This is a transcript of the Gastropod episode, The Brightest Bulb, first released on December 22, 2020. It is provided as a courtesy and may contain errors.
Student 1: Add barley, onions and shallot… Oh my god, I can’t pronounce that. Shallots. And cook until soft.
Student 2: Wait, what meat is this?
Student 1: Lamb.
Student 2: Medium rare lamb? Mmm. LAUGHS
Student 2: How do you know what it’s done though?
Student 1: I don’t know when it’s done.
CYNTHIA GRABER: Back in the days when we could hang out in groups indoors, we spent an afternoon cooking lamb stew with a bunch of teenagers in the kitchen lab of North Carolina State University.
NICOLA TWILLEY: We were there at the invitation of our old friend Rob Dunn, who many of you will remember fondly from our sourdough episode. These days, he’s got a whole new question he’s trying to answer.
GRABER: Does adding alliums like garlic and onions and shallots to your dishes help make them safer to eat? We of course are Gastropod, the podcast that looks at food through the lens of science and history, I’m Cynthia Graber—
TWILLEY: And I am Nicola Twilley, and this is a really intriguing question. Did garlic start out as a food additive, something that we added to our lamb stew to preserve its shelf life, and only later become something that we just enjoyed the taste of anyway?
GRABER: And a lot of us do enjoy it. In fact, my people have long been known as garlic eaters. Is that a compliment?
TWILLEY: Sure it is. Meanwhile, since we’re talking alliums in general: I would love to stop breaking down into floods of tears everytime I chop an onion or shallot. Why is that so emotional for me?
GRABER: And what does garlic have to do with the first recorded labor strike in history?
TWILLEY: We are about to take a short break from releasing new episodes—do not worry, we’ll be back in February, and we’re going to be working hard until then on everything we have in store for you in the new year!
GRABER: But before that, we wanted to give a shout-out to some new listeners at the supreme fan level who help support the show: Jasmin from Medford, Mass., Benjamin Wymer, Rose Rodriguez, Adam Hart, an anonymous listener from Kalgoorlie, Australia, Marilyn from Florida, Jiann Mok, Ben Ford, Monica Granucci, Peggy, Carlos Valenzuela, and Matt Griessler.
TWILLEY: We also wanted to give a special thank you to two major incredibly generous donors this year, Wendy Taylor and Tilia Jacobs. Tilia even supported the creation of an entire episode, our most recent one on growing food in the desert. If you too would like to support an entire episode, or something along those lines, we would love to hear from you!
GRABER: And finally, a huge thank you to ALL of you. Thanks for giving Gastropod support as a gift, thank you for your support of the show at whatever level works for you, and really, thanks to all of you for listening. We do this for you, and we couldn’t do it without you.
TWILLEY: This episode was also made possible thanks to generous support from the Alfred P. Sloan Foundation for the Public Understanding of Science, Technology, and Economics, as well as the Burroughs Wellcome Fund for our coverage of biomedical research.
TWILLEY: This whole experiment got started because of a food history mystery: why do people use spices?
ROB DUNN: If you look at spices globally, not everybody uses spices. Not all places use spices. And so the question then becomes what triggers people to add garlic, to add onion, to add pepper to their food?
TWILLEY: This, of course, is Rob Dunn, he’s a microbiologist at North Carolina State University. And just to get things straight from the start: Rob is using the term spice in a very expansive way. He means pretty much everything we add to food that isn’t much of a source of nutrients or energy—the things we add just for flavor.
GRABER: There had been a theory that spices were used to cover up the scents and tastes of food that had started to go off, and because that happens more quickly in hotter climates, that’s why those regions use more spices. But scientists say that’s likely not true, because the food would have still tasted bad, and it still would have made people sick.
TWILLEY: What is true is that people in hot countries do traditionally use more spices. Rob told us about some research done by a biologist called Paul Sherman, who gathered together and analyzed a whole set of recipes from around the world.
DUNN: Northern China, fewer spices than southern China. Colder India, fewer spices than warmer India. Denmark, Norway, Finland, plenty of daily recipes with no spices whatsoever. And then as you move to the tropics, more and more kinds of spices.
GRABER: Paul wondered if maybe all those spices were actually helping kill harmful microbes—drink!—and preserve the food.
TWILLEY: Because for sure, in hot countries, food spoils more quickly. Any harmful microbes it contains multiply faster in the heat. And that’s another drink.
GRABER: And Paul knew that some spices—including garlic and other alliums—have been shown to kill microbes in petri dishes in the lab.
TWILLEY: The chemical that makes chile peppers hot has the same effect in the lab. Same for chemicals in nutmeg and black pepper and thyme—lots of the things that give our dishes an extra shot of flavor.
GRABER: And this made Rob think about how spices might have been used at the dawn of agriculture, in the Fertile Crescent, where it is indeed really hot. They might have been microbe killers.
DUNN: And this idea that spices might help preserve foods has also been called the leftover hypothesis. And so you can think about this in a sort of historic context, that if, you know, if you make a bunch of food in the evening, the odds that some some’s around in the morning is pretty high. And so that’s twelve hours. It goes to lunch that’s a little longer. If we’re thinking Fertile Crescent it might be 100 degrees out. And so even if you just got a few more hours out of a food, it’s potentially a big impact.
TWILLEY: The leftovers problem is as old as humankind. Ever since the dawn of time, microbes have been trying to eat our food. And ever since the dawn of time, some of those microbes have also been able to make us sick.
DUNN: You could get sick from the stuff that came in the food. You could get sick from stuff from other people. You could get sick from what was in the vessel that you were using. And nothing was being refrigerated ever. And so potentially the spices then occupy this very, very important role.
TWILLEY: So according to this theory, spices might have been saving our ancient ancestors’ lives? Maybe.
GRABER: Maybe. But no one knows.
DUNN: But as we looked at the literature it became clear that while people had studied aspects of this question, they’d never actually done the simplest thing, which was to make a dish and then to figure out what happens when you when you leave that dish out with and without the spices.
GRABER: To be honest, this surprised us. It seems like a pretty obvious question to ask and then to study. But it turns out that it’s kind of interdisciplinary, and Rob says this might be why no single scientist’s lab had taken it on. So he decided to partner on this study with Ben Chapman, also at NC State. Ben studies food pathogens.
DUNN: Ben’s in a department that emphasizes food safety. I’m in the Ecology Department. Down the road is a food science department. And we each have our sort of purview of what kind of science that we’re supposed to do. And for none of us is this kind of experiment part of our job. For all of us, it’s like somebody else’s thing. And so on the one hand, that’s what makes it so fun to collaborate. And the other hand, it’s why no one’s done it before, even though it seems so obvious.
TWILLEY: To finally do this important but long overlooked experiment, Rob and Ben roped in a bunch of child labor. Or in other words, they partnered with a local high school science group, the “Spice is Nice” club.
DUNN: And working with the kids is really fun because they all think like, Well, how do we not know that? Like, are you guys just stupid? Like, is it just you that are stupid or is it all y’all. And so there’s this interesting moment in which they start to realize, Oh, no one knows this.
GRABER: And the students were ready to help them find out. There are a lot of things we add to our food that have strong flavors—spicy hot chile peppers, numbing Sichuan peppercorns, aromatic herbs like basil and sage, and strong flavored plants like garlic and onions.
TWILLEY: All these spices have flavors we crave now—but Rob says the chemicals in these plants are meant to be off-putting to animals—including human animals.
DUNN: And so you’ve got garlic and its defenses against what might eat it. You’ve got thyme and mint that have, the leaf actually has a teeny tiny little sack of chemicals that when you rupture the leaf, they burst open. And so they’re things that are meant to ward us off, that we’ve decided we would add in.
TWILLEY: With so many spices to choose from, where to start?
GRABER: They decided to narrow it down and start just by focusing on alliums—garlic, onions, leek, chives, shallots, all those delicious stinky bulbs. In part because these might be some of the earliest spices we used.
DUNN: So the first example of spice use I’ve found is from a Mesolithic pre-agricultural series of sites in northern Europe. And in those sites, they found pots with meat in them and with different alliums, so different garlics.
GRABER: Ben and Rob and the team did a trial version of the experiment, they made a recipe for an ancient stew that they made with and without alliums, and they left each version sitting around for a week.
DUNN: And so what you’re now smelling is this dish made without the alliums.
TWILLEY: I’m going to waft. SNIFF.
GRABER: You look like you’re about to throw up.
TWILLEY: It’s… It’s turned, I would say. LAUGHTER.
GRABER: OK, so my turn. OK. I’m preparing. I should say this is my birthday. This is what I get to do on my birthday! Science.
TWILLEY: It doesn’t—it doesn’t hit you at once. So don’t—don’t do much.
GRABER: SNIFF. Oh, yeah. There we go. LAUGHTER. Yeah, that’s pretty unpleasant.
TWILLEY: While we retched politely, Ben told us what was making this week-old allium-free stew smell so gross.
BEN CHAPMAN: There’s likely some mold. There’s likely some yeast and there’s likely some spoilage microorganisms of the bacterial variety that are all working together on sugars that are in there and starting to convert those sugars into things that they can use to grow and create a bunch of byproducts that we’re not super happy with from a human smell or taste. So as much as I’m—I think we’re good with smelling the aroma, this isn’t something that I would want to taste right now. SNIFF. Oh man, that does not smell great.
GRABER: There was a visual and smell difference in the samples with and without the alliums, and this was a clue that alliums might be important. Alliums have certainly been important throughout human history—there are hundreds of species of alliums, all seem to be edible, and we’ve eaten a lot of alliums over thousands and thousands of years.
TWILLEY: There seem to be wild alliums on every continent but Antarctica and Australia, although these days they’re eaten in both those places and everywhere else too.
GRABER: But it’s actually kind of weird that they’re so universally loved—they should be universally hated. Because they all contain sulfur compounds.
ERIC BLOCK: The thing to remember about sulfur is that of all the elements, we are able to detect extremely tiny quantities of sulfur compounds. And I’m talking about parts per trillion, like a drop of water in a swimming pool.
GRABER: Eric Block is professor emeritus of chemistry at SUNY Albany, and he has been studying garlic for decades. He wrote an entire tome on the subject called Garlic and Other Alliums, the Lore and the Science. And he says actually all humans instinctively hate the smell of sulfur.
BLOCK: And it has to do with the fact that sulfur is associated with putrefaction. That is the breakdown of life. And because something that is in the process of dying or decomposing often is associated with toxic microorganisms, animals have become able by survival to detect signs of putrefaction, signs that something is rotting and is unsafe to eat.
TWILLEY: Eric says that the name allium actually comes from an ancient Greek word that means “to avoid” because of that sulfurous smell.
DUNN: And so these are the same kinds of compounds that get associated historically with the devil. The devil is sulfurous. Right. So I think the idea that there’s some innate predisposition to not liking them seems at least plausible. And if that’s true, it then makes it an even more interesting question: why do we start adding them to our food?
GRABER: It seems like we’d avoid all these sulfurous plants entirely—but Rob’s theory, building on the leftovers hypothesis, is that maybe we taught ourselves to like them because our ancestors noticed that adding alliums when they cooked helped make their food safer to eat.
TWILLEY: And then we could have learned to like it really quickly.
DUNN: One thing we do know is that once you do add something like this to your food, it’s pretty easy, in a generation to learn to love it, even if you have an innate aversion to it. In utero, babies actually experience the aromas of the food that their mother is eating. Their little fetal sniffer actually smells those aromas. And anything experienced in the womb gets a positive hedonic valence, to use the lingo. The babies think it smells good regardless of what it is. If one generation, it’s off putting but beneficial; the next generation, it will be beneficial and liked. And in a generation you can start to have it be part of your culture.
TWILLEY: So the liking is a side-benefit. But of course even once we started to like the taste, it doesn’t mean the garlic and other alliums stopped doing whatever good stuff we thought they were doing. And we clearly thought they were doing something.
GRABER: In addition to maybe helping preserve the food, alliums might have been used as medicine. Researchers have seen monkeys use garlic in ways that look like they’re self-medicating, and onions and garlic and other alliums have been used in traditional human medicine around the world.
TWILLEY: Garlic especially—it was used in some of the earliest dishes found, but it’s also one of the very few plants that shows up in all the world’s healing traditions—in traditional Chinese medicine, in Indian Ayurvedic treatises, and in Western folk medicine too.
GRABER: In fact, the origin story of the country of Korea is based on two medicinal plants—one of them is garlic.
SONJA SWANSON: I’m going to start the story the way that my mom always started telling me fairy tales and folktales, which is the Korean version of “once upon a time”: Yetnal-ae, yetnal-ae.
TWILLEY: This is our one and only amazing Gastropod fellow, Sonja Swanson. You may remember her from gathering mesquite in our desert agriculture episode as well as leading us through a tasting of Korean hangover remedies in our hangover episode.
GRABER: And now she is our resident expert on Korea’s origin myth.
SWANSON: So there once lived a bear and a tiger who desperately wanted to become human. So they prayed to Hwanung, who was this heavenly being, and Hwanung says, Sure, but you got to do two things. One, you have to go live in a cave for 100 days. And two, the only thing you can eat is a bundle of mugwort and these 20 bulbs of garlic. So they go in the cave, and the tiger gives up after a few days. But the bear perseveres, and so Hwanung turns her into this beautiful woman. And then he decides to become human too, because why not? And then they get married, and they have a son named Dangun. And then Dangun goes on to found the first Korean kingdom. So basically, Koreans exist because of garlic and garlic runs in our blood.
TWILLEY: But why garlic? Why was garlic the thing that turned a bear into a beautiful woman?
SWANSON: That is an excellent question. I read a couple different theories about this. So. So one is that in order to, you know, go through this transformation, these animals needed like a sacred power. And ancient people really believed that garlic had the power to drive away evil spirits and fend off pestilence. So consuming the garlic would just drive out any animality from them and help them become human.
GRABER: And the second theory?
SWANSON: So the other reason has to do with garlic’s partnership with mugwort, which was the herb that they had to eat with the garlic. So mugwort is kind of seen as this female herb, it’s used to treat women’s ailments all around the world. Its Latin name is actually Artemisia for Artemis, the goddess of childbirth. And then garlic is the male counterpart. And that’s partly because a bulb of garlic is said to resemble a scrotum. So the male and female energy kind of combined to parent them into becoming a human.
GRABER: And today Koreans eat about 17 pounds of that scrotum-like garlic per person per year—we Americans eat only about two pounds each a year.
TWILLEY: But garlic wasn’t only seen as magical in ancient Korea. The earliest recorded mention of garlic’s special powers comes from an Egyptian papyrus that was written about 3500 years ago.
ROBIN CHERRY: It’s a beautiful scroll and it has 22 different uses for garlic. And it’s everything from tumors and heart problems to skin disorders, parasites. And that medical catchall, general malaise.
TWILLEY: Robin Cherry is the author of Garlic: An Edible Biography. And she told us about one particularly intriguing medicinal use of garlic, which was in ancient Egypt, as a fertility test.
CHERRY: Well, there was a test that they would stick a clove of garlic in a woman’s vagina. And if you could smell the garlic on her breath the next day, then she was fertile.
GRABER: From scrotums to the vagina. The thought at the time was that if a woman was blocked somehow, basically that block would mean she wasn’t fertile and couldn’t get pregnant, and also that the garlic smell wouldn’t get through the block. If she did smell of garlic, there was no block.
CHERRY: But garlic really is absorbed into the skin. So you probably had a lot of false positives.
TWILLEY: Eric told us that actually you can rub a clove of garlic on your feet and end up with garlic breath, so that’s a fun one to try at home even if you don’t have a vagina.
GRABER: Not that we recommend putting a clove of garlic in your vagina either. Despite the fact that some people believe it can help cure a yeast infection, doctors say garlic could actually cause infections. Do not put it in your vagina.
TWILLEY: But moving on from vaginas, which I guess we have to, garlic wasn’t just a diagnostic. It was seen as health-giving throughout the ancient world—as a strengthening food good for workers and soldiers.
CHERRY: The slaves who were hired to build the pyramids were fed garlic to keep up their strength. And when it was taken away, they refused to work until it was reinstated.
GRABER: Yep, you heard that correctly, the first labor strike in recorded history took place because the slaves weren’t getting enough garlic. Once they got their rations of garlic reinstated, they got back to work.
TWILLEY: As we know from “Joseph and the Technicolor Dreamcoat”—
GRABER: Or from going to Hebrew school, as well as celebrating Passover every year—
TWILLEY: Also valid. But my point is that those slaves—some of them were definitely Jewish. And they loved their garlic extra much.
CHERRY: The, the book of Ezra encouraged, required, in fact, Jews to eat garlic on Friday nights, which is the eve of the Sabbath, because it served as an aide to passion and fertility and so would enhance the marital relations, also known as sex, that couples were encouraged to enjoy as part of the Jewish Sabbath observance.
TWILLEY: That’s the original reason that Jews became known as garlic eaters. It was clearly a compliment.
CHERRY: It was a combination of the Bible and just, over history, Jewish food used a lot of garlic. So Jews called each other garlic eaters as a positive thing.
GRABER: My people have gotten a lot of things wrong about food—I’m looking at you, Manischewitz—but garlic is one thing we got right. And that’s still true today. My mom is so unable to cook without garlic that I still remember when I was a kid, we had a friend of my parents over for dinner who was allergic, and my mom had no idea what to cook for him that didn’t have garlic in it. She was completely stumped.
TWILLEY: But back to the compliment question. I spoke too soon. Jews might have called each other garlic eaters as a term of affection, but others quickly turned it into an insult.
CHERRY: It became used as a very negative thing, going back to ancient Rome, when Marcus Aurelius would call Jews those rascally garlic eaters.
GRABER: And Jews weren’t the only ones who were derided as garlic eaters. It was used as a negative for southern Italians, and it also was used in general to refer to the lower class.
CHERRY: So Shakespeare mentioned garlic in five of his plays. And it was never used as a positive thing. It was always used to describe someone as a lowly peasant. Most famously, it was in A Midsummer Night’s Dream where Bottom extols his actors to “eat no onions nor garlic, for we’re to utter sweet breath.”
TWILLEY: This was a big shift. Way back in ancient Rome, even the emperors were open about their passion for garlic—Emperor Nero apparently loved it so much he is often credited with inventing garlic mayonnaise, or aioli.
GRABER: A similar shift took place in America. The founding fathers apparently loved garlic, but, by the 1900s, it was solidly avoided by rich WASPs because it was associated with poor European immigrants.
TWILLEY: By then, people who’d managed to elevate their social status wanted to distance themselves from any reminders of their peasant past—including any reminder of their bodily functions. And garlic has a way of reminding you and everyone around you that you are an animal who eats. WASPs weren’t going for that earthy, peasant-y vibe.
GRABER: Robin remembers how extremely cautious her mother was around garlic.
CHERRY: I remember taking one clove of garlic, cutting it in half and spreading it over a flank, an entire flank steak that was designed for four people. So that was kind of the extent of it. So it’s not something I grew up eating a lot of.
TWILLEY: The same garlic phobia was pretty common in the UK as well: I remember the advice to rub a garlic clove around the salad bowl. Not put a garlic clove in the dressing. But just like sex and drugs, the 60s were a decade of garlic experimentation.
HOST: Ok, what are we gonna do with this?
JULIA CHILD: Well, then we’re going to turn this into a garlic mayonnaise, an aioli.
HOST: How much garlic—
CHILD: You can use as much garlic as you want. As someone said, there’s no such thing as a little bit of garlic.
HOST: That’s true, you have a point there.
CHERRY: It was really Julia Child, I think, who, you know, really transformed American cooking. And she taught her readers and the people who watched her show that it was not something you should consider low class, but that you could really enjoy it. And so she and James Beard introduced things like chicken with 40 cloves of garlic or mashed potatoes with 30 cloves of garlic. And she really let people know that it was okay. And I think that was really the transformation.
GRABER: I once made a soup of 20 cloves of garlic but then I did something dumb: I touched my eyes, and I basically burst into tears.
TWILLEY: That was dumb. But with alliums, tears are part of the package. Especially with another popular allium: onions.
GRABER: We as a species have been weeping as we chopped our onions for millennia. But scientists only recently discovered exactly what’s behind those tears. It’s complicated, but what happens is when we chop the onions, it releases an enzyme that was just discovered in Japan in 2002. It’s called the onion lachrymatory factor.
TWILLEY: Lachrymation is the technical term for crying. And what that lachrymatory factor enzyme does is it rearranges some molecules in the onion, and turns them into this sulfurous gas that floats up in the air.
GRABER: When that particular gas meets nerve endings in your eyes, well, it hurts.
TWILLEY: That same molecular rearrangement happens in shallots and also in leeks, although there’s less pain involved there. But it doesn’t happen with garlic—the chemical reaction is subtly different, and so you don’t cry. Unless you stick your fingers in your eyes, like you did, Cynthia.
GRABER: When it comes to painful onions, though—scientists have been working on breeding tear-free versions, and they’ve had some success. We have the story of the onions and why you still can’t find them in your grocery store in our special supporters’ newsletter—go to gastropod.com.
TWILLEY: Along with Eric Block’s top tips for what you can do to reduce the floods of tears that normally accompany the onion chopping experience.
GRABER: But the point here is that the sulfurous, stinky, sometimes painful chemicals that all alliums create, not just onions, they’re only released by cutting—or chomping, if you’re a hungry insect.
BLOCK: As soon as you even so gently touch the plant, put a little pressure on a cell, it bursts and the enzyme, it mixes with the precursor. And abracadabra, you have the strong odor of the garlic.
TWILLEY: Science has proven that if you want the maximum garlic flavor, you should crush your garlic rather than chopping or mincing it—Eric told us that crushing breaks down more of the garlic cell walls, so you get more mixing, and thus more reactions happening, and thus more of that chemical that gives garlic its fabulous aroma: allicin. Not Alison the name, a-l-l-i-c-i-n the chemical!
GRABER: Eric also told us the best thing to do after you crush it is to let your garlic wait around for about 10 minutes before you cook with it, that gives the enzymes just the right amount of time to do their work and give you the most allicin, and the most aromatic, delicious results.
TWILLEY: Eric didn’t explicitly say my next piece of advice, but it is common sense: if you’re cooking something with maximum garlic flavor, do make sure that you and anyone you are going to be spending time with both eat the dish. Because you will, of course, end up with garlic breath. For a while.
BLOCK: Because the garlic breath is due to ingesting garlic and having it pass through the digestive process into the body. And once it gets into the bloodstream, because the compounds that are associated with garlic breath are actually quite stable, they will persist until ultimately the liver, which is the cleansing organ in the body, denatures these compounds and renders them non-volatile and non-odorous.
GRABER: We’ve already talked about the fact that we humans are super sensitive to the sulfur aromas produced by a bulb of garlic. And so we can smell garlic on people’s breath for up to 48 hours after they’ve eaten a particularly garlicky meal.
BLOCK: Now, some people are better at it than others at cleansing what is in their bloodstream. So some people may have very active livers which rapidly remove and deactivate garlic breath, if you will. Other people are not so fortunate and may be on the other side where they are deficient in their abilities to neutralize these smells and may smell, you know, for days and days. Those poor, unfortunate people should probably avoid eating garlic.
TWILLEY: This part of today’s episode is making me sad. I am a poor unfortunate person whose body is not very good at handling the chemicals that make garlic so potent—in fact, in my old age, I have become so bad at it that I react to garlic in a most unfortunate way. I still love the smell and the taste, but I really don’t do well when I eat it anymore, even cooked. It is the most depressing thing.
GRABER: But your affliction, Nicky, was actually helpful to me this year—one day, I thought my partner Tim was felled by COVID because he spent the entire day feeling sick and lying on the couch with zero energy. But I did some research on garlic sensitivity because I know of your reaction to it, and I’d made a yoghurt sauce with plenty of raw garlic the night before. Turns out all those symptoms are indeed related to garlic. There was one further incident like a week later, and now we know. It wasn’t COVID, it WAS the garlic. So now, no raw garlic for Tim. So far he can still eat it cooked.
TWILLEY: I’m glad my personal tragedy was of service. And at least I can still enjoy the smell of garlic, which is a powerful thing. Traditionally, it offers protection against all kinds of bad things. In Sweden, it’s supposed to protect cows from trolls.
GRABER: And if you are unlucky enough to meet a vampire, you better hope you have garlic breath, because that’s the proven way to put them off drinking your blood.
XANDER: Ok so, crosses, garlic, stake to the heart.
BUFFY: That’ll get it done.
XANDER: Cool. Of course, I don’t actually have any of those things.
DOCTOR: Sleep well, Miss Lucy. Ze garlic will protect you!
BLOCK: Going much further back in time, people in ancient times, thousands of years ago would wear garlic in amulets around their neck. And place little packets of garlic on the doorposts. It was thought that evil spirits could cause disease. And by using garlic, which had a very strong odor that might repel a disease, and those ideas were then brought forward in time and, and used during the plagues and in this unusual face mask as well.
GRABER: Eric is describing strange beaked masks that plague doctors wore in the 1600s, and they’d put garlic and other herbs in the beaks of these masks to help protect the doctors from the plague, in theory anyway.
TWILLEY: Those masks are quite a look. But, actually, if that garlic had been crushed 10 minutes earlier to release the allicin, it might—might—maybe—have worked!
BLOCK: And allicin is quite an amazing molecule because not only is it biologically active and solution, but it’s also, it can be vaporized. And it’s one of the rare examples of a volatile antibiotic. So simply by inhaling allicin, one might be able to treat infections with it.
GRABER: Unclear whether garlic helped fight the plague, but cleaning up infections is one of things that garlic has been used for over centuries. It was put on open wounds, before we had antibiotics.
TWILLEY: In World War I, the British government actually put out a call for the public to save garlic, so that they could send it to the front to help treat wounded soldiers in the trenches.
GRABER: But you had to be careful and not use too much garlic juice on your skin for too long, because it can cause a pretty nasty burn.
BLOCK: And in fact, there are people that have applied—I can give you one anecdote. I think when some young men were trying to avoid military service, and think this was in Israel, they applied garlic to their knees. And then showed up at their—for their medical examination and said, Look, doctor, I have this bad problem with my knees. I can’t serve in the military. And it turned out that they had actually rubbed garlic on their skin and produced a pretty nasty second degree burn.
TWILLEY: So garlic has powers. Louis Pasteur was the first to actually show that yes, garlic does kill microbes in the lab. In the 1850s, Pasteur put some garlic in a bacteria-smeared petri dish, and the bacteria in a circle all around each garlic clove died.
GRABER: This might in fact be why people kept using garlic on the battlefield, but after the second World War, we had penicillin, and so garlic, with its potential to burn skin, was pretty much abandoned.
TWILLEY: Antibiotics are great and all, but Eric says garlic has been credited with many many medical powers over the past century—
BLOCK: Well, essentially, it’s an A through Z list of all known afflictions of mankind that have been claimed to be treated by garlic, from high blood pressure and cancer and viral infections and colds to all sorts of conditions.
GRABER: In recent decades, scientists have done some studies that seem to show that garlic might be helpful for some health conditions, like reducing blood pressure.
BLOCK: It’s a mixed story because a lot of the papers that appear in the scientific literature are done in petri dishes. Garlic and its components are wonderfully effective when they are used in test tubes and in cultures. The problem is that the relatively simple structure of the compounds in garlic is readily broken down in the digestive system and in the blood to things that are no longer active.
TWILLEY: That magical allicin—it is a potent molecule, but Eric isn’t sure that its powers will actually transfer from the petri dish to a human body—it just gets broken down too quickly.
GRABER: That said, garlic’s abilities to kill microbes might be useful.
BLOCK: I just read a paper about the use of garlic as a gargle for the prevention of cavities. So in the mouth, if you were to gargle with garlic, you would reduce the population of the bacteria that can cause dental cavities. So, of course, you’d come out with pretty horrible, bad breath.
TWILLEY: When the cure is worse than the disease. But this kind of important research does give us hope that maybe garlic in food might kill some microbes—at least before we eat it.
GRABER: In other words, maybe Rob and Ben’s experiment will work.
DUNN: We’re going to slowly get started today and we’re going to a series of things. So we’re going to start by having Dr. Tate Paulette, an amazing Mesopotamian archaeologist, talk to us a little bit about the context of the recipe we’ll be making today.
TWILLEY: OK, we’re back in North Carolina, in the kitchen at NC State. And while Rob talks to the “Spice is Nice” kids, we can introduce you to Tate. He is particularly interested in food and the connection between food and politics. The sites where he does his excavations are some of the earliest centralized cities in human history, and he says food played a major role in government.
GRABER: But he can’t find a lot of actual recipes.
TATE PAULETTE: Recipes are very rare in the whole Mesopotamian writing tradition. But what you get lots of is documents that have to do with delivery of ingredients. These texts were often being produced by the state or by big temples. And they cared a lot about their storage facilities and exactly how much stuff they had in them and how much stuff was made with that, if they sent it out to the brewery or to the kitchen. So we get lots of documents about that, listing ingredients. They loved listing things and a lot of them were foods.
TWILLEY: I like lists too. They’re very soothing.
GRABER: But eventually the Mesopotamians did write down some recipes in addition to their food lists. And just a few dozen of those recipes have survived on clay tablets, they’re the very earliest recipes ever found—
PAULETTE: They date to about 1730 B.C. into this old Babylonian period. So were four of these texts. They’re held at Yale.
TWILLEY: We’ve talked about these clay tablets in our recipe episode. There’s a recipe for a pie with lots of tiny little birds in it. There’s a couple of veggie sort of broth-type recipes, with currants and dill and three types of alliums: leeks, onions, and garlic. And there’s some recipes for meat stews, again with all the alliums.
PAULETTE: And almost certainly the recipes we’re looking at are not recipes for everyday people. We don’t really know that much about these, about the context of them, because unfortunately we don’t really know where they were excavated. They came off of the art market, which means we lose all kinds of information about their broader context. And so we don’t even know exactly what site they were excavated from. But our assumption is usually that these have something to do with elite-level dining.
GRABER: Rob also pointed out that this is just the moment that these recipes were actually written down, similar stews with lots of alliums were probably eaten for thousands of years before that. In fact, as he already mentioned earlier this episode, a mesolithic hunter-gatherer meal was found with remnants of garlic.
TWILLEY: For their experiment, Rob and Ben and the “Spice is Nice” club chose a simple recipe from the tablets called Stew of Lamb.
PAULETTE: Stew of lamb. Meat is used. You prepare water. You add fat. You add fine grain salt, dried barley cakes, onion, Persian shallot and milk. You crush and add leek and garlic. That’s the whole recipe.
GRABER: Not very specific. Nobody knows exactly how the barley cakes were made either, but Ben came up with a recipe based on other old ones. He prepared them before the students showed up—basically he just parboiled some barley, mixed it with flour made from an ancient version of wheat still around called einkorn and with animal fat and then toasted spoonfuls into hard biscuits that could be added to the stew where they kind of rehydrated like dumplings. He explained it all to the students.
CHAPMAN: What we did was take the barley and boil it for about eight minutes. Barley is a grain. If you guys want to pass this around and feel what it feels like. Don’t eat it after all of your classmates have put their hands in it.
TWILLEY: With that quick food safety warning, plus some words of wisdom about knives and gas stoves and being careful, the students divided into three different groups. One group was making the recipe exactly as it was written except they were leaving out salt. Another group made the recipe with salt but without any of the alliums—they left out the leeks and the shallots and the garlic.
GRABER: And of course one group made the recipe in its entirety, with the salt and the alliums—that’s the control.
TWILLEY: So the hypothesis that Rob and Ben and the kids were trying to test is that the alliums in this ancient recipe were going to keep the stew safer by stopping some microbes from growing. To figure that out, they needed a version with the alliums and one without, to see the difference.
GRABER: And they also made a version without salt, because salt is important for food preservation. Savory fermented foods nearly always have lots of salt. This way, they could see if there’s a difference in the microbes growing in the version with the alliums compared to the version with the salt.
STUDENT 1: Add barley, onions and shallot—oh my god, I can’t pronounce that. Shallots. And cook until soft. Add whole milk and water, crumble barley cakes into the stew. Allow pot to simmer until the meat and the grain soften. Serve with garnish or crushed leek and garlic and fill lab jars half of with—with soup. Screw on the lids and fill out the observation sheet.
GRABER: Some of the students were more hesitant than others—some were pretty nervous about sauteing the onions and then the meat.
STUDENT 2: Should we put it on medium?
STUDENT 3: Cook the meat…
STUDENT 2: How much has to be crumbled into it?
TWILLEY: Others were pretty sophisticated.
STUDENT 4: I can’t see the—whatever Gordon Ramsay calls it—
STUDENT 5: The fond, the fond, no more fond.
TWILLEY: This was my favorite moment, when one of the teenage chefs got all worried about getting a good fond—which is a fancy French word for the brown stuff left on the pan after you sear meat, which you then deglaze to make a delicious French gravy or jus.
GRABER: She knows her food TV better than I do—I’d never heard the word before! We checked in on some students who were trying to figure out if the milk had curdled like it was supposed to.
STUDENT 6: A little bit, not quite yet. Yeah.
STUDENT 7: I think it looks like clam chowder. Is what I—is the best comparison.
STUDENT 6: It smells good. I think it smells good.
TWILLEY: Once the students were done cooking, it was over to Lauren Nichols who works with Rob in his lab. She was in charge of ladling the three different stews into jars for the experiment.
LAUREN NICHOLS: Now, I’m just going to divide this evenly between three of these mason jars. And one will go to each of the two schools. And then we will keep one replicate.
GRABER: While this was going on, Natalie Seymour—she works in Ben’s lab—she had been preparing another batch of stew so the students could have a chance to taste the same recipe they’d made.
TWILLEY: And the verdict was pretty positive.
STUDENT 8: It was really good. I don’t know what it tastes like though. It’s very thick and everything.
STUDENT 9: I got a nice lamb chunk. It looks a little, little rare. Not going to lie. All right. Ready? One, two, three. TAKING A BITE. Mmm. It’s super like creamy and thick. Like very—it tastes like—it feels like pudding almost. I, I did eat lamb for the first time. I don’t regret it. It was really good. LAUGHS.
GRABER: And of course Nicky and I had to take a taste, too.
GRABER: It looks like the inside of chicken pot pie, which is not actually that attractive.
TWILLEY: It’s beige. Whatever.
TWILLEY: Beige, beige food is great.
GRABER: I mean, I love beige food. This is just kind of gloppy, too.
TWILLEY: OK. I want the lamb chunk.
GRABER: I do, too. There should be more than one.
GRABER: See if I can get one here. Yeah, there’s another one down there.
TWILLEY: Oh yeah. Here we go.
GRABER: Yep. Mmm. It’s good.
TWILLEY: It’s great.
GRABER: It’s savory and umami and creamy.
TWILLEY: Creamy. I would eat more.
GRABER: I think I’m gonna eat more. Here.
TWILLEY: Why not?
GRABER: No one else is eating it. We’re good.
TWILLEY: Everyone else got busy with clean up. Tate showed some of the students how to write Mesoptamiam script. And we chowed down. And then Rob sent the students away with strict instructions on their next steps.
GRABER: He told them they had to carefully note how the sample looked and smelled every day, for the next ten days. They could not miss a single day.
DUNN: And I have no idea what we’ll see. But it’s going to be fun and stinky.
STUDENTS: Thank you! CLAPPING
TWILLEY: After the ten days, Rob and Ben collected the jars and they sampled the contents, and they sent those samples off to a lab to be genetically sequenced, so they could see exactly what was living in each of those jars.
GRABER: We were planning on checking back in with the team a few months later in the spring to find out the results. But, the pandemic hit, the folks in the sequencing lab couldn’t work, Rob and Ben couldn’t get into their labs, and everything was on hold for basically a year.
TWILLEY: But finally, a couple weeks ago, Rob emailed to say the results were back, and so we hopped on the official platform of 2020: Zoom.
TWILLEY: Can you hear us yet?
DUNN: Hey Nicky.
TWILLEY: How are you?
DUNN: Good, how you doin’. Hey Cynthia.
GRABER: Nice to talk to you again.
TWILLEY: Okay. And now I think we have Ben.
CHAPMAN: Hey guys.
TWILLEY: I’m going to start with the first and most obvious question, which is what did you find?
DUNN: So the first thing, the first result that we get back is basically a list of which kinds of bacteria are in each sample and then how much of each one. And so the first thing that we see is that in these samples, in the old stew, in the very old, old stew, that we see all kinds of bacteria that we don’t really want to ingest.
GRABER: Rob found a bunch of microbes growing that are pretty bad news and they’re usually associated with your gut. Unsurprisingly.
DUNN: And so it’s a whole circus of species you don’t really want to be ingesting too often. And so that’s the first thing. So when you leave your stew out, bad things grow readily.
TWILLEY: In fact, we do not need science to verify this one: leaving your lamb stew on the countertop for ten days is a terrible idea.
GRABER: But we did need science to tell us something else that was pretty interesting.
DUNN: What we see is that, yes, they’re super, super different bacteria if we change the ingredients.
TWILLEY: In other words, the experiment really worked. All three stews had very different microbes living in them.
GRABER: The one without salt had a lot more of a particular bacteria that is the most common cause of foodborne illness in the US. Not super surprising—as we said, salt is a preservative.
TWILLEY: But what about alliums? That’s what we’re here for! And it turns out that when Rob and Ben compared the stew without alliums to the regular salty garlicky oniony one, they saw something interesting.
DUNN: When we leave the alliums out, so our garlic and onions and leeks, we see tons of Klebsiella bacteria. And so this is another one of these gut microbes that can be an opportunistic pathogen. It can cause diarrhea. It can actually cause pretty severe infections.
GRABER: Basically the takeaway is that garlic and the other alliums are helping keep the Klebsiella down, it’s helping kill them off.
TWILLEY: Ben and Rob hoped they’d see that the alliums did something, but these findings really exceeded their expectations
CHAPMAN: I think the surprise for me was how striking the control is different from once we started removing alliums and salts. That in this kind of like cool concoction, all of a sudden, if we start taking out garlic, that it matters for the microbial population.
DUNN: And just how big those changes are, I think, surprises me, even with our small sample size on this very preliminary experiment.
GRABER: Of course after ten days left out, even the allium-rich version had some pretty unappealing and potentially harmful bugs in it. But what about how we think our ancient ancestors might have used garlic, to help keep food good for only another six to eight hours or so? They probably weren’t holding onto their leftover lamb stew for ten days.
CHAPMAN: We always have these trade-offs in science, especially when we’re trying to get a first look at what might be going on. And so that was one of them for this one. And so we erred on the side of long term. And so it’s a much better chance that we’re going to see some effect of what the garlic can do.
TWILLEY: Basically they deliberately let the stew get super funky in case the difference was really small and only showed up when the bacteria had had enough time to go really wild.
GRABER: So we don’t have a sample from the stews after just six or twelve hours, to see whether garlic could have kept anyone who ate stew the next morning safe. But Rob’s colleague Lauren said that what we do have is the student data—every day, students examined their stews and recorded their observations.
NICHOLS: And so they were taking pH measurements and also describing the smell. So for example, the control that had all of the ingredients, within two or three days, the descriptions were really just like onions. Onions, and mild rot. Whereas at that point some of the ones with no alliums, for example, they didn’t even trust enough to smell or were already describing as “puke” or “vomit.”
GRABER: Rob said the puke smell is a known sign of a bad news bug, and so it at least smelled to the students like the alliums were helping keep the food safe for a bit longer.
DUNN: And so if you’re thinking about how a traditional scientist in the kitchen is figuring out what to use and what not to use—well, if one of these versions of the dish smells like vomit after two days and one doesn’t, that’s a really easy thing to learn. And so I think we’re, we’re seeing some kind of glimpse, too, into how one might begin to learn from culinary experiments or begin to learn from them thousands of years ago, even without the year-long effort in sequencing that kept us from talking to you for so long.
TWILLEY: Rob says there’s also still plenty of data to come—the results of the fungus sequencing aren’t back yet, so we don’t know what impact alliums have on fungal growth. And they haven’t gone into the detail on which particular strains of each microbe were in the stews—some strains are more dangerous than others. So that research still lies ahead.
GRABER: But based on how clear it was that alliums did have an impact on the microbes in the stew, the team is now coming up with other experiments they might do in the future to try to tease out the full effects of cooking with alliums.
TWILLEY: One question that couldn’t be teased out in this experiment is which allium is doing what? Do you need all three, or is the garlic doing most of the microbe killing?
GRABER: There’s a hint from research done in petri dishes. Onions do kill microbes in the lab, but garlic appears to kill even more. So it seems like garlic has stronger microbe-killing firepower—but we just don’t know. Maybe they boost each other by being cooked together. That works still needs to be done.
TWILLEY: But even sticking with the ancient recipe, with all the alliums mixed together, Rob still has more questions.
DUNN: One is that we sort of loosely approximated an ancient stew but we didn’t approximate its situation. And so I think one thing we could do is to think about, well, how do we make this stew more like it would have been made in the time that it was being made. And how do we think about what the pathogens that would have been the biggest risk at that time were?
TWILLEY: Our suggestion—the Gastropod special request—is that next time, they should take samples every few hours or so for the first couple of days, to see when it starts to get bad, and whether the garlic helps push that back. That’s what I want to know: Do shallots and leeks mean I can have lamb stew for breakfast even if I forgot to refrigerate it?
GRABER: Well, at the moment, Ben, who is a nationally recognized expert on food safety—he’d tell you to put it in the fridge.
CHAPMAN: So, no, I’m still gonna trust the sort of modern refrigeration practices to focus on my food safety aspects. But that’s my bias as a food safety researcher.
TWILLEY: The fridge, a magical magical appliance, even more magical than garlic. Did I mention I’m writing a book on it?
GRABER: Yes, you did. Many times in fact, and I’m looking forward to it.
TWILLEY: So Ben says stick to the fridge, and Rob also has some culinary advice as we head into the holiday season.
DUNN: So if anybody has any doubt about their holiday meals, the key take home is to add more garlic and more salt. LAUGHTER
GRABER: And that is it! For this episode, and for 2020! Huge thanks once again to the Alfred P. Sloan Foundation for the Public Understanding of Science, Technology, and Economics, as well as the Burroughs Wellcome Fund for our coverage of biomedical research. Thank you so much for your support of Gastropod.
TWILLEY: Thanks also to our amazing Gastropod Fellow, Sonja Swanson. We would not have made it through 2020 without her.
GRABER: Thanks to Rob Dunn, Ben Chapman, Natalie Seymour, Lauren Nichols, Robin Cherry, and Eric Block, we have links to their labs and their books and their research at gastropod.com.
TWILLEY: We’ll be back in early February. Enjoy the break, keep in touch, and all our best for a happy new year!