What are probiotics?
According to the WHO definition of probiotics, they are live microorganisms that, when consumed in adequate amounts, can confer health benefits. These microorganisms are commonly bacteria and yeasts and are found naturally living in the human gastrointestinal tract, forming the so-called intestinal microbiota, as well as in other places in the body such as the mouth, foot, or in the case of women, also in the vagina.
Characteristics of probiotics
For a probiotic to be considered as such, it must meet a series of characteristics.

Probiotics have long been used as a way to improve gut health and treat gastrointestinal disorders. These microorganisms have been shown to have a positive effect on the balance of gut bacteria, helping to maintain a healthy gut microbiota.
Probiotics are also available as supplements, usually capsules or tablets, with a combination of bacteria and yeast, although fermented foods such as yogurt, kefir, kimchi and sauerkraut are also commonly found.
It is important to keep in mind that not all probiotics are the same, they differ by genus, species and even strain of each microorganism, with each strain having different effects on the organism. Therefore, it is important to choose a probiotic that suits individual needs and seek medical attention or pharmaceutical advice before starting to take probiotic supplements.
Probiotics and Prebiotics
We should not confuse Probiotics with Prebiotics.
Probiotics are microorganisms, bacteria and yeasts that exert a beneficial effect on our organism, while prebiotics are dietary fibers that probiotics feed on.
In short, a prebiotic is the food of a probiotic.
What are probiotics used for and what are their benefits?
Probiotics have numerous health benefits, and have been studied extensively in recent years because of their potential to improve gut function and promote overall health. Today, many researchers continue to conduct clinical studies on the health benefits of probiotics.

In addition, probiotics may also be beneficial in treating other health conditions. Some strains have anti-inflammatory, antioxidant and anti-tumor properties. They have also been suggested to help strengthen the immune system and prevent infections.
One of the main benefits of probiotics is that they can help keep the gut microbiota balanced and healthy. But in addition, they are also beneficial for the vaginal, oral or skin microbiota, contributing to their balance and healthy state.
The intestinal microbiota has a great influence on the rest of the body through the gut-brain axis, which is a connection regulated at a neuronal and immunological level. Therefore, having a healthy and balanced intestinal flora will make our whole organism feel better, with a stronger immune system and less risk of infections or other health conditions.
Some of the main benefits of probiotics are:
In summary, probiotics provide a wide range of health benefits, from improving intestine function to boosting the immune system and reducing inflammation.
How do probiotics work?
Probiotics act in the body in several ways:
On the one hand, they are beneficial bacteria that colonize the intestine and replace pathogenic bacteria that cause infections and other health problems. They also produce antimicrobial substances such as bacteriocins that prevent colonization of the intestine by pathogenic microorganisms, thus rebalancing the intestinal microbiota. All these substances produced by these microorganisms are beginning to be called postbiotics.

In addition, probiotics can stimulate the body’s immune system, helping to fight infections and reduce the risk of chronic diseases. These bacteria also synthesize short-chain fatty acids that are needed by some intestinal cells for the nutrient absorption process.
In the case of the vaginal microbiota, these microorganisms produce certain acids that reduce the pH of the vagina to values that prevent the growth of pathogenic species, as in the case of Candidia albicans infections,
In general, probiotics have the potential to improve intestinal health, strengthen the immune and digestive system, and prevent chronic diseases. However, it is important to keep in mind that the effects of these microorganisms may vary from person to person and from the particular species and strain of probiotic.
Are there risks associated with probiotics?
Probiotics are generally considered safe for most people, but, nevertheless, we cannot say that they are completely risk-free, as the health status of the person, the dosage, and the particular strain may influence.
In certain types of cases, such as immunosuppressed patients or sick premature babies, there may be some adverse effects, such as some type of infection. In these cases, it is important to consult with the specialist, especially if the patient is taking some type of immunosuppressive drug since they can trigger allergic reactions.
Other possible side effects are gastrointestinal, with some episodes of gas, bloating the first few days or diarrhea, which are usually mild and disappear after a couple of days.
In addition, many probiotics are categorized as GRAS (Generally Recognized as Safe) by the US FDA and/or QPS (Qualified Presumption of Safety) by the European EFSA, i.e. they have the approval of these organizations that allow affirming the safety of these particular strains.
Finally, there is more and more documentation and clinical studies carried out on all types of populations, we can verify that the cases of adverse effects are really isolated.
What are probiotic foods?
Probiotic foods are those that carry live beneficial microorganisms that can improve intestinal health.
Some foods rich in probiotics are:
When you go to the store to buy yogurts, make sure that the label says yogurt, because you can find many fermented milks, but they are not yogurts. Only fermented milks with Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus can be called yoghurt.

It is important to choose natural, unprocessed probiotic foods for the greatest health benefits. It is also advisable to consume a variety of probiotic foods to get a wide range of beneficial bacteria.
Probiotic supplements

Origin of Probiotics
The origins of probiotics date back to more than a century ago, when the scientist and Nobel laureate Elie Metchnikoff (1845-1916) discovered that populations consuming a type of fermented milk had a greater longevity than the rest of the population.

Later, a French pediatrician, Henry Tissier, observed “Y” shaped bacteria (i.e. bifid shape) present in infants’ feces. He also observed that the amount of these bacteria present in the body was lower in those children who had episodes of diarrhea. Tissier succeeded in isolating this bifid-form bacterium, a Bifidobacterium.
On the other hand, in 1917, the German scientist Alfred Nissle managed to isolate a non-pathogenic strain of Escherichia coli from the feces of a German soldier who, being in an area with a high prevalence of shigellosis, unlike his comrades, did not present any diarrhea symptoms.

Pharmacist – Complutense University – Madrid – Spain
Diploma in Ophthalmic Optics and Optometry – Univ. of Barcelona – Spain.