Trade, tyranny, and untapped potential: The history and science of spices

For thousands of years, the rise and fall of empires and the global economy were closely tied to something you might not expect: spices. The spice trade began around 1000 BCE, localized to southeast Asia and the Middle East. But by the beginning of the next millennia, it had rapidly expanded and nations vied to control it. Today it’s typically far less work to find and purchase spices you want, but just because they’re no longer starting wars that upend nations doesn’t mean they’re any less important. Because while you might think spices are mostly about making your food taste good, science — and particularly chemistry — is finding they can do a whole lot more.

Transcript of this Episode

Sam Jones: For thousands of years, the rise and fall of empires and the global economy were closely tied to something you might not expect: spices. The spice trade began around 1000 BCE, localized to southeast Asia and the Middle East. But by the beginning of the new millennia, it had rapidly expanded and nations vied to control it.

Today it’s typically far less work to find and purchase spices you want, but just because they’re no longer starting wars that upend nations doesn’t mean they’re any less important. Because while you might think spices are mostly about making your food taste good, science — and particularly chemistry — is finding they can do a whole lot more.

Welcome to Tiny Matters, a science podcast about the little things that have a big impact on our society, past and present. I’m Sam Jones and I’m joined by my co-host Deboki Chakravarti.

Deboki Chakravarti: In today’s episode Sam and I will be talking about a handful of spices, and sharing some of the fascinating history and science behind the molecules they contain, some of which are referred to as bioactive — meaning they have a positive effect on our health, possibly even preventing disease. So first off, let’s talk about foods, and just how much we can learn from exploring what’s in them.

Sam with Kantha: From my standpoint, I hear a lot about marine bioactive compounds that researchers are looking to for new drug development, but I find that I see less about finding active compounds in our foods. And so I'm wondering if you feel like that's the case too, and if so, why?

Kantha Shelke: You've made a very keen observation, and I'm hoping that you're wrong, but I think you're right. And I'll explain why…

Deboki Chakravarti: That’s chemist Kantha Shelke, the founder of Corvus Blue, a contract food science and research firm and a senior lecturer at Johns Hopkins University. She specializes in the chemistry and regulation of ingredients.

Kantha Shelke: Both marine and food derived compounds have been researched, but the marine bioactive compounds are getting more attention because of their role in drug development. They have very unique capabilities. They're often potent compounds. Food-derived bioactives, especially those from spices, those are very important for human health and for overall health, but they're also a part of our daily life.

Deboki: We can find spices, which are plant-derived substances that we often use for food flavoring or color, in our gardens, our kitchens and our pantries. In comparison, Kantha told us, something like a molecule from a sea sponge may sound more exciting, and even have a kind of science fiction feel.

Kantha Shelke: Whereas things from foods sounds like a salad, sounds like you're making a juice or an extract. So I think that might be one issue.

Deboki: Another possible issue, she says, is that, compared to novel compounds, the ones in food might seem old and obvious. But she argues we should be working to change that perception.

Sam: I had to think a lot about spices when chatting with Kantha and working on this episode and it was hard to think of a favorite. But depending on my mood I love cayenne pepper, which we’re going to talk about today. Deboki, do you have a favorite spice?

Deboki: Ooh, this was surprisingly hard. I asked my husband because he does almost all the cooking in our house so I figured he would know, and he said Posh Spice, which wasn’t helpful. But then he said Szechuan peppercorn, which I think is probably true. I love Szechuan food, and those peppercorns give it a lot of its intensity.

Sam: I also love Szechuan food, but I always love a Spice Girls reference. So today we’re going on a little spice tour, if you will. But before we do please remember, we are not MDs and we are never giving medical advice on Tiny Matters. Always talk to your doctor before making any big dietary changes.

Kantha Shelke: I love ingredients, so anything to do with how ingredients are grown, how they are harvested, how they are processed and handled, how they are shipped and how they are turned into food products, but also what those ingredients do to the human body as in the clinical physiological effects, what happens to the ingredients when you process them in a certain way, all the way to understand what happens to an ingredient when it comes into a food product.

Deboki: Kantha says spices are an essential part of who she is, having grown up in India.

Kantha Shelke: So we, I think more than any other nation in the world, are known for spices and how we use them, not only as part of our culinary rituals, but also our personal care rituals.

Deboki: So there’s a handful of spices we’re going to talk about today, starting with one Kantha really loves: saffron. Saffron comes from the Crocus sativus flower, commonly known as the "saffron crocus.” The beautiful, bright orange saffron threads you might see in food are actually the stamens of the flower, the little filaments at its center that release pollen. Kantha remembers picking them as a kid.

Kantha Shelke: It was part of our afternoon activity during the springtime when the saffron crocuses would peep out of the snow, and our school teachers would take us to the gardens and we would pick the saffron out, and then we would bring it in. There would be a treat usually for what we did, and it would be this wonderful dessert, which is a creamy pudding either with rice or with vermicelli. And it had sugar and nuts and different dried fruits, and then these strings of saffron on it. So that for me is what my childhood was made of.

Sam: We’re going to talk about some of the compounds in saffron that are intriguing scientists, but first… let’s talk about how expensive saffron is, because that actually caught me off guard. Saffron can cost thousands of dollars per pound — one reference I found priced it at around $10,000 per pound. Yes, you are typically using minute amounts of the spice, but that still makes it the most expensive food on Earth.

In fact, you need to harvest around 50,000 flowers to get that pound of saffron, because each flower only has a few saffron threads.

Deboki: But beyond being a luxury spice, what scientists are now discovering is that saffron contains some important compounds, particularly compounds called crocins that Kantha told us are becoming increasingly recognized for their potential health benefits.

Kantha Shelke: They are responsible for the deep orange color, that golden color, but they also have some very unique antioxidant, anti-inflammatory, and most importantly neuroprotective properties.

Deboki: Evidence is mounting that these compounds could help protect our central nervous system, particularly by blocking the activity of free radicals. Free radicals are molecules with an unpaired electron, which makes them unstable and highly reactive. They are made naturally when our cells generate energy, but in high amounts, they can lead to serious cell and tissue damage. That damage has been linked to chronic inflammation and a number of diseases, including Alzheimer’s and Parkinson’s.

Sam: Last year, researchers showed that one of the crocins — often just referred to as “crocin” which I know is confusing — can reduce neuroinflammation and cognitive impairment in mouse models of Alzheimer’s disease. Scientists also studied the effect of crocin in rats with brain ischemia, which is where there isn’t enough blood flowing to the brain, leading to the death of brain tissue. They found that giving the rats crocin helped prevent cell death in the hippocampus, improving their memory. There have been a number of other rat and mouse studies and even studies in fruit flies that have shown crocin might have a number of positive effects related to cognition and memory.

Deboki: It’s much more challenging to investigate the effect of saffron’s molecules in the human brain, but there has still been some interesting work. One study that I found fascinating looked at crocin’s impact on participants undergoing methadone maintenance treatment. Methadone is a synthetic opioid and highly effective medication used to treat opioid use disorder, but it has also been associated with depression and anxiety. After eight weeks of being given either a placebo or 30 mg of crocin per day, the participants given crocin showed a significant decrease in both depression and anxiety.

Sam: Which is so interesting to me, and potentially super valuable. I’m excited to see where all of this research goes, because based on the number of publications I was seeing, it has definitely picked up over the last decade. So now I want to talk about a spice that I think everyone knows and I would guess has been told to consume at one point or another: ginger. During my first trimester of pregnancy when I had some nausea I had multiple doctors tell me that a ginger chew or hard candy could help a bit.

Kantha Shelke: Ginger is one of the oldest spices, and it was valued for a very long time for settling your stomach. Sailors noticed that if you took a piece of ginger, it calmed your stomach, especially when you were in turbulent seas. And they would actually take a piece of ginger… wrap a piece of bread around it and then consume it.

But there's something fascinating about ginger's chemistry, and that is it matters what kind of ginger you use.

Deboki: In fresh ginger there’s a lot of a compound called gingerol. It’s responsible for that spiciness and warm feeling you get from ginger. But Kantha told us that when ginger is dried, you get something called shogaol. And shogaol, particularly 6-shaogal, is responsible for those anti-nausea effects.

Kantha Shelke: Now in sushi, you know how they have pickled ginger? … That pickled ginger, it has a very different compound. It's a milder compound. It's called zingerone. Now this one has a slightly sweet taste, but it also acts as an antibacterial.

Deboki: Kantha told us that the original reason that you get pickled ginger with your sushi is so that, as you eat, the zingerone can counter any bacterial pathogens that may be lurking in the uncooked fish.

Sam: I had no idea. And now I’ve just started liking the taste of ginger on sushi. Win-win I guess.

Kantha Shelke: It really matters, therefore, is it fresh, dried or pickled, because each one of them is very different…But the most fascinating point about ginger that I like is that Queen Elizabeth I apparently created the first gingerbread man where she made cookies with this because they would have travelers coming to the castle, the palace, and who often because of their travels had upset stomachs. So she would make these gingerbread cookies and give them to the travelers. And that's how ginger got into cookies.

Sam with Kantha: Oh, I love that. That's such a fun story… Well, now to pivot to a spice that I think some people might say is less soothing, but is delicious is … cayenne pepper, and more specifically capsaicin because I feel like in my research, that's where I've found a lot of people are looking into capsaicin to help with a number of things. One thing that I think is so interesting and maybe counterintuitive to some is that it's being looked at for treating pain, and it seems to actually be quite effective at it. I mean, there's over the counter stuff that you can buy that is formulated with capsaicin for that purpose. And so I'm wondering, what is going on there? How does that work? How are we treating pain with something that people find painful?

Kantha Shelke: Very, very, very true. Well, you are absolutely right, but did you know that …cayenne pepper has been used for thousands of years, not just for the spicing, but to relieve pain. It was native to Central and South America, and so the Aztec and Mayan cultures apparently used them in their traditions and particularly when they got injured. So how does this work? People have always wondered, shouldn't that hurt you more? Because when you put it in your mouth, it burns you.

Deboki: When you use cayenne pepper on your skin, its active compound capsaicin will bind to cell receptors on pain and heat-sensing neurons. It essentially tricks your nervous system into thinking you’re on fire in that area, rerouting your body's pain signaling.

Kantha Shelke: So it's sort of like, I'm going to hurt you more here so you'll forget that pain there. And it's a very odd combination of how it actually counters the pain, and it'll slowly bring the pain down.

Deboki: In addition to pain-regulating lotions and patches, capsaicin is the active ingredient in pepper spray. Kantha also told us that people will sometimes add capsaicin to water and sprinkle it on their plants to deter deer, squirrels and other animals. But apparently birds are fine with capsaicin, because unlike us mammals, they don’t have the pain receptors that capsaicin binds to.

Sam: Alright, on to another molecule that I think some people would also call spicy, although in a different way than capsaicin. I’m talking about cinnamon, a spice Kantha told us that, at points over the last millennia, has been considered worth its weight in gold. In ancient Egypt it was used in embalming, and in China and India it has been used in traditional medicines, believed to help with a number of conditions. In the 16th and 17th centuries, the Portuguese and Dutch battled over what is now Sri Lanka to gain control of the cinnamon trade.

Deboki: The main compound in cinnamon is cinnamaldehyde, which gives cinnamon its smell and flavor. But it is also a natural antimicrobial — killing bacteria and fungi — and an insecticide.

Kantha Shelke: It doesn't affect cats and dogs and other animals, but it's very effective against insects.

Sam with Kantha: It's fascinating how some species just are not responding to certain compounds the same way. I mean, it makes sense, right? …But it is interesting to think that for capsaicin, it could work as a pesticide, but not for birds. For cinnamaldehyde, you're going to be able to target insects, but not a lot of other animals.

Kantha Shelke: But cinnamon, also cinnamaldehyde, is also being considered as a very good natural antimicrobial because it kills bacteria like E. coli. And I believe that's the reason how cinnamon came to be used in Asian cooking …We did not have access to refrigeration or cold weather, so meat had to be cooked immediately. If not, it was stored with spices like this that helped prevent it from spoilage. And that's how that combination happened to come around.

Deboki: This all tracks with what I learned about Indian food growing up, and why our food has all these spices in it. Obviously it helps that the spices like cinnamon make our food taste really good, but it’s cool that there’s this additional functionality.

Sam: I was looking into it more and cinnamon is used in so many Asian dishes, even ones I hadn’t thought of like in different braised meats and stews in Chinese cooking or Vietnamese pho broth. It’s just really cool.

Deboki: OK we have one more spice we want to talk about today: turmeric. On the outside it looks a lot like ginger and it’s actually part of the ginger family. But when you cut it open it’s a bright orange, similar in hue to a cooked sweet potato. Turmeric is a big part of Indian culture. When I got married, I did this Bengali tradition called the “gaye holoud,” which translates to “turmeric on the body,” where our family and family friends put turmeric on my face.

But not all the news around turmeric has been good. It's possible you’ve seen this spice in the news, particularly over the last few years, for less savory reasons. There have been a number of recalls of turmeric due to lead contamination, mainly traced back to Bangladesh and India, where the United States gets most of its turmeric. Lead is incredibly dangerous for anyone — high levels can lead to permanent brain damage and even death — but it’s particularly dangerous for children as their brains develop, putting them at risk for hearing loss, learning difficulties, and neurodevelopmental disorders, including schizophrenia.

Sam: Back in 2010, the Times of India reported that during a raid of a spice-manufacturing plant by the Indian Food and Drug Authority, over 100 bags of raw turmeric were found to be contaminated with lead chromate. In 2014, researchers collected turmeric samples from 18 households in rural Bangladesh and found that lead concentrations could be up to 483 ppm. For reference, the allowable level of lead in turmeric is 2.5 ppm. In 2019, a much larger study in Bangladesh showed similar levels of lead in turmeric.

So why lead? Well, lead chromate, also known as chrome yellow, is a pigment. And it’s sometimes used to hide the marks of pests or other aesthetic blemishes and to make the spice look brighter to attract buyers who will then process it and sell it in bulk.

Following the 2019 study, the The Bangladeshi Food Safety Authority cracked down on lead chromate adulteration in turmeric, and a follow up study in 2023 that looked at over 600 market turmeric samples showed that lead concentration decreased from 47% in 2019 to 0% in 2021. Lead levels in the blood of turmeric mill workers also dropped significantly. This whole lead chromate issue has nothing to do with turmeric itself, but I felt like we needed to address it. OK, so, on to the positives.

Kantha Shelke: I have a special place in my heart for turmeric because it is one of the most revered spices both in medicine and in cuisine for millennia… So in Asian culture, it's usually known as the golden goddess because it's used in healing, it’s used in balancing of digestion. One of the reasons, again, it's used in our cooking is because it works with the other compounds. And the magic in turmeric comes from its bioactives, a family of compounds called curcuminoids.

Deboki: The best known of the curcuminoids is curcumin, which is touted for its antioxidant and anti-inflammatory properties. And, in part because of those qualities, it is being studied as a compound that could be used to prevent or treat cancer. In looking into cancer research in particular, I came across a review article that found, from 1983 to 2018, 4,738 papers were published on curcumin and cancer. So to say this compound is “of interest” feels like a serious understatement. But while scientists have seen in vitro it can affect a lot of signaling pathways and molecules involved in cancer, it’s hard to pinpoint exactly how it would work as a method to prevent or treat the disease.

And curcumin on its own is not super bioavailable, meaning it isn’t well absorbed into the body. Combine it with other compounds, though, and it becomes more impactful.

Kantha Shelke: When you take turmeric and you combine it with black pepper — and black pepper contains piperine — they combine together and they become far more bioavailable.

So I remember my grandmother, the minute we started coughing, she would warm some milk with a couple of black peppercorns that were cracked, only cracked so we could pick them out. So she'd put them and then she'd warm the milk, and then she would stir in some honey and turmeric. And that's what today I think the various coffee shops are selling. But it goes back to my childhood.

Sam with Kantha: What do you think the least appreciated spice with the most potential is in terms of bioactive compounds?

Kantha Shelke: To me, that's like asking a person, a mother, which one of our children is a favorite… But what you are going to see now is another range of spices that are going to gain prominence. So cumin seeds, whether they are black cumin or just regular cumin, have a number of properties.

We've been having problems with chickens and salmonella in chickens. Well, there's been some research that's been done in a couple of universities here that have shown that the oil or just the black cumin seed, if added to the chicken feed, actually cuts down their salmonella content. So it acts as an antibacterial, which then goes back to cumin is always a component of every Indian chicken curry dish because you want to make sure that you are countering, even though it is cooked, you're making sure it's countered.

Deboki: I had no idea that black cumin seed was being pursued as an antibiotic alternative to reducing Salmonella in chicken feed. Both Salmonella and antibiotic resistance are such huge issues at poultry farms, so it’s great to see people pursuing these kinds of reduction strategies. But cumin doesn’t stop there.

Kantha Shelke: Cumin oils are now being used as facials. So you want to manage to balance the microbes on your skin. So this used to be the regimen of queens like Cleopatra. They're now coming back and you'll see black cumin oil and fennel also for that matter, in various personal care products.

Sam: Spices really do it all. After chatting with Kantha I Googled “cumin oil for…” and the first thing that popped up was “cumin oil for hair.” I had no idea this was such a big industry. We’re all just trying to have hair like Cleopatra I guess.

All right, shall we Tiny Show and Tell?

Deboki: Yeah, let's do it.

Sam: Mine is highly unrelated.

Deboki: Me too.

Sam: Okay, then I'll just go first.

Deboki: Cool.

Sam: So, Deboki, I want to tell you about how flamingos trap prey.

Deboki: I'm excited.

Sam: This is something I really hadn't thought about, I think of flamingos as, how we all picture them, right? They're kind of standing up, they're not in super high water most of the time. They can cruise around in water, but you don't see them as much like that. But I came across this fun new study about how they've developed a bunch of different techniques to essentially create a water tornado or vortex to trap their meal.

Deboki: Oh.

Sam: So, the study included watching the behaviors of Chilean flamingos in the Nashville Zoo, as well as looking at 3D printed models of their feet and L-shaped bills. So, what the researchers found was that the flamingos used their webbed feet to churn up sediment at the bottom, and then they'll have their heads underwater and they'll draw the sediment to the surface by jerking their heads upwards, but they continue to keep their heads facing upside down, and they'll move their beaks really quickly, something that at least in the press release they call chattering. And it kind of makes sense if you think about the super fast opening and closing of their beak. And I guess that stirs up these smaller vortices that will then funnel the sediment and food into their mouths, where then they can strain it out. So, it's like violent filter feeding.

Deboki: Right, yeah.

Sam: But yeah, I just thought that was kind of cool, because I hadn't really thought about it.

Deboki: Yeah, but I feel like I think of filter feeding as so passive, but it's like that, especially what you're talking about, that's pretty intense.

Sam: Exactly.

Deboki: Well, I have a Tiny Show and Tell for you that I think might actually be a sequel to a Tiny Show and Tell I think you did a while ago.

Sam: Oh.

Deboki: Which was about the RSV vaccine. So, there's now exciting news, because basically this past year there have been two different RSV vaccines available, there is a vaccine that's given to pregnant people in their third trimester, if that happens between September and January, which is when RSV season happens, and so that particular vaccine will basically help with the immunity of the baby when they're born because the mom will produce antibodies that get passed to the fetus and they'll continue having those antibodies after they're born. There's also been another vaccine that's actually an antibody treatment that babies can get when they're younger than eight months old, when they're going into RSV season.

So, these are relatively new vaccines, and so the Centers for Disease Control and Prevention published a report about their effect, and it's been really good news. So, RSV stands for respiratory-

Sam: Syncytial.

Deboki: Whatever. RSV is a virus, it's a respiratory infection, and it usually results in the hospitalization of around 58,000 to 80,000 kids younger than five every year, and it's particularly challenging for newborns. So, it can be really scary to get for babies who are in that zero to two month age. And so, researchers looked at RSV hospitalization rates, and they compared those rates for this past year to the rates from between 2018 and 2020, so basically pre-pandemic levels. In one measurement, they found that hospitalizations for newborns between zero to two months went down 52%, and the other measurement was down by 45%.

Sam: Wow.

Deboki: And they also saw that when they looked at infants from zero to seven months, hospitalizations also went down. The one piece of not good news was that hospitalizations for toddlers and kids up to five years old were actually higher this year, which indicates that RSV was more severe this past year, and one of the things that's important to remember is that these kids, they weren't getting the vaccine. So, this actually suggests that hospitalization drops we saw for the other age groups might be an underestimate of just how good these vaccines were, because…

Sam: If the strain was that bad this year and we were still seeing a drop that says something.

Deboki: Yeah, exactly. So, I just think that's really good news.

Sam: That makes me happy, because I got the RSV vaccine, even though I didn't fall in that window because of my due date, I still got a prescription from my doctor and was able to get it.

Deboki: That's great.

Sam: Just to be super careful.

Deboki: Yeah, we were able to get the RSV vaccine for my son when he was, right before he was starting daycare, and it was a huge relief to be able to get that. Because I definitely remember they sent us messages through the winter of just how many kids were getting RSV and flu, and so it's just such a relief to have had that RSV vaccine, and to know that if he got it, it might not necessarily prevent RSV, but it was going to make a big difference in his chance of having to get hospitalized.

Sam: Absolutely. Well, thanks Deboki.

Deboki: Thanks for tuning in to this week’s episode of Tiny Matters, a podcast brought to you by the American Chemical Society and produced by Multitude. This week’s script was written by Sam, who is also our executive producer, and edited by me and by Michael David. It was fact-checked by Michelle Boucher. Sound design is by Michael Simonelli and the Charts and Leisure team.

Sam: Thanks so much to Kantha Shelke for joining us. Go rate and review us wherever you listen, it only takes a minute and it makes a huge difference. Get us on those charts! We really appreciate it. And we will see you next time.

References:

Trade, tyranny, and untapped potential: The history and science of spices

Transcript of this Episode

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