Science Friday - How Poisons Have Shaped Life On Earth

Episode Date: November 2, 2023

When you think of poisons, you might think of chemicals like cyanide, arsenic, or the deadly concoction left out for rats. But have you thought of acorns? What about the cup of coffee you had this morning? Or the mums growing in your window box? Toxicity is all in the eye—or bloodstream—of the beholder.A new book describes the story of nature’s endless array of toxins, and how they shaped life on earth, including ours.Guest host Flora Lichtman talks with Dr. Noah Whiteman, evolutionary biologist at University of California, Berkeley and the author of Most Delicious Poison: The Story of Nature’s Toxins – from Spices to Vices. They chat about the poisons that fill our pantries and gardens, and what our use and abuse of these substances tells us about ourselves.To stay updated on all things science, sign up for Science Friday's newsletters. Transcripts for each segment will be available the week after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

What if I told you that poisons are all around us? But just because they're poisons doesn't always make them unsafe. If it's toxic to an insect, it doesn't always mean it's going to be toxic to us. But we ought to carefully look at that. It's Thursday, November 2nd, but surprise, surprise, it's also Science Friday. My favorite poisons are coffee, eucalyptus, aspirin, and although they're technically poisons, they weren't designed to hurt me. guest host Flora Lickman talks with Dr. Noah Whiteman, evolutionary biologist at UC Berkeley, and the author of Most Delicious Poison, The Story of Nature's Toxins from Spices to Bices about how nature's giant cold churn of poisons shaped life on earth.

Welcome to Science Friday. Well, thank you, Flora. It is wonderful to be here. Let's start with getting our terms straight. Will you define poison for me? Well, that's going to be hard, Flora, because... I like to start with a hardball on the show. I would say that my definition of poison, as I talk about in the book, it sort of, I would say, is a chemical that is produced. In our case, we're talking about other organisms producing them. So these are like biological poisons, toxins.

And for me, the definition is really a chemical that damages cells and the, you know, the ability of cells to operate. And toxins can be sort of adaptive. In other words, they can be produced because they give the bearer an advantage, usually with respect to other organisms, so an offense or defense, or something could be toxic like carbon dioxide that is just a byproduct of metabolism. So the way I think about it, when I think about these poisons as adaptations, is, you know, whether they give their bearers an advantage through the top.

toxic mechanism. Okay, so toxin and poison the same thing or different things? Well, I would say they're probably different in the sense that a poison, it sounds like there's intent there, right? Yes. And so, and I think that's important because, of course, when we think about evolution, you know, we don't think of intent, but we think of what has been selected for through evolution by natural selection in this case to give the cell or the individual that is producing that chemical an advantage somehow. Okay, so a toxin, like oxygen can be a toxin at a certain dose, but a poison is something that an organism makes to fend off other organisms. Exactly. Okay. Tell me what led you to write this book.

So I had been studying poisons that are produced by plants that they use to defend themselves against enemies like caterpillars. And one of the ones that I focused on was the monarch butterfly, which obtains poisons from the mills. milk weeds that they eat. And the monarchs get them when they're caterpillars, when they're eating the plant and they imbibe these toxins, they keep them in their body. And that's what protects the monarchs from bird attack, which is also why they're brightly colored. That's sort of co-evolved with the toxicity part, the warning coloration part. Oh, they co-opt the toxin from the plant? Yes. So it's cool. It is. And so then, okay, I was studying that. And then at the same time, sadly, my father was suffering from alcohol use disorder, which is sort of the more modern term

for alcoholism. And he'd been spiraling for decades and eventually died in 2017 from complications from that. And it was in the aftermath of that that my world's kind of collided that I've tried to keep apart, the sort of professional scientific life and this world of pain, you know, when it comes to thinking about my dad and his situation. And I realized that he was using alcohol to, you know, numb his pain and keep his own demons at bay. And in a way, it wasn't that different from what the monarchs were doing at a superficial level. And so I think to make sense of it all, I began to sort of look at these two threads and then started weaving them together. And the book was born, I think, is a way to cope with all of it. Hmm. I'm sorry about your father. I'm,

I read in your book that your dad was a naturalist, too. It seems like that's another thread to this. Yes, he was. And so we lived in northeastern Minnesota first in Duluth and then about an hour north of there in the middle of a bog. And I say bog like a Minnesotan. I'm sure he noticed that. B-O-G is what I'm trying to say.

As a Midwesterner, I embrace it and celebrate it. Thank you. Well, yeah, so he was an outdoorsman and knew a lot about, nature and taught me a lot about what I knew about the natural world up there. And that kind of stuck with me. That has served me well throughout my life. And it's something I've taken for granted, I think, being exposed to all of these creatures from a very young age and with a lot of information about them, which came partly through my dad, who sort of gave me the skills to learn more, if that makes sense, to be curious and to just appreciate all of life, whether it was a caterpillar or a bear or a tree

or a blade of grass. You know, your milkweed work makes me wonder, how many poisons do I encounter every day? Like, say I'm on a walk in my neighborhood. This is going to be a hard assignment, but give me two common poisons that you think will surprise me. Well, if we were walking together,

at some point, you'd be like, Noah, slow down. There's a lot going on. You'd be pointing out more than two. Is that what I'm gathering? Yes. You can't follow directions, Dr. Whiteman. So, but if we walked by a foxglove plant, have you ever seen a foxglove plant? They have kind of pretty pink, purple, white flowers.

Tall. Tall. And apparently are called foxgloves because someone thought foxes could fit their paws in the floral tubes. That is so cute. I love knowing that. Thank you. I know. So, but the truth is behind that cuteness is something pretty toxic.

So the same kinds of toxins that milkweeds produce are also produced independently in the fox level. And they evolve to do that independently, which is really interesting. And so there are heart poisons in those plants. And what's interesting about those is that, you know, they probably evolved at high concentration to prevent, you know, organisms from eating them. But at the same time, humans have co-opted those. And William Withering conducted the first clinical trial in modern medicine in Britain, hundreds of years ago using Digitalis box glove to treat congestive heart failure.

Wow. And we still use that drug, the drugs that are in those plants. So that's one. And then the other, let's go back to your acorn because there is a set of toxins that is very ubiquitous across plants. And they're called tannins. And oaks are famous for making tannins, including what you mentioned in the acorn, which are filled with them. and so to eat them, they need to be treated to get rid of the tannins.

And so the tannins bind to our salivary proteins, and that helps sort of keep them away from our digestive tract. But if there's too many, they sort of get through and they can cause problems. What kind of problems? Like, could they be deadly if you have enough of them? Yeah, so there's a set of tannin-like compounds in green tea, and that compound has been used as a weight loss supplement. and it was so dangerous at high levels that has caused people to have to have liver transplants, for example. Wow. Yeah.

And as you said before, there's some nuance here. And it is the, as Paracelsus said, it's the dose that makes the points in, right, at some level. You know, a biting a foxhole plant isn't going to cause huge problems, but it quickly escalates, if that makes sense. You know, there are, obviously there are millions of species on this planet. What percentage of species have to deal with toxins or make toxins? or have been shaped by toxins? That is a great question. Most are dealing with them at some level.

If you think about just plants and the insects that eat them, the two of those groups are most species of life on Earth that have names, which is amazing. And it is hypothesized that chemicals produced by the plants in defense against those herbivores are partly responsible for driving the diversification of each person. group, and that is it called the theory of co-evolution. And even things like bacteria are, you know, of course their worlds are mostly chemical. And you can think of the battle between bacteria and fungi, like penicillin, right, is a chemical that is produced by fungi that

kills bacteria. And we've co-opted that. So toxins are actually shaping life on this planet. Yes, that's the idea that they're, that, that, I'm with you. And, you know, one of the ways I like to think about it is that organisms that can't move very fast or don't move much at all, things like plants, mushrooms, many, many microbes, and even small animals, they're the ones that use toxins as often as defenses. They can't run away. They can't run away. They're stuck in the ground or close to that. Yeah. Let's talk about my favorite toxin coffee. Yes, coffee. Mine too. And I only had one cup this morning. I'm working on my second cup. And I know the dose that I need in order to sort of make it through the day, like you do probably, right?

Yes. I love to think about my coffee routine. And I gather from your book that you also like to think about this. I do. So I have a chapter on caffeine and nicotine. and in that chapter, I do talk a lot about coffee, tea, and chocolates, which all produce caffeine, or in the case of chocolate, theobroming, which is a derivative of caffeine. And what's interesting is that caffeine was one of the, I don't want to say first, but very early

alkaloids, which is another type of chemical family that plants make, that was sort of nailed as an insecticide, natural insecticide that evolved five different times, at least in plants. And the study that focused on this, the title was something like, you know, caffeine is a natural insecticide. And I think this surprised a lot of people and may surprise you. Well, I mean, I have lots of questions about this. Like, at low levels of poisoning, do insects display the same traits as I do when I'm over-caffeinated? Or do they get, like, jittery and have darting eyes? They do. too much, tend too fast. They do have seizures, actually. It's more of a problem for them than it is for us, I would say. Well, I was going to ask, like, if I'm overcaffeinated, does that mean I'm being low-level

poisoned? Well, you know, there is a limit on what is safe to consume. You know, if it's toxic to an insect, it doesn't always mean it's going to be toxic to us, but we ought to carefully look at that and think very carefully about the dose. And so, yes, there are safe. levels of caffeine to consume. For humans, it's about 400 milligrams a day, I think. And if you go above that, yes, there can be toxic effects. And people have hurt themselves. And unfortunately, have ended up ending their lives because of overdoing it. This is Science Friday from WNYC Studios. I'm talking all things poison with Dr. Noah Whiteman, author of Most Delicious Poison. Are there other toxins in coffee beans and can you prepare coffee so that there's less of them?

Yes. So one of the illustrations in the book, which was done by Julie Johnson, is of a French press, which I used to use, and pour over little ceramic thing with a paper filter in it. And then there are three chemicals illustrated. One is caffeine, of course. And then the other two are turpanoids. So turpenoids are the most. diverse natural products that are produced by other organisms. And one is called cathostal conveniently, C-A-F-E-S-T-O-L. Get it, Caffa-S-A-S-T-O-L. And then the other is called Cawi-A-L, and that is probably derived from this Arabic word for coffee. And those two diterpenoids are also found in coffee beans,

and they are the most potent inducers of LDL cholesterol in the human diet. Wow. In other words, they raise the bad cholesterol levels. And so that may pose a problem if it's long-term heavy use. I mean, this is the reason why so many people are on statins in the United States, high, you know, LDL levels. So that's a potentially long-term health issue there. So the paper filter removes almost all of those two diterpenoids, kathostol and kawial,

that the French press plunger does not. And the same is true for boiled coffee, whereas the paper filtered ones and actually the gold mesh filter ones in an auto drip, this is very nuanced. They also remove them. Paper filter. Paper filter. Add it to your cart. Or gold mesh for an auto drip, if you're fancy.

So I learned from your book that, you know, my pantry is filled with toxins, red pepper flakes, nutmeg. I want to talk a little bit about how our. taste for toxins shaped history. Tell me about that, how these spices went global. Right. Well, there was this strange obsession with Asian spices in Europe for a long time in Middle Ages. And, you know, part of the mystique was that these were things that were unusual and couldn't be grown or purchased locally in Europe. But many of them actually do trigger these particular receptors in our mouths called TRP receptors like the red pepper receptor, the wasabi receptor, the mint receptor,

and those seem to titillate our tongues in some way that we like. But there were other things going on culturally in Europe that are really interesting about why this sort of obsession with spices and why food was so spiced and all of that. So this was sort of, you know, at its zenith in the middle, late part of the 15th century and kept going, but that pushed European nations to begin to go around Africa, to try to get to Asia in search of things like black pepper, ginger, nutmeg, maize, clothes. And eventually, Columbus, of course, right, is motivated by the same thing and ends up in the Bahamas, even though he thinks it's Southeast Asia in search of spices. So these chemicals that the plants are making presumably as defenses against pathogens and things like insects, you know,

they're not making them for us, but we're searching them out. And the consequences of that are enormous, of course, because the 500 years that have gone by since have all been sort of triggered by these initial events. Our taste for spice and toxins, what do you think it tells us about ourselves? Well, that's a really interesting question. For me, you know, when I look at how other organisms deal with these things and things like monarchs that are seeking them out right that are sequestering them that are using them as tools and they're not alone many other animals do this as well and you know that's innate i would say in them and in us we have this culturally transmitted very similar cultural evolutionary history where we're doing the same thing every human society

taps into these chemicals and plants fungi and other organisms and so in a way we're participants in this war of nature too, just like them. We're not divorced from the natural world. We depend on it, just like they do. When I think about my interaction with nature, of course, it's wonderful to have a vista in front of you or to see a beautiful bird, but to actually experience it through smell or taste

or through sort of what it does to my behavior or my thought process, you know, there's not much else like that, right? And so in my mind, this chemical channel that you and I were talking about, that's part of this web of life, it sort of allows us to have a more intimate interaction with it, I think. Noah, thanks for joining me today. Oh, it was my pleasure. Thank you so much. Dr. Noah Whiteman is an evolutionary biologist at UC Berkeley and the author of Most Delicious Poison. To read an excerpt, visit sciencebride.com slash poison.

That's it for today's show. a lot of folks help put this show together, including Melissa Mayers, Danielle Johnson, Beth Rami, Nahima Ahmed. Tomorrow, join us for a roundup of this week's biggest news in science. I'm Rasha Aureti. I'll see you then.