The world of probiotics — often improperly referred to as lactic acid bacteria — is vast and full of resources. With the importance of the gut microbiota for various aspects of health now well established, supplementation with live microorganisms represents a widely recognised tool for wellbeing.

Let us look in greater detail at the characteristics, properties and uses of probiotics.

What are probiotics and why are they important?

The WHO and FAO classify probiotics as live microorganisms capable of conferring benefits on the human body, provided they are taken in adequate quantities. They are bacterial strains and yeasts that have been extensively studied for their respective properties.

Being viable components, probiotics are able to supplement and rebalance the microbial population residing in the gut, establishing a symbiotic relationship with the human body. This collection of microbes, which proves to be quite heterogeneous, is known as the gut microbiota and is associated, within the body, with important functions. Contributing to the efficiency of the microbiota essentially means promoting overall wellbeing — hence the undisputed value of probiotics.

Understanding probiotics

Given its complexity, the subject of probiotics has several points worth examining. Chief among these is the difference between probiotics and prebiotics, which is sometimes overlooked due to the similarity between the two terms. For practical purposes, it is also worth clarifying the possible probiotic sources, along with a brief overview of the mechanisms of action.

Differences between probiotics and prebiotics

Often found together in targeted supplements, probiotics (pro-biotics) and prebiotics (pre-biotics) are two components of a different nature. Whereas probiotics are defined as live organisms that function to supplement the microbiota, prebiotics are non-living substances capable of modulating the microbiota itself and supporting its sustenance. In practice, they are fibres that cannot be assimilated by the human digestive system but can be used by microorganisms for their fermentation processes. Among prebiotics, notable substances include inulin, fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS).

As with live microorganisms, the intake of prebiotics is also based on specific requirements. Their use, in particular, must be entirely safe for human health. Secondly, it must correspond to adequate daily quantities, ensuring a certain degree of efficacy.

Supplements containing both probiotics and prebiotics are defined as synbiotics. Taking both components in combination allows their synergistic effect to be harnessed.

Prebiotic substances can also be obtained from common plant-based foods. These include legumes and cereals such as barley, spelt and oats, as well as vegetables such as asparagus and artichokes, and fresh fruits such as apples, pears and bananas.

Main types of probiotics and their sources

As mentioned above, probiotics consist of bacterial strains and yeasts. Among bacteria, in particular, several species of lactobacilli (such as rhamnosus, reuteri and casei) and bifidobacteria (such as bifidum and lactis) stand out, while among fungal strains the species Saccharomyces boulardii is notable.

Sources of probiotics include appropriately formulated supplements (as we will see later) and specific foods. Characterised by the fermentation process, these foods constitute a source of live microorganisms and are therefore classified as probiotic foods. Among these are miso, tempeh and natto, derived from soya, as well as kombucha, obtained from the fermentation of sweetened tea, and sauerkraut, derived from the fermentation of white cabbage. Particularly interesting are the various types of kefir, a well-known probiotic food derived from animal milk, plant-based drinks or water. By virtue of the absence of chemical treatments, organic apples also represent a good source of lactobacilli. In general, apples are particularly rich in pectin, a fibre with a pronounced prebiotic action, and therefore also rich in microorganisms. Apples from organic farming, in particular, are not subject to the harmful effects of pesticides and thus display a richer and more heterogeneous microbial flora. Other probiotic foods include apple cider vinegar, pickled cucumbers and kimchi, a Korean preparation made from fermented vegetables and spices.

Obtained through the acidic fermentation of milk, yogurt does not, contrary to popular belief, fall among probiotic foods. The bacterial strains responsible for this fermentation process, namely Lactobacillus bulgaricus and Streptococcus thermophilus, remain in the yogurt; however, once ingested, they do not survive gastric acidity. This is a fundamental requirement for the probiotic potential of microorganisms. In any case, several types of yogurt fortified in this respect are commercially available.

Probiotic foods:

• miso
• tempeh
• natto
• kombucha
• sauerkraut
• kefir
• organic apples
• pickled cucumbers
• apple cider vinegar
• kimchi

How do probiotics work in our body?

The efficacy of probiotic microorganisms is closely linked to their ability to reach the intestinal tract while still viable. Here, they come into contact with the resident microbiota, supplementing it both qualitatively and quantitatively. In a broader sense, this has an impact on various aspects of health.

Health benefits of probiotics

The benefits associated with probiotic intake are numerous. Chief among these is undoubtedly digestive efficiency, although the effects on immune function perhaps represent the most interesting aspect.

The impact of probiotics on digestive health

A microbiota rebalanced through probiotic supplementation is beneficial for our digestion. By acting on the food substrates introduced each day, the microbiota participates in the assimilation of nutrients, promoting the absorption of certain micronutritional components such as iron and magnesium.

Imbalance in the composition of the microbiota is known as dysbiosis and is associated with an inflammatory state. This condition underlies various problems, such as indirect food intolerances. These are not caused by the specific food — as is the case with lactose intolerance — but by the inflammation that impairs intestinal function. Probiotic supplementation can undoubtedly help in overcoming dysbiosis, promoting the restoration of optimal digestive function.

Probiotics and the immune system: a vital connection

Several studies clarify and confirm the deep connection between the microbiota and the body's natural defences. Of particular relevance is the ability of the intestinal bacterial flora to modulate the immune response, enhancing its proper activation. Certain products of microbial metabolism (such as short-chain fatty acids) are capable of producing molecular "stimuli" directed at anti-inflammatory responses, the production of antimicrobial components and the differentiation of immune cells (regulatory T lymphocytes). In essence, the microbiota is able to interact and communicate with the human immune system, contributing to the maintenance of a state of internal equilibrium (homeostasis). In this context, defensive capabilities against real threats are promoted, as is the recognition of harmless factors.

The effects of the microbiota on defensive capabilities are also "direct" in nature. Specifically, the intestinal flora is capable of preventing pathogenic bacteria from colonising the gut, by depriving them of nutrients, producing antimicrobial components (known as bacteriocins) and generating hostile microenvironments (through alteration of pH).

Taking probiotics may therefore prove beneficial in restoring these mechanisms where the microbiota is insufficiently efficient in this regard.

Probiotics for skin: benefits and advice

Several scientific studies link the functioning of a healthy microbiota to skin wellbeing and, for example, to the optimal management of acne: a connection known as the gut-skin axis. Although laboratory experiments suggest significant benefits for the skin, clinical studies on supplementation are scarce, both with regard to oral intake and topical applications. Nevertheless, favourable results are observed, particularly in relation to oral supplementation. These effects stem from the modulation of the resident microbiota, which leads to an anti-inflammatory response and the restoration of intestinal integrity. Other effects concern the molecular mechanisms that occur in our cells and that also influence skin health.

Other benefits of probiotics: mood and general wellbeing

Mental discomfort, in the form of anxiety, stress and depression, is linked to microbiota imbalance. It is no coincidence that various neurotransmitters involved in mental wellbeing — such as serotonin, glutamate and GABA — are produced in the intestine. Dysbiosis, among other things, can compromise the production of these substances, and is associated with anxiety, depression, sleep disorders and other related symptoms. The connection between the intestinal system and the brain is known as the gut-brain axis. To date, probiotic supplementation is considered a useful tool for mental health as well, forming the basis of psychobiotics.

Among the further benefits linked to restoring microbial imbalance is the endogenous production, carried out by the microbiota itself, of certain vitamins. These are, in particular, vitamin K, which is involved in blood clotting and bone health, and folates, which contribute to cardiovascular health and other aspects of health.

Selecting and using probiotics

Probiotic sources come in the form of foods or specifically formulated supplements. For a probiotic supplement to be effective, the microbial intake must, by definition, exceed a certain quantity considered sufficient. The European Food Safety Authority (Efsa) requires, among the fundamental characteristics of these products, absolute safety for human health.

How to choose the right probiotic for you

A general requirement when choosing a probiotic is, therefore, the number of live cells per daily dose. Several studies agree on the minimum quantity needed for intestinal colonisation, equal to 9 billion probiotics. A further aspect concerns the composition of each product. Given that every individual has their own bacterial flora, the best way to achieve a certain effectiveness of treatment involves using a broad-spectrum product, and therefore one composed of multiple bacterial strains. In this way, the supplementation of missing or deficient types is ensured.

For more targeted choices, relating to the different microbial species, as well as to the combined intake of probiotics and prebiotics, it is good practice to consult a qualified professional (a doctor and/or nutritionist), who will be better able to tailor the supplementation to the specific issue.

An important aspect concerns individual allergies and/or intolerances. The probiotic label, in this regard, provides information about the content of gluten, lactose, soy or other components that may be problematic for the consumer. It is therefore preferable to read the accompanying instructions carefully before using the supplement.

Tips for taking probiotics: dosage and timing

Taking into account the quantitative requirements, each manufacturer will provide specific instructions regarding supplement dosages. As a general rule, it is preferable to take probiotics on an empty stomach, in order to reduce the impact of gastric juices on the ingested microbial components.

Combining fermented foods and probiotic supplements

Incorporating fermented foods into one's daily diet undoubtedly benefits the microbiota, as it promotes a certain heterogeneity. However, the exact microbial composition derived from the specific food is not known, let alone the viability of the ingested cells. It stands to reason that consuming a fermented food is not the same as taking a specific probiotic supplement. The use of a targeted probiotic formulation can, in any case, be combined with the consumption of fermented foods, as possible options within a varied and balanced diet.

Practical considerations on probiotics

Appropriate use of probiotics cannot be separated from certain considerations regarding the periods of intake, any antibiotic therapies, and potential adverse effects.

How long should you take probiotics?

Probiotic supplementation proves effective only when it is continued over time. As a rule, it is preferable to take the probiotic for approximately one month, every day throughout that period. Subject to medical advice, a cyclical supplementation schedule may be considered.

Probiotics and antibiotics: how to protect the intestinal flora

As necessary and crucial as they are in many cases, antibiotic therapies have negative effects on the gut microbiota, both by disrupting microbial heterogeneity and by promoting the development of resistant and/or pathogenic strains for the human host. In order to limit the damage caused to the intestinal flora, it is advisable to take probiotics during antibiotic therapy. In particular, probiotic intake should be taken two to three hours apart from each dose of medication, and for at least two weeks after the end of the course of treatment.

Side effects and precautions when using probiotics

In healthy individuals, the use of probiotics is not usually associated with adverse effects. It is important, as already stated, to pay attention to the information on the label, to help manage any intolerances and/or allergies optimally. For immunocompromised individuals or those convalescing after surgical procedures, it is preferable to seek medical advice, as the intake of probiotics could be contraindicated. For preventive purposes, the same criterion should be applied for any ongoing medical condition or drug therapy.

Conclusion

In summary, probiotics are live microorganisms that are beneficial to the human body. By supplementing the gut microbiota and improving any dysbiosis, probiotics act on various aspects of health, such as digestive function, immune efficiency and mental wellbeing.

For correct supplementation, it is preferable to take probiotics after consulting a doctor, identifying the most suitable product for individual needs. Equally, it is important to assess possible contraindications, avoiding potential adverse effects. In any case, the use of probiotics should be placed within the context of a varied and balanced diet.

Frequently asked questions (FAQ)

What are probiotics? Probiotics are live microorganisms capable of providing benefits to the human body, provided they are administered in adequate quantities. These are, specifically, bacterial species (lactobacilli and bifidobacteria) and yeasts, such as Saccharomyces boulardii.

What are probiotics used for? As live microorganisms, probiotics supplement and support the gut microbiota. The benefits for the human host are numerous, relating to various aspects of health. These include digestive health, immune efficiency and mental wellbeing.

When should you take probiotics? Probiotics should be taken in connection with the specific condition to be treated, after consulting a doctor. For effective treatment, it is preferable to take probiotics on an empty stomach, for a period of one month.

Where are probiotics found in food? Probiotics can be obtained from fermented foods, such as kefir, sauerkraut and kombucha, as well as miso, tempeh and organic apples. There is also no shortage, at a commercial level, of foods fortified with probiotics (e.g. yogurt). The intake obtainable from fermented foods is not comparable to that from dedicated formulations, either in terms of composition or microbial viability.