MARY LOUISE KELLY, HOST:
And it is time now for science news roundup from Short Wave. That is NPR's science podcast. I am joined this week by Emily Kwong. Hi there.
EMILY KWONG, BYLINE: Hi.
KELLY: And Hannah Chinn - hey to you in our New York bureau.
HANNAH CHINN, BYLINE: Hello. Hello.
KELLY: Y'all have brought us three science stories that caught your attention this week. Lay them on me.
CHINN: All right, we have the microbes behind great-tasting chocolate.
KWONG: How birds at sea defecate way more than scientists thought.
CHINN: And the molecules that might be responsible for your daytime sleepiness.
KELLY: I am here all day and every day for great-tasting chocolate. What do we get?
KWONG: Fantastic. OK, so published in the journal Nature Microbiology, this research focuses on cocoa beans.
KELLY: Cocoa beans, which make chocolate, which grow on trees.
CHINN: Yeah, they do. And depending on where you go, you kind of get different flavor profiles from those cocoa beans. So it could be fruity or floral or spicy. And a team, led by scientists at the University of Nottingham, wanted to figure out what was driving these different flavor profiles, specifically at the level of microbes.
KELLY: The level of microbes, so very, very tiny microorganisms - how are microbes involved in how chocolate tastes?
CHINN: Well, after farmers pick cocoa beans, they ferment them, kind of let them sit in boxes or bags for days on end.
DAVID GOPAULCHAN: They do this because this is what has been taught to them for generations, so from their parents.
KWONG: Research fellow David Gopaulchan said it's during fermentation that these microbial communities emerge, and they give rise to all kinds of flavor compounds for the chocolate.
KELLY: Never thought about this - do we know which microbes produce the best-tasting chocolate?
CHINN: Well, Mary Louise, best is kind of subjective, but the researchers did sample the microbes from three different farms in Colombia. They genetically sequenced the DNA from these microbes, and then they built a computer model to see how those tiny organisms interacted. Then they went full Willy Wonka.
KWONG: Basically, the team created a cocktail of these microbes to start performing fermentation directly on beans in the lab to create their own chocolate flavor compounds, and it worked. Professional tasters confirmed that these beans, fermented with a synthetic microbial community, exhibited flavor notes similar to fine chocolate.
KELLY: Really? I'm skeptical.
KWONG: Yeah.
KELLY: What did they taste like?
CHINN: David said it was really fruity, kind of bright and berry flavored.
KELLY: So I'm thinking through the implications, more chocolate, that - I'm pro-more chocolate.
(LAUGHTER)
KELLY: But if scientists can just create - recreate chocolate flavors in a lab, what does that mean for the poor cocoa bean and for small-time chocolate farmers?
KWONG: Yeah, I mean, it could be disruptive, but one thing to know about the state of chocolate right now is that there's a worldwide cocoa shortage due to climate change. Maybe this science could lead to fermentation starters that can make the process more predictable.
KELLY: Wow. OK, on a considerably more disgusting note, let's move on. Story No. 2, the bathroom habits of seabirds - why - who wants to study this and why?
CHINN: (Laughter).
KWONG: It was kind of an accident. So a post doc from the University of Tokyo, Leo Uesaka, was actually looking at the legs of these seabirds, which are called streaked shearwaters. He was studying how the birds take off from the water. And to do that, he'd strapped cameras to their bellies facing backwards towards their behinds. And that's when he noticed something that really caught his interest.
CHINN: Which was that they almost always took off to poop, and they were doing it way more and way more regularly than he thought they would. So Leo started a whole new research project to investigate.
KELLY: And what did he find out?
CHINN: Well, he ended up combing through more than 30 hours of bird bathroom tape, which he describes as...
LEO UESAKA: Mentally difficult.
(LAUGHTER)
KELLY: Oh, go science.
(LAUGHTER)
KELLY: Such a labor of love.
KWONG: That's what we chant to ourselves every day in the mirror.
KELLY: Yeah.
KWONG: And Leo found that, while at sea, these birds defecate an average of every four to 10 minutes, and that didn't change based on their eating habits. They were going that often. And after doing some calculations, Leo concluded that birds lost 5% of their body mass every hour...
CHINN: (Laughter).
KELLY: Every hour.
KWONG: ...From defecating.
KELLY: I mean, I guess if you're going every four minutes, I buy that. But I'm trying to figure out, still, that - we've all seen birds go to the bathroom. We've all seen that they do this frequently. Is this really groundbreaking?
KWONG: (Laughter).
CHINN: Well, a lot of estimates for how much seabirds excrete is based on land observations. But Leo's cameras and the research that he published in Current Biology gave both him and us a rare look at the bird's behavior at sea.
KELLY: At sea - and why is that important?
KWONG: Well, one reason is that feces, or guano, is important for how nutrients cycle in environments. Independent biologist Daniel Plaza studies how ecosystems function. And he says that fishing regulations, catch limits, they can be based on researchers' estimations of how much fish the birds need to eat to survive.
DANIEL PLAZA: If we underestimate how much poop they are doing, and it probably is connecting with how much food they are taking, we also underestimate how much food they need.
CHINN: So basically, if birds are eating way more than previously thought, we'd need to reduce fishing further to give the seabirds more opportunities to catch the fish that they need to survive.
KELLY: Moving right on.
CHINN: (Laughter).
KELLY: Our last story, we are tackling the causes of daytime sleepiness. I'm going to refresh my coffee and chug some caffeine while we work our way through...
CHINN: Yes.
KELLY: ...This one. But daytime sleepiness, excessive daytime sleepiness, is this common?
KWONG: Apparently, yes - excessive daytime sleepiness, EDS, happens when people fall asleep repeatedly during the day. This condition affects up to 1 in 3 people in the U.S. It's very common. And while it's often linked to sleep deprivation or other circadian disorders, EDS can still happen to people who are getting a full night's sleep. Plus, it's correlated with a higher risk of things like cardiovascular disease or hypertension.
KELLY: One in 3 people, you said.
KWONG: Yeah.
KELLY: Hannah, how do we find out if we're among them?
CHINN: Well, there's this survey called the Epworth Sleepiness Scale that's designed to measure daytime sleepiness. It basically gives you a list of activities - anything from reading a book to watching TV to riding in a car - and then it asks, how likely are you to doze off during each of these activities?
KELLY: And I'm going to guess that if you have a high likelihood of dozing off during multiple things, like watching TV, riding in a car, you're going to score higher on this sleepiness scale.
KWONG: Yes. Researchers gave this survey to 6,000 volunteers, and then they collected their blood samples to see if there were any molecules in the volunteers' blood that were associated with higher or lower self-reported daytime sleepiness.
CHINN: I just talked to Tariq Faquih. He was a lead author of this study, which just published Tuesday in the journal, eBioMedicine. And that study focused in on metabolites, these little molecules that can come from things like diet or medication.
TARIQ FAQUIH: The most popular one, I think people know, is cholesterol. It's one of many, you know, like, thousands of metabolites in our bodies. There's so many of them.
CHINN: Altogether, Tariq and his team looked at 877 different metabolites, and then they found 10 that seem to be linked either positively or negatively to people's self-reported sleepiness.
KWONG: Notably, a metabolite of tyramine, which is found in fermented foods - aged cheese and alcohol - was associated with higher rates of self-reported daytime sleepiness, particularly in men.
CHINN: And on the other hand, they found that Omega-3 and Omega-6 fatty acids, which you find in foods like fish or vegetable oils or nuts and seed, were associated with lower rates of reported sleepiness.
KELLY: So what does this mean for me? (Laughter) Let's bring it back to what we should...
CHINN: Great question.
KELLY: ...Be eating. Sounds like more fish, less old cheese...
KWONG: (Laughter).
KELLY: ...And alcohol if we want to stay awake.
KWONG: Your charcuterie board is doomed (laughter).
CHINN: So it's really too early to tell. Tariq wants to do a clinical trial next, giving people different types of diets, maybe richer in certain metabolites and not others, to kind of see how they affect people's daytime sleepiness.
KWONG: So we'll come back to you and let you know when the food to sleepiness science is a little more clear.
KELLY: I will look forward to it. Emily Kwong and Hannah Chinn from NPR's science podcast Short Wave, which you can follow on your podcasting platform of choice for new discoveries and everyday mysteries and all the science behind the headlines. Thanks to you both.
KWONG: Thank you, Mary Louise.
CHINN: Thank you so much.
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