Dr. Neal Barnard, an adjunct professor of medicine at the George Washington University School of Medicine in Washington, D.C., has spent his career leading numerous research studies investigating the effects of diet on the body. Though his groundbreaking study was specific for type 2 diabetes, it was during this time that it became clear to Dr. Barnard that certain foods may negatively affect the lungs. “The idea that food could somehow affect your lungs is something that is not necessarily intuitive,” Dr. Barnard said.
He discovered two other studies, one at Harvard University and another at Columbia University, explaining how these foods may affect the lungs. Some studies have found that consumption of processed meats may be associated with reduced lung function or an increased risk of COPD, though other factors also contribute. “In a large Harvard study, frequent consumption of processed meat was associated with nearly triple the risk of COPD and aggravates the effects of smoking. Studies show that the nitrates and nitrites in these foods can create reactive oxygen species, or free radicals, which can damage delicate lung tissues,” Dr. Barnard explained.
Understanding the Microbiome “Garden”
Microbiome has become a hot topic for many health articles, but how it works throughout the body, not just in the gut, is something many people don’t understand. Until about 15-20 years ago, the respiratory tract was considered a sterile environment. Then, the first culture-independent study confirmed 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” belief and introduced the lung-gut axis. It is now understood that airways have a dynamic microbial ecosystem.
“I think of it like a garden, where the seeds you plant are microbes which can include bacteria, viruses, fungi and others,” Dr. Barnard said. “The soil, which can cause the seeds to flourish or die out, is whatever is ingested. The foods you eat provide an environment for bacteria to grow. If you eat a meat-heavy, fatty diet, what grows is more likely to produce carcinogens. If you eat fruits, veggies, whole grains and beans, it produces healthier soil so helpful bacteria will flourish.”
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 inhalation, interactions with the immune system and environmental conditions. So, the “soil” is created by whatever is in the blood that is passing through your lungs and the secretions that are produced within the lungs. “Certain secretions favor the growth of certain bacteria. For instance, people with cystic fibrosis grow Candida. And people with COPD usually grow Haemophilus or Proteobacteria. Even with lung cancer, we see different species growing,” Dr. Barnard continued.
Unfortunately, for many chronic diseases, producing secretions that grow unwanted bacteria is not entirely under the patient's control because it is, in part, a genetic trait. But adjusting your diet is something that anyone can do to help create the proper “soil”.
The Right Foods for Your Microbiome
Dr. Barnard’s years of research have led him to strongly believe that if you are looking to improve your microbiome, increased fiber intake is essential. He finds this especially important for anyone looking to rebuild “good soil” after a sickness or course of antibiotics. “If someone had pneumonia and they took a course of antibiotics, for example, probiotic supplements may have little to no effect. Instead, a diet rich in fiber can allow the heathiest natural bacteria to propagate.”
This fiber can be found in beans and legumes, vegetables and fruits. “So many of us grew up in a culture of cheese and meat heavy meals, but none of those foods have any fiber, it only comes from plants.”
Additionally, Dr. Barnard says to take a look around your grocery store and focus on foods with bright colors that show you what nutrients they contain. This is an idea supported by the European Lung Foundation who introduced nutrition as its latest theme for their healthy lungs for life campaign. One of their infographics states, “Eat the colors of the rainbow.”
“It sounds funny, but that red color of a tomato is showing the lysopine inside. You can see the beta carotene in carrots and sweet potatoes in that bright orange color. Powerful antioxidants are represented in blueberries and blackberries. If we select these foods, they can help knock out free radicals and reduce inflammation.” This may be particularly helpful for people with chronic lung disease, like COPD, asthma and bronchiectasis, which all have components of inflammation in the airways.
Nutrition and COVID-19
COVID-19 has made all of this more critical because a spotlight was shown on lung disease. During that time, many studies sought to identify factors that could prevent or cause severe illness. One study called the COVID-19 Symptom Study evaluated more than 600,000 people and found that people on a more plant-based diet were less likely to have severe illness. Another study, combining findings from six different countries, found that those on a plant-based diet had a lower risk of severe illness than people on a meat-heavy diet, like keto. In fact, those diets may increase your risk of severe COVID-19. Then, in 2024, a summary article that looked at a number of studies found the exact same pattern, that people on high protein diets had a much higher risk (4x) compared to those not on those diets.
Why Nutrition Matters
Though Dr. Barnard’s clinical research was not specifically focused on lung function, it raises the strong likelihood that diet affects the lungs. “If someone has a family history of COPD or a history of tobacco use and they're thinking, I'm at high risk. What can I do? In addition to quitting smoking, cleaning up the diet can make a difference."
As president of the Physicians Committee for Responsible Medicine, Dr. Barnard leads programs advocating preventive medicine and good nutrition and believes that this is something every medical education should include. “Nutrition is a key part of medical care. We eat many times a day, so it's like medicine. If we are choosing the healthiest foods, we can improve our health.”
Blog last updated: December 2, 2025
