Bacteria which protect health

The human body is home not only to its own cells but also to trillions of tiny organisms, most of which live in the digestive system. These are known as gut bacteria. For a long time, bacteria were thought of only as harmful. Today, research shows that many are, in fact, essential for our health. They help us digest food, protect us from infections, train the immune system, and even influence mood.

How gut bacteria develop

Gut bacteria begin colonising us at birth. Babies delivered naturally acquire their first microbes from the mother, while those born through Caesarean section get a different mix from skin and surroundings. Breast milk contains unique sugars that nourish beneficial bacteria and help them grow. As children are exposed to new foods, their gut bacteria become more varied. By adulthood, trillions of microbes form a stable community that supports health throughout life.

Digestion and nutrition

One of the key roles of gut bacteria is aiding digestion. The body cannot break down certain fibres and complex carbohydrates on its own. Bacteria in the gut handle this process and produce short-chain fatty acids, which give energy to intestinal cells and strengthen the gut lining.

These microbes also make vitamins such as vitamin K and some B vitamins. They support the absorption of minerals like calcium, iron, working every day to support nutrition.

Support immune system

The gut is also central to immunity, as it carries about 70 per cent of the immune cells. Good bacteria help these cells identify dangerous germs, while ignoring harmless substances like food. They also produce natural antibiotics that block harmful microbes. By occupying space and consuming nutrients, they leave little room for dangerous bacteria to grow.

Gut–brain axis

A fascinating discovery in recent years is the gut–brain connection. Gut bacteria communicate with the brain through nerves, hormones and chemicals. Some even produce serotonin, a key neurotransmitter that regulates mood. When the gut microbiome is disturbed, it can contribute to anxiety, depression or poor sleep. This shows that gut health is deeply tied to mental health.

Diet and gut bacteria

Diet is the biggest factor influencing gut microbes. Foods rich in fibre — such as fruits, vegetables, legumes, whole grains and nuts — feed beneficial bacteria and promote their growth. These, in turn, produce protective substances that support the body. In contrast, processed foods, excess sugar and unhealthy fats disturb the balance of the microbiota.

Overuse of antibiotics, stress, poor sleep and inactivity also weaken gut health. On the other hand, a Mediterranean-style diet rich in plant foods, olive oil, fish and nuts has been shown to nurture a healthy gut. Fermented foods such as yogurt, idli/dosa, dhokla, kanji, pickles, kimchi, kefir, etc, are especially valuable because they provide live bacteria that strengthen the gut microbiome.

Probiotics, prebiotics, and synbiotics

These are the most helpful tools to improve gut health:

Probiotics: Live beneficial bacteria found in foods like yogurt and kefir or in probiotic supplements are useful in restoring balance after infections or antibiotics.

Prebiotics: Plant fibres that feed good bacteria are present in garlic, onions, bananas, apples and asparagus.

Synbiotics: A mix of probiotics and prebiotics, these provide both bacteria and the food they need, making them more effective. Foods such as yogurt with added fibre, fermented milk products with fruit are synbiotic.

Protects against diseases

A balanced gut microbiome protects against many chronic illnesses. An imbalance, known as dysbiosis, has been linked to obesity, diabetes, heart disease, inflammatory bowel disease, and certain types of cancers. Healthy bacteria reduce inflammation, improve blood sugar control and limit the spread of harmful microbes. Maintaining gut health through diet and lifestyle can, therefore, lower the risk of long-term diseases.

Normal gut bacteria are silent allies working inside our body every day. They help break down food, produce vitamins, protect against harmful germs, train our immune system, and even influence our mood. Their wellbeing depends on what we eat. A fibre-rich diet with fruits, vegetables, and fermented foods, along with probiotics and prebiotics, helps them thrive. By caring for our gut microbes, we allow them to care for us, keeping both body and mind healthy.

— The writer is Professor and Head, Department of Microbiology, Government Medical College and Hospital, Chandigarh