Science Friday - Biodiversity Report And The Science Of Parenting. May 10, 2019, Part 2

Episode Date: May 10, 2019

According to a new UN report on global biodiversity, as many as one million species—both plants and animals—are now at risk of extinction, according to a new UN report on global biodiversity. That number includes 40% of all amphibian species, 33% of corals, and around 10% of insects. One might assume that this type of devastating species loss could only come as a result of one thing—climate change. But in fact, as the report highlights illustrate, it’s deforestation, changes in land and sea use, hunting, poaching, pollution, invasive species—in short, human interventions—that are causing species to disappear at a rate tens to hundreds of times higher than what has been seen over the last 10 million years. Walter Jetz, professor in ecology and evolutionary biology at Yale University, joins Ira to discuss why the damage we do to biodiversity in our lifetimes may never be undone. Plus, if you're a new parent, you’ve probably had one of these nights. You’re up at 3 a.m., baby screaming, searching the internet for an answer to a question you’ve never thought to ask before: Are pacifiers bad for your baby? What about that weird breathing? Is that normal? Or is it time to head to the emergency room?  Emily Oster is a health economist and mother of two who had a lot of those same questions as she raised her kids. She dove into the data to find out what the science actually says about sleep training, breastfeeding, introducing solid foods, and lots more in her new book, Cribsheet: A Data-Driven Guide to Better, More Relaxed Parenting, from Birth to Preschool. Ira chats with Oster and Nikita Sood of Cohen Children’s Medical Center, who monitors the underground market for breastmilk and explains why parents should be cautious.  Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Irafledo. Coming up in a little bit, Emily Oster, author of CribSheet, is here to answer your parenting questions with research, what the evidence says about long-term benefits of breastfeeding, the effects of daycare on development. What would you like to know? You make the call, but only if you make the call. 844-724-8255-8-44-Sci-C-Talk or tweet us at SciFri. First, you might have heard the news this week that as many as one million species, both plants and animals, are now at risk of extinction, according to a new UN report on global biodiversity. That number includes 40% of all amphibian species, 33% of corals, and around 10% of insects. Now, you might assume that this type of devastating species loss could only come as a result of one thing, climate change. But as the report highlights, it's a perfect storm of deforestation, changes in land in sea use, hunting and poaching, pollution, the introduction of invasive species. In short, a whole bunch of human activities that in addition to rising global temperatures are causing species to disappear at a rate, quote, tens to hundreds times higher than what we've seen over the last 10 million years.

For example, over a thousand amphibian species, sometimes thought of as the canary in the coal mine of biodiversity crisis, have been newly assessed as threatened or endangered, according to a new study out this week in current biology. Walter Yetz, who is the lead author on that study, and also one of the authors on the recent UN biodiversity report joins me to talk about them both. He is director of the Center for Biodiversity and Global Change at Yale University. Welcome to Science Friday. Thank you. Now, the report highlights say 1 million species are threatened with extinction. What proportion of species on Earth is that?

The report assumed that about 8 million species are on Earth, and that's obviously a very highly debated number. We could have a whole separate program on the scientific debate on that. However, I think it's fair enough to use it as an initial ballpark. Many scientists would argue it's many, many more, perhaps twice, three times, four times as many. that are yet to be discovered. Only about one, a little over one million are described right now. So this report is making the assumption,

well, let's say there are about 8 million species in total. We have assessed about 100,000 species formally to date through an expert process. And out of that, if we sort of run the proportions against the various groups and then extrapolate from there, then that would get us to about a million out of the eight million species threatened. And was this very surprising about just how many would become extinct? Oh, no, it doesn't surprise me at all. And I worry.

In fact, our study points out that the number may even be larger, certainly for amphibians. That's what we find, and we can talk more about it in a moment. It's not surprising at all. And I would say it's actually a conservative estimate because, you know, insects, for example, have only been assessed in a very limited way. Actually, the percentage, and I think you mentioned, that comes from, that's used for insects, is about 10% being thought of, is being threatened right now.

But they're really the grand portion of that 8 million species that are being talked about here. And that 10% estimate right now comes from a very small number. It's mostly European bees, and a lot of tropical biodiversity has not even been assessed. at all. You know, I think people may be surprised to see how much of human activity is involved

in the extinctions of these and not just climate change is, but we mostly hear about climate change in the environmental movement. Is it so focused on climate change as some of these other human activities, like poaching and pollution, which

once a big deal for environmentalists, don't get enough attention? Well, I wouldn't argue that, but we need to think about climate change. And some of the species threats that we are talking about here are actually climate change driven. We are already seeing the effects of climate change on some species populations.

And this is the big issue to think about going forward. But already now, we have seen over 800 vertebrate extinctions since the medieval times. As you said, orders of magnitude. You summarized it beautifully. Orders of magnitude more than expected from a background rate of extinctions. And we have a very clear connection between these various impacts that you have mentioned, deforestation, land use change, invasions, et cetera, et cetera, on species. So the evidence is there.

And I agree with you that there should be more. attention to the benefits that we humans directly from nature and we get them now that we are losing day by day by day through stuff that's actually much, in some ways, you could argue, much easier to manage and control than climate change. There's obviously we need to think and do something about climate change. But a lot of the impacts we're talking about here that are driving species to extinction and make us lose nature's benefits are due to the. local and regional decisions that could be very easily affected by us getting involved, for example, as people. I don't think people really appreciate what is out there in biodiversity. Why biodiversity and loss of it is so crucial.

I mean, there are drugs and potential cures and stuff out there in nature where we have seen them before, which we may never even know about because they'll be gone. That's right. And don't forget, there are some species we haven't even discovered yet. We may lose them before we even discovered them before we could enter them into the equation. And, you know, the benefits we get from nature are manifold. And it was great to see that report come out. It was hard work by hundreds of scientists over the past years.

It is an IPCC-type process, and thankfully the governments are now involved in actually discussing this report and thinking about then policy. changes from there. So it's a wake-up call, and it's a really important wake-up call about the ongoing loss of biodiversity of species and ecosystems. And we're talking about, for example, there was already an earlier UN report on pollination services. So bees, for example, are providing billions of dollars of pollination services to us

humans annually. If you think about insect feeding animals and frogs actually are a really important group in that regard. Let's get to that. Your amphibian study, you had a published a separate study this week about amphibians, which we always think as the canaries, right, in the coal mine about the state of the environment. Exactly. So think about amphibians, so frogs, toads, salamanders, et cetera. They are actually, you would think, well, what's that amphibian species going to do for me. However, as a group, they are not just canaries about the health of the environment overall and thereby many other benefits that we derive from nature, but they also carry benefits very, very directly. They are really important pest controlling animals that

provide unmeasured, unfortunately, services on a daily annual basis everywhere. where they occur. They are also known to have a whole range of compounds that have medical purposes. So think about, many of you may have heard about the poisoned dart frogs. So there are some species where the skin of a single animal would have enough toxins to kill 10 humans. And there is actually another example closer to home, not quite as toxic, thankfully. The Houston Toad and highly threatened now, but similar to the, that poison dart frog that I mentioned, this species and others, have toxins, serotonins that have been serving really important purposes in medical research, and some of their natural

compounds have supported a whole range of drugs. Why are they, you know, so to speak, being singled out by nature to disappear so quickly? You know, they are getting hit from all sides. Amphibians are really getting it from all sides. They are highly impacted by, say, species invasions, invasive ants, for example, tackling a lot of the juvenile frogs here in parts of the United States and elsewhere. They are getting hit by land use change directly. They're often distributed, very narrow ranges. They're very restricted in their geographic range compared to birds, for example.

Their range is on average about six times smaller. So any human impacts that are happening, any deforestation that's happening is much more quickly going to wipe out the frog than it's going to wipe out a bird species. And moreover, they have a really interesting physiology that makes them very sensitive to the microclimatic conditions around them. So any small changes, even if they're not losing habitat directly, but something may have happened a few hundred yards away, may affect their microclimate and thereby impact their population. So they're really dropping like flies right now. And they are among the vertebrates, the group, that's already seen the most extinctions in the last 100 years. One quick question before we go. Is there any way to turn this around by having governments or people become more aware and do something about this?

Well, first of all, I think thanks to new research, new remote sensing, for example, new scientific approaches, the sort of big data modeling that we and others are trying to do. You can actually now begin to pinpoint the species that are most strongly threatened by extinction and pinpoint the places thereby that as we need to do triage, we never have enough funds or resources or time to do conservation. We can more effectively identify the places where we want to be active. And I think as we identify these places, we all can get involved in lobbying for this group and lobbying for these places.

And some of these places are actually close to home. I mentioned that Houston Tote, there are many other species close to home that are affected by habitat loss. And we can get involved now by supporting organizations that are setting up conservation activities by perhaps even in our own backyard,

do stuff that is just more supportive of nature. wildlife. Thank you very much, Professor Yetz, for taking time to be with us today. Happy to. Walter Yetz spelled J-E-T-Z, who is very much involved in doing this. He's director of the Center for Biodiversity and Global Change at Yale University. We're going to take a break when we come back. We're going to answer your parenting questions. To swaddle or not to swaddle? Are you really long? Are there long-term benefits of breastfeeding? Emily Astor, author of the new book, CribSheid, is here to take your questions. Give us a call 844-7.

824-8255-844-Sight Talk. We'll be right back after this break. This is Science Friday. I'm Ira Flato. If you're a new parent, I'm guessing you've had one of those nights every now and down in Europe at 3.30am, 3.30 a.m., the baby is screaming. As you ask the Internet a question you've never thought to ask before,

are pacifier is bad for your baby? What about that weird breathing? That's normal or not, or is it time to head to the emergency room? And once you Google it, you get the blog. the random websites, a few news articles, but whom do you trust? My next guest, Emily Oster, is a health economist, a mother of two who's had a lot of those questions, and she's raised her own two kids thinking about them. So she dove into the data.

What does the science actually say about, let's say, co-sleeping or breastfeeding, introducing solid foods, potentially allergenic, like my throat foods? She wrote about the science of pregnancy in her first book, Expecting Better, and now she's back with CribSheet, a data-driven guide to better, more relaxed parenting from birth to preschool, and it's not just about the babies, it's about you too. What research is out there on parents as they fumbled through life with a new kid with the emotional tank running dry,

and what about dealing with the grandparents? We want your questions. Give us a call 844-7-2-2. 248255-844-Sai Talk, or you can tweet us at SciFRI. Emily Oster, Professor of Economics at Brown, author of CribSheet. We have an excerpt up at our website, ScienceFriday.com slash crib sheet. Dr. Oster, welcome to Science Friday. Thank you for having me.

And thank you for being here. There's a lot of mythology about parenting out there, isn't there? There is. There seems like sometimes there's only mythology and not facts, but there are some facts. And so what headed you down this road to take this all on? So I had kids was sort of the short answer to that question. And I found that I was trying to answer a lot of the questions that new parents have or in the first book that pregnant people had.

And I didn't find the answers out there that I wanted or I didn't find the synthesis of the data. And so I started doing a lot of that myself, looking at all the papers, reading them, thinking about which pieces of evidence were better than others. And then ultimately, the book is really a result of that. You know, your writing reminds me of Michael Lewis of Moneyball, who had to go through all the mythology by looking at the data and change the old paradigm? I'll take that comparison. All right.

Let's dig into this. Let's dig into some of these topics. You cite an interesting study in the book, which links swaddling to more REM sleep. Tell us about that. Yeah, so the swaddle stuff is super interesting. So swaddling for people who are listening who are not parents refers to wrapping up your baby pretty tightly in blankets, and people do that because they think it improves sleep.

But I wanted to see if that's true. This sort of seems like something that maybe people would just say. There'd be an old wives tale. But actually, it's not. And so the data there is very nice. So researchers wrapped up some babies in some swaddles, and they put sensors on them and also videoed them. So very comfortable baby, I'm sure, sleeping in the midst of video cameras covered in sensors.

But they can look at the same baby when they're swaddled and when they're not. And what they see is that when the baby is swaddled, they have the same kind of initial arousal. So when babies are sleeping, at some point they'll sort of sigh or move a little bit. And then later they'll startle and then later they'll wake up. and that when they are swaddled, the little movements are less likely to turn into big movements, and they are less likely to turn into waking up, whereas if they're not swaddled, that's more likely to happen. So it seems like that's the mechanism by which the swaddling is actually improving the length of sleep for babies and for moms and dads. Also good.

Let's go to the phones because there's so many people. Let's go to Anna in Madison, Wisconsin. Hi, Anna. Hello. Hi, go ahead. I have a question for Dr. Astor. I have a 13-month-old who is still breastfeeding, and I know that in general in the U.S., we tend to aim for that first year,

and so we've made it that far. But I know that in other countries and the World Health Organization recommends two years, so I'm kind of confused about, like, if he getting a lot of additional benefit now for that next year or so, and what are the, you know, reasons to continue as he seems to still enjoy it, but it's a lot of work for mom. Yeah. Yeah, so breastfeeding. Okay. So I talk in the book that the best evidence that we have about breastfeeding is really about breastfeeding at all versus not at all. So by going past the year, you've already gone really pretty far. And even when we look at the question of breastfeeding at all or not, the benefits seem to accrue mostly early on in life. So there's less diarrhea, maybe fewer ear infections, fewer. allergies for the first year. But there are some of the things that you're told about the

benefits of breastfeeding like IQ obesity reductions. Those actually don't seem to be borne out in the best data, even if we look just at the basic question of breastfeeding at all, let alone looking at what we'd call extended breastfeeding. To answer the question about policy, I think there's a reason that the WHO pushes further than the American Academy of pediatrics, which is that in places with less clean water in developing countries, there's more benefits to breastfeeding because otherwise the kids will be having more unclean water. But in the U.S., I think there just isn't a lot of evidence that would suggest that continuing is going to have a lot of benefits for your baby unless you want to do it, which is great

and is a good reason to continue. We had a tweet from someone who wanted to know, what is the best way to wean your kid off of breastfeeding. Unfortunately, that is something actually looked in the data. There's not a lot of data on that. Some kids will just decide that they want to stop. If you have an older kid, they often won't decide they want to stop, and people have a lot of suggestions.

Some of it's just going to be about what is going to work for your kid. Let me just go to a quick call from Rainbow in Berkeley, California. Hi, welcome. Hi, this is Rainbow, and I'm an MPH, Master's in Public Health, as well as a PhD in nutrition. And I have read about some of Dr. Oster's work, and it seems to discount a lot of the nutritional benefits, especially the high fiber content, which helps promote a healthy microbiome for the new baby. And also it just seems to discount the trouble that women go to breastfeed, and that it kind of distorts the WHO's standing that breast is best,

and that breastfeeding is important for at least the first year, but definitely longer. So that's my comment. Thank you very much. Okay. So I mean, so I will say what I try to do in the book is really cut into the data and what does the data actually say about the benefits. I think the discussion of the microbiome is super interesting, but also we don't know that much about that yet.

And to the extent there are benefits, we would expect them to show up in outcomes. So the book is pretty focused on outcomes. And I will reiterate, I actually think it's really important. that we provide supports for women who want to breastfeed. I think in some ways the most frustrating part of this is that we're telling people this is so important and then making it really difficult for them. So I actually have a whole chapter in the book about how to make breastfeeding work if you want that to work for you.

But what I think is more troubling is a lot of women end up feeling very bad if they can't breastfeed or if it doesn't work for them. I think that shame is not helpful early on in life, your kid's life. You know, I was looking through your book and I tried to keep track of how many times the word breastfeeding. was mentioned. I lost track after, I don't know, 20, 35 times. People really are asking most about this. And I can see from our calls, I think we may have even one more. John from Cincinnati, welcome to Science Friday. Hi, Ira. It's finally nice to get on the program. My first daughter, she's three months old. She's a little colicky, and she has eczema a little bit on her chest and neck.

could she be allergic to something that mom is eating such as dairy or eggs, and would it be best to eliminate those foods from mom's diet, or would it be best to switch to a formula? Let me just say in advance that Dr. Astor is not a doctor. Emily Astor is not a doctor, and she can't really make any really recommendations individually, but we'll speak in general terms, right? Emily? Yeah, absolutely.

Absolutely. Yeah. So what I was going to say is, I was, in fact, exactly going to say I'm not a doctor. But when you look at the evidence on colic and what kinds of things affect colic, there is a bit of evidence that these kind of elimination diets for moms can have some impact on colic. It's not super compelling and the effects are not that big, but it's not that hard to test. So if someone was in this situation, let me veer away from saying for you. someone was in the situation, sometimes what people will recommend is try dropping something for a few days and seeing if things improve. And that could work, it might not. And most babies do get over a colic not that long from three months. So hopefully that will improve on its own, even in the absence of any dietary changes. Let me go to a tweet from Jessica Rodriguez. Actually, she mentions on Facebook, and she says, safe sleep on back, nothing in crib is so

important, but it's the opposite of how my newborn wants to sleep, snuggled in blankets with mom. How do you help newborn sleep safely so I can get sleep, too? Yeah, this is such a hard, this is such a hard space because especially newborns really struggle to sleep and parents and parents struggle to sleep. And we do have these recommendations about safe sleep and, and they have a bunch of different pieces. The baby should be on its back, alone in the, in the crib, in the parents' there's a few of them. So I will say I think the evidence in favor of back sleeping is very compelling. So the effects on reductions in SIDS, which come from a bunch of different kinds of sources,

are really convincing. So even though it is true, a lot of babies prefer to sleep on their stomach, the evidence suggests that the recommendation for back sleeping has been really important for policy. The question about co-sleeping, which I get a lot, this ends up being very fraught in the discussion. So you'll see sort of one camp telling you, like, this is the most important thing you can do to be with your baby is to go sleep with them. And then others will say this is extremely dangerous. And I think what the evidence shows is that there are some safer and less safe ways to do this.

So if you're going to go sleep with your baby, it should be in a bed with no covers and no pillows, and you should not smoke or drink alcohol. If you do that, I think the data does suggest that there are some risks, although they are relatively small. And I think that we sometimes struggle to talk about risks like this and to think about them. But I think in some ways done as safely as possible, you might think about the risk as kind of smaller than the risk you're taking from putting your kid in the car. And so there's a sense in which parents kind of need to think that through for themselves and make the choice that's right for them. 844-724-8255 is our number talking with Emily Oster about crib sheet, a data-driven guide to better, more relaxed parenting from birth to preschool. You know, I'm an older, I'm an older parent, and I remember T. Barry Brazelton was my Bible when I was growing up, and I've seen a lot of stuff that I talk to my kids who are also adults about, that take it, they take it for granted that this is the,

common knowledge when they didn't you know years ago people were talking about it in different ways do you do we have a you know are you the new dr spock or t barry brouselton or not yet i mean you know i think um i i'm not sure there will ever be a a new doctor dr spock and i certainly don't don't think it's uh it's me but i do think that there's that there's a space here in the in the sort of modern era for kind of trying to collate some of the noise of these sort of studies that are everywhere and as people are more interested in making evidence-based choices, helping people understand what does the evidence actually say, not just what does one study say, but what is the whole literature say about some question.

I'm Ira Flato. This is Science Friday from WNYC Studios. talking with Emily Oster about her new book, Cribsheet. So many people are calling in. Camille Silberman on Twitter writes, is there a golden window for sleep training, like four to six months, just curious? Yeah, not in the data. So there's a point at which, when kids are very small,

some people will tell you you can sleep train like a 10-week-old to go to sleep at night, but a 10-week-old typically cannot sleep all the way through the night. Most kids are not going to be able to sleep all the way through the night, you know, 12 hours until something like six or seven or seven months. So depending on exactly what you're trying to accomplish, the age is going to differ. I think many people anecdotally find it much harder to sleep, train, much older kids, because they are able to talk and negotiate. So maybe the window is before they can explain why you shouldn't do it. Let's go to a quick question before the break. Kelly in Sacramento. Hi, Kelly. Hi there.

Go ahead. My daughter is four years old and through the years, she'll go through periods where she cries a lot. Most of the time when I drop her off at school, she doesn't cry, but right now she's in a period where it seems like she's crying about everything. And I'm having a hard time figuring out where's the line between me coddling her and me saying, you know what, like, I just need to move on. Your crying is becoming an inconvenience every time I say no or every time I have to do something you don't like. But I don't know where that line is and how do we determine that?

And are we coddling our kids too much right now? Yeah, that is a really good question. And I feel that I could have called in with that question because, you know, I feel like the book sort of stops at three, and actually most of it is about much smaller kids. And I feel like as kids get, as kids get older, some of these questions get much more complicated and much less amenable to data. So the data is not going to tell you when is the right time to stop coddling. There's a little bit of stuff in there around discipline. What about younger? What about then younger kids? Crying is a normal thing, right? I mean, that's... Crying is a normal. Crying is a normal thing.

and we can think about questions about like discipline, which is sort of related to this, is, you know, if you want to encourage your kid to not engage in some negative behavior, you know, how can you do that? And I think the evidence there would suggest that the most important thing is consistency. So is if you, you know, say if you do X, Y will happen, that you follow through. If you say, if you throw the cauliflower, I'm going to take away your cookie, you have to take away the cookie. That's different than the question of how should you react to a kid who cries when you're going to. you drop them in daycare, where I think probably the best evidence we have is just from what people

have told you for 50 years, which is smile and wave goodbye, and they're going to stop crying when you leave. And as your kids get older, are you going to follow them more evidence? I don't know. I feel like the data isn't as good on older kids, and the questions are more complicated and more kids-specific, so I haven't made any progress on how another book would look. That is interesting. The data is not as good. That itself is a commentary. All right, stay with us. For after the break, we're talking with Emily Oster, author of Cribsheet, a data-driven guide to better, more relaxed parenting, from birth to preschool. We could all use advice on that.

And our number, 844-8255. You can also tweet us at SciFry. We'll be taking a break. Back with Emily after this break. Stay with us. This is Science Friday. I'm Ira Flato. If you're just joining us, we're talking with Emily Oster, health economist at Brown University, about her new book.

Krib Shida, data-driven guide to better, more relaxed parenting from birth to preschool, which answers a lot of common parenting questions about everything from swaddling to breastfeeding and answers it with evidence-based research. I'd like to bring on another guest now who recently presented her work on the underground market for breast milk at a meeting of the Pediatric Academy Societies in Baltimore. Nikita Sude is a research assistant at Cohen Children's Medical Center as part of Northwell Health in New Hyde Park, New York. She's here in New York Studios.

Welcome to Science Friday. Hi, it's great to be here. I have to admit something really awful. Okay. I never heard about an underground market for breast milk. To be fair, I hadn't either before I started doing this kind of research, so you're okay. Describe the market for me. Yeah, so, I mean, I guess for listeners who are unfamiliar, a lot of,

even though the science says, you know, encourages breastfeeding for the first six months of life and, you know, ideally a year, not a lot of. not every parent is able to do that. And so there's this thing called donor breast milk, where parents who aren't able to personally supply enough breast milk can get it from another source to feed their infant. And this sort of practice is called milk sharing. And so there's two ways to do it.

There's milk banks, which, you know, if you think of them sound similar to blood banks, it's more regulated, blood is, or the breast milk is pooled, donors are screened, things like that. But there's also, So the more popular version that's really, really also getting even more and more popular is informal milk sharing, which is this underground sort of system where parents are able to connect directly with one another and exchange breast milk. So a lot of that happens online, whether that's through milk sharing websites or social media sites on Facebook groups and things like that.

And so it's done a great job in connecting people to breast milk they need, but obviously it's a little concerning too. Well, you have to trust the person you've never seen or talked to. You have known nothing about that person to give your baby breast milk. No, exactly. And in an ideal world, you know, you'd be able to trust another parent. And, you know, we like to think that. But I think experience has shown that, you know, you can't really trust everyone that you meet on the Internet, unfortunately. And there has been, you know, some research into whether or not this milk is safe.

What kind of stuff might be unsafe about the milk, for example? Yeah. So, I mean, inherent with any sort of exchange of human fluids. there's a risk of contamination, and that's especially true for this informally shared milk. You know, donors aren't screened. The milk isn't tested, and so there's a really high risk of contamination with bacteria, with viruses, with even medication, and things like that. And so there's actually, there started to be more and more studies examining this kind of stuff,

and there was, for example, a 2013 study published in pediatrics that looked at milk that was purchased through a milk-sharing site online. And 74% had gram-negative bacteria and would have failed, you know, milk bank level criteria. Wow. 74%. So give me an idea of the cost of buying. Yeah. So, you know, it's really not an easy process.

It can be actually quite financially burdensome. I guess for a sense of comparison formula, it typically costs around 8 to 31 cents an ounce. And given that, you know, I think it's a three-month-old baby will consume 30 ounces a day, that amounts to maybe as much as $10 a day to feed that child. Informally shared milk can be free on certain sites where you just pay for shipping, although, you know, it's not screened. It's not medically safe. But you can also have to pay as much as $4 for some of that milk, which adds up to about $120 a day. Wow. Wow.

Wow, wow. 8447248255. I want you to stay with us for the hour. Is that okay? Yeah, thank you. Because we have lots of questions here. Emily, what do you think about this breast milk market? So this is a super interesting market, economists-like markets. You know, I think there's a sense in which we have generated an attitude that breast milk is so sacred and so important that you,

you would be better off giving your kid breast milk that has bacteria in it than you would giving them formula. And I think that that's probably in many cases not true. And I think it is part of this kind of cult around breastfeeding. And I do think that it is maybe a byproduct of some of the claims that are made that are not all as well supported in the evidence. I would rather have us spend more time helping women try to breastfeed and then not shaming them if they can't. Here's a tweet from Karas says, has Dr. Oster looked at any research about cannabis use and breastfeeding as marijuana restrictions loosen? No, go ahead. No, well, Nikita, have you come across this and talking with moms looking for breast milk that this is a concern of theirs?

Yeah, I mean, this is definitely not the first time I've sort of heard this type of question. What we tend to do is actually for this study, we were looking a lot on parenting blogs, which influence a lot of the parenting advice like you're saying Dr. Ostra. And so we found a lot of questions about cannabis use and breast milk and whether or not that's an issue. Unfortunately, I haven't personally done any research into it. And I think more research needs to be done. But I would, you know, I think it's.

You would think, Emily, that this sure is going to come up with the loosening of cannabis restriction. Yeah, it is. But I think until we see more time with these loosened restrictions, it's a very hard thing to study because now most of the studies would be based on a time when the cannabis use was illegal and so people don't want to tell you or the kinds of women who are using cannabis are sort of more different. And so I think that I think we will see more of this over time, but I don't think the evidence is there yet to say either way. I agree too. I think even

beyond just, you know, with the legalization, seeing cannabis in breast milk, I think in general what I've found is that there's not actually that many studies that have been done looking at informally shared milk and donor breast milk in general, even though this has been around for, I think, longer than, you know, cannabis has started to become legal. And so I definitely think there needs to be a lot more research done in these areas so that we can, you know, give definitive recommendations and say what the science says about the risks.

Before you go to the phones, let me ask you, Emily, as possibly soon-to-be grandparent myself, what's the best way to treat your, you know, your mother, your father with the kid, with the newborn? You mean like how should they treat the grandparents? Yeah, how should they treat the grandparents? How should the grandparents treat the kids or their kids or their grandchildren? So it's interesting. I don't think there's a huge amount of data on this.

I think being supportive is probably the most important thing. but I think part of what's hard about the interactions between grandparents and grandkids is that there are changes in recommendations over time, and it can be hard to not share the experiences that you had, because, of course, they're in many ways very valuable, but also in some ways outdated. So people bring this up to me all the time around the issue of back sleeping, that when we were kids, you put your baby to sleep on their stomach, now the recommendation is to go to sleep on the back,

and I think that a lot of people are getting sort of tension with their parents, about that change in recommendation. You know, it worked for me. You should do this too. You said in the book that you should have a frank exchange of views with your kids. Let me put it that way. And have to have that discussion about how to treat each other. Yeah, absolutely.

I think that talking things through. Yeah. Just let me go to the phones. Speaking of talking it through, let's go to Christina in Noon and Georgia. Hi, Christina. Hi, there. How are you doing? Hi there.

Go ahead. Yes. My question would be basically about letting your child cry to go to sleep. What would be the recommendation about that? And if there's any data that supports crying for so many minutes versus holding the baby, you know, soothing it to sleep and at what age would you recommend allowing them to cry it out? There's a lot of evidence on this. And I think that people worry about kind of two things.

One is, does it work? and the other is, is it going to damage my kid? And this is a place where, unlike in some aspects, we actually have very good data, I think, because we have randomized trials, some of which follow kids until they're, you know, five or six, so not just two days after this happens. And I think broadly the evidence is very reassuring,

sleep training, letting your kid cry it out, does improve kids sleep. It also improves parents' sleep and actually has pretty big effects on depression, on reducing maternal depression, improving marital satisfaction. So I think there are some reasons to do it. In terms of long-term impacts,

there's no evidence of negative long-term impacts or any long-term impacts in any direction. So I think that for parents who want to do that, that is really reassuring. It doesn't mean everybody's going to want to sleep train their kids. That is a pretty personal choice, and it is very hard to listen to your kid cry, but it does have some of these sort of good effects

down the road in terms of improving sleep, there actually isn't too much guidance about which of the many different technologies. Should you go in every three minutes? Should you go in every 10 minutes? Should you not go in at all? All of these things seem to work kind of fine. You sort of like pick a lane and stick with it. And that's kind of what the guidance is.

Nikita, you also looked at the history of wet nursing, right? Tell us about that. Isn't milksharing just like a modern version? of wet nursing. That's probably one of the most common themes we saw in our study when we were getting a lot of information from mothers who had participated in milk sharing. And so we wanted to look into that so we could say definitively

whether or not it is comparable. And, I mean, this wet nursing has been around for so long. I mean, like centuries upon centuries, thousands of years. It's mentioned in the Bible, and a lot of religious texts. And the fact of the matter is, is that in those ages, wet nursing was really the only way of feeding a child if the mom couldn't breastfeed personally. Because there was no formula. There were no safe bottles.

There was no pumping for later use or storing breast milk. And so, you know, it was out of necessity. And because of that, it was very, very well known. It was very common. And therefore, it was very well regulated. And so there were contracts that existed between wet nurses and the families that employed them. There were medical tests that were required. And so it sort of lends itself to being more similar, actually, to the milk bank process, which is, you know, where there's medical screening, there's strict regulations, things like that, than this, you know, underground milk sharing market that's taking place online.

We've had some tweets from a couple of people who said the same thing about Amanda says, proud milk shareer, I donated to over five families, never asked anyone for a dime. It's an act of love from one mom to another. And we've had a few similar tweets. I guess that is opposed to what you would say get the prices you were mentioning at the milk banks, right? Yes, no, definitely. So, I mean, even Milk Bank, because of the processes of, like, medical testing and things like that, it is quite expensive.

It can be as much as $3 to $5 an ounce. And we have, I mean, we've encountered thousands of, of women in our research who have participated in milk sharing who have donated so many ounces and done a lot of good work. And I think it's great, but I think that there needs to be also regulations in place that we know that the risks that are being undertaken and we can make sure that this milk that's able to be donated can be done in a safe way, ideally through a milk bank. I'm Ira Plato.

This is Science Friday from WNYC Studios, talking with Emily Oster. And the key to suit. Emily, we've, you know, basically talk, I'd say 90% about the mothers here. Any advice, any of the research talk about fathering? Yeah, so there's, so I think, you know, one thing that I spent some time on in the book about fathers is, you know, when we think about postpartum experiences, there's a lot of emphasis on maternal depression and making sure that that women are not depressed. To be clear, there's not enough emphasis on that, but there is more than on dads. But one of the things that I think people are increasingly recognizing is that postpartum mental health issues can affect all of the people in the family. And I think that's a place where we could be a little more cognizant of the fact that, you know, when people are tired, that affects their mental health. In general, this is a stressful experience.

And we want to be careful to be paying attention to the mental health of all the parents, not just the birth mom. Any research on how much more stressful single parenting is? You know, there's not that much. I mean, I think the circumstances that lead to single parenting are pretty varied, and so the answer to that is likely to vary depending on whether you're a single parent by choice or not by choice and how involved the other parent is, and so that makes it hard to draw broad conclusions. Well, in Ed tweets, baby lead weaning for solid seems to be a trend. My wife and I freak out after seeing our seven-month-old gag and trying solid foods.

Thoughts? So there are a lot of different good ways to introduce food to your kids, and so one of the things I think was actually surprising to me is I was given when my daughter was born, her daughter was old enough for this. I was given this sort of strict instructions about rice cereal and then oatmeal and then these vegetables and all in this particular order. And I think it turns out that there's no particular reason to introduce things in that way. There's also nothing wrong with doing it in that way. But people have increasingly been interested in this idea of baby-led weaning. It has some value because it's in some ways easier to not deal with baby food. But people do worry that their kids gag.

I think the evidence suggests that it isn't dangerous, although it also doesn't have some of these benefits like lower obesity that people have have touted. So if you want to go for that, that's great. If you don't, if it makes you nervous, do something else. And one thing you might do is read the new book by Emily Oster. Her new book is CribSheet. We have so many people, so much more time that we don't have. We have an excerpt of the book up at ScienceFriiday.com slash crib sheet. You'll also find a Nikita Suz's list of advice up there if you're a pregnant parent considering buying breast milk. And that's a ScienceFriday.com slash crib sheet. Thank you both, Nikki.

Nikki sued is research assistant at Cohen's Children's Medical Center, part of the Northwell Health in New High Park, New York, and Malini Oster, Health Economist at Brown University, author of Cribsheet. Thank you both. Thank you for having time to be with us today. Thank you so much. You're welcome.

Good luck with the book. BJ Leatherman composed our theme music and a few program notes. To all our Texas fans, the sci-fight crew and I will be hitting a road this August. We are coming to San Antonio. We want you to join us Saturday, August 10th for Science Friday Live from your great state. We're going to talk about science stories in the San Antonio area. We'll have, well, San Antonio, I'll have live music and more.

And that's Saturday, August 10th, info and tickets at sciencefriiday.com slash San Antonio. And another note, Science Friday is clicking up a new science history podcast. We want to hear what you think. So we are reaching back into the science history vaults, dusting off stories that you've never heard in school. So please help us out. Go to ScienceFriady.com slash survey to hear an exclusive sneak peek of our first episode, then answer a few questions, your listeners, your questions, your answers will help shape this new show. We want your advice. ScienceFriday.com slash survey.

Listen and tell us what you think. And thanks. Have a great weekend. We'll see you next week. I'm Ira Flato in New York.