Stomach Bacteria Could Prevent Asthma Several years ago, researchers proposed the provocative idea that bacteria living in the human stomach could be responsible for the development of some stomach ulcers. New research suggests, however, that those bacteria may not be all bad.
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Stomach Bacteria Could Prevent Asthma

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Stomach Bacteria Could Prevent Asthma

Stomach Bacteria Could Prevent Asthma

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This is Talk of the Nation: Science Friday. I'm Ira Flatow. A little bit later in the hour, a green powerboat sets a record for making it around the world faster than anybody else and oil drilling. But first, Helicobacter pylori. H. pylori is an intestinal bacterium that has made a home for itself in the human gut for thousands of years, and it's a common cause for stomach ulcers. Researchers say it's been all but eradicated in the last few decades by better hygiene and antibiotics.

But while ulcers are on the decline, another health problem is on the rise, and you know, that's asthma. Well, is there a connection between the two? Could be. There is a new study published this week in the Journal of Infectious Diseases that suggests that H. pylori, the bacteria in our gut, may not be all bad after all. They may, in fact, be protecting kids from childhood asthma. Here to talk about the stomach bug and asthma is Martin Blaser. Dr. Blaser is chair of medicine and professor of microbiology at New York University here in New York City. Welcome to Science Friday.

Dr. MARTIN BLASER (Chair, Departments of Medicine and Microbiology, New York University Langone Medical Center): Good afternoon.

FLATOW: Good afternoon. How can a bacterium in the gut protect the respiratory system?

Dr. BLASER: Well, I think your viewers - your listeners might be interested to know that most of the cells in the human body are bacteria. They're not human cells at all. They're bacterial cells, about 90 percent.

FLATOW: Is that right?

Dr. BLASER: Yeah, and not just for humans, but for just about all animals, and these bacteria have been living in us as long as we've been humans and beforehand. They're not accidental at all, and they're probably playing many different roles in human physiology. We have been interested in Helicobacter for more than 20 years. And in particular, as you mentioned, we're particularly struck by the fact that Helicobacter pylori, an organism that has been with us at least since humans left Africa, is disappearing, and it's been disappearing very rapidly, as you said. From our most recent work, the work that Dr. Yu Chen and I did, less than six percent of U.S. children have Helicobacter pylori today.

FLATOW: And so, at the same time, you're seeing a rise in asthma?

Dr. BLASER: As Helicobacter is declining, ulcers are going away, stomach cancer is going away, and diseases of the esophagus, like reflux, esophagitis is rising and so is asthma.

FLATOW: Can you create a one-on-one comparison or link between the two?

Dr. BLASER: Well, we have been interested in this trend for a number of years and showed about 10 years ago, this - an inverse relationship between Helicobacter and GERD or reflux and some of its consequences. And because some patients with GERD also have asthma, and sometimes when you treat GERD, asthma gets better. We thought if Helicobacter could be protecting against GERD, it could be protecting against asthma.

So, Dr. Chan and I began a study, actually a couple of years ago, where we looked at national data, the NHANES dataset, which is a random nationwide survey. We looked at NHANES III and we - which was done in 1988 to 1991. And Dr. Chan found more than 7,000 records of people who had information on Helicobacter status and asthma status. And we found that people who had Helicobacter were less likely to have asthma than people without. But it wasn't just asthma. It was also hay fever, and it was eczema and skin sensitization, all of these allergic manifestations that run together.

We were very excited about this result because we had an earlier result in New York that showed almost the same findings. So, more recently, we did the study that was just published this week looking at NHANES IV, now, almost 10 years later. And in particular, our first two studies suggested that if Helicobacter had some protective role, it was in childhood onset asthma, the asthma that occurs very early in life and not an adult asthma. And NHANES IV was weighted toward more children. And we also found more than 7,000 records of people who we could study. And we found again the same inverse association between Helicobacter and childhood asthma very specifically.

FLATOW: So, you didn't - are you saying you didn't find that association in adults?

Dr. BLASER: We did not find it in adults, and in particular, I want to emphasize we're talking about when asthma arises. There is childhood asthma, which arises very early in life. It's associated with these other allergic conditions. Adult-onset asthma can be related to allergy. It can be related to smoking and other factors. Whatever the case, we did not find any relationship with H. pylori.

FLATOW: So, you're saying than in doing all this research, it may be the allergy reaction in general in different kinds of illnesses that have a relationship with the bacteria?

Dr. BLASER: That's right. In other words, it could be. I mean, one possibility - there are really two major possibilities. One is that our studying Helicobacter is just a marker for something else, something makes Helicobacter go away and that's also affecting the real protective factor against asthma. It could be antibiotics affecting another bacterium. The other possibility is that H. pylori itself is protecting against asthma, and we don't have any proof, but that's the hypothesis I favor. And we think that Helicobacter is helping arm the immune system in a way that regulates allergy.

FLATOW: Wow. Can you set up an experiment that would test that hypothesis?

Dr. BLASER: Well, we're trying to test the hypothesis in a number of ways. We may be able to collaborate with colleagues and look at animal models of asthma. There's a model of asthma in rhesus monkeys. We're interested in studying the kinds of regulatory cells and the kinds of regulatory substances in the blood of people who have Helicobacter and do not have it so that we can further develop the mechanisms of the association.

FLATOW: So, did this decline in H. pylori happen when antibiotics - post-World War II antibiotics took over?

Dr. BLASER: As far as we can tell, the decline in Helicobacter began early in the 20th century, but has continued and was probably accelerated after World War II with the invention and widespread use of antibiotics. And in that sense, the U.S. is leading the rest of the world, but the rest of the world seems to be catching up. Asthma is quite epidemic in the U.S. and other Western countries.

FLATOW: So, if it's not linked to those antibiotics originally, then it's linked to other things like hygiene, things like that?

Dr. BLASER: Hygiene, cleaner water, smaller family size. Most people haven't given much thought to it, but one of the things that we know is that families are a lot smaller than they used to be. And families are very important for transmission of microbes and other infectious agents. And this may be changing, kind of, human ecology.

FLATOW: Now, there was this research that has been talked about on and off for the last few years. It's talking about, if kids are exposed to playing in the dirt, they get fewer cases of asthma.

Dr. BLASER: Right. So, - I can't tell you that much, but my general view is that the microbes in dirt are irrelevant. They're not really adapted for humans. However, the microbes that have been living in humans in our ancestors for millions of years and now are disappearing, I think, are much more relevant. I've called this the disappearing microbiota hypothesis. It's a little different than the hygiene hypothesis, and in this case, Helicobacter is kind of the indicator of that phenomenon. Helicobacter is a dominant organism in the stomach. And if an organism disappeared in the colon, the skin, the vagina, we probably wouldn't be able to detect it.

FLATOW: Let me get a quick question from a listener. And let's go to Rick in Louisville. Hi. Welcome to Science Friday. Are you there?

RICK (Caller): Hi. Yes. Thanks for taking my call. My question is, I guess likely unrelated to the Helicobacter bacteria, but apparently one of the hypotheses behind the emergence of inflammatory bowel diseases like ulcerative colitis is that it might have something to do with the disturbance of the equilibrium of bacteria in the gut. And I was wondering if your guest had some comments about that. And one of the things that is apparently is also very highly prevalent to (unintelligible) so much in the Asian countries and...

FLATOW: Let me get an answer.

Dr. BLASER: Well, you know, you really said the keyword, which is equilibrium. That's really how we are viewing this, that we live in some kind of equilibrium with our microbes. And our hypothesis, at least with relation to the stomach and asthma is that that equilibrium has been disturbed. As I said before, that equilibrium could be disturbed in many places of the body except that we don't have the candidates right now. We don't know exactly which microbe it could be.

FLATOW: That's fascinating. Again, you say that there are more microbes, more germs living in our body than cells.

Dr. BLASER: Yeah. Ninety percent of your body is microbes.

FLATOW: And we don't understand then.

Dr. BLASER: We understand very little. And that's one of the reasons that the National Institutes of Health has made the human microbiome one of their research projects over the next four years. To really understand what are the normal microbes of the human body and how they affect human health and disease.

FLATOW: So, when we treat disease, we don't know anything about most of the germs that are living in us.

Dr. BLASER: Well, exactly. You know, like 20 years ago if I told you that every time you turn the ignition on your car, the polar ice cap is going to melt a little, you would have laughed. If I tell you today that every time you take an antibiotic, you're chipping away at your microbiome and the microbiome that you transmit to other people, and that all these 50 or 60 years of antibiotics are actually changing our microbial composition that's about as far-fetched as the other thing was.

FLATOW: Yet, we do what we do and we must learn to understand it if then, as you say, if we're going to be treating illnesses.

Dr. BLASER: Right. Our hypothesis is that every time somebody takes an antibiotic, say for throat infection or an ear infection, it's having an effect on the microbiota. Again, using Helicobacter as the indicator, there's evidence that this is correct. FLATOW: But you're saying also it started before we even took antibiotics.

Dr. BLASER: It did because it had, at the least, it had to do with the transmission of the microbes from person to person. And that's where issues like crowding, cleanliness of the water, and issues like family sides. You know another thing that could affect it is that more babies are born today from cesarean sections rather than going through birth the traditional way. More babies are fed with formula than being breast-fed. All of these things affect the microbes that are being transmitted, let's say, from mothers to their children.

FLATOW: Fascinating, Dr. Blaser. Fascinating. Thank you for taking time to be with us.

Dr. BLASER: My great pleasure.

FLATOW: And good luck to your research.

Dr. BLASER: Thank you so much.

FLATOW: Dr. Martin Blaser is professor of microbiology and chair of medicine at New York University. We're going to take a break, switch gears, and come back and talk to the captain of a racing boat. A boat that set a world's record of time, speed for going around the world. And it's not made out of your uncle's - this is not your uncle's car. So, stay with us, we'll be right back.

(Soundbite of music)

FLATOW: I'm Ira Flatow. This is Talk of the Nation: Science Friday from NPR News.

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