Gut health is taking a hit from the air people breathe in Indian cities, gastroenterologists say, as fine particles in polluted air disturb the bacteria in the intestines and raise the risk of digestive trouble. Doctors report more patients with bloating, acidity, constipation and irritable bowel symptoms on days when air quality is poor. The connection is less widely known than the harm air pollution does to the lungs, but doctors say it deserves the same attention.
The link starts with the particles themselves. Fine particulate matter, known as PM2.5, is small enough to pass deep into the lungs and set off inflammation across the body. Some of those particles are cleared from the airways by mucus and swallowed, so they reach the intestines directly. Once there, they can harm gut health by irritating the gut lining, upsetting the balance of gut bacteria and weakening the barrier that keeps harmful microbes out of the bloodstream.
How polluted air affects gut health
Research published in the journal Environment International found that long term exposure to polluted air can change the make-up and working of the gut microbiota, harming gut health and raising the risk of digestive disorders and metabolic conditions such as obesity and diabetes. Findings reported in an MDPI journal point the same way, showing that inhaled particulate matter can move to the gastrointestinal system through mucociliary clearance, which sweeps mucus and trapped particles out of the airways.
Dr Neeraj Dhamija, a surgical gastroenterologist at Sir Ganga Ram Hospital in New Delhi, has said the link between air pollution and acid reflux is still being studied, but early research points to inflammation, oxidative stress and changes that weaken gut health. Acid reflux happens when stomach contents flow back into the food pipe because the ring of muscle at its base does not close as it should. People who already live with gastro-oesophageal reflux disease may feel worse during spells of heavy pollution, according to a report in the journal Frontiers in Public Health.
Doctors in Delhi have seen the pattern in their clinics. In November 2024, doctors in the capital reported a rise in digestive disorders such as irritable bowel syndrome and inflammatory bowel disease while air quality stayed poor, with Delhi’s average air quality index at 358 at 7.30 am on 6 November that year. Dr Harshal R. Salve of the Centre for Community Medicine at AIIMS in New Delhi said long term exposure sets off free radicals and inflammatory responses that can lead to inflammatory disorders of the digestive system.
Gut health and the bacteria that keep digestion steady
The gut is home to trillions of microorganisms that help digest food and support immunity. Pollution can cut the number of helpful bacteria and let harmful ones grow, a shift linked to constipation, diarrhoea, bloating and, over time, longer lasting disease. Dr Sukrit Singh Sethi, a consultant in gastroenterology at Narayana Hospital in Gurugram, has said that harmful particles and gases in polluted air, once inhaled, can lead to systemic inflammation and oxidative stress, which disturb gut health and the microbiome.
The symptoms that follow are often mild at first. People notice heaviness after meals, more gas, irregular bowel movements or a dull stomach ache that comes and goes. Doctors say these signs are easy to dismiss, but they can point to gut health under strain. A weakened gut barrier can also let more of what should stay in the bowel pass into the bloodstream.
Children and older people feel the effects sooner, and so do people who already live with bowel disease. A study in the United Kingdom found that young people aged five to 23 with higher exposure to nitrogen dioxide, a part of traffic exhaust, were more than twice as likely to develop Crohn’s disease as those with lower exposure.
Protecting gut health on high pollution days
Doctors say a few daily habits can lower the strain on the gut when pollution is high. Eating fibre rich food, drinking enough water and keeping meal times regular helps the bowel keep its rhythm. Food rich in antioxidants, such as citrus fruit and nuts, can help the body deal with the oxidative stress that pollution brings, according to Dr Salve. Staying indoors when air quality is very poor, and wearing a mask outside, cuts the particulate matter that reaches the lungs and the gut.
Anyone with bloating, indigestion, constipation or stomach pain that lasts more than a few weeks should see a gastroenterologist, who can test whether pollution, diet or another cause sits behind the trouble. The link between dirty air and the gut is still being mapped, but doctors say the evidence so far gives reason to treat gut health as one more thing that polluted air can harm.