Beneficial bacteria: what are they and what benefits do they have on our body?

These microscopic unicellular organisms, lacking a nucleus, that multiply by simple division (asexual) or by the production of spores, they can be pathogenic or beneficial bacteria for humans. Both types are capable of colonizing the body in the short or long term.

We have approximately 39 trillion bacteria living in the body. This means that, for each cell that makes us up, there are a minimum of 1.3 microorganisms inside a human. These living beings include 150 times more genetic information than the genome of our species.

With all these data we want to make it clear that bacteria colonize the skin, the digestive tract, the upper respiratory tract, the vagina, the penis, the mouth and many other cavities in contact with the outside. This is a good thing. If you want to know everything about beneficial bacteria, read on.

So not all bacteria are bad?

When we mention the term "bacteria" and "human body", we instinctively think of infections and diseases. Nothing is further from reality, as there are millions of microorganisms that live inside us without causing us any harm (they are diners) or even benefiting us (symbionts).

Almost any space in the body that is in contact with the outside has bacterial colonies. According to the Intramed portal, the total number of these microorganisms and their genetic material is called microbiome. On the other hand, the microbial population of the different ecosystems of the body is known as microbiota.

All of these colonized systems encompass the mouth, skin, sexual organs, upper respiratory tract, eyes, and, of course, the digestive system. On the other hand, when bacteria infiltrate closed systems they can have devastating effects. This is the case with endocarditis (infection of the heart), for example.

The gut microbiota is the clearest example of an effective microbiome, Well, according to the portal Gut Microbiota for Health, the large bacterial community in this system includes at least 1000 types of bacteria, which weigh up to 2 kilograms of the total mass of a person. Of course, conceiving life as it is today would be impossible without these microorganisms.

The intestinal microbiota is a clear example of coexistence between bacteria and humans.

To learn more: Endocarditis, an infection of the heart

What benefits do these bacteria generate in our body?

Beneficial bacteria for humans, also known as symbiotes, they have many positive effects. We will tell you some summarized in informative documents, such as the one presented by the Spanish Society of Infectious Diseases and Microbiology (SEIMC).


Many types of intestinal bacteria have enzymes to metabolize cellulose, hemicellulose and pectin in simple sugars that can be absorbed by the human body. This represents approximately 10% of the caloric intake in an adult.

Other of these colonies are capable of synthesizing vitamins, such as B12 and K, which cannot be produced by human cells. Thanks to them we are able to digest substances that would otherwise be impossible.


As indicated by the portal Biocodex, the microbiota located in all parts of the human body has a clear defensive function. The microorganisms that colonize us make it more difficult for other pathogens to settle, since they are occupying spaces and resources essential for an infection.

Besides this, other bacteria have an active defensive function. An example of this are those of the genre Lactobacillus, present in the vagina. These produce lactic acid, a compound that maintains the pH between 3.8 and 4.4. This medium is very unfavorable for various pathogens.

Immune system specialization

The intestinal flora is one of the first microorganisms with which a human being comes into contact. Keeping things simple, we can say that these early colonizing bacteria "teach" the lymphocytes which agents in the environment are beneficial and which pathogens. This encourages a specialization of the immune system.

Probiotics and beneficial bacteria in the intestinal flora

You may have heard a lot about probiotics in recent times, as many benefits have been discovered in recent decades. According to the Mayo Clinic, a probiotic is a food or supplement that contains living organisms responsible for maintaining or improving the microbiota normal.

This term should not be confused with that of prebiotic, since the latter refers to foods that act as growth promoters of beneficial bacteria already present. In general, they are rich in fiber and other plant elements.

Among the benefits of probiotics on intestinal flora and well-being we find the following:

  • They reinforce the activity of the immune system.
  • They displace harmful microorganisms and prevent their proliferation.
  • They help digestion.
  • They collaborate in the formation of essential nutrients, such as vitamin B12.
  • They stimulate the formation of lactic acid, which lowers the intestinal pH.
  • They favor the absorption of calcium, magnesium and iron.
  • They reduce the symptoms of certain pathologies.

As indicated by the Anales de Pediatría portal, we are not moving from a theoretical field. Probiotics have been shown to be helpful in treating acute diarrhea in children, traveler's diarrhea in adults and infections by Helicobacter pylori.

There are probiotic foods, such as yogurt, kefir, or sauerkraut, present in typical food chains. These contain live bacteria that are beneficial to humans.

Foods such as yogurt or kefir are natural stimulants for the health of the gut microbiota.

You may be interested: Probiotics for babies

Bacteria are beneficial if they do not pass into the blood

As with everything in life, bacteria beneficial to humans can have double standards. In immunosuppressed people or in certain intestinal motility disorders, for example, negative bacterial overgrowth may occur.

Furthermore, when a bacterium (good or bad) enters the bloodstream and multiplies, we are in a very dangerous situation. In summary, we can affirm that bacteria are allies, as long as they proliferate in the ecosystems that correspond to them and never grow out of control.