Episode 39: Pregnancy and the allergic trajectory
Pregnancy and the allergic trajectory
Could the diet and lifestyle of a mother during pregnancy influence whether her baby will develop eczema? Our podcast guests are studying the role that diet and the gut microbiome in pregnancy play. Join Dr. Carina Venter and Dr. Susan Lynch as we discuss what pregnant mothers can do to reduce the chances of baby developing eczema or allergies. (And if you like our podcast, consider supporting it with a tax deductible donation). Read the transcript.
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Prenatal influences on eczema
[00:00:28] Lynita: Hello and welcome to the eczema breakthroughs podcast. . We know that a child is more likely to develop eczema and allergies. If their mother has allergies. But could the diet and environment of a pregnant mother start the chain reaction that leads to these conditions for her child.
This is a question that our two guests today are researching. Joining me today are Dr. Susan Lynch. She is the director of Benioff Center for Microbiome Medicine and Professor of Medicine at the University of California, San Francisco. Her research focuses on how the microbiome of a baby interacts with the developing immune system to influence risk of allergic diseases.
And also joining me is Dr. Carina Venter. She is a professor of pediatrics at the Allergy Immunology Section at Children's Hospital Colorado and University of Colorado Denver School of Medicine. Her research examines how nutrition and other modifiable factors contribute to the development of allergic diseases in children. Both of you, welcome to the podcast.
[00:01:33] Dr. Lynch: Thank you.
[00:01:34] Dr. Venter: Thank you.
[00:01:35] Lynita: When I first listened to you both speak, which was at the Quad AI conference earlier this year, I didn't immediately see a connection between your research areas. Actually though on closer inspection, I found there were many overlaps between the work that you're both doing.
Dr. Venter, your focus is more on dietary impacts, and Dr. Lynch, your focus is more on the microbiome. But you are both looking at the impacts before and immediately after birth on the immune system and how that can trigger the path of allergic conditions.
Dr. Venter, I would like to start with you and I'd like to ask you about immunonutrition. Immunonutrition sounds to me like a diet for a healthy immune system. Can you elaborate?
[00:02:17] Dr. Venter: Yes. Immunonutrition is looking at all forms of Food intake and how it really affects not just the immune system, but the microbiome epithelial barriers, then the immune system and also interacts with epigenetics and genetics. Because allergy is an epithelial disease of the gut, the skin, the lungs, and the nose. And so it is really looking at all forms of food intake. So the total diet.
[00:02:44] Lynita: Right, so it sounds like that what we're eating really has a knock on effect right through our health. how our is shaped and how the microbiome then shapes our immune system. And then how our microbiome immune system reacts to allergies.
[00:02:59] Dr. Venter: Yes.
[00:02:59] Lynita: And It can start before birth. So what you're looking at is the things that a mother is eating.
[00:03:06] Dr. Venter: Yeah when we actually look at associations between normal healthy eating, as we define it, the healthy eating index, or even the Mediterranean diet index, we don't see any association eating according to those diet patterns in pregnancy but perhaps there is a way of healthy eating that is also disease specific, and perhaps that's not the exact same foods that we need. For allergy prevention, and so my association studies, and I do want to make clear that I really need to do randomized controlled trials are showing that really yogurt important, and perhaps vegetables are more important than eating fruit it's also important to reduce intake of foods that's , low in fiber, high in sugar, and also high in fat. So, I'm wishing I can give you a clear answer to say that, you know, Eating vegetables and yogurt are the two magic foods that's going to cure all, all allergic diseases. But we're definitely not, not anywhere close to making recommendations yet.
[00:04:07] Lynita: I will make sure I keep buying my yogurt and I'll keep encouraging my kids to eat their vegetables. It's just an ongoing challenge. Dr. Lynch, is there anything you wanted to add to that and how that, plays out in the allergic outcomes.
[00:04:22] Dr. Lynch: Yeah, no, I love Dr. Venter's work and the idea of a holistic diet as opposed to focusing on specific dietary components. I absolutely agree that that's the way forward. I guess how I think about our diet is yes, our diet can shape the microbiome we know that consuming processed foods is associated with allergy and asthma development.
We also know on the flip that, you know, a more balanced diet. Balanced fiber rich a healthy fat rich diet can prevent disease development. We're really focused on how diet shapes the microbiome. But what's emerging is that the types of microbes in your gut also shape the molecules that are made off your diet.
And they, in turn, shape your immune response. So, it's not simply that the diet shapes the microbiome. It also provides food for microbes to transform into molecules that shape immune responses. And that's what's particularly important, not just in very early life but also during pregnancy we have a great example of that in a study where we found that pregnant individuals who avoided cow's milk, had a very different vaginal microbiome. So suggesting that their diet may be influencing their microbiomes across their system, but also they bore infants that were more likely to have cow's milk allergy.
So during pregnancy, avoiding these antigens in cow's milk was associated with more cow's milk allergy, in their infants. And that's well known. There's some really beautiful studies that have demonstrated that early introduction of foodstuffs like peanuts actually prevents allergic peanut allergy from developing in childhood.
So I think for years we thought about allergen avoidance. We thought that if we avoided it, then we won't develop allergies to it. And it's actually the opposite is true. That exposure to those allergens and early life seems to train our immune response and allow it to be tolerant towards those antigens.
So the idea of a very holistic diet, where we are exposed to a whole of antigens all the time. Makes perfect sense in that context that you are training your immune response and that of the fetus in utero to be tolerant to those antigens and postnatal life.
[00:06:45] Lynita: Right. So don't try and focus on one specific thing in your diet. But generally eat a healthy diet. And don't avoid things from your diet. And the yogurt is interesting because it's known as something that contains bacteria. That's good for us. So, is there a link between eating yogurt? Because it's got good bacteria in it. And helping develop a healthy microbiome.
[00:07:05] Dr. Lynch: 1st thing I would say is, and we need to think about this for every food we consider is that not all yogurt is created equally. Right? I mean, we have a range of yogurt products in the market from those that contain live microbes that are fermentative right through to those that are just enriched in processed sugar. It's all yogurt, but it's not all equal. And I think we have to be really conscious about what we pick up off the shelf. What is in it and what we're consuming or what our children are consuming. To really understand what's, healthy for the system.
[00:07:40] Dr. Venter: I totally agree on that, there's no real regulation of the term, a probiotic yogurt or a live yogurt.. Look for the ones like Dr. Lynch just said that at least has no sugar added. And then a probiotic. That's already a good start.
In the study that I did. we did see this very strong effect of yogurt but, I almost don't want to mention this because Dr. Lynch does such beautiful microbiome studies, but we did actually look at the microbiome of the infants at one month of age. And the mothers who were eating more yogurt and vegetables had a microbiome shift of the infants towards the bifidobacteria. Which is what you would like to have at one month. And I'm saying this very carefully because wasn't really a big cohort, but it was still interesting that we got that shift. And then, like Dr. Lynch said, I love the work on the molecules that the microbiome produce. And that's really what we needed to know is what molecules are these kids producing, but we haven't got that data in the cohort. So sometimes we have snippets of data that give us hope, but it's always so much nicer if you can tell the whole story.
[00:08:52] Lynita: for sure. So having a healthy diet based on whole foods feeds our gut microbiome and allows it to develop in a way that provides the molecules our immune system needs to function properly without overreacting to allergens. Did I explain that correctly?
[00:09:10] Dr. Lynch: Yeah, that's a really good summary. And I think even eto xpand upon it, the microbiome is producing molecules as it has done over evolution in the human body. And some of those molecules actually quench inflammation things like short chain fatty acids, for example, only made by fermentative microbes in the gut, they are energy sources for the cells that line the intestine. . They are anti-inflammatory. So, that's just 1 example of a suite of molecules that are made by microbes in the gut that are required for proper functioning of the gut and quenching of inflammation in the gut.
[00:09:45] Lynita: So eating a healthy diet is just as important for our gut microbes as it is for us.
[00:09:51] Dr. Lynch: Right. What we're seeing over and over is it's an erosion of microbial function in the gut that's associated with allergy development.
And that can come about because of antimicrobial administration , or diet that has skewed the microbiome and has led to the extinction or loss of fermentative organisms that prefer fibers and vegetables and fruits but the, the bottom line is that what we eat. influences how our microbes function and what they produce, influences how our host cells respond to stimuli that might be inflammatory.
And pathogenic microbiomes in very early life are driving inflammation and quenching the capacity for the immune response to dial back down. And that is , the crux of allergic disease development. And this is occurring in the earliest phases of postnatal life.
[00:10:47] Lynita: Yeah, one thing that you did say in your talk, was the meconium, the first poo that a baby does, you can detect differences in the microbiome then. So that microbiome is already in the baby based on the environment and the diet that the mother may have had, which just blows me away to think that, you know, maybe my son was born already going down that track. And I was fearful that that would be the journey for my second child as well. So talking to mothers that are maybe feeling those emotions about having a second child what would you recommend? I know we've talked about diet, but is there anything else? Would you recommend a pet for people that live with allergies?
[00:11:34] Dr. Lynch: So here again, the devil's in the details exposure to pets during pregnancy and an early certainly is protective against allergic disease development. But here's the rub. If you already have established allergies, exposure to a pet may exacerbate those allergies. So it's really about early exposure to antigens, pet associated antigens that seems to be where the protection is mediated.
[00:12:08] Lynita: Right.
[00:12:09] Dr. Lynch: We performed a very nice study where we examined the the vaginal microbiome during pregnancy and asked what it related to in terms of exposures of the, the pregnant individual during the pregnancy, and dietary exposures were really one of the key features and stress and depression and exposure to farming environments was the other thing that related to the type of vaginal microbiota that we found in those pregnant individuals. So suggesting that, your stress levels, depression diet and your environmental exposures may shape your microbiome during pregnancy. We also demonstrated that the types of microbes that were shared between the mother and her infant related to whether the baby went on to develop allergies and asthma or not, and was related to whether the mother had allergies and asthma.
So it showed for the first time that there is a heritable microbial component of allergic disease. Which is really exciting. The safest way to manipulate a microbiome during pregnancy is through diet.
[00:13:24] Lynita: So someone who's living with a lot of inflammation in their body during pregnancy because they've got eczema, is their microbiome going to be different and the microbiome that they pass on to their child going to make it more likely that they will or won't have eczema ?
Dr. Lynch: Yeah, it's a great question. It's one we're answering right now. Our data will be ready in about a month. So maybe a little premature to answer, the question is whether their gut microbiomes are different during pregnancy, which you might imagine would lead to differences in heritable microbes for their babies, but also whether differences in their gut microbiome prenatally are reflected in the breast milk, which would suggest that we may be nourishing babies differently if we are atopic versus non atopic status, during pregnancy. There is data out there from many years ago that atopic mothers the longer they breastfeed, the higher the risk their babies have of developing atopic disease. So that's what has suggested to us that perhaps there are differences in the microbiome of those who are allergic versus non allergic during pregnancy, and that is reflected in in the breast milk postnatally.
[00:14:37] Lynita: So that almost sounds to me, and correct me if I, if I fail to understand it properly, That maybe it's not the best option for an allergic or highly atopic mother to breastfeed for six months or longer.
[00:14:51] Dr. Lynch: . I think from our studies, we'll have a greater sense of whether, that's true or not. and what the nature of those differences may be.
[00:14:59] Lynita: Yep, okay, we'll have to wait and see what your data comes out about that.
[00:15:04] Dr. Venter: But, but I think, you know, Dr. Lynch nicely, highlighted it, the issue why our breast milk studies are so confusing is because nobody look at the components of breast milk when they look at allergy outcomes. And when people like Dr. Lynch do studies where breast milk components are better characterized, it help us so much more to understand where the breastfeeding are protective or not. And that mom with eczema, if we change her diet, are we going to do anything to her eczema at the time? And are we able to actually change anything to what's going to happen to their child's eczema? And we still need to understand about nutrition and allergy outcomes and the microbiome and, and, and everything. So I think it's exciting times for us working in this field.
[00:15:53] Lynita: I think it's exciting times for mothers that are starting to get some answers about what they can do, I think it's a big difference from 10 years ago.
[00:16:01] Dr. Venter: You know, that none of what we're doing is trying to say to mothers, you didn't eat that, or you should have eaten more of that. It's really just a learning episode. And I I'm sure Dr. Lynch must have seen the paper. It's data we have from children born in lockdown, and could really very nicely study how diet affected those children's microbiome. And, we saw beautiful spikes for what walnut does to the microbiome walnut in particular increase their production of one of the butyrate producing bacteria, which is one of these short chain fatty acids that Dr. Lynch talked about, and that was associated with less eczema in the child. Now, again, I'm nowhere near saying let's feed all babies walnut so they don't have eczema, but getting back to the basic message of let's diversify diets and let babies eat, because every food plays a role.
[00:16:54] Dr. Lynch: I agree. And I would add, let's diversify diets for pregnant individuals as well, so that we can prime that immunity in utero. I think it's a really key message.
[00:17:07] Dr. Venter: Yeah, in pregnancy, when we counted all the unhealthy foods, we had highly, highly significant association with increased eczema in particular and so again, I totally agree with Dr. Lynch, we should just diversify the diet, but focus on diversifying the healthy foods.
[00:17:24] Lynita: So diversity is really important to our diet, but , the type of diversity is quite important. So we want to diversify all those healthy things like different types of fruits and vegetables and things like yogurt that might also provide some healthy bacteria and try and reduce those things that are ultra processed.
[00:17:43] Dr. Lynch: Yes, even regular processed foods that have added sugar. I mean, what we keep seeing in our studies is that the babies who are on the trajectory to develop allergic disease have these really sugar loving microbiomes, they've been primed to love sugar And we think that that's coming through either the breast milk or formula or the maternal prenatal diet as well. So I, I think whole foods
[00:18:09] Lynita: So the best diet is high in vegetables and whole foods with fewer processed foods that are high in sugar for mother and baby. And if a mother's going to change something in her diet, is it better that you change her diet or her child's. If she had a choice,
[00:18:25] Dr. Venter: You have the best effect on prevention is when mom has a healthy diet and her child has a diverse diet. And then mom is the most important factor. So if you have to pick, pick mom. But the good news is then if you didn't have a healthy diet in pregnancy, that child's diverse and healthy diet still has a preventative effect. So it's not that everything is lost by the time the baby is born. But please no, not an unhealthy mom and baby with a non diverse diet.
[00:18:56] Lynita: Is there anything else that you'd recommend for pregnant or prospective mothers?
[00:19:00] Dr. Lynch: Think it's European advocating for longer maternity leave. And time with baby and time to actually nourish the mother and the baby appropriately. I think all of these approaches are relevant, right? The dietary part, the microbial part, reducing stress exposure to biodiversity and being out in green space exposure to pets that reduce stress and also introduce microbes into the living environment. There's a number of approaches that we can take, to try and mitigate allergic disease.
[00:19:33] Dr. Venter: I totally agree with that, you know, depression or stress in pregnancy itself reduces your microbial diversity and what we want to see in the gut. So these are the things to think about.
[00:19:46] Lynita: Fantastic. I want to say thank you really to both of you for the work you're doing. It's, it's going to make a difference and it's so nice to hear what we can do and we will be following your research.
So thank you to you both and really appreciate your time.
[00:20:01] Dr. Lynch: Thank you so much.
Dr. Venter: Thank you
Research mentioned
