What is Microbiota?

The microbiota is the trillions of bacteria in the colon. These bacteria are highly dependent on the food we eat. Learn all about the inhabitants of your gut, how they affect your health, and how you can improve the composition of bacteria by changing your eating habits.
Not so long ago, it turned out that these bacteria perform a number of functions important for the human body. Today, scientists call the microbiota a new organ that deserves a separate study.

The diversity of the microbiota indicates the approximate number of species of bacteria that inhabit the intestines of each person. Each type of bacteria has its own functions and tasks, while they often “back up” each other. The more bacterial species, the more possible mechanisms of regulation and compensation, and the more stable the system as a whole. When switching to an unbalanced diet or after taking antibiotics, if one or more key species disappear from the community, other species will take over their functions in a diverse microbiota. In a poor community, such a reaction may not occur, and dysbiosis will occur – a violation of the species composition of the microbiota. Dysbiosis can lead to illness. For example, in patients with inflammatory bowel disease and metabolic disorders, the diversity of the microbiota is significantly lower than in healthy people.

Where do bacteria come from in our intestines?

Bacteria colonize everything around and within us. They love warm and humid environments. In the human body, most of the microorganisms are found in the mouth and intestines. Bacteria begin to colonize our body while we are still in the womb. It used to be thought that the placenta and amniotic fluid were sterile, but recent research suggests that this is not the case.

It is not yet clear how bacteria enter the placenta, but there are suggestions that this is influenced by the microflora of the vagina, bacteria in the oral cavity, which in small numbers can enter the bloodstream, and the intestinal microbiota, where immune cells (dendritic) select certain bacteria that will enter the the placenta. However, large-scale colonization of the intestines with bacteria occurs during childbirth, breastfeeding, and when the baby begins to eat solid foods. By the age of 1.5–3, a human microbiota profile is formed, which contains more than 1000 species of bacteria. Caesarean section, antibiotic use, imbalance of bacteria in the mother’s intestines, premature birth, refusal to breastfeed are factors that negatively affect the formation of the microbiota.

Why exactly the intestines?

The task of the intestine is to absorb the maximum amount of nutrients, and this requires a large surface area. To fit it, the structure of the intestine is tightly adjacent folds with villi and microvilli. Because of this, the intestines are often compared to velvet fabric.

The surface of the intestine is covered with a mucous layer – mucin. It protects intestinal cells from aggressive microbiota. Mucin is renewed every hour, as part of this layer is carried away by fecal matter as it moves through the intestines.

A humid, warm environment with many folds and growths is an ideal environment for bacteria to grow. You may have heard the myth that the number of bacteria is 10 times the number of cells in the human body. The human body weighing 70 kilograms and growing 170 centimeter contains about 30 trillion cells and 39 trillion intestinal bacteria. Although the ratio is not 1:10, the number is still impressive.


Why do we need bacteria?

The human digestive system is designed in such a way as to break down all incoming food into simple molecules: to make them available for absorption by cells and penetration into the bloodstream. At the same time, there are substances that our body cannot digest – complex carbohydrates.

Complex carbohydrates are made up of long chains of sugar molecules that the enzymes of the gastrointestinal tract cannot break apart. There is simply no information in the human genome about compounds that break down complex carbohydrates, but the genes of intestinal bacteria encode tens of thousands of such enzymes (polysaccharide lyases).

It would seem, why do we need complex carbohydrates, if even our DNA does not say what to do with them? In the process of breaking down complex carbohydrates, bacteria synthesizes vitamins and short-chain fatty acids – the main source of energy for intestinal cells.

A person has a beneficial cooperation with bacteria: we feed them, and they feed us.

Another plus of this cohabitation is that the genetic material of bacteria is more flexible. These microorganisms adapt much faster to changes in the environment, unlike humans. A striking example of this, although negative for us, is the resistance of bacteria to antibiotics, which is now being observed more and more often.


How microbiota works?

I’ve already mentioned that gut bacteria help metabolized fiber and produce short-chain fatty acids and vitamins. It may feel like every bacterium is doing all this, but it is not.

Microbiota is an ecosystem with its own orders and laws. It can be compared to a metropolis, whose inhabitants have a variety of professions.

Part of the bacteria works for the good of the whole city and monitors pathogenic microorganisms so that they do not disrupt order and start a revolution. Some bacteria are passive: they do not benefit the city, but they also do not create problems. And the third part is constantly plotting a plan of how to capture the city and plunder everything that has been acquired. It depends on our diet, which of these three representatives will be more.

Complex carbohydrates are food for law-abiding microbiota citizens who take care of their home. True, this is not a ready-made dish that we serve on a plate. To such tiny creatures, the complex carbohydrate molecule looks more like a felled oak tree. To remove branches, prepare a log, saw it, make firewood and matches, you need a variety of bacteria.


What is butyric acid and why is it needed?

If some kind of bacteria is missing, the process of breaking down carbohydrates, synthesizing short-chain fatty acids and vitamins will be less efficient. Therefore, the more various foods with fiber we eat, the higher the variety of beneficial bacteria and the more stable the situation in the city, despite petty hooliganism on the part of pathogenic microorganisms.

A number of bacteria that inhabit our gut are associated with better indicators of health status. They are predominant in people with low levels of systemic inflammation and a healthy digestive system. Among these bacteria are probiotics. These include those microorganisms, the consumption of which has been shown to improve human health.

Probiotics have a positive effect on immunity, metabolism and food absorption. Other bacteria for which no causality has been established, but which are associated with gut health, are referred to in this section as «beneficial»


What are probiotics?

Probiotics are bacteria that have been shown to benefit the human body. The most common probiotics are lactobacilli and bifidobacteria. Other microorganisms can also be classified as probiotics, such as the yeast Saccharomyces boulardii.

For the first time the term “probiotic” was introduced by the Nobel laureate, biologist Ilya Mechnikov. He suggested that the bacteria in yogurt may have beneficial effects on the gut microbiome. After that, scientists continued to explore the idea and use the term “probiotic” – which means “for life.”

In the human intestine, probiotics compete with harmful bacteria, inhibit their growth and maintain the protective barrier of the intestinal wall. Thus, they reduce the likelihood of inflammation.


What foods contain probiotics and are they beneficial?

The main source of probiotics in the diet is fermented foods. For their production, they usually use sourdough with microorganisms and sugar, which is food for them. The bacteria eat simple carbohydrates, multiply and secrete compounds that give the characteristic flavor. 

Fermented foods include yogurt, kefir, sauerkraut, kombucha, kimchi, pickles, miso, cheese, dough, or bread sourdough.

Not all fermented foods contain live bacteria. For example, cheeses are pasteurized, and sponge bread is baked at a high temperature. Beneficial bacteria die under these conditions.

There is now emerging evidence that even dead probiotic bacteria may be beneficial. But in any case, they are not considered probiotics. Scientists suggest calling them paraprobiotics.

To be considered probiotic, a product must contain at least 107 live microorganisms (CFU) per gram or milliliter until the expiration date.

Such labeling can be found in the description of the composition, however, not all manufacturers of fermented products indicate the content of beneficial bacteria.

Do bacteria survive in the stomach?

The human stomach is an unfavorable environment for probiotics. Therefore, the more bacteria there are in the product, the higher the likelihood that some of them will survive and reach the intestines.

Studies show that bacterial survival in gastric juice is improved in the presence of simple carbohydrates: glucose, fructose, sucrose and lactose. Lactose is a sugar found in dairy products.

Plain yogurt or kefir with enough microorganisms can be a good source of probiotics.

It is not worth adding sugar specifically to improve the survival of bacteria, since it does not contain useful trace elements. Instead, you can add fruit for an extra serving of vitamins and fiber.


How to increase probiotic bacteria if you are lactose intolerant?

Lactose intolerance is observed with lactase deficiency. Lactase is an enzyme that breaks down lactose in the small intestine. When this enzyme is low, the whole lactose enters the large intestine and begins to interact with the bacteria of the microbiota, which causes unpleasant symptoms. Someone cannot drink cow’s milk, but tolerates fermented milk products and cheese, and someone does not tolerate everything that contains lactose. In the latter case, you can ask a therapist or nutritionist about enzyme preparations that help the body break down lactose.

Lacto- and bifidobacteria, like many other beneficial bacteria, feed on prebiotics – certain types of fiber. Therefore, if for some reason you cannot or do not want to eat probiotic foods, you can add foods rich in prebiotics to your diet.


Should you include probiotics in your diet as a supplement?

In medicine, probiotics are used to reduce the risk of developing Clostridium difficile infection when taking antibiotics. Clostridium difficile is a bacteria that can lead to diarrhea and life-threatening complications.

An analysis of 39 studies found that taking probiotics during antibiotic treatment reduced the risk of developing Clostridium difficile infection by 60%.

If your doctor has prescribed antibiotic treatment for you, ask him about the need for probiotics in your particular case. For people with severe medical conditions and weakened immune systems, the risk of taking probiotics may be greater than the benefit.

For people without diagnosed medical conditions, probiotics are considered safe, but there is no conclusive research yet that they give any positive result in this case.

Most likely, it makes no sense to include probiotics in the form of supplements in the diet of healthy people.


How to stay healthy with diet?

For the body to continue to effectively resist infections after 45 years, it is important to monitor your diet. The abundance of fiber in the diet will help to reduce the number of Bacteroides and ensure the restructuring of the microbiota.

If you add fiber-rich foods to your diet, the composition of your microbiome will change with age: new beneficial bacteria will appear in your gut. Conversely, regular consumption of processed foods that are devoid of fiber – processed foods, fast food, sugary sauces with a lot of sugar – will lead to the growth of bacteria that will attack the intestinal wall as you age. 2020-01-15-Microbes-and-body-weight

Another way to diversify your microbiome is to add more exercise to your schedule. The microbiota adapts better to age in those who move a lot and often spend time outdoors. Physical activity in the body reduces the level of low-density lipoproteins – the so-called “bad” cholesterol, which causes atherosclerosis.

This helps the gut bacteria get rid of the extra work of digesting fatty compounds and become more actively involved in maintaining immunity. Also, in physically active people after 45 with a changed microbiota, the composition of bacteria synthesizing indole, a protective substance that protects the intestinal walls and fights inflammation, increases.


Copyright Anna Shelomentseva 2021