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Gut flora and probiotics

The microbes usually live symbiotically and derive nutrition from the food that we eat

Dr Gita Mathai Published 24.03.21, 12:30 AM

The human body has a nine-metre-long alimentary canal that is open to the environment at both ends. It is populated with millions of microbes: bacteria, viruses and fungi. In addition, there are harmful intestinal parasites (worms, amoebae, giardia) that might also be present. Our alimentary canal gets populated with gut organisms soon after birth, during normal vaginal delivery. This does not occur during a Caesarian birth.

It is these organisms that help the newborn digest milk. If a C-section delivery is followed by limited breastfeeding, the populating of the gut with good microbes is delayed and different. Some researchers feel that this difference is the reason for the increase in asthma, allergies and obesity in children. It may even contribute to their craving for fast food and overeating due to lack of feeling of satiety.


The microbes usually live symbiotically and derive nutrition from the food that we eat. All through life, they secrete chemicals that are responsible for functions such as immunity and digestion. These bacteria also produce vitamins such as B12 and K. The other chemicals they secrete have different effects on various systems of the body. People with neurological diseases such as Alzheimer’s, Parkinson’s, depression, schizophrenia and autism have different gut microbes. This particular balance of flora also has a link with obesity. People who “put on weight easily” and find it impossible to “get it off” have been found to have certain specific types of gut flora.

Antibiotics act as an indiscriminate army. They cannot target only the disease-causing microbes and end up killing many good organisms too. That is why, quite often, people develop diarrhoea after a course of antibiotics. The vitamin production in the gut also gets reduced leading to vitamin deficiency and causing fissures in the angle of the mouth or the tongue.

To prevent these side effects, sometimes probiotics are administered either along with or after a course of antibiotics. The supplements are usually in the form of capsules or sachets that contain live cultures of lactobacillus, bifidobacterium and the yeast Saccharomyces boulardii.

Sometimes probiotics are combined with prebiotics. These are then called synbiotics. Prebiotics are compounds like pectin, which serve as food for probiotic organisms.

Since probiotics are live organisms, they often have to be stored in the fridge, reconstituted as instructed and taken before the expiry day. These supplements (but not natural forms of probiotics) should be avoided in critically ill people, those on cancer treatment or those who have recently undergone surgery. They should also be used with caution in children.

The gut flora can be improved without expensive supplements:

Going without food, but not water, for 24 hours helps to develop a healthy gut biome.

Regular exercise changes the gut flora such that immunity improves and inflammation becomes less. This is seen particularly in endurance athletes. But the effect wears off if exercise is discontinued.

Avoid highly processed foods with trans fats, preservatives and colouring, especially high-calorie snacks of no nutritional value.

Do not replace sugar with artificial sweeteners because you are diabetic or in an effort to lose weight; they disrupt the metabolism of the microbes.

Eat at least four helpings of different-coloured fruits and vegetables a day.

Drink 2.5 to 3 litres of water a day.

Coffee and tea, particularly green tea as well as nuts contain antioxidants called polyphenols. Good microbes thrive in their presence.

Add fermented food to your diet. Taking 30ml of homemade curd first thing in the morning will help repopulate the gut.

The writer is a paediatrician with a family practice at Vellore and the author of Staying Healthy in Modern India. If you have any questions on health issues please write to

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