Why one in ten children have a food allergy | Dr. Gideon Lack
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Welcome to ZOE Science and Nutrition, where world-leading scientists explain how their research can improve your health. Allergies are on the rise. In just three years, we've seen a 72% increase in children hospitalized from severe reactions. Allergic diseases affect nearly a third of the world's population. Some scientists say we're in an allergy epidemic. So how on earth did we get here? And what should we do?

Few in the world are more qualified to tell us than today's guest, Professor Gideon Lack. Gideon's groundbreaking research into allergic reactions in babies, which took place over five years, led to a complete U-turn on public health guidelines in multiple countries, including the US and the UK. He found that the things we were doing to prevent allergies were not just ineffective, they were actually contributing to the rise. In this definitive episode on allergies,

Gideon shares what he's learned from a life dedicated to research in this field. He tells us why he thinks WHO guidance is wrong and he offers practical advice on treating allergies and preventing them from developing in the first place.

Gideon, thank you so much for joining me today. It's my pleasure, Jonathan. So we have a tradition here at Zoe, which is a very difficult tradition for professors, which we always start with a quick fire round of questions. And we have very strict rules. So the rules are you can say yes or no, or if you absolutely have to, you can give us a one sentence answer. Are you willing to give it a go? Yes. All right. Are we currently in an allergy epidemic? Yes.

Can you develop an allergy at any point in your life? Yes. Can you take measures to prevent allergies from developing? Yes. Are most people doing the right thing to prevent allergies developing in their children? No. Are there treatments that can make life-threatening allergies become non-life-threatening? Yes. Should schools be banning nuts if it deprives millions of healthy snacks? No.

It's going to be very controversial. I definitely want to get into that.

Gideon, what's the biggest misconception about allergies? The biggest misconception, specifically about food allergies, is that we will protect our babies and children against developing allergies by avoiding those foods in their diet, providing a sort of immunological cocoon where they're not exposed to these dangerous foods out there. And this is just wrong.

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I have a 16-year-old Gideon and I have a five-year-old. And one of the things I'm really struck by is the completely different advice I had about how we should feed them and indeed what we should do while their mothers were pregnant between those two. And so I remember with my eldest, you needed to avoid any exposure to nuts because you might have all of these allergies as a result. And with my daughter, it was like, oh,

oh, I was telling my wife, make sure you're eating peanuts while you're pregnant and make sure that as soon as she starts to eat, she's exposed to all of these things. So there's this radical change in the way that I was bringing up my two children with 10 years between them. And I know that that is directly related to your own research. So I'm really excited to talk about it. And I think also, it's quite rare often to speak to

a scientist who has managed to shift guidelines in the US, in the UK, in terms of medical advice. We constantly speak to nutritional scientists who tell us that the evidence for something is compelling, but they have not managed to shift any of the guidelines. So I think you should also be feeling pretty proud that not only have you done this research, you've also managed to get governments to listen.

Well, thanks. And I can relate to what you're saying. And I stand guilty as charged because when I was a training pediatric allergist living in Denver at the time, and we had our three children, I was driving my poor wife crazy, giving her advice to avoid all these foods.

And that's what I did for a while until I changed my way of thinking. Are your children all right or did they develop allergies as a result? They didn't develop food allergies, thankfully. In sort of very simple terms that we can understand, what is an allergy and how is that different to an intolerance? Because we talk quite often on the show about sort of food intolerances.

But an allergy is not the same thing is what I understand. So an allergy is an aberrant reaction of the immune system against a foreign protein. And there are lots of foreign proteins around us, some which we breathe in, such as pollens or dust mites or cat dander that are particles floating in the air. Some are foods that we ingest.

In terms of thinking about allergy, we need to think about the role of our immune system. The primary aim of our immune system is to fight infection: parasites, bacteria, viruses.

But the immune system can launch an attack on just about any protein. So the immune system has to learn very early on who are the good guys, like pollens or milk or egg or peanuts, who are the bad guys, certain virulent pathogens. And

It does so very early on in life. The immune system even has to develop tolerance to our own body tissue because if it doesn't do that, it starts to attack inside and we get autoimmune illnesses.

So an autoimmune illness is when the immune system turns in on itself. An allergy is when the immune system turns against exterior benign, in fact, often very healthy foreign particles or proteins such as foods. So acquiring tolerance, learning to distinguish between friend and foe is a key role of the immune system.

And Gideon, does that all... Because you talk about learning, which makes it sound like it's something that happens in our childhood. Does it finish or is it continuing all the time? So the body presents...

itself to itself in a paradoxical way to learn what belongs to it. And proteins are circulated through specialized cells in the immune system into a specialized immune organ in the chest called the thymus gland. And there, the body learns these are my own tissues.

I will never attack these. And this is what happens while I'm a fetus. This happens during fetal development because the immune system is already developing very early on. You're saying that when I was a tiny fetus or my children were tiny fetus, like literally every little protein that my body has made up is sort of going through this special process.

part of me to sort of say, ah, tick, this is part of Jonathan. That's exactly it. It's a sort of checklist. This is okay. This is okay. This is okay. That's amazing. Sometimes that breaks down later in life and that tolerance is lost and you get autoimmune disease. So you start attacking the cells of the pancreas that produce insulin because the body thinks...

These cells are noxious, or the proteins on them are, and you get autoimmune type 1 diabetes or multiple sclerosis or celiac disease. So there's a whole host of autoimmune agents where tolerance breaks down. So tolerance is really critical. And in allergy...

we either fail to acquire tolerance to friendly or innocuous external agents such as foods or pollens, or we lose that tolerance. And so does that process continue for the rest of my life? Because when I was a fetus, I wasn't being exposed to pollen, presumably, or certainly not eating any foods. Normally, it does continue. Occasionally, it breaks. The immune system has long-term memory.

So if it encounters a pathogen or you have immunization, you're protected for a long period of time. Occasionally, you'll require a booster to jog your memory.

If the immune system learns that a food is a good thing, is friend not foe, during the first months and years of early childhood, it will retain that memory for a long time. And we'll probably come back to that later in the interview where we now are able to demonstrate this phenomenon of long-term tolerance because the immune memory remembers, ah, I met this peanut when I was a little kid or baby,

I'm now going to tolerate it at 13 or 14 or 15 years of age. So in my first couple of, I'm thinking about, again, all my little children, they have this habit of, which is universal, right? Putting everything in their mouth all the time, whether food, but everything else.

that's the time presumably therefore when your immune system is experiencing most of the things in the outside world for the first time and it's making this decision that you know tick I'm happy or cross you know this is some horrible bacteria and I need to do something. Absolutely and I think what Freud describes as the oral phase where babies want to put everything shove everything in their mouths I think has a

plays a really strong evolutionary role in our previous evolution and in the current evolution of the baby's immune system because the baby is actively, whatever foods the parents are eating, it's making a gram for wanting to put it in its mouth and eating it. And there's a purpose behind that quite apart from nutrition. That's fascinating. I've always thought that like this thing about small children, they're constantly trying to kill themselves, but you're saying this might be one of the reasons why they're picking

picking up everything and putting it in their mouth from food to dirt. Absolutely. And dirt to dirt as well. And in fact, in rural societies and traditionally, babies were not just putting foods, but also soil into their mouth and a whole host of bacteria. I'm not suggesting that's a good thing, but there's certainly an element of getting exposure to dirt and foods through the mouth. Can I follow up this question with what happens when they're

is an allergic reaction? Because I think many of us are aware that this can be like a life-threatening risk as a result. What actually happens that's going on, and particularly in some of these worst-case scenarios that people are always so worried about?

Yes. So initially you'd asked me, and I didn't quite answer your question on the distinction between a food allergy and a food intolerance. So a food allergy is potentially more dangerous. That is a directed attack on the immune system against a foreign protein such as peanut or egg or milk. What happens there is during the development of allergies very early in infancy, the

The body starts to make allergic antibodies against the food. They're called IgE antibodies. And these antibodies recognize subsequently the food when the food is ingested for the first time, such as peanut or egg. And that...

triggers a whole cascade of events with the release of histamine, hence the use of antihistamines to treat allergy, and other chemical mediators in the body.

Ultimately, what that can result is in facial flushing, hives, swelling of the face, vomiting, wheezing, and eventually it can have cardiac effects and can be life-threatening and lead to death. And this all happens very rapidly. This can happen within minutes. Food intolerance, on the other hand, is not mediated by the immune system. It can be due to just the chemical properties or pharmacological properties

properties of a certain food, such as caffeine causing tremor or causing diarrhea. That's not an allergy. And some people are more sensitive than others.

And I understand that one of the things, because you're talking about sort of swelling, that one of the risks to have friends with children with some of these nut allergies is worrying that the swelling is sort of in your throat and that actually basically you would cease to be able to get air. Is that a common risk that comes out of this allergy? Is that one of the key things that is what makes it so common?

So swelling in the throat is commonly perceived. It's not visible externally. There's irritation in the throat, sensation of a lump in the throat, difficulty swallowing. That leads to severe anxiety.

Occasionally there is sufficient swelling to completely obstruct breathing, but in children that's not the usual cause of death. The usual cause in children is spasm of the muscle, smooth muscle, around the airways and the lungs, so the child gets an acute asthmatic attack.

and oxygen levels drop, and eventually the child can suffocate. That's the worst. And although, thankfully, that happens rarely, that is every parent's worst nightmare.

I asked this question in the beginning about whether there's an epidemic of allergy, and you said yes. Can you share, like, how has this changed over the last, you know, I don't know, 100 years or whatever it is, and how many people in the U.S. or the U.K. actually suffer from allergy? Well, 100 years ago, virtually no one was talking about peanut allergy. Today, 2% of schoolchildren in the U.K.,

that's one in 50 have peanut allergy alone. 8%, almost one in 10, will have some form of food allergy during childhood. So it's gone from almost nothing to almost one in 10. It's gone from less than 1% or less than 0.5%. There's been a 10, 20-fold increase, at least in food allergies over the last 40 to 100 years. Some people would argue, well,

Maybe this is genetic, and there's no doubt that there's a family tendency towards allergies, but our gene makeup did not change in 100 years. It takes tens or hundreds of thousands of years for our gene makeup to change, for our genetics to change, and therefore it has to be something in our environment, in our behavior, in our culture, which has led to this rise in food allergies.

I feel that I have seasonal allergies, what we call hay fever in the UK. And I don't remember having this as a child. I feel this is something that actually I really developed and seems to have got more severe in my adulthood. Am I just imagining that? Or does it all have to happen when I'm a child? Or actually, can you develop these allergies as you're older? So your observation is really correct.

The respiratory allergies, hay fever and asthma, tend to kick off later in life. Eczema and food allergies start very early on, and there's a very tight relationship, which we may go into later, between eczema and food allergies.

That may be because the root of sensitization, in other words, the root of becoming allergic for respiratory allergens, perhaps we believe occurs by inhaling these allergens through continual exposure as you grow older, as you spend more time outdoors, as you play sports.

sports, you inhale those allergens and that leads to an allergic response. That's not necessarily the way it happens, but typically eczema starts, kicks off in the first months of life. Food allergies develop within the first one to three years of life, as early as the first 12 months of life. And then the hay fever and asthma tend to develop later.

Some people would argue, and if you look for it carefully, you do start to see the origins of respiratory allergies, hay fever and asthma, actually occurring earlier in childhood. And I have seen hay fever in infants as young as 12 months of age, but that is uncommon.

That's really interesting, Gideon. So I know we're going to talk a lot about these food allergies and with children, which are obviously like being the center of your research and other things, I think, as you said, is every parent's sort of nightmare and fear. Can we just spend a moment on the adult allergies before we go into that? And I'm sort of curious, what are the main allergies that adults develop?

That's a changing feast. And the reason for that, of course, so in the past, the main allergies that adults had were fish, shellfish, and some nuts as well. And by the way, there's a mild form of shellfish.

adult and teenage allergy, which you can also see in school children. That's called food pollen syndrome or oral allergy syndrome that is secondary to development of hay fever. So a lot of people with birch pollen allergy

will develop mild allergies to peaches, cherries, apple, and certain nuts. These tend to be mild reactions, and that's because the protein in birch pollen is structurally very similar to the protein in these fruits and nuts. Can I make sure I've understood that? So you could be allergic to the pollen from a particular tree,

That then means that I start to become allergic to a set of foods? To a set of plants and vegetables and fruits, especially if you've eaten raw. That's because they have a similar structure

to the protein in birch pollen, which was the primary source of sensitization. And do many people have this birch pollen allergy? That's extremely common. About 30-40% of the population have birch pollen allergy, and a third to a half of those will have this. Very often they're not aware. It's a mild form of allergy in general. They will either dislike raw apple or they'll get a bit of tingling in their mouth.

Interestingly, it's the same mechanism as the dangerous food allergies, but because the proteins are unstable, they get

altered immediately the moment they enter the mouth or with a bit of heat processing. They change structure and the reaction is not as violent. So that's very common. You said 30 to 40 percent of people are allergic to this birch pollen, so it's a lot. Other than apples, what were the other foods that might... It can be a very wide range, but typically apples, peaches, cherries,

plums. A lot of people refer to the stone-containing fruits. It can be others as well. It can be kiwi. It can be soy. Some people react to edamame beans or soy milk or tofu, which is plant and which contains that same structural protein. But these tend to be mild. This we've been seeing for a while. The serious allergies that adults develop tend to be, or in the past have been, fish, shellfish, nuts.

But this is all changing. Why is it changing? Because children are now developing for the first time during the last few decades, egg, milk, and peanut allergy.

Peanut allergy tends to last for life. About 20 to 25% will outgrow their peanut allergy. The other 75% will have persistent peanut allergy. So by implication, if we're now seeing this epidemic of peanut allergy developing in young babies and children, and it persists, this is becoming a bigger problem in young adult life. Same with all the other nuts and

Same with sesame seed. These are increasing in prevalence in childhood, persisting into adulthood. So the picture is changing. You asked about an epidemic. About 8% of children, primary school children, have a food allergy.

three to four percent of adults, young adults, now have a form of persistent food allergies. It's a huge shift then from almost none to like one in 25 now of adults moving towards one in 10, you're saying, as children continue to age. And the studies come from UK, other European countries, and the US, and the numbers are very similar. And interestingly, until recently, people used to say, well, peanut allergy is

primarily an Anglo-Saxon problem. It occurs in English-speaking countries. Why? Because those are the countries that eat a lot of peanut butter. But in fact, a recent Scandinavian study has shown that the rate of peanut allergy in Sweden and Norway is identical to the UK and the United States, 2%, one in 50 children. If you think about that...

That's about 14,000 new babies in the UK alone who will be developing peanut allergy every year, year on year. So over 10 years, you'll have 140,000 new cases of peanut allergy in the population based on our current birth rates. So Gideon, now I've got to ask you,

what's going on. And I know this was your own research. It's this wonderful story that you shared with me actually just before we were starting the show about sort of the light bulb moments in your own life that sort of led to your research here.

Well, there were a few light bulb moments. Unfortunately, the light wasn't quite as bright, or perhaps I was too dim, and it took a while for the penny to drop. But there were a series of observations that puzzled me. One goes back very early to when I was training and doing research, and I noticed that the way you made...

little mice pups allergic to foods such as peanut or egg was by rubbing it very gently in low doses on a braided skin, suggesting that they became allergic through inflamed skin.

In contrast, if you gave peanuts or egg or milk to a young mouse pup, you could never induce allergies in that, and that first exposure protected it long-term. And I remember asking my professors at the time, "Well, why are we telling babies not to eat the foods if these foods are protecting mice? Why are we thinking differently about human babies?"

When guidelines started changing, parents, mothers were coming to me and saying, look, I don't understand what's going on. I took all the advice from my doctors. I avoided peanuts during pregnancy, during breastfeeding. I didn't give it to my little boy or girl. And at three years of age, they ate peanut butter, developed a severe allergy with the first known exposure. And I

I started to realize with these very digital parents that avoidance was not the way forward. I suppose the key turning point was when I gave a lecture in Israel, I was invited to speak about peanut allergy. And my first question, as I often ask, this was an audience of about 200 pediatricians and allergists, asked, "How many of you have seen a case of peanut allergy in the last year?"

less than a handful put out their hand. And in the UK, even if, you know, pediatricians, allergists, GP, virtually everyone would have put up their hand. It was like completely, incredibly rare there. And here you would have said every single doctor would have seen it. So there were two explanations. One is they really don't see peanut allergy.

or they weren't diagnosing it correctly. The latter was very unlikely. Actually, many of them were colleagues who'd been trained like me in the US. Not wishing to belittle my specialty, it is not that difficult to diagnose peanut allergy when the parent comes and tells you. Sometimes it is, but very often, in most cases, the history is very obvious. So I started to think, is this a real difference? Could this be genetic? And then...

it dawned on me, gosh, well, the Israeli population, Jewish population, largely Ashkenazi of Eastern European origin, North African and Spanish origin. And I see a lot of that same population in London, and they have food allergies. So it didn't seem to be the case. A key observation, which the Israeli doctors and parents of children were telling me, was that the first snack in

in the Israeli diet was, or the first food, was peanut. For babies. For babies. And it's funny, but there's a joke in Israel that the first three words that a baby learns to say are mother, father,

Bamba, Bamba being the name of this peanut snack. And it's so much part of the culture, babies are eating this from four months of age. So we decided to formally test this in this observational collaboration, where we took

5,000 Jewish children from Jewish day schools in the UK and compared them with 5,000 Israeli school children who shared a common, not identical genetically, but shared a common ancestral genetic background and looked at the rate of peanut allergy. And indeed, it was tenfold higher in the UK children and almost non-existent in the Israeli children.

And we again, we quantified the amounts of peanuts the babies were eating in Israel, which was extremely high. In the UK, it was zero. So we confirmed it through an observational study. That's still not evidence. There could be other factors. There could be differences in sunlight, lifestyle. Vitamin D is thought to influence allergies, more sunlight.

So you sort of had a hypothesis now. We had a hypothesis, exactly. But you hadn't proven that it was the peanuts because maybe it was some other thing they were eating or whatever else that was different at this point. Correct. And Gideon, how long did it take you from the point that you'd sort of had this light bulb moment in Tel Aviv to actually getting the first child to participate in this RCT, this randomized control trial? The light bulb moment was in about...

2002, 2003. But it took a long time to execute the study, of course, because we took these 640 babies, high risk of developing food allergy. Why? Because they had eczema. And I alluded to earlier that

allergies we believe develop through the skin in babies with eczema or dry skin. So we chose a group of high-risk babies where you would actually see peanut allergy.

And we randomly allocated these 640 babies to either complete avoidance of peanut for the first five years of life, similar to previous guidelines in the US and UK. And the other half actively ate this Israeli snack or peanut butter, in some cases peanut soup.

What happened? So we followed this group of 640 babies all the way through to five years of age. And it's, you know, remarkable testimony to these families and to the whole research team that we were able to evaluate peanut allergy in 98% of these babies who

who turned five years of age. So virtually everyone stuck with the study. Dropout rates are usually much higher, but these families were so committed that that gave us a lot of statistical power to analyze virtually the whole population. And sure enough, we found that the rate of

peanut allergy in the avoiding group was close to 20 percent um on that on average 17 so it was 20 in the avoidant group but it was less than three percent in the consuming group

And there was about an 85% reduction in the rate of peanut allergy. There was an 85% reduction in the level of peanut allergy in the group that you were giving peanuts to, despite the fact that all the advice had been like, make sure that whatever you do, you don't give your children any peanuts. Absolutely. And we were not expecting this degree of efficacy. We were expecting...

a 30, 40, 50% reduction, but we got a substantial reduction that really is comparable to the efficacy of a vaccine. Vaccination rates very often will usually give 80, 90% protection

And so were you shocked by this? Because, I mean, that is amazing, right? Normally, we talk to a lot of scientists about their studies. It's extremely rare when you have a randomized control trial to have that, like, 85% lower. As you said, it's like some magic drug. Yeah, we were thrilled, but pleasantly surprised. We hadn't anticipated that degree of an effect. Moreover, because this was a very high-risk group, close to 40% of these babies were

in the entire group were already making low levels of allergic antibodies to peanuts because they were being exposed to peanuts that their parents ate through the skin. And we only knew about these blood levels later, but what I'm saying, I suppose, is the immunological process of becoming allergic had already started, the ball had started rolling

when we intervened in many of these babies. And despite having these low-level allergic antibodies,

we were able to halt the peanut allergy, or to stop it in its tracks. So that was what really surprised me. I had expected that once you've got allergic antibodies to peanut in the bloodstream, the dyes cast. There's no going backwards. Peanut allergy is going to develop. That was not the case. And it would be a bit like saying, well,

to give a drug in the early stages of a disease, take COVID and reverse it. So we were able to do what we call primary prevention before there were any signs of the disease and secondary prevention once the disease had started to develop. - That's amazing. - And that to me was really striking.

And the irony is it's just, we're not talking here about fancy vaccines or immunotherapy. We're just talking about a very simple, cheap, effective and safe strategy, eating the food. So how has that led to change in guidelines, you know, in the US, in the UK, in other countries? So I was really gratified to see very rapid response.

in the guidelines. The first big set of guidelines came actually from the NIH, who funded the study in the United States. It's a government agency, and they thought it was important to get the message out, saying that babies as early as four to six months of age should eat peanuts. The Australians were the next to take it on, and then American professional bodies, others. We eventually

took on these guidelines in the UK, I still think they've been watered down a bit and are not specific enough. There's a difference about the UK guideline versus the US guideline you described? Well, they came later. And the emphasis more is that delaying introduction of these foods beyond six months of age could increase the risk of these allergies.

That's a sort of, I would say, that's the half-full or negative way of saying it, rather than actively give peanuts to babies. It's softer, and the message hasn't gone out. And, you know, we learn, we all learn as we go along. And I was involved in consulting to the first U.S. guidelines. My views on how the guidelines should be formulated have changed. And it's an evolving process. Initially, the guidelines said,

apply this mainly to children with eczema. It then became apparent that it's not only children with eczema who develop peanut allergies, but children with dry skin who develop peanut allergies, and even some children without any skin problems. And for this policy to be effective, it has to be applied to the whole population.

And one of the things we also learned during the LEAP study, there were 76 babies who we evaluated at the beginning of the LEAP study who could not be enrolled. Why? Because they already had peanut allergy. So they were excluded from the study because this was a study about preventing peanut allergy. Now, you can't prevent something that is already there.

So one of the things we've learned is the intervention has to be very early, ideally by six months of age, and in babies with eczema, by four months of age. The peanut has to be introduced. So timing is critical and timing.

Quantity is critical. In the LEAP study, we gave these babies six grams of peanut protein a week, which is about the equivalent of 25 grams of peanut butter, which is close to two heaped tablespoons of peanut butter a week. That's a lot. If we say give your babies peanuts, most parents interpret it as a tip of a teaspoon once every few weeks, and that does nothing.

It would be a bit like taking the results of COVID vaccines and the high success rates and saying, well, we don't have enough vaccine. Let's give it to more people. Let's dilute it tenfold and give tiny amounts of vaccine. That's not going to work. So you need to make sure there's enough exposure. And your other one, I think what you're saying is that...

You feel the guidelines in some countries, and I think the UK is an example here, are not strong enough about saying you really should be introducing your babies to peanut and doing it sort of regularly and in enough quantity to make sure that they understand that this is a safe food rather than they're...

immune system saying this is something really dangerous. So the problems in the guidelines, and that's normal. Guidelines take time to fully fledge out the detail. But there's also other problems. For years, we've been making parents fearful of

peanuts, but not only peanuts, other foods as well, egg and milk, and talking about delaying all these foods. So there's a culture of food phobia, food fear, and food avoidance. And for parents, especially first-time parents,

It's a big deal giving a food very early on in life. And so Gideon, just before we switch to actionable advice, which is always really important and I want to really talk about that, I just want to ask one other question that hasn't come up here, but there were a lot of questions from our listeners around this, which is, do we know of any connection between allergies and the microbiome? Because we talk about the microbiome quite often on the show.

on this show, often talking about gut health and how it affects other health. And there seems to be lots of evidence that our microbiome itself is very influenced by our experience in the first couple of years of life and that we put our children in cotton wool not only to do with peanuts, right, but also in terms of exposure to

the world, we definitely don't encourage our children to eat dirt anymore. Although I have been much more tolerant of that with my daughter than I was with my son, again, with this shift in my personal understanding.

You've talked a lot about the skin and how this might be the source of these allergies. Is the microbiome not really part of this story, or is there some role? There's no question that the microbiome is very much a part of this story and is tantalizing lines of evidence. I would not say the evidence is conclusive. I think our

a whole understanding of the microbiome. And we're not just talking about the gut microbiome, but the skin microbiome, the nasal respiratory tract microbiome.

are very likely to play a critical role, but we really are in our infancy of understanding this, quantifying the microbiome. I mentioned to you these studies in mouse models, where mice were given egg or milk and orally by Gavage and could never become allergic.

Now, there was one really important clue there that Japanese investigators found. If they took germ-free mice, those were completely sterile mice who were reared without any bacteria inside them, and they gave them

milk or egg, these mice did not get the immunological protection or tolerance, and they could become later allergic. Gideon, can I just make sure I've got that particularly? You were motioning with your hand. I want to make sure that it was clear for people listening. You're saying that these mice that didn't have any microbes inside them, even if they ate eggs, instead of saying, oh, this egg is safe, that didn't work and they could still end up being allergic? Exactly. So in other words,

In the mouse model, consuming the food was a necessary factor, necessary condition to prevent allergy, but not a sufficient condition. In addition, you needed a microbiome in the mouse's gut.

to prevent it. So there's something about the microflora that is doing something to promote immunological tolerance. This process is called oral tolerance induction, and we think of the gastrointestinal tube as a digestive tract, but it also has an important immunological role in establishing tolerance to these foods. And there's no doubt that

the bacterial flora in our gut must be playing a very important role. Quite how we don't understand, and the two ways of thinking about the microflora, everyone is talking about the diversity of the microbiome, having a lot of different species in a sort of perfect balance, contributing to good health and tolerance.

I tend to think more of it in Darwinian competitive terms because all these bacteria in the gut and on the skin are competing for resources in the same environment.

It's competition between different species from the same resources. And if the good guys leave, the bad guys get in. So what I'm alluding to is that in allergy, we don't really know whether it's good bacteria that are protecting or whether it's an absence of good bacteria that allow the bad guys to come in.

And I have one particularly bad guy in mind, and that's a bacteria that is very common on human skin called Staphylococcus aureus, which is related to Staphylococcus epidermis. Both can cause infections, but Staphylococcus aureus is present in about 30% of babies with eczema on the skin. It's often frequently carried in the nose.

And there's a lot of data now showing that that promotes allergic responses. So having an imbalance in the skin or in the gut could potentially allow this microbe to grow and then promote allergies. In 2022, we took a huge risk. We put our reputation on the line to prove that ZOE membership could improve the health of millions.

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Simply go to zoe.com slash podcast. Okay, back to the show. Often when we talk about the microbiome, we tend to talk about the gut microbiome. This is like by far the largest set of bacteria, but I know that there's a skin microbiome as well. And it seems like you're talking a lot about the fact that the way in which we are tending to get these allergies is because things are sort of penetrating through our skin, which they're not meant to. Do we know why that might be happening now? No.

when it wasn't happening? You know, you were saying 100 years ago people weren't getting this peanut allergy. Is there something happening with the skin now that was not true 100 years ago? So you've actually just touched on the most difficult question to which we really don't have an answer in empirical terms. We do have, I think, workable hypotheses as to why this has happened. And it's related in a very broad sense to the hygiene hypothesis.

So 100 years ago, or even less, 40, 50 years ago, people were having a bath once a week. They weren't having two showers a week, applying all these soaps and cosmetics and cleansers to their skin. They weren't bathing as often, either.

And we know that frequency of bathing in early infancy is associated with an increased rate of allergies, also more eczema. Suddenly we have all these products, even washing powders, that are there in nanogram or picogram quantities

tiny, tiny quantities even after washing the clothes. And these are, they really are toxins in a sense that disrupt the skin barrier. So if you think of it, we've got the stratum corneum, this thick surface of dead cells on the skin that were

shaving off, essentially, washing off, rubbing off, while applying all these products. And in so doing, we are actually damaging the skin barrier and we're altering the microbial balance on the skin barrier. We're getting rid of

a whole host of bacteria that may be playing an important role. Let's face it, it's not very pleasant being in a room with smelly people, and we've got the advantages of unlimited hot water, showers. We are clean. We don't smell the way our ancestors did, and our skin has altered beyond recognition compared to our ancestors even 50 or 60 years ago.

And that coincides very much with the increase in skin disease that we're seeing in very young children. And we should be thinking not only about eczema, but dry skin.

And so, Gideon, are you saying that we should all stop washing, which is probably not going to be the most popular advice that's ever been given on this podcast? No, I'm not saying that. Well, actually, some advice has been given that very early on in infancy, babies should be bathed once or twice a week early on during the time when there are risk of developing eczema. And I'm not saying they shouldn't be cleaned, but they shouldn't. And that soap shouldn't be applied. But we

We don't have enough empirical evidence to say stop washing. So this is an area of really ongoing active research to try and understand this better? It's an area of ongoing research. In fact, one area of research we're pursuing and we're embarking on is a study called the SEAL study, stopping eczema and allergies. We were taking very young babies with dry skin

And we are applying a particular kind of emollient lotion to the skin that has some unique properties to try and restore the skin barrier. And in the babies who develop eczema, we are proactively applying.

treating one's steroids. This is a randomized controlled trial, and the idea is that if we can really preserve that skin barrier very early on, we can prevent the development of all food allergies through the skin, because we think it's not only peanut, but egg and milk and other food allergies develop that way. As

And so this is fascinating. I can see there's a whole podcast I'm gonna have to come back to talk about this. I would like to make sure that we sort of switch to talking about actionable advice because I think we've picked up pieces as we go along, but I'd really like to make sure there's really clear advice for our listeners. 'Cause it seems like there is really strong scientific evidence.

should we maybe start at the beginning so maybe thinking about you know with very young children or maybe even earlier maybe even starting back i'm thinking about pregnancy what is the advice that you would be given to anyone to try and make sure that their children don't develop any of these allergies so during pregnancy there's very little we know about there's certainly no

good reason for mothers to be avoiding foods in their diet. Mothers should eat a normal, healthy, well-balanced diet unless they let their tastes, you know, and food preferences direct them, what they normally eat in the family. The only, and I don't think the evidence is strong enough, but this is an observation, that there are two studies now showing that babies who are born into a home with a dog

have about a 50% reduced chance of developing food allergies. Kevin, can I just confirm you say that? If I have a dog in my family, I halve the chance of my children... No, no, I didn't say that. No, that is an observational association. It's not evidence.

In order to do that, you'd have to do a study that I've actually been toying with, which is called the Bow Wow Study, where you would take a thousand families and randomly, during the third trimester, put a dog in the home, in half, the other half not. Getting this study off, launching it is...

Very difficult. I'm not sure it's going to happen. And then if you saw that, that's like the LEAP study. It's a randomized intervention. At the moment, we just have observation, but they're pretty compelling observations, and they fit with what we know from

German, Swiss and Austrian farming studies that babies spending time in cow sheds for more than X hours a week will significantly protect against allergies. This all goes back to the hygiene hypothesis, getting in contact with a whole host of bacterial flora. After the baby is born,

I'm a big promoter of breastfeeding. And I would say exclusive breastfeeding for the first three months of life. And this is where I have to say, you know, my personal belief and the data we've

differs from the World Health Organization guidelines, which promote exclusive breastfeeding for six months. I would say in babies with eczema, as early as three to four months of life, start introducing them to peanut, egg, milk, the common food allergens.

regularly, frequently, not large amounts of time, small amounts of time, but so that they get enough over the course of a week and continue that every week. So I'm a big proponent of early weaning in combination with breastfeeding. And Gideon, one of the things I'm very conscious of is just how hard it is to be a young mother with a baby and just how difficult that is to manage. And then there's always this immense amount of pressure

of all the things that you have to do just right or you're a bad person and you fail, what parts of that advice you feel are like the crucial things that you feel can really make this big

big difference to whether or not your child is going to develop this very severe, potentially life-threatening allergy. So I do think early weaning is important. I'm also very conscious of what you say about the anxiety and burden, the parental pressure. But at the moment, I think moms are being unfairly sort of targeted for

towards exclusive breastfeeding for six months, which is something that very few mothers are able to do. I believe in exclusive breastfeeding for the first three or four months of age, then weaning, and continuing breastfeeding at least and beyond one year of age. But breastfeeding doesn't mean breastfeeding to the exclusion of foods. And indeed, most mothers find it very difficult to exclusively breastfeed their babies. Babies start to get hungry, they cry.

And in fact, in a randomized control study, which we conducted called the EAT study, which was supported by the Food Standards Agency, MRC, together with my colleague Michael Perkin, we found that the babies who were exclusively breastfed for the first three months and started eating egg, peanut, milk, wheat, slept better than the babies who were exclusively breastfed.

And if you think about sleep difficulties in babies, that's one of the most stressful things in families where the baby doesn't sleep and cries all night and the family's up all night. The rate of severe sleeping difficulties was halved in the babies who started to eat these foods very early on. And that's what happens in traditional societies. This is not a particularly difficult thing

complex intervention. Babies have a natural appetite. They start looking and are interested in foods. What I would say, introduce the foods but in a family and baby friendly manner. Let the baby play with the food, touch the food,

give the food in palatable ways, appealing ways. It should always be smooth, slippery, easy to swallow. And I would say particularly focus should be given on the babies with eczema and dry skin. Even if your baby has rough skin, that is an indicator that the baby is at risk for food allergies. And Gideon, you mentioned about the breastfeeding, and I know there's lots of different reasons why people talk about breastfeeding.

Is there any particular link with allergies? Is there a reduced risk if you're breastfeeding versus using baby formula? So the evidence is not good either way. Breastfeeding...

Unfortunately, it does many wonderful things and it's essential, but there's no good evidence. There's an interesting theory that it's the early colostrum in the milk, which is rich. It's the milk that's produced over the first few days of life that has a different quality to it, that has a lot of antibodies in it and cytokines. Those are molecules that

are important in regulating the immune system that the ingest ingestion of the early milk is particularly important but breastfeeding is important just to be really specific because we've talked a lot about peanut is it mainly peanut that you're worried about and making sure that babies have from early age and if there are others what are the other key foods if anyone's listening to this thinking about their children or their grandchildren or whatever that

So the most common allergies in the UK are egg, peanut, milk, wheat, sesame, then kiwi and fish, but also all the multiple tree nuts, cashew, pistachio, walnut. So if you think about it, say you've got to have this all in one go in two weeks, that's a big workload. But if you think about it, our...

Diets are hugely diverse. Babies are growing, their appetites are developing, and this has got to be done in a child-friendly way. So I usually say, when I see babies about four months of age, I say, take the pureed vegetables and rapidly start egg and peanut and sesame and wheat. Don't give huge quantities at a time, but give these very frequently, three, four, five times a week.

And then as the baby's a few months older, you start gradually to introduce the other tree nuts. What's really important, and this is, you know, as a piece of practical advice, I would say the foods that you eat in your household are the foods that you need to focus in terms of giving your baby very early on. Because they're going to be exposed on their skin. Because they're going to be exposed through the skin, exactly. You know, if I see a patient in my clinic with cashew allergy...

I can guarantee you, I'm going to ask the parents, what's your favorite nut that you're eating the family at home? It's cashew nut. Do you know someone for whom this episode would be really important? If so, how about you share it with them right now and give them the gift of knowledge from a world-leading expert? I'm sure they'll thank you. Can I... I know we're running a bit out of time and I want to make sure that I get past just that.

that very first stage because we asked this question at the beginning about should schools be banning nuts as a result of this because it obviously deprives everybody else of nuts. I think we had actually quite a common question from our listeners about should peanuts be banned from planes? Could I open a thing on planes? You're one of the very world experts on this. What was your view? Not everyone has the same view. I understand parents who have a child with peanut allergy,

or egg allergy who want the food banned from the school. But if you start to think about it, there are more deaths due to milk allergy in children than due to peanut allergy. They're pretty equivalent, but slightly more deaths due to milk allergy. Are we going to start banning milk and dairy products in schools? I don't think it's realistic. Schools need to be very cautious. Families need to be cautious.

And it's a difficult thing to swallow, but patients with food allergy need to learn to live with the enemy. Just the way you can't prevent allergies developing by wrapping a child in an immunological cocoon.

I don't believe in having children sitting at separate tables, banning foods on airlines and elsewhere, because before not long we'll be banning egg, milk, peanut, sesame, cashew. It's ironic to me that peanuts are banned on some airlines, and yet they're serving you snacks of cashew nuts. There's an arbitrariness to it.

and the parent of a child with milk would like to see milk banned at school. Thankfully, and we haven't spoken about that, there's been an explosion in the number of strategies we have now to treat food allergies. This is something the NHS is not

providing sufficient. This is the health system in the UK. Well, this is not prevention now. This is treatment. So you can actually desensitize. And this is something we are doing now where you can introduce tiny amounts of peanut or egg or milk and increase the dose till children are well protected against significant quantities of food allergens so that they will feel safe when the food is around them.

And that's something we need to see more of. There are other strategies to treat food allergies too. There's a range of molecules called monoclonal antibodies that protect children and adults against multiple food allergies once they've already developed them. So I think we're going to see a big seed change. With these new treatments, people will feel safer.

And this is because it will reduce their level of allergy. It will release their sensitivity. So if it means they eat half or a whole peanut by mistake, nothing, well, it's likely that nothing is going to happen to them. It will mitigate the risk. But, you know, we have to be cautious in life, but

And I see it's particularly difficult striking the right balance in families. I see families who get it just right, some families who are cavalier and they just don't read labels and child has recurrent reactions, some families who just won't let their children go to birthday parties. So...

I think this idea that we can avoid all these allergens in schools doesn't really match with the reality of daily living. Also, the child needs to learn for themselves to look

to look, to read labels. Then you mentioned airlines, so it is very difficult to aerosolize peanuts. That is when basically peanuts become dispersed, peanut particles or molecules become dispersed in the air. So for example, someone who has cat allergy,

They walk into a room where there's a cat, they immediately start sneezing. There's a cat in the air. If someone walks into a room with peanuts, they may smell the peanuts, they won't like it. That is extremely unlikely to cause an allergic reaction because the peanut molecules are quite heavy and they don't disperse into the air. They don't become, well, the word I used, aerosolizable. They're not respirable. Obviously,

Obviously, if someone is grinding or crushing peanuts in front of you, it's a different story. There are some allergens that can become dispersed in the air quite easily. So I don't see peanuts and nuts as a big risk on airplanes. What I always tell my patients is check the seats, run your hands through the cracks, make sure there are no bits of nuts that a previous passenger has left behind. I'm not personally concerned that...

peanut on the airplane is going to cause problems. Again, you know, this same problem you can have on an airplane, far out in the countryside, traveling, backpacking in a foreign country. This is the problem for people with food allergies. There's always the unexpected.

Now, and I do, there's an issue of psychology here as well. When you're in a tube up at 10,000 meters and you're having a reaction and there are no doctors or medical facilities around, I understand it is anxiety producing. So I'm not encouraging that, you know,

nuts and peanuts are given to every person on board because that's going to make it very unpleasant and uncomfortable but the bigger plane the bigger problem on planes actually um that i've come across and heard of is milk and fish fish is very aerosolizable disperses in the air milk and people in fact people with fish allergies if they walk

through an open fish market or shellfish market, they'll start wheezing and having a lot of- That's really interesting. So I guess I have always assumed it's very much around nuts. And you're saying that actually there are lots of people with these allergies to things like milk and fish, and potentially because those spread more easily in the air, you might actually be causing more issues to people than you are with your nuts.

Well, I think Gideon, it's a brilliant insight actually, I think into the challenges for people who are living with these allergies. And obviously, I guess you always worry even more with your children with these. I have many more questions, but we've definitely hit time. I would like to do a quick summing up and will you please correct me if I got any of this wrong?

So we started by saying there's just been this epidemic of allergy. You said like a 10 to 20 fold increase over the last 50 years or so, such to the point that in somewhere like the UK or the US, you know, close to one in 10 children have an allergy. And I think you said about 2% of them specifically have a peanut allergy. Correct.

that the allergy is your immune system responding. You said to like a protein and the issue is that actually that protein is perfectly healthy for you, like a nut or a piece of egg. So it shouldn't be going crazy, but it's saying like, wow, this is like a virus like COVID or something. And so it's failed to learn the difference between something that is friendly and is dangerous.

that our immune system is sort of trained. And you said there's this amazing thing going on as we're a fetus where like every bit of our own body is sort of going in front of the immune system. So it learns, yeah, tick, that's all right. That's a bit of your liver, you know, that's all right. Versus then discovering things on the outside are bad.

and that what seems to be going on is that anything that comes in through our skin your immune system is saying well that's really bad stuff shouldn't be coming in through your skin so this is obviously something dangerous whereas generally if it comes in through your mouth it's saying well this is food so i'm going to be happy and that's what has been happening is for

for whatever reasons, a lot of children are building up these allergic responses to things like nuts and eggs and all the rest of it. And there's been this huge increase. There are also adult allergies. And you said that it's not uncommon for these sorts of pollen allergies to develop as you're older. As I've had in my own case, you gave this brilliant story about, I think you said 30 to 40% of people have a birch pollen allergy. And then if you do that, actually you do have a sort of

mild allergy against apple and peaches and cherries. So all these people claiming that they have this, which I've always been a bit suspicious about, it's actually true, but it's quite mild. It's not going to lead to these sort of scary outcomes that we talk about with peanuts. And then we talked about, I think, what is sort of the central thing in your research, which is allergies with children and particularly your research on peanuts.

where you really reversed everything that certainly I was taught as I think about my son growing up, which is that you should avoid your children having exposure to any of these allergies. And you had this amazing study, the LEAP study, where you showed an 85% reduction in babies developing allergies if they're actually exposed to this peanut sort of as early as possible and as often as possible. And therefore, the guidance that is really across the world now is completely different from what

many listeners may think it is because it's such a big change, which is basically when you're pregnant,

Don't cut out allergens. You shouldn't be trying to avoid this. And once your child is born, you're saying from four months, you're saying that the formal WHO guidance is from six months, but expose them to all of these products as soon as possible. Frequently and regularly. Frequently and regularly. So once isn't enough, frequently and regularly. And you mentioned egg, peanut, milk, wheat,

Sesame, I think is your top, but the biggest guidance I took away from this is it's the stuff in your own house that you most want to expose them to, because that's actually what they're most at risk of delivering, you know, getting an allergy to. So if you are eating eggs, that's clearly right at the top. You know, if you never have sesame in the house, maybe that's slightly later in the, in the sort of level of, of focus. And it's nearly always going to be egg and milk and in the UK in many or most households, peanut butter in the US old households, peanut butter.

But as we're moving towards vegan vegetarianism, we have more nut butters. We have now a whole host of nut butters in our home. So if you're using almond butter around the house, you want to make sure they're getting exposure to that early.

You have this brilliant thing, it's seriously consider having a dog because although you haven't done the randomized control trial, there is like quite strong observational evidence. If you have a dog, you reduce these level of allergies by like 50%. And then I think we finished with something quite controversial, which you said sort of divides a little bit your patients, which is that, you know, this is a life-threatening allergy and risk for children. On the other hand, we're seeing this sort of explosion of these different allergies and

And you would probably not go as far as saying you should ban all nuts from schools, never allow anyone to open a nut on a plane. There's a balance of risk and benefit because these are also obviously very healthy foods. And I think left with this really positive sign that there's increasing medical interventions that even if you have this allergy, you can really reduce it so that the peanut allergy goes from life-threatening to something where you could...

be exposed to half a peanut and be okay. Absolutely. Jonathan, you put it much better and more succinctly than I could have. So I don't think I really have anything to add to that. Well, can I just say, thank you so much for taking the time. Thank you for doing these amazing studies. You know, I think that there's something really wonderful to have a chance to talk to someone who's done the primary research and then managed to get it pushed through very fast into changing guidance.

And I think your big message, what you're saying to me before the call is that there's still a lot of people aren't really aware of this shift in guidance. So if you know someone who's maybe pregnant or about to have children, then...

I think you're saying like, please pass on that message, the information that they might well have been told only 15 years ago has completely reversed. It does remind me a lot of nutrition podcasts where we talk about the guidance that we gave about low fat or whatever. They're like, oh, we completely believe the opposite. And this is an example where

It's the progress of science, which is exciting, right? There is the data now that really, I think, is very strong to say you really want to make sure you expose your children to these foods. And one of the messages I do give to my patients is try and overcome the fear. The problem in allergic families or once there's a phobia of foods, it's the fear of

the peanut and these allergens early on, especially in high-risk families, where that fear leads to avoidance. So the fear becomes a self-perpetuating prophecy, and the fear leads to the allergy. And I

I think we do need more support amongst the whole healthcare community in a sense to hold people's hands, to guide parents. We need more positive thinking about early introduction of foods so that families are encouraged to do so. Absolutely. Gideon, thank you so much. Thank you, Jonathan. Been a real pleasure. Same here. Thank you, Gideon, for joining me on Zoe Science and Nutrition today.

We learned simple, valuable information to help combat allergies and discovered that the microbiome plays an important role in protecting us from these conditions. I hope you found this as helpful as I did. If you'd like more nutrition and health advice from our expert guests, the team has put together a guide packed with actionable advice, which you can download for free at zoe.com slash podcast. Now, if you listen to the show regularly, you probably already believe that you can transform your health by changing what you eat.

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