Probiotics: do you need a supplement, or is your diet enough?

Probiotics are more than capsules with billions of bacteria. Find out how probiotics, fermented foods and prebiotics differ, when it makes sense to reach for a dietary supplement, and why what we “feed” a healthy gut microbiome matters even more. We also look at probiotics for children and women, and at how and when to take them.

What will you learn in this article?

1. What probiotics are and how they work
2. Probiotics, prebiotics and fermented foods
3. Are fermented foods as effective as probiotic capsules?
4. Why prebiotics also matter for the gut microbiome
5. Probiotics and prebiotics: why it makes sense to combine both
6. When does it make sense to take probiotics?
7. Saccharomyces boulardii
8. Probiotics for children: when to start and which to choose
9. Probiotics for women: digestion, immunity and intimate health
10. Probiotics during pregnancy and breastfeeding
11. When and how to take probiotics
12. How to take probiotics with antibiotics
13. How to support the gut microbiome without probiotic supplements
14. Key takeaways

What are probiotics and how do they work?

According to the internationally recognized definition, probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit [1].

When choosing probiotics, it is important to distinguish between individual strains. The effects of probiotics are strain-specific, so results obtained with one particular strain cannot automatically be applied to other bacteria of the same species [4].

Nor is it true that the higher the CFU count (colony-forming units), the more effective the probiotic. The number of microorganisms is only one of several factors. What matters more is the specific strain, the dose and its stability, and above all whether the strain has been clinically studied for the purpose you want to use it for.

Probiotics, prebiotics and fermented foods

These terms are often confused, yet they refer to different things:

• Probiotics are specific live microorganisms that, when administered in adequate amounts, confer a proven health benefit [1].
• Prebiotics include certain types of fiber, such as inulin, fructooligosaccharides (FOS) or galactooligosaccharides (GOS), which serve as food for beneficial gut microorganisms and support their growth [2]. Acacia fiber is also a prebiotic fiber.
• Fermented foods are produced by the action of microorganisms, but the presence of live cultures alone does not automatically make them probiotics.
• Synbiotics combine live microorganisms (probiotics) with prebiotics that support their growth and activity [3].

Telling these terms apart matters most when deciding whether it makes sense to reach for a probiotic dietary supplement, or whether it is better to focus mainly on the variety and composition of your diet.

Are fermented foods as effective as probiotic capsules?

Not always. Fermented foods usually do not state exactly how many and which live microorganisms they contain. It also depends on how they are produced and stored: some products are heat-treated after fermentation and therefore no longer contain live microorganisms. If you buy fermented foods, choose those that have not been pasteurized and contain live microorganisms that can support gut health.

Foods that contain live microorganisms include:

• natural yogurt with live cultures,
• kefir,
• sauerkraut,
• kimchi,
• some fermented soy products, such as natto, tempeh or miso,
• other traditionally fermented foods, such as kombucha or traditionally fermented pickles.

Why do prebiotics also matter for the gut microbiome?

When caring for the gut microbiome, it is not enough to think only about populating the gut with more beneficial microorganisms. It is just as important to give them enough “food”. That is exactly what fiber and other prebiotic substances are for.

Fiber that is not digested in the digestive tract reaches the large intestine, where gut microorganisms ferment it. This process produces short-chain fatty acids (SCFAs), such as acetate, propionate and butyrate, which have a range of beneficial effects on health [7]. Different types of fiber do not necessarily affect the microbiome in the same way [7].

Foods rich in fiber and substances that gut microorganisms can use include:

• vegetables,
• fruit,
• legumes,
• whole grains,
• nuts and seeds,
• onion and garlic,
• asparagus,
• chicory,
• foods containing resistant starch.

A varied diet provides different types of fiber that can support the diversity and stability of the gut microbiome. If you are not used to eating much fiber, it is better to increase the amount gradually. A sudden increase in intake can cause bloating in more sensitive people.

Probiotics and prebiotics: why does it make sense to combine both?

Probiotic microorganisms and prebiotic fiber can work together to create a favorable environment for the gut microbiome. In the long term, it can therefore be useful to think not only about supplementing probiotics, but also about supporting the microorganisms that already naturally live in our gut.

When does it make sense to take probiotics?

Probiotics are not a universal supplement that every healthy person should take preventively. Their effect depends on the specific microorganism, its dose and the health issue it is used for. That is why it is better to consider them for specific problems related to the gut microbiome rather than taking them preventively without a specific reason.

One of the best-studied areas is the prevention of antibiotic-associated diarrhea. Systematic reviews and meta-analyses show that the specific strain Lactobacillus rhamnosus GG can help reduce the risk of antibiotic-associated diarrhea in both children and adults [4]. The yeast Saccharomyces boulardii is similarly well studied in this area [5].

Saccharomyces boulardii

Saccharomyces boulardii differs from most common probiotics in that it is a yeast, not a bacterium. This is what makes it interesting when someone is taking antibiotics, because yeasts are not sensitive to the antibacterial action of antibiotics in the same way as bacteria [5].

Traveler’s diarrhea is another common digestive problem. Some probiotics, especially the strains Lactobacillus rhamnosus GG and Saccharomyces boulardii, may help reduce its risk. You can read more about preventing traveler’s diarrhea, suitable probiotic strains and other recommendations in our article Digestive Problems While Traveling: Prevention of Traveler’s Diarrhea and a Travel First-Aid Kit. [6] [11]

Probiotics for children: when to start and which to choose?

In most cases, there is no reason to automatically give probiotics to every healthy child. As with adults, the foundation is a varied diet, enough fiber and a reasonable intake of fermented foods.

Expert recommendations set out specific situations in which selected probiotic strains make sense, for example the treatment of acute gastroenteritis or the prevention of antibiotic-associated diarrhea [9][10]. On the other hand, expert recommendations do not support the blanket use of probiotics without a clearly defined health benefit [10].

For young children, it is not advisable to go only by the number of billions of CFU. What matters more is whether the specific strain has enough clinical evidence for the given situation, and at what dose it was tested.

How to give probiotics to babies and young children?

For infants and young children, it is best to choose a form that can be dosed safely and easily, such as probiotics in powder form. For infants, premature babies or children with a more serious health condition, always consult a pediatrician before using probiotics.

Probiotics for women: digestion, immunity and intimate health

For women, probiotics are often promoted not only to support digestion but also for better immunity and intimate health. The female microbiome has its own specifics, and bacteria of the genus Lactobacillus are particularly important in the vaginal microbiota [8].

A systematic review of randomized trials on probiotics for bacterial vaginosis and candidiasis described improved clinical outcomes and restoration of the vaginal microbiota with the strains studied, which included Lactobacillus crispatus, Lactobacillus rhamnosus GR-1 together with Lactobacillus reuteri RC-14, and Lactobacillus paracasei LPC-S01 [8].

Can probiotics help with intimate health?

Research into probiotics for women’s intimate health is ongoing, and some specific strains show promising results [8]. However, probiotics do not replace treatment of bacterial vaginosis, yeast infections or other infections. If problems arise, it is best to first find out their cause and discuss any treatment with a doctor. Read also our article Urinary tract infections: prevention and support for the body, not only in winter.

Probiotics during pregnancy and breastfeeding

During pregnancy and breastfeeding, the gut and vaginal microbiome naturally change, influenced by hormonal changes. In healthy women, bacteria of the genus Lactobacillus usually predominate; they create an acidic environment and help prevent the overgrowth of unwanted microorganisms. Disrupting this balance may increase the risk of some infections, such as bacterial vaginosis.

Probiotics can be one way to support this balance, but their effect depends on the specific strain and health issue. Some studies are looking at their effect on the vaginal microbiome, maternal immunity or the risk of atopic eczema in children.

To support the microbiome, however, a varied diet rich in fiber and suitable fermented foods is what matters most. During pregnancy and breastfeeding, we recommend always choosing probiotics based on the specific strain and discussing them with a doctor or pharmacist.

Why is the mother’s microbiome important for the child?

The mother’s microbiome can also influence the development of the child’s immune system. Microorganisms are passed from mother to child mainly during birth and then through breastfeeding. A healthy maternal microbiome can therefore be one of the factors that contribute to the natural development of the child’s microbiome and immunity.

When and how to take probiotics?

There is no single universal rule for when to take probiotics. Some bacterial strains may be better taken with food, before a meal or on an empty stomach. We therefore always recommend following the manufacturer’s instructions for the specific product.

Far more important than the time of day is taking them regularly and sticking to the recommended dose. If the manufacturer recommends taking the product with food, it does not really matter whether you take it with breakfast or dinner.

The dosage also always varies depending on the specific strain and the purpose of use. So it is not true that the more probiotic microorganisms (CFU), the better. Studies with specific strains usually use precisely defined doses, so it is best to follow the manufacturer’s recommendations.

How to take probiotics with antibiotics?

Antibiotics affect not only the bacteria causing the infection but also the entire gut microbiome. Using probiotic supplements is therefore useful in this situation, especially in relation to antibiotic-induced diarrhea [4][5].

An interesting option is Saccharomyces boulardii, because it is a yeast, not a bacterium, and common antibiotics therefore do not affect it in the same way as bacterial probiotic strains.

How to support the gut microbiome without probiotic supplements?

If you do not have a specific reason to take probiotics, you can start with these steps:

Eat as varied a diet as possible. Alternate different types of vegetables, fruit, legumes, whole grains, nuts and seeds.

Make sure you get enough fiber. Fiber is a key source of nutrients for gut microorganisms [7]. If you eat little of it, increase the amount gradually and drink more fluids as well.

Include fermented foods. Kefir, yogurt with live cultures, sauerkraut or kimchi can be a good addition to your diet.

Combine fermented foods with prebiotic foods. From the point of view of long-term microbiome care, this combination makes more sense than focusing only on the number of bacteria in a single capsule.

Key takeaways

Sources:

[1] Hill C, Guarner F, Reid G, et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11(8):506–514. Available at: https://doi.org/10.1038/nrgastro.2014.66

[2] Gibson GR, Hutkins R, Sanders ME, et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Nat Rev Gastroenterol Hepatol. 2017;14:491–502. Available at: https://doi.org/10.1038/nrgastro.2017.75

[3] Swanson KS, Gibson GR, Hutkins R, et al. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of synbiotics. Nat Rev Gastroenterol Hepatol. 2020;17:687–701. Available at: https://doi.org/10.1038/s41575-020-0344-2

[4] Szajewska H, Kołodziej M. Systematic review with meta-analysis: Lactobacillus rhamnosus GG in the prevention of antibiotic-associated diarrhoea in children and adults. Aliment Pharmacol Ther. 2015;42(10):1149–1157. Available at: https://doi.org/10.1111/apt.13404

[5] Szajewska H, Kołodziej M. Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea. Aliment Pharmacol Ther. 2015;42(7):793–801. Available at: https://doi.org/10.1111/apt.13344

[6] Connor BA, Leung DT. Travelers' Diarrhea. In: CDC Yellow Book 2026: Health Information for International Travel. Centers for Disease Control and Prevention, 2025. Available at: https://www.cdc.gov/yellow-book/hcp/preparing-international-travelers/travelers-diarrhea.html

[7] Vinelli V, Biscotti P, Martini D, et al. Effects of Dietary Fibers on Short-Chain Fatty Acids and Gut Microbiota Composition in Healthy Adults: A Systematic Review. Nutrients. 2022;14(13):2559. Available at: https://doi.org/10.3390/nu14132559

[8] Zuñiga Vinueza AM. Probiotics for the Prevention of Vaginal Infections: A Systematic Review. Cureus. 2024;16(7):e64473. Available at: https://doi.org/10.7759/cureus.64473

[9] Szajewska H, Guarino A, Hojsak I, et al. Use of probiotics for management of acute gastroenteritis: a position paper by the ESPGHAN Working Group for Probiotics and Prebiotics. J Pediatr Gastroenterol Nutr. 2014;58(4):531–539. Available at: https://doi.org/10.1097/MPG.0000000000000320

[10] Szajewska H, et al. Probiotics for the Management of Pediatric Gastrointestinal Disorders: Position Paper of the ESPGHAN Special Interest Group on Gut Microbiota and Modifications. J Pediatr Gastroenterol Nutr. 2022;76(2):232–247. Available at: https://doi.org/10.1097/MPG.0000000000003633

[11] Steffen R. Epidemiology of Traveler's Diarrhea. Clinical Infectious Diseases. 2005;41(Suppl 8):S536–S540. Available at: https://academic.oup.com/cid/article-abstract/41/Supplement_8/S536/569219