chocolate products. Those are the two compounds that cause problems.
Speaker 1: Okay, this is kind of a key point. The ban
Speaker 1: chemicals that make chocolate bad for dogs are caffeine and theobromine,
Speaker 1: which is basically another form of caffeine. It's not some
Speaker 1: exotic toxin or chemical. It's basically what we all drink
Speaker 1: every day when we drink coffee or tea. Now does
Speaker 1: caffeine or theobamine have some kind of special effect on
Speaker 1: dogs that they don't have on us? Not really, Okay,
Speaker 1: So then what do these compounds do to the dog.
Speaker 1: Let's say a dog eats a bunch of the baking
Speaker 1: chocolate or stip some coffee.
Speaker 2: What is it going to do to their.
Speaker 3: Body once it's absorbed. The theobromine caffeine effect the cardiovascular
Speaker 3: system and the nervous system. So you know, if you
Speaker 3: drink three or four cups of coffee in the morning,
Speaker 3: you get a little bit nervous, your heart rate can
Speaker 3: go up. These compounds are also diuretics, so you increase
Speaker 3: your own production. That's why you have to go to
Speaker 3: the bathroom after a few cups of coffee. But the
Speaker 3: primary adverse effect is on the nervous system and our hearts.
Speaker 3: So the heart rate goes up, you get a little
Speaker 3: bit excited. With a really large dose, you could have seizures.
Speaker 3: The most serious consequence is cardiac a arrhythmius, so your
Speaker 3: heart rate changes. Of the dogs, the dogs are people
Speaker 3: or any other species or animal that get into a
Speaker 3: sufficient amount.
Speaker 1: Like the same effect caffeine has in us it's having
Speaker 1: on the dog. In other words, caffeine and theobromine have
Speaker 1: the same effect on us as they do on dogs.
Speaker 1: These chemicals are as toxic to them as they are
Speaker 1: to us. But we drink coffee and eat chocolate all
Speaker 1: the time. So how does that make sense. Well, the
Speaker 1: answer is that while humans and dogs react to caffeine
Speaker 1: and theobromine in the same way, there are differences that
Speaker 1: affect our exposure to them. The first one is that
Speaker 1: dogs are smaller than us.
Speaker 3: Well, it gets back to how much the dog actually
Speaker 3: ingest on a body weight basis, So we could be
Speaker 3: intoxicated by these products as well if we ate enough
Speaker 3: of them. These compounds can't be toxic to us, So
Speaker 3: if a child got into baking chocolate and ingested half
Speaker 3: a package, you might have a very sick child.
Speaker 1: Yeah, so most dogs are smaller than us. For example,
Speaker 1: a tiny shoe walla weighs about four pounds, so a
Speaker 1: cup of chocolate milk to them would be the equivalent
Speaker 1: of an average American eating ninety spoonfuls of cocoa powder
Speaker 1: in one city. If you did that, you'd be pretty
Speaker 1: sick too. The second difference that affects how much chocolate
Speaker 1: dogs eat if the dogs don't seem to have a
Speaker 1: lot of self control.
Speaker 3: The other thing about dogs, why it's a problem. If
Speaker 3: you have a dog, you know, they're very indiscriminate eaters.
Speaker 3: They eat things and then ask questions later. If it's edible,
Speaker 3: it's going to be very attractive for a dog. So
Speaker 3: if they have access to a pan of brownies, they're
Speaker 3: not going to stop with one brownie. You know, they're
Speaker 3: going to clean up the entire pan of brownies. So
Speaker 3: cats are about as sensitive to the chemicals and chocolate
Speaker 3: as dogs are. But cats are not going to sit
Speaker 3: there and eat a whole package of baking chocolate. Dogs
Speaker 3: if they have access to something, they don't have any
Speaker 3: self control, so they will eat everything there that's in
Speaker 3: the package, whereas a person. You know, baking chocolate is
Speaker 3: fairly bitter, so maybe a child might taste a little
Speaker 3: bit of it, but they're not going to sit there
Speaker 3: and eat the whole package.
Speaker 2: I don't know.
Speaker 1: I know there's some chocoholics who might dig into that
Speaker 1: whole bag, right right, Okay. The last difference between people
Speaker 1: and dogs is the dogs don't metabolize theobromine as well
Speaker 1: as humans. Here's how doctor Schmid explains it.
Speaker 4: Yeah, so in toxicology, we talked about a half life,
Speaker 4: and the half life is the length of time it
Speaker 4: takes the body to rid itself of half of the
Speaker 4: amounts of that toxic component or what substance or drug
Speaker 4: or what have you. And so the half life, the
Speaker 4: amount of time it takes for dogs, in particular, to
Speaker 4: rid the body of the theobromine, is much longer. In dogs,
Speaker 4: it's about seventeen and a half hours, whereas in humans
Speaker 4: it's just a few hours. And that definitely contributes to
Speaker 4: the toxic effects that we see in dogs, and it
Speaker 4: also contributes to the length of time that we see
Speaker 4: or the duration of time that we see those effects.
Speaker 1: So there is a difference between dog and human biology.
Speaker 1: In terms of chocolate, the abromine and caffeine have the
Speaker 1: same effect on us, but it takes longer for dogs
Speaker 1: to break down those chemicals, so the effects last longer. Now,
Speaker 1: most articles you read online will tell you this is
Speaker 1: the main reason dogs can't eat chocolate, but actually both
Speaker 1: experts agree that much bigger factors are a that dogs
Speaker 1: are smaller and b that they can't stop themselves and
Speaker 1: will eat huge amounts of chocolate if they have access
Speaker 1: to it. Okay, the last question I asked doctor Poppingay
Speaker 1: was now, why can't dogs metabolize these compounds as well
Speaker 1: as humans? What's the difference?
Speaker 3: They have different enzymes in their liver that break down compounds.
Speaker 3: Every species says a little bit different. A good example
Speaker 3: of a species difference is cats. You should never give
Speaker 3: a set of metaphen or tilen all to a cat
Speaker 3: because they can't metabolize the compound like we can or
Speaker 3: dogs can. So cats are very sensitive to the adverse
Speaker 3: effects of a set of menifin.
Speaker 2: I see, so it's genetic.
Speaker 3: It's genetic in the sense that it's a species difference.
Speaker 1: Why do you think there are these differences in species.
Speaker 3: Ah, that's a good question. That's kind of a evolutionary question,
Speaker 3: and it probably goes back thousands, if not tens of
Speaker 3: thousands of years.
Speaker 1: Okay, when we come back, we'll actually try to answer
Speaker 1: this question by going back in history with a dog
Speaker 1: geneticis to where dogs came from. Don't go anywhere, we'll
Speaker 1: be right back.
Speaker 2: And we're back. Okay.
Speaker 1: The last person I talked to was doctor Maya Arrand,
Speaker 1: a professor at the University of Copenhagen. Here's what she does.
Speaker 5: So my name is my aunt, and as well as
Speaker 5: being a vet with a specialty and oncology, I'm also
Speaker 5: a researcher in genetics and focus a lot on comparative genetics,
Speaker 5: looking at genetics between humans and animals. And then I've
Speaker 5: also worked a lot with dog evolutions, looking at bay
Speaker 5: see how wolfs goot domesticated into dogs as we know
Speaker 5: them today.
Speaker 1: Now, the reason I talked to doctor Arrand is that
Speaker 1: I wanted to know why dogs can't process chocolate as
Speaker 1: well as people can. And it turned out that doctor
Speaker 1: Aaron can paint a pretty interesting picture of why dogs
Speaker 1: might have ended up that way and spoiler alert, it
Speaker 1: might all be our fault.
Speaker 2: Okay.
Speaker 1: I started off by asking her to recap what we
Speaker 1: know about where dogs come from. So can you give
Speaker 1: us a brief history of dogs, like where did they
Speaker 1: come from?
Speaker 5: So dogs really originated from the gray wolf and they
Speaker 5: were domesticated, well, actually, no one really knows exactly, but
Speaker 5: as early as forty thousand years ago. Some say, oh,
Speaker 5: it's definitely just one event that happened twenty three thousand
Speaker 5: years ago in Siberia, but there's also suggestions that dog
Speaker 5: domestication has been happening several places around the world. Somewhere
Speaker 5: along the time, there's been some wolves that were maybe
Speaker 5: less fearful of humans and have sort of been more curious,
Speaker 5: and those are the ones that have sort of been
Speaker 5: closer around humans. There's also a theory that they have
Speaker 5: maybe been interested in scavenging, so scavenging around the places
Speaker 5: where humans have lived, and these factors sort of led
Speaker 5: to humans and wolves being in closer proximity. And then
Speaker 5: the exact sort of domestication, if it's been humans taking
Speaker 5: wolf puppies because they look cute or how this happened
Speaker 5: is not exactly sure.
Speaker 1: Interesting so at some point. The first dogs were just
Speaker 1: domesticated wolves, and so they look like wolves, but now
Speaker 1: they look like Chihuaha's and poodles.
Speaker 5: Yeah, so there has been a lot of heavy selection
Speaker 5: towards the dogs that we known in today, and yes,
Speaker 5: originally the dogs that existed many thousand years ago, they
Speaker 5: have looked or resembled much more the gray wolf as
Speaker 5: we know it today. But what really happened is, obviously
Speaker 5: people have selected for dogs to be used for different purposes.
Speaker 5: They have chosen dogs that fitted to a certain purpose
Speaker 5: and tried to breathe these together.
Speaker 1: Okay, so only up to about twenty to forty thousand
Speaker 1: years ago, there were no dogs. There were just wolves.
Speaker 1: And then one or two kinds of wolves started hanging
Speaker 1: around people and a best friendship was born. So every
Speaker 1: dog today signed this belief came from those first wolves
Speaker 1: that were friendly to humans. So how do you go
Speaker 1: from a huge, fierce looking gray wolf to poodles in chiwalas?
Speaker 5: Significantly? I think around two hundred years ago, aways sort
Speaker 5: of the first kennel clubs we're established, and their people say,
Speaker 5: now we're going to create these different breeds of dogs,
Speaker 5: and we have to have pedigrees so we can sort
Speaker 5: of be sure that we're only breeding dogs from the
Speaker 5: same breed, and there we've sort of selected very stringently
Speaker 5: towards the breeds that we have today. This has had
Speaker 5: some consequences, and it doesn't mean that there is a
Speaker 5: lot of inbreeding within certain dog breeds. And there's also
Speaker 5: been some sort of negative health consequences that we don't
Speaker 5: really see in their ancestors, as in the gray wolf.
Speaker 1: Oh so the big diversification that we've seen dogs today
Speaker 1: only maybe mostly happen in the last few hundred years.
Speaker 5: I mean, if you look at sort of old paintings,
Speaker 5: you can definitely see there's sort of different dog phenotypes.
Speaker 5: But now we have these really different breeds. That's really
Speaker 5: something that's only happened very recently. And what happens every
Speaker 5: time you sort of do this selection is you create
Speaker 5: what we call a genetic bottleneck, is where you have
Speaker 5: only a small amount of genetic material that goes further
Speaker 5: to great and new population. And this does I mean
Speaker 5: that you will have a lot of sort of inbreeding
Speaker 5: within different dog breeds.
Speaker 1: What you're saying makes me wonder if one of those
Speaker 1: negative consequences could have been an intolerance for chocolate.
Speaker 5: So that's a really interesting question why dogs don't tolerate
Speaker 5: chocolate very.
Speaker 1: Well, Okay, this is where it gets interesting. Doctor arend
Speaker 1: has been a part of several teams that have sequenced
Speaker 1: the dog genome. That means they catalog the genes in
Speaker 1: dog DNA, and there are two studies that tell an
Speaker 1: interesting story about dogs and potentially chocolate. In the first study,
Speaker 1: doctor Aren't and other researchers compared the DNA of dogs
Speaker 1: to the DNA of wolves. Here's how she describes it.
Speaker 5: Yeah, so that's really my favorite part of my research
Speaker 5: because it was such a clear signal we saw some
Speaker 5: years ago. We decided to look at the differences between
Speaker 5: wolves and dogs. So basically, sequence the pool of different
Speaker 5: wolves from different parts of the world, and then sequence
Speaker 5: of different dog breeds and then try to look at differences.
Speaker 5: And what we could see is, obviously we found a
Speaker 5: lot of signals that were related to newer developments. So
Speaker 5: this suggests that obviously there's difference in behavior and how
Speaker 5: the brain functions between wolves and dogs.
Speaker 1: All Right, the first difference they saw between dog and
Speaker 1: wolf DNA was in genes related to their brains, and
Speaker 1: this makes sense because we know that one big difference
Speaker 1: between dogs and wolves is that they behave differently. Wolves
Speaker 1: are wild and dogs are domesticated. But then they saw
Speaker 1: another clear difference.
Speaker 5: But one of the sort of really strikingly clear signals
Speaker 5: we also saw was related to the digestion of starch.
Speaker 5: We know that wolves are really cardivores, so they tend
Speaker 5: to eat meat only. So there are hunters in the
Speaker 5: wildlife and they will mostly eat and hunt different types
Speaker 5: of prey. And we look at dogs, it seems like
Speaker 5: they are sort of closer to on their wards, so
Speaker 5: they can also tolerate other substances, or they can also
Speaker 5: sort of feed on starch containing foods.
Speaker 1: Okay, what they saw was that the genes of dogs
Speaker 1: were also more adapted to eat starches, meaning that when
Speaker 1: they were wolves they only ate meat, but once they
Speaker 1: became dogs, their digestive system changed so they could eat
Speaker 1: basically carbs like rice and wheat. What does this mean?
Speaker 5: So what we could see in our research was we
Speaker 5: really found relatively strong signals that suggested that dogs have
Speaker 5: not only been domesticated sort of in relation to their
Speaker 5: behavior to living humans, but actually they also seem to
Speaker 5: have adapted to the diet that we eat.
Speaker 1: Does that mean that dogs can digest sugars more?
Speaker 5: Yes, that's definitely our theory.
Speaker 1: What doctor rn is saying is that as dogs became
Speaker 1: dogs and started living with humans, they adapted to our
Speaker 1: or diet, and that meant being more omnivorous and being
Speaker 1: able to eat a wider range of foods, including perhaps chocolate.
Speaker 1: I wonder if this adaptation being able to eat more
Speaker 1: sugars has made them more prone to eating the chocolate
Speaker 1: we leave around, Meaning like, if I leave a chunk
Speaker 1: of chocolate with a wolf, would the wolf want to
Speaker 1: eat this? Maybe not because it wouldn't taste good or
Speaker 1: wouldn't have that drive to eat it.
Speaker 2: What do you think?
Speaker 5: So that is a really good question. One of the
Speaker 5: things we did see in our data originally was some
Speaker 5: of the taste receptors in the tongues, and there potentially
Speaker 5: could be some differences there, But it's definitely something that
Speaker 5: would make sense that as part of this adaptation, that
Speaker 5: maybels actually think that this chocolate didn't taste good and
Speaker 5: dogs would be more sort of interested in it. But again,
Speaker 5: that would be a very theoretical question. I don't think
Speaker 5: anyone's sort of shown that.
Speaker 2: Okay.
Speaker 1: The second interesting thing doctor arn has found when looking
Speaker 1: at the DNA of dogs is that actually dogs do
Speaker 1: have a gene that can help them metabolize chocolate or theobromine.
Speaker 5: One of the interesting things we saw in our new
Speaker 5: reference genome was we found a duplication, So that means
Speaker 5: that instead of just having one copy of a gene,
Speaker 5: you can have multiple of a gene called SIP one
Speaker 5: A two, and that is a gene that encodes enzyme
Speaker 5: that's important for digesting what called cenobiotics, for instance, theobromine
Speaker 5: that the body doesn't produce itself. And we can see
Speaker 5: that based on the twenty seven other dogs we had
Speaker 5: in our data set, that some dogs have two copies
Speaker 5: of the SIP one A two and then some dogs
Speaker 5: would have up to five copies.
Speaker 1: So dogs have multiple copies up to five of a
Speaker 1: gene that would produce an enzyme that would help them
Speaker 1: break down theobromine, the chemical in chocolate. They can make
Speaker 1: them sick, but for some reason the gene doesn't get used.
Speaker 5: Specifically, it's SIP one two that's been associated with theobromine digestion.
Speaker 5: And then there's actually also one that's called sip to
Speaker 5: E one I believe, which also been linked to theobromin digestion.
Speaker 5: And the dogs have both of these genes, so it's
Speaker 5: not like they're missing one or it doesn't exist. And
Speaker 5: that's why, Well, if they have the genes that required,
Speaker 5: why do we eat then see that they get this
Speaker 5: chocolate toxicos is more frequently than you would see, you know,
Speaker 5: the species, And that's maybe down to the way the
Speaker 5: genes are expressed, so that maybe just not expressed in
Speaker 5: a high enough amount.
Speaker 1: So they have the gene to process theobromaine. We just
Speaker 1: don't know why they don't express it enough to help them.
Speaker 5: Yeah, I guess that would be the theory that they're
Speaker 5: not expressing it high enough or fast enough as they
Speaker 5: are in humans.
Speaker 1: Doctor arn says that a possible theory is that dogs
Speaker 1: have the genes to break down the chemicals and chocolate,
Speaker 1: but maybe changes in other parts of the DNA are
Speaker 1: preventing these genes from expressing themselves to actually make the
Speaker 1: enzymes to digest chocolate. One potential source of these changes
Speaker 1: could be the interbreeding that's happened in dogs over the
Speaker 1: last few hundred years.
Speaker 5: So there have been people showing that there have been
Speaker 5: two sort of small genetic variants in the SIT one
Speaker 5: agen that we can see that occurrent dogs, and they
Speaker 5: have hypothesized that these genegrants made the one A two
Speaker 5: gene function worse, so when it was translated into enzyme,
Speaker 5: that enzyme wasn't as good as digesting deobromine.
Speaker 1: So it seems like maybe a possible picture. We can't
Speaker 1: say anything for certain, but a possible picture is that
Speaker 1: dogs adapted to human diet, but something happened along the
Speaker 1: way that made them not adapt to theobromaine digestion, which
Speaker 1: kind of puts them in this bad spot where they're
Speaker 1: adapted to eating our food, but just not this one
Speaker 1: particular food. And so that's why it's such a problem today.
Speaker 5: Yeah, I think probably that is pretty correctly.
Speaker 1: Put In other words, it's because of us that dogs
Speaker 1: can and want to eat foods like chocolate, but along
Speaker 1: the way they might have lost been able to digest
Speaker 1: the chemicals and chocolate maybe also because of us and
Speaker 1: all the interbreeding we've done to them. So maybe the
Speaker 1: problem is we need to give more chocolate to dogs.
Speaker 5: Yes, tell us, I said evolution doesn't happen over time,
Speaker 5: and for that selection to happen, there will be a
Speaker 5: lot of dogs that would not do well. Yeah, so
Speaker 5: I think the better idea is probably not to give
Speaker 5: dogs chocolate.
Speaker 1: Yeah, we'd better for humans just to stop eating chocolate,
Speaker 1: or at least humans with dogs.
Speaker 5: Well yeah, I'm not sure if humans should completely stop
Speaker 5: eating chocolate, but they should be more careful lenient around
Speaker 5: where dogs can get access to it.
Speaker 2: That makes total sense, all right.
Speaker 1: To recap, the answer to the question why can't dogs
Speaker 1: eat chocolate seems to be mainly the dogs are smaller
Speaker 1: than us, and they are which makes it easier for
Speaker 1: them to overdose on the caffeine, the bromine and fad
Speaker 1: in chocolate. And on top of that, they've lost the
Speaker 1: ability to quickly break down some of these chemicals, maybe
Speaker 1: because of us. So if you own a dog, be
Speaker 1: sure to put away or eat all your spared chocolate.
Speaker 2: And that's just dogon good advice.
Speaker 1: Thanks for joining us, See you next time you've been
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