An average human body contains approximately 3.7 trillion of cells. But, have you ever given thought as to how many microbial cells are hosted on and within our body? You may be definitely surprised because it is really a high number compared to the human cells that we have in our body. According to scientific findings, the number of microbial cells on and in our bodies is nearly 10 times higher than the number of human cells. So, do you still think that it is fair to say our body is owned only by ourselves? Is it only we who are living in our bodies?
Human microbiota
The surface of the human body - in and out - contains trillions of microorganisms and collectively these microorganisms are called ‘human microbiota’. Mainly they are bacteria. These bacteria can be found on the skin, in the mouth, intestines and in so many other places of the human body. The majority of these microbes are harboured in our large intestine (colon) making a complex resident community which is predominated by bacteria.
 Gut microbiota could potentially
influence weight gain and fat deposition in humans
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Other than bacteria, there are several species of fungi, archaea and viruses as well. Relatively, microbial cell density of bacteria in the small intestine is lower than that of in the large intestine. Bacteria that reside in the human intestine are known as ‘gut bacteria’. Most of the gut bacteria remain harmless to humans, but a very few of them could cause harm only when their number exceeds a particular threshold value under specific conditions.
However, the gut microbiota is unique to a person. The composition of the microbiota that you have in your body may be different from what your mother, father and your partner have in their bodies. The number and the species of gut bacteria you have in your body may depend on your own dietary habits, age and sex, type of birth delivery, breastfeeding and use of antibiotics. We can externally take in beneficial gut bacteria to our bodies as probiotics with certain foods such as yoghurt and curd.
Since most of the gut bacteria live symbiotically in the human intestine, they play several important roles in improving our health. As an example, gut bacteria can produce vitamins (e.g., Vitamin K) which are essential for humans. Also, friendly gut bacteria are essential for maintaining a healthy gut barrier against pathogenic microorganisms which can populate in the human gut and cause diseases in humans. They are important for energy regulation and modulation of immunity by communicating with our immune system as well.
Disadvantageous effects
Nevertheless, there are some newly-discovered disadvantageous effects of these gut microorganisms. Prevalence of obesity has increased in the last few decades. It has become a major problem among adults and children due to their improper lifestyles. If you are an obese person who wants to lose your weight by several kilogrammes, you may enrol in a weight-loss programme. But, sometimes even with a change of diet, exercise and behaviour, you may not lose weight to the extent you want and in such situations, your gut microbiota may matter. Recent researches have revealed that the gut microorganisms, especially those residing in the large intestine play a critical role in determining obesity. Simply, your gut microbiota can cause you to gain weight!
Influencing weight gain
There are several mechanisms proposed through which gut microbiota could potentially influence weight gain and fat deposition in humans. One such method is that some bacteria of gut microbiota can break down or digest dietary fibres which cannot be digested by humans and harvest energy for their consumption. The adverse effect of this is that the digestion of those dietary fibres will end up with short chain fatty acids which accumulate in the adipose tissue of the host human. Fat accumulation will ultimately cause obesity.
This phenomenon is known as the ‘energy harvest hypothesis’. This happens when your gut microbiota is more diverse with so many bacterial species which are capable of digesting different types of food.
Another mechanism proposed by scientists to explain the relationship between gut microbiota and obesity is its ability in suppressing one of the enzymes which catalyses the breakdown of fatty acids in liver and muscle fibres and as a consequence of which increased fat accumulation occurs in the host liver and muscle tissues.
Gut bacteria play an important role in inflammation and there are several hypotheses built on this idea. One is, we might be eating too much of proteins and some bacteria in our intestine may ferment them, resulting in harmful fermentation products which can enter into our bloodstream. Those will be taken to the liver where they turn on inflammatory responses. This may lead to increased fat deposits and decreased fat export. Then, these inflammations can lead to a leaky gut as well.
Another interesting fact about gut microbiota is that they can communicate with our brain via neurotransmitter signals and make us feel hungry. This feeling may affect the number of times that you eat per day and also how much you eat at a time. Our gut microorganisms send signals to the brain asking for more food or telling it when we are full! If our intestine contains several different types of microorganisms, they will never seem to get full! This feeling makes us greedy and eat frequently. Obviously, this habit leads our weight to increase.
Avoiding harmful effects
We can adjust our diet so as to facilitate friendly or beneficial microorganisms in our gut microbiota and increase their number in our guts.
However, a universal diet plan cannot be recommended as the composition of gut microbiota is unique to each person; so the requirements may differ from person to person.
But, generally, the food that is enriched with prebiotics or probiotics help to maintain a healthy gut by facilitating the growth of beneficial bacteria in the gut.
Probiotics and prebiotics
Probiotics are live microorganisms - particularly specific strains of bacteria which are directly added to gut microbiota to restore the population of beneficial bacteria in our guts. Mostly, probiotics are included in fermented foods such as yoghurt, sauerkraut and curd. In contrast to probiotics, prebiotics mean a special form of dietary fibres that act as fertilizers for the beneficial microorganisms and promote their growth in the gut. Prebiotics are found in food that is rich in fibres such as fruits, vegetables and whole grains.
As plant-based diets (vegetarian food) contain fibres in high contents, they facilitate the growth of beneficial gut bacteria, reducing the levels of disease-causing pathogenic bacteria in obese people.
Therefore, try to replace your meaty diet with more vegetables, fruits and grains as much as you can. It is really important to breastfeed children at least during the first six months after their birth. That is because, in the first two years, the baby’s microbiota gets continuously developed and becomes rich in beneficial bacteria which can consume the sugars (lactose) in breast milk. So, when your infant is fed with breast milk, friendly gut bacteria will be facilitated and make your baby healthy in return.
At the same time, as a habit, you can minimise the use of artificial sweeteners and processed food for the benefit of your friendly gut microbes. Other than dietary habits, good sleep, stress-free mind, enough water and controlled use of antibiotics will definitely help you to maintain a healthy gut dominated by beneficial microorganisms.
All the above health tips are recommended for a healthy gut. Ultimately, live a life close to nature! Let’s not forget our gut microbiota and maintain good habits to secure their inbound relationship for more years to come.
Prebiotics are found in food that is rich in fibres such as fruits, vegetables and whole grains
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