Updated: Jan 27
What is gut microbiota?
The gut microbiota refers to the array of friendly microorganisms that co-exist in our gut, with the majority residing in the large intestine. It is predominantly made up of bacteria, while viruses, fungi (such as yeast) and protozoans are also present. It is also referred to as gut flora, analogous to vegetation in a garden.
Although the actual number is unclear, over 1000 different species of bacteria have been identified in the gut, which form an ecosystem of their own. Due to the variety of important effects this has on human health and even behavior, it is now considered as a virtual organ and rightly so because of its mutually beneficial (symbiotic) relationship with the human body.
How does it develop or change?
As a newborn, we get our first dose of microbes from our mother and the immediate surroundings (hospital environment, family and nurses or people who handle the baby). This initial lot, which has a long-term impact on health, mainly consists of bacteria that help in the digestion of milk and varies with the birthing process and type of feeding (mother’s milk vs. formula milk). Its composition rapidly changes according to the environment, diet and interactions with people and more or less stabilizes around the age of 3. After this point, changes in the gut flora composition are mainly influenced by diet, lifestyle, geography/ climate, illnesses and certain drugs, especially antibiotics.
What roles does it play in immunity and general well-being?
The gut microbiota primarily help in the digestion of various foods especially difficult-to-digest components, such as the dietary fibres, and conversion into easily absorbable nutrients. This is important for maintaining a favorable environment along the intestinal lining for the optimal functioning of a multitude of metabolic pathways in the body. This includes fat metabolism, energy balance, and appetite regulation, thereby leading to countless beneficial effects.
Another major role of the gut microbiota is defending the body against disease-causing microorganisms by creating a hostile environment for them to establish themselves in the gut.
Certain immune cells are strategically placed in the vicinity of these microbes and can communicate with these organisms. Thereby, they trigger defence mechanisms when dangerous/ unwanted microbes or events are detected. Impaired immune-system-microbiota interactions affect far-off organs and are implicated in many diseases.
Although the exact mechanism is unknown, a strong association between the gut microbiota and brain development, as well as behavior, has been observed.
The microbiota has also been found to affect the way certain drugs work, producing different outcomes in people with differences in the gut microbial composition.
What can affect the co-existence of the gut flora?
Imbalance occurs when there is disproportionate growth of a certain type or types of bacteria in the gut. This can be caused by
Dietary preferences (eg., sugary/ vegan/ meat-based)
Additives or chemicals in food (eg., emulsifiers, preservatives)
Certain habits (eg., smoking)
Drugs (eg., antibiotics used to treat infections or present in food)
Environmental factors (eg., cleanliness)
What happens when there is imbalance in the gut flora?
Changes caused by the above factors include
Decrease in the overall variety or specific types of gut flora (For eg., only certain bacteria/microbes can survive when pH changes in the gut)
Selective growth of antibiotic resistant bacteria, leading to difficult-to-treat diseases
Existing bacteria acquiring antibiotic resistance from new incoming ones
Triggering certain dormant species to cause diarrhea
Drastic changes in the composition of the gut flora may increase the risk of a variety of diseases and metabolic disorders, such as obesity, irritable bowel syndrome (IBS), colon cancer, heart diseases, lung diseases and diabetes.
In addition, its implications have been proven in neurodevelopmental disorders like autism and Alzheimer’s disease, inflammatory diseases like atopic eczema and auto-immune diseases like rheumatoid arthritis.
What should one do to maintain it in a healthy state?
Prebiotics are dietary nutrients that are not easily digested by the digestive enzymes but can be broken down by the gut flora into simpler absorbable nutrients, thereby conferring health benefits.
Probiotics are live bacteria and yeasts that are beneficial to humans when given in specific forms and amounts. These are naturally present in fermented food, such as yoghurt and idli, or can be supplemented as tablets, syrups or probiotic-fortified foods.
Antibiotics have direct and substantial impact as they destroy beneficial microbes as well in the process clearing the disease-causing microbes. Thus, it is important that we replenish the depleted gut flora by oral supplementation. Please ask your doctor for a probiotic supplement when you are prescribed an antibiotic.
Note: Please consult a medical professional or a trained nutritionist regarding specifics of your health and symptoms or before changing your diet or trying something new.
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British Medical Journal, Nature Outlook, Experimental & Molecular Medicine, Physiological Reviews, Nature reviews Neuroscience, Springer link, Oxford Academic, Cambridge University Press, Nature, Science Magazine, Wiley, Wolters Kluwer Health, Inc., ScienceDaily
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