Probiotics – how to choose a strain suited to your needs
Probiotics are live microorganisms found naturally in fermented foods and dietary supplements. Find out how the main types (Lactobacillus, Bifidobacterium, Saccharomyces) differ, how to read strain designations on labels, why the number of strains isn’t everything, and why communication about probiotics in the EU requires particular caution and a research-based approach.
Probiotics are one of the most recognisable segments of modern supplementation – and at the same time one of the most burdened by marketing narratives that go far beyond what we can reliably say in the light of current knowledge. The FAO and WHO definition describes probiotics as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host”. This is a scientific definition – yet within the European regulatory framework, it has significant limitations in terms of communication. The European Food Safety Authority (EFSA) has so far not approved ANY specific health claims relating to probiotics. All applications submitted (including those for “supporting immunity”, “regulating digestion” and “restoring gut flora”) have been rejected due to insufficient evidence meeting European standards. For this reason, when communicating about probiotics, we focus on taxonomic descriptions, traditional uses in food fermentation, and a research framework with a strong emphasis on caution. This guide will organise your knowledge of the most popular strains and help you make an informed choice.
What are probiotics – microbiological basics
Probiotics are live microorganisms – primarily bacteria of the genera Lactobacillus and Bifidobacterium, but also yeasts (Saccharomyces boulardii) and certain other bacterial strains. They occur naturally in fermented foods (kefir, natural yoghurt, sauerkraut, kimchi, kombucha, miso, tempeh) and in dietary supplements in the form of capsules or powders.
From a biological point of view, precise strain nomenclature is crucial. The taxonomic hierarchy in microbiology comprises:
Genus (e.g. Lactobacillus, Bifidobacterium) – the broadest level of classification.
Species (e.g. Lactobacillus rhamnosus, Bifidobacterium lactis) – more precise.
Strain (e.g. Lactobacillus rhamnosus GG, Bifidobacterium lactis BB-12) – the most precise designation. Each strain has its own alphanumeric identifier.
This distinction is of fundamental importance. Two preparations containing ‘Lactobacillus rhamnosus’ may contain different strains with distinct properties. Only a specific strain, tested under specific conditions, can be the subject of scientific evaluation – not the entire species or genus. That is why a transparent manufacturer always states the full strain designation on the label.
The second key parameter is the number of live colony-forming units (CFU). Standard doses in supplementation are usually 1–50 billion CFU per day, although some clinical trials have used significantly higher doses. The CFU count should be stated at the end of the product’s shelf life, not at the time of manufacture – this is a quality distinction that sets conscientious manufacturers apart from less scrupulous ones.
Lactobacillus – the broadest group of probiotics
Lactobacillus is a genus of lactic acid bacteria naturally present in many fermented foods – yoghurt, kefir and pickled vegetables. It is also the broadest and most common group found in probiotic supplements.
Lactobacillus rhamnosus – one of the most extensively studied species in the scientific literature. The most popular strain is L. rhamnosus GG (an abbreviation of ‘Goldin and Gorbach’ – the surnames of its discoverers). Traditionally present in the human gut. It is sometimes considered as part of a conscious supplementation routine, although it lacks health claims approved by the EFSA. Communication in the context of tradition and research framing.
Lactobacillus acidophilus – a classic strain found in yoghurt and kefir. One of the longest-known microbiological strains – described as early as the beginning of the 20th century. Traditionally associated with milk fermentation.
Lactobacillus gasseri – a strain naturally present in the human microbiota, including the mouth and the digestive tract. Traditionally found in preparations intended for adults.
Lactobacillus plantarum – a bacterium found in many fermented plant-based products (sauerkraut, kimchi, pickled gherkins). Characteristic of a diet based on traditional European and Asian fermented foods.
Lactobacillus reuteri – a strain present in the microbiota of many mammals, including humans. Traditionally found in probiotic preparations.
Lactobacillus casei – a strain widely used in the dairy industry, present in many fermented products.
Bifidobacterium – gut bacteria
Bifidobacterium is a genus of bacteria naturally present in the human digestive tract , particularly abundant in breastfed infants. In adulthood, they constitute a smaller proportion of the microbiota, but are still present and are often included in probiotic preparations.
Bifidobacterium lactis – one of the most extensively studied species. The popular BB-12 strain is found in many commercial preparations.
Bifidobacterium longum – present in the human microbiota from infancy through to old age, one of the more ‘stable’ inhabitants of the gut.
Bifidobacterium breve – particularly important in the infant microbiota, but also present in adults.
Bifidobacterium bifidum – a classic strain with a long history of microbiological research.
From the perspective of informed supplementation, multi-strain preparations often combine Lactobacilli and Bifidobacteria – both groups can complement each other in a complex preparation.
Saccharomyces boulardii – the yeast ‘outsider’
Saccharomyces boulardii is a yeast, not a bacterium – which makes this strain unique amongst probiotics. It was isolated in 1923 from lychee fruit by the French scientist Henri Boulard. Traditionally found in preparations intended for adults.
A distinctive feature of S. boulardii is its natural resistance to bacterial antibiotics (as it is not a bacterium). Its safety profile has been described in numerous clinical trials, although – like other probiotics – it lacks health claims approved by the EFSA. Communication in the context of tradition and research framing.
[products:28-strain-probiotic-with-FOS-30-capsules, 18-strain-probiotic-with-FOS-30-capsules, Lactobacillus rhamnosus-probiotic-60-capsules, Lactobacillus gasseri-with-FOS-60-capsules]
Multi-strain vs single-strain preparations
There are two philosophies behind the formulation of probiotic preparations on the market – and both have their supporters and justifications.
Multi-strain preparations (e.g. 18 strains, 28 strains) are based on the assumption that strain diversity better reflects the natural complexity of the human microbiota and may have a broader potential range of effects. They are often combined with prebiotics (most commonly FOS – fructooligosaccharides or inulin), which act as a nutrient source for probiotic bacteria.
Single-strain preparations provide a high dose of a single, specific strain with a well-documented profile. This approach is characteristic of more ‘targeted’ supplementation – where an informed consumer chooses a specific strain whose profile best suits their needs.
From the perspective of modern supplementation practice, both strategies are valuable and are not ‘competitive’ – they can be used sequentially or at different stages of a conscious health routine. It is worth discussing your choice with your GP, a dietitian or a gastroenterologist – particularly if you are considering probiotic supplementation in the context of specific health issues.
Number of strains – why “more” does not always mean “better”
Probiotic marketing often highlights high figures – “30 billion CFU”, “28 strains in a single capsule”. These are impressive figures, but they require critical evaluation.
Number of CFU (colony-forming units) – doses of 1–50 billion CFU per day are generally appropriate. Higher doses do not always mean “better” – once a certain threshold is exceeded, additional billions of bacteria do not generate proportionate benefits and may place a strain on the digestive system. The most important thing is that the CFU count is stated at the end of the use-by date, not at the time of manufacture.
Number of strains – 28 strains sounds impressive, but if each is present in a microdose (e.g. 100 million CFU each), then none of them reaches the threshold at which they were traditionally studied. On the other hand, a preparation containing 5–10 well-dosed strains may be more valuable than a ‘30-strain complex’ in trace amounts.
Standardisation of the total CFU count – a reputable manufacturer declares the total CFU count per daily dose (e.g. “at least 25 billion CFU at the end of the expiry date”), rather than just the number of strains. This figure is more important for assessing the actual dose.
Prebiotics – food for probiotic bacteria
Prebiotics are food components that are indigestible to humans but are fermented by gut bacteria. They act as ‘food’ that helps maintain beneficial microorganisms in the digestive tract. The most commonly used prebiotics in supplements:
FOS (fructooligosaccharides) – short chains of fructose. FOS and inulin have EFSA-approved health claims relating to fermentation in the large intestine and the maintenance of normal blood glucose levels (under specific conditions of use).
Inulin – longer fructose chains, naturally present in chicory, Jerusalem artichoke, garlic, onions and leeks.
GOS (galacto-oligosaccharides) – galactose oligosaccharides, naturally present in mammalian milk.
Synbiotic preparations (probiotic + prebiotic in a single capsule) combine live cultures with their natural nutrient source – this is a more comprehensive solution, particularly for those just starting a probiotic routine.
[tip: Conscious probiotic supplementation requires regularity – taking a probiotic supplement just once rarely makes a real difference. Traditionally, probiotics are taken for a minimum of 4–8 weeks, once a day, on an empty stomach or with a light meal. The best time is in the morning, before breakfast – stomach acidity is usually lower then, which increases the chances that the probiotic bacteria will reach the small intestine alive.]
Natural sources of live bacterial cultures in the diet
Probiotic supplements are not the only source of live bacterial cultures. Traditionally, people obtained them from fermented foods – and this approach remains the most natural way to support the microbiota.
Plain yoghurt – a classic source of Lactobacillus and Streptococcus thermophilus. The EFSA has approved the following claim: live bacterial cultures in yoghurt improve the digestion of lactose contained in the product in people with lactose intolerance. This is the only EFSA-approved claim concerning live bacterial cultures in food products.
Kefir – fermented milk with the addition of kefir grains containing a complex microbiota of lactic acid bacteria and yeasts. A traditional Caucasian drink, popular in Poland for decades.
Sauerkraut – a classic Polish fermented food, naturally rich in Lactobacillus plantarum, L. brevis and other lactic acid bacteria.
Kimchi – a Korean fermented mixture of vegetables (mainly Chinese cabbage) with spices. Rich in a variety of lactic acid bacteria.
Tempeh, miso, natto – traditional fermented soya products from Asian cuisines.
Kombucha – a fermented tea drink made with a tea fungus (SCOBY).
Including 1–2 portions of fermented products in your daily diet provides natural support for your microbiota without the need for supplements. During periods of particular need (e.g. after a course of antibiotics – following consultation with a doctor), supplementation can be a valuable addition.
How to read a probiotic label – a practical guide
Making an informed choice of a probiotic supplement requires paying attention to specific elements of the label:
1. Full strain designations – not just “Lactobacillus rhamnosus”, but “Lactobacillus rhamnosus GG” or “Lactobacillus rhamnosus LR-32” with a specific identifier.
2. Number of CFUs per daily serving – with a clear statement as to whether this refers to the time of manufacture or the end of the use-by date (the preferable option).
3. A list of all strains – with proportions or a statement of the total number of CFUs.
4. Presence of a prebiotic – FOS, inulin or GOS as a nutrient source for the bacteria.
5. Resistance to stomach acid – whether the product is in enteric-coated capsules, whether the bacteria are microencapsulated, or whether other protective technologies are used.
6. Storage conditions – some preparations require refrigeration, whilst others are stable at room temperature. A reputable manufacturer will state this clearly.
7. Clean list of excipients – a short list free from artificial colourings, sweeteners and preservatives. You can find out more in the article how to read a dietary supplement label.
[note: Vitaler’s offers four different probiotic preparations tailored to various needs – ranging from comprehensive formulas containing 28 and 18 strains with FOS to single-strain Lactobacillus rhamnosus and Lactobacillus gasseri with FOS. Each comes in a pure formulation free from artificial colourings, preservatives or unnecessary fillers. It is worth discussing your choice of a specific preparation with a doctor or dietitian – particularly if you are considering supplementation in relation to specific health conditions.]
Safety and key situations requiring consultation
[warning: Probiotic supplementation is not recommended in the following situations: severe immune disorders (pharmacological immunosuppression, cancer treatment, congenital immune disorders), patients who have undergone organ or bone marrow transplants, patients with central venous catheters, severe pancreatitis, and critically ill patients. In these groups, probiotics may pose a real risk and their use requires the consent of the attending doctor. Probiotics in the first months of a baby’s life – only as recommended by a paediatrician. Probiotics during pregnancy and breastfeeding – consult your gynaecologist. Antibiotic treatment – consult your doctor about when and which probiotics to take (usually a minimum of 2 hours’ interval between the antibiotic and the probiotic). Any chronic digestive complaints (chronic diarrhoea, constipation, abdominal pain, blood in the stools, malabsorption, unexplained weight loss) require consultation with a gastroenterologist, and NOT self-administration of probiotic supplements. They may indicate conditions requiring diagnosis – ranging from food intolerances to inflammatory bowel disease, coeliac disease or other conditions requiring specialist treatment.]
The regulatory status of probiotics in the European Union
This is an important part of educating the informed consumer. The EFSA (European Food Safety Authority) has not yet approved ANY health claims relating to probiotics. All applications submitted by manufacturers – including those commonly used in marketing communications such as ‘supporting immunity’, ‘regulating digestion’ and ‘restoring gut flora’ – have been rejected due to insufficient evidence meeting European regulatory standards.
In practice, this means that marketing communications regarding the ‘effects’ of probiotics must be conducted with great caution, based on taxonomic description, traditional use and research framing. Informed consumers should critically evaluate products whose marketing goes beyond this framework – claims such as “cures”, “restores the gut flora” or “boosts immunity” are illegal in the case of probiotic supplements.
This does not mean that probiotics “do not work” – it means that the available scientific data has not yet met EFSA’s high standards. Research into probiotics is ongoing worldwide, and the coming years may see the approval of the first specific claims. Today, however, making an informed choice of a probiotic supplement requires accepting this state of affairs and adopting an approach based on a transparent description of the strains, their traditional uses and promising, albeit still preliminary, research.
FAQ – frequently asked questions about probiotics
Do probiotics need to be kept in the fridge?
It depends on the specific product. Some strains are temperature-sensitive and require refrigeration (from the moment of manufacture until opening). Others are stabilised by microencapsulation or other technologies and can be stored at room temperature. A reputable manufacturer clearly states the storage conditions on the label – always check this information. Once the packaging has been opened, most products should be kept in the fridge to ensure maximum shelf life.
How long can probiotics be taken for
Traditionally, probiotics are taken in cycles – 4–8 weeks of regular supplementation, followed by a break of several weeks. Long-term use of the same strains over many months has not been well researched and may not provide any additional benefits. A sensible routine often involves alternating between different preparations (different strains in different cycles) whilst also incorporating natural sources of live bacterial cultures into the diet (kefir, fermented foods, natural yoghurt).
Should probiotics be taken during or after a course of antibiotics?
This question requires consultation with the doctor prescribing the antibiotics – the decision depends on the specific antibiotic, the medical condition and the patient’s general health. A general rule: if your doctor recommends probiotics during a course of antibiotics, leave at least a 2-hour gap between taking the antibiotic and the probiotic (the antibiotic would destroy the newly ingested probiotic bacteria). Saccharomyces boulardii has a special status here – as a yeast, it is not sensitive to bacterial antibiotics. Always discuss this with your doctor.
Is it better to take kefir or a probiotic supplement?
This is not an ‘either/or’ question. Natural sources of live bacterial cultures (kefir, natural yoghurt, fermented foods) form the foundation of a healthy diet that supports the microbiota and should be incorporated into the daily dietary routine of most adults. Probiotic supplements can be a valuable addition during periods of specific need (following a course of antibiotics with your doctor’s approval, during periods of intense stress, or whilst travelling) – they provide significantly higher and more concentrated doses of specific strains. The most effective strategy combines both approaches. Read more in the article on sodium butyrate and gut health .
Summary: An informed choice of a probiotic supplement is based on an understanding of the taxonomic hierarchy (genus – species – strain), the correct interpretation of the CFU count (ideally stated at the end of the use-by date), the difference between multi-strain and single-strain preparations, and a critical assessment of marketing claims. Lactobacillus, Bifidobacterium and Saccharomyces boulardii are the three main groups of probiotics – each with a rich tradition in probiotic preparations and a promising, albeit still preliminary, research profile. The most effective strategy for informed supplementation is to combine natural sources of live bacterial cultures (kefir, natural yoghurt, sauerkraut, kimchi) with periodic supplementation using high-quality preparations when specific needs arise. An important caveat: the EFSA has not authorised any health claims regarding probiotics – an informed consumer accepts this status and assesses products based on the manufacturer’s transparency, the quality of the strains and the purity of the formulation, rather than on marketing promises. Any chronic digestive complaints require consultation with a gastroenterologist, rather than self-medication with probiotics.