Episode #59 The Lung-Gut Axis: Where Nutrition & Lung Health Intersect with Dr. Neal Barnard

Welcome back to Lungcast, the monthly respiratory health podcast series from the American Lung Association and medical news site hcpive.com.

I'm your host, Dr. Albert Rizzo, Chief Medical Officer for the American Lung Association.

Before we introduce our topic and our guest today, just a reminder that Lungcast is available on all your favorite streaming platforms. Subscribe to Lungcast on YouTube to get new and archived episodes, as well as interview segments and highlights as they come out. A link to the show page, along with the ALA and HCP Live homepages for Lungcast, can be found in each episode description.

For those who prefer podcasts, you can subscribe to Lungcast on Spotify, Apple Podcasts, and other favorite listening platforms. You can also register for more respiratory news and insights at both lung.org and hcpive.com.

Our topic today is one that has been a source of discussion about our health for many years: the role of diet and nutrition. Today, we’re going to focus specifically on nutrition’s impact on our gut microbiome.

First, let me clarify a few terms. Microbes—which can include bacteria, viruses, fungi, and others—colonize our intestines. The colonies they live in are called the microbiota of our intestines. What the microbiota does in terms of metabolic functions, genetic output, protection, and physiologic and structural functions—particularly with regard to the immune system—is what we call the microbiome.

Recent studies suggest that the intestinal microbiome plays an important role in modulating the risk of several chronic diseases, including inflammatory bowel disease, obesity, type 2 diabetes, cardiovascular disease, and cancer. It is also now understood that diet plays a significant role in shaping the microbiome. Experiments show that dietary alterations can induce large, temporary microbial shifts within just 24 hours. Given this association, there may be therapeutic utility in altering our gut microbiome through diet.

But you may be asking, “This is Lungcast—what does the gut have to do with the lungs, and how does it impact chronic lung disease?”

There is something called the lung-gut axis. The respiratory tract was long considered sterile until about 15–20 years ago. The first culture-independent study confirming the presence of a lung microbiome was published in 2010 by Marcus Hilty and colleagues, while studying the airways of individuals with asthma. This debunked the “sterile lung” dogma.

We now know the airways have a dynamic microbial ecosystem. Unlike the intestinal microbiota, the lower respiratory tract is one of the least populated sites in the human body. Its composition depends on colonization from the upper respiratory tract via saliva micro-inhalations, interactions with the immune system, and environmental conditions.

We also know the intestine and lungs develop in parallel after birth, with constant communication between the two. The bacteria most common in the lower respiratory tract are the same as those found in the intestine.

To inform us more on the role of our gut and lung microbiomes—and, importantly, how diet and nutrition can impact them—our guest today is Dr. Neal Barnard. Dr. Barnard is an adjunct professor of medicine at the George Washington University School of Medicine in Washington, D.C., and has led numerous research studies investigating the effects of diet on diabetes, body weight, hormonal symptoms, and chronic pain. His groundbreaking study on dietary interventions in type 2 diabetes, funded by the National Institutes of Health, paved the way for viewing type 2 diabetes as a potentially reversible condition.

Dr. Barnard has authored more than 100 scientific publications and 20 books for both medical and lay readers, and he is the editor-in-chief of The Nutrition Guide for Clinicians, a textbook made available to all U.S. medical students. As president of the Physicians Committee for Responsible Medicine, he also leads programs advocating preventive medicine, good nutrition, and higher ethical standards in research. His work has contributed to the acceptance of plant-based diets in the Dietary Guidelines for Americans.

I’m pleased to have him weigh in on nutrition and its potential impact on lung health and chronic lung diseases.

Dr. Barnard: It’s good to be with you today. Thank you for the kind invitation.

Dr. Rizzo: Thank you. Before we speak specifically about the lungs, when during your career did you develop an interest in—and then devote your research to—the important role of nutrition in general well-being and its contribution to chronic diseases?

Dr. Barnard: The turning point was more than two decades ago. Our research team received an NIH grant to study type 2 diabetes. We asked: could dietary changes improve management of type 2 diabetes? What we discovered didn’t initially seem to have anything to do with lung health. But when we removed fatty foods—meats, dairy products, greasy foods—something happened. Fat dissipated from muscle and liver cells, which we could measure with MR spectroscopy. As that fat went away, insulin sensitivity improved, and diabetes control became much more effective. Patients needed less medication, sometimes none at all; sometimes the disease went away completely.

Among the worst foods were processed meats—hot dogs, bacon, salami. Around the same time, other researchers were finding that diet played a role in lung conditions like COPD. Two large studies in 2007—at Columbia and Harvard—showed that people who ate the most processed meats had more than double the risk of COPD. Why? The nitrates and nitrites in these foods can create reactive oxygen species, or free radicals, which damage lung tissue.

So, while we originally focused on diet for diabetes, we realized it also applied to lung disease. If someone quits smoking, their lungs are fragile. By improving their diet, you may help protect them further. That was my introduction to how diet changes the pulmonary environment.

Welcome back to Lungcast, the monthly respiratory health podcast series from the American Lung Association and medical news site hcpive.com.

I'm your host, Dr. Albert Rizzo, Chief Medical Officer for the American Lung Association.

Before we introduce our topic and our guest today, just a reminder that Lungcast is available on all your favorite streaming platforms. Subscribe to Lungcast on YouTube to get new and archived episodes, as well as interview segments and highlights as they come out. A link to the show page, along with the ALA and HCP Live homepages for Lungcast, can be found in each episode description.

For those who prefer podcasts, you can subscribe to Lungcast on Spotify, Apple Podcasts, and other favorite listening platforms. You can also register for more respiratory news and insights at both lung.org and hcpive.com.

Our topic today is one that has been a source of discussion about our health for many years: the role of diet and nutrition. Today, we’re going to focus specifically on nutrition’s impact on our gut microbiome.

First, let me clarify a few terms. Microbes—which can include bacteria, viruses, fungi, and others—colonize our intestines. The colonies they live in are called the microbiota of our intestines. What the microbiota does in terms of metabolic functions, genetic output, protection, and physiologic and structural functions—particularly with regard to the immune system—is what we call the microbiome.

Recent studies suggest that the intestinal microbiome plays an important role in modulating the risk of several chronic diseases, including inflammatory bowel disease, obesity, type 2 diabetes, cardiovascular disease, and cancer. It is also now understood that diet plays a significant role in shaping the microbiome. Experiments show that dietary alterations can induce large, temporary microbial shifts within just 24 hours. Given this association, there may be therapeutic utility in altering our gut microbiome through diet.

But you may be asking, “This is Lungcast—what does the gut have to do with the lungs, and how does it impact chronic lung disease?”

There is something called the lung-gut axis. The respiratory tract was long considered sterile until about 15–20 years ago. The first culture-independent study confirming the presence of a lung microbiome was published in 2010 by Marcus Hilty and colleagues, while studying the airways of individuals with asthma. This debunked the “sterile lung” dogma.

We now know the airways have a dynamic microbial ecosystem. Unlike the intestinal microbiota, the lower respiratory tract is one of the least populated sites in the human body. Its composition depends on colonization from the upper respiratory tract via saliva micro-inhalations, interactions with the immune system, and environmental conditions.

We also know the intestine and lungs develop in parallel after birth, with constant communication between the two. The bacteria most common in the lower respiratory tract are the same as those found in the intestine.

To inform us more on the role of our gut and lung microbiomes—and, importantly, how diet and nutrition can impact them—our guest today is Dr. Neal Barnard. Dr. Barnard is an adjunct professor of medicine at the George Washington University School of Medicine in Washington, D.C., and has led numerous research studies investigating the effects of diet on diabetes, body weight, hormonal symptoms, and chronic pain. His groundbreaking study on dietary interventions in type 2 diabetes, funded by the National Institutes of Health, paved the way for viewing type 2 diabetes as a potentially reversible condition.

Dr. Barnard has authored more than 100 scientific publications and 20 books for both medical and lay readers, and he is the editor-in-chief of The Nutrition Guide for Clinicians, a textbook made available to all U.S. medical students. As president of the Physicians Committee for Responsible Medicine, he also leads programs advocating preventive medicine, good nutrition, and higher ethical standards in research. His work has contributed to the acceptance of plant-based diets in the Dietary Guidelines for Americans.

I’m pleased to have him weigh in on nutrition and its potential impact on lung health and chronic lung diseases.

Dr. Barnard: It’s good to be with you today. Thank you for the kind invitation.

Dr. Rizzo: Thank you. Before we speak specifically about the lungs, when during your career did you develop an interest in—and then devote your research to—the important role of nutrition in general well-being and its contribution to chronic diseases?

Dr. Barnard: The turning point was more than two decades ago. Our research team received an NIH grant to study type 2 diabetes. We asked: could dietary changes improve management of type 2 diabetes? What we discovered didn’t initially seem to have anything to do with lung health. But when we removed fatty foods—meats, dairy products, greasy foods—something happened. Fat dissipated from muscle and liver cells, which we could measure with MR spectroscopy. As that fat went away, insulin sensitivity improved, and diabetes control became much more effective. Patients needed less medication, sometimes none at all; sometimes the disease went away completely.

Among the worst foods were processed meats—hot dogs, bacon, salami. Around the same time, other researchers were finding that diet played a role in lung conditions like COPD. Two large studies in 2007—at Columbia and Harvard—showed that people who ate the most processed meats had more than double the risk of COPD. Why? The nitrates and nitrites in these foods can create reactive oxygen species, or free radicals, which damage lung tissue.

So, while we originally focused on diet for diabetes, we realized it also applied to lung disease. If someone quits smoking, their lungs are fragile. By improving their diet, you may help protect them further. That was my introduction to how diet changes the pulmonary environment.