Could Your Gut and Oral Microbiomes Be the Reason You Catch Colds Frequently: Expert Insights

Most people know the feeling when someone in the family or office starts coughing, and within days, the nose runs, the throat scratches, and congestion settles in. This person frequently catches colds. Yet right next to them, others carry on without sniffles for months. While these viruses often expose people similarly in shared environments, the difference in symptoms suggests factors beyond mere exposure.

A growing body of research highlights a key influence, the microbial communities in the gut and mouth, which help modulate the immune system’s response to these common invaders. Our expert, Dr Debojyoti Dhar, Co-founder & Director at Leucine Rich Bio, BugSpeaks, Bengaluru, explains why some people catch colds more often and the significant role your gut and oral microbiomes play.

How the Gut Shapes Immunity Far Beyond Digestion

Your gut houses the largest collection of immune cells in the body and acts as the main training ground for immune responses. Dr Dhar explains that bacteria living along the intestinal lining constantly interact with these cells, teaching them when to attack and when to stand down.

“Certain species break down dietary fibre into short-chain fatty acids, such as butyrate, propionate, and acetate. These travel through the bloodstream and calm inflammation everywhere, including the lungs,” Dr Dhar explains.

This direct line of communication, also called the gut-lung axis, explains surprising findings. According to Dr Dhar, people with a wider variety of gut bacteria tend to clear respiratory viruses faster and suffer milder symptoms. “When diversity falls, the signals weaken, and the lungs become more vulnerable,” he states.

Influenza studies show that patients with depleted gut microbes face longer hospital stays and higher complication rates. “The same pattern repeats with common cold viruses, such as rhinovirus, coronavirus strains, and adenovirus. The gut quietly sets the tone for how the entire respiratory tract responds,” Dr Dhar adds.

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The Mouth as the First Battlefield

The mouth meets respiratory pathogens first. Saliva bathes incoming air and food, while the tongue, gums, and teeth host their own dense bacterial communities. Dr Dhar notes that in a healthy state, beneficial streptococci and other residents compete for space, produce natural antimicrobial compounds, and keep the mucosal surface intact. Consequently, pathogens struggle to gain a foothold. Things change quickly when the balance tips.

• Frequent sugary snacks feed acid-loving species that erode enamel and crowd out protectors.
• Mouth breathing, common with chronic nasal blockage, dries surfaces and favours anaerobic troublemakers.
• Smoking directly damages tissues and shifts the community toward inflammatory types.
• Even common medications, like antihistamines or blood pressure drugs, reduce saliva flow, weakening the body’s natural washing and defence mechanisms.

Dr Dhar warns, “Small amounts of oral contents reach the lungs every night through silent aspiration. In a balanced mouth, this causes no trouble. However, when harmful species dominate, they tag along and prime the lower airways for trouble. Dentists see this pattern often; patients with recurrent sore throats or sinus infections usually show distinct oral bacterial profiles heavy in pro-inflammatory strains.”

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Early Life Sets the Foundation

The story often begins much earlier. Babies born by caesarean section miss the vaginal microbial seeding that vaginally delivered infants receive. Antibiotic courses in the first years can wipe out sensitive pioneer bacteria before resilience builds.

Dr Dhar describes that children with lower gut diversity tend to catch more ear infections and colds. “These same children often carry higher loads of potentially pathogenic oral bacteria. By adulthood, the pattern often locks in – some people sail through winter, while others stock up on tissues every season,” he notes.

The Role of Daily Habits in Your Immune System

Dr Dhar underlines that daily habits leave clear marks on how our immune system reacts when a virus attacks. He highlights several factors that weaken our microbial guard:

• Diets low in vegetables, fruits, legumes, and whole grains starve fibre-fermenting bacteria.
• Items high in emulsifiers and sugars favour species that trigger low-grade inflammation.
• High cortisol levels can suppress helpful microbes.
• Poor sleep disrupts the daily biological rhythms these microbial communities follow.
• No physical activity reduces gut motility, circulation, and discourages microbial diversity.

“All these factors add up over months and years, slowly shifting the balance toward frequent infections,” Dr Dhar warns.

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Practical Ways to Shift the Balance

To bridge the gap and boost immunity, Dr Dhar suggests several lifestyle adjustments:

Focus on Fibre

Daily plates loaded with vegetables, beans, whole grains, nuts, and seeds feed the bacteria that produce protective compounds. Traditional foods such as curd, idli batter, dosa, pickled vegetables, and kefir all deliver live cultures that compete with unwanted bacteria.

Oral Hygiene

Routine brushing and flossing remove harmful biofilms, while tongue scraping clears bacteria that accumulate overnight. Saltwater rinses can help restore pH and wash away debris. Staying hydrated is also essential to keep saliva flowing, which is naturally packed with defences.

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Probiotics and Prebiotics

“Certain probiotic strains, such as specific Lactobacillus or Bifidobacterium types, have been shown to potentially shorten cold duration and reduce severity when taken regularly during winter months,” says Dr Dhar. He also suggests that prebiotic foods like garlic, onions, bananas, and oats selectively nourish existing helpful residents.

Lifestyle

Your lifestyle is the key to solve most of your health problems. Seven to eight hours of sleep, being physically active, and stress management not just boost your immunity to fight cold, but also to deal with other chronic illnesses. Furthermore, quitting smoking brings rapid oral improvements within weeks. Nasal saline irrigation can also clear passages, reducing the need for decongestants that dry the mouth.

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Bottomline

Our gut and oral microbiomes shape our day-to-day resilience against respiratory viruses far more than most realise. As our expert, Dr Dhar suggests, simple, consistent choices regarding food, hygiene, sleep, and movement nurture these communities effectively. While these changes take weeks or months to manifest, the payoff is seen in fewer sick days and quicker recovery times.