Probiotics and Good Bacteria: What Is Really Worth Knowing
Probiotics are often called good bacteria. They are found in supplements, yoghurt, kefir and other fermented products.
In this article you will learn what probiotics are, what research shows, why it is important to look at the strain and how to read the label.
In brief. Probiotics are live microorganisms that, in an adequate amount, may be beneficial to health.1 Their effect depends on the specific strain, so studies of one product cannot be applied to another.1 There are no EU-authorised health claims for probiotic supplements.3 For people with a severely weakened immune system they may be unsafe.2
What are probiotics?
Billions of bacteria live in the gut – they are known as the gut microbiota. Probiotics are live microorganisms that, when consumed in adequate amounts, may be beneficial to health.1
Most often these are lactic acid bacteria (Lactobacillus), bifidobacteria (Bifidobacterium) and the yeast Saccharomyces boulardii.
Why is it important to look at the strain?
A probiotic's name consists of three parts: genus, species and strain. Different strains of the same species may act differently.1
Example. The label “Lactobacillus acidophilus La-14” is more precise than “Lactobacillus acidophilus”. The letters and numbers at the end (La-14) denote the strain. Only by the strain can a product be linked to specific studies.
What do probiotic studies show?
The best-studied area is diarrhoea during antibiotic use. In a review involving 6,352 children, diarrhoea occurred in 8% of those who took probiotics and in 19% of the control group.2 Lactobacillus rhamnosus and Saccharomyces boulardii appeared the most suitable, taken at 5–40 billion CFU per day.2
These results relate to specific strains, doses and circumstances. There is less research in other areas so far, so results depend on the specific product and situation, and if you are taking antibiotics, it is worth discussing a probiotic with a doctor or pharmacist.3
Can probiotics be obtained from food?
Yes. Live cultures in yoghurt or fermented milk improve lactose digestion of the product in individuals who have difficulty digesting lactose.³ That is why yoghurt is often suitable even for those who tolerate milk poorly.
Kefir, sauerkraut or kimchi also contain live microorganisms, but their amount and types vary. Fibre from vegetables, legumes and wholegrain products is also important for gut bacteria.
How to read a probiotic label
| What to look for | What it means | What it means for you |
|---|---|---|
| Strain | The letters and numbers after the species name (e.g. I-3799). | Choose products that state the strain. |
| CFU | Colony-forming units – the amount of live microorganisms. | More is not necessarily better – what matters is the amount used in studies. |
| Storage | Some products need to be stored in the refrigerator. | If stored improperly, fewer live bacteria remain. |
| Prebiotics (FOS, XOS, inulin) | Fibres that bacteria feed on. | For some people they may cause bloating at first. |
Who should be cautious?
- People with a severely weakened immune system, those who are seriously ill or have a central venous catheter – cases of serious infections have been described, so take probiotics only if your doctor allows it.2
- Children and infants – consult a paediatrician.
- Pregnant and breastfeeding women – consult a doctor.
- People taking antibiotics – it is worth taking the probiotic and the antibiotic at different times. Discuss the timing with a pharmacist.
Mild side effects occur, such as bloating or gas.2 If diarrhoea is severe, lasts a long time, contains blood or is accompanied by a fever, see a doctor. A supplement is no substitute for a varied diet.4
Selected products with good bacteria
Commercial information. These are products available in our shop. This is not an effectiveness ranking. Before buying, check the composition and directions for use on the product page.
Saccharomyces Boulardii - 60 vcaps - NOW Foods
The yeast Saccharomyces boulardii (strain I-3799), 10 billion CFU per capsule. The manufacturer states to take it between meals.5
Lactobacillus Rhamnosus with FOS - Probiotics - 5 Billion - N60 - Swanson
Lactobacillus rhamnosus, 5 billion CFU, and 100 mg FOS per capsule. The strain is not stated on the label. Storage in the refrigerator is recommended.6
Acidophilus Two Billion - 100 vcaps - NOW Foods
Lactobacillus acidophilus (strain La-14), 2 billion CFU per capsule, with no additional ingredients.7
Probiotic-10 & Bifido Boost - 90 vcaps - NOW Foods
A blend of 10 strains, 25 billion CFU and 1 g of XOS prebiotics per serving (3 capsules). All strains are stated on the label.8
Frequently asked questions
Do probiotics need to be taken continuously?
Usually not. In studies, probiotics were generally taken for anywhere from a few days to a few weeks.2 Discuss the duration with a doctor or pharmacist.
What is the difference between probiotics and prebiotics?
Probiotics are live microorganisms, while prebiotics are fibres that gut bacteria feed on. They are found in onions, garlic, bananas and wholegrain products.
Does yoghurt replace a probiotic supplement?
Not always. Yoghurt is a beneficial food, but it may contain other strains and different amounts than the supplements that have been studied.
Scientific sources
- Hill C, Guarner F, Reid G et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11(8):506–514. doi:10.1038/nrgastro.2014.66
- Guo Q, Goldenberg JZ, Humphrey C et al. Probiotics for the prevention of pediatric antibiotic-associated diarrhea. Cochrane Database Syst Rev. 2019;4:CD004827. doi:10.1002/14651858.CD004827.pub5
- Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods (consolidated version). EUR-Lex
- Directive 2002/46/EC on the approximation of the laws of the Member States relating to food supplements. EUR-Lex
- NOW Foods. Saccharomyces Boulardii, 60 capsules. Product label.
- Swanson. Lactobacillus Rhamnosus with FOS, 60 capsules. Product label.
- NOW Foods. Acidophilus Two Billion, 100 capsules. Product label.
- NOW Foods. Probiotic-10 & Bifido Boost, 90 capsules. Product label.
Disclaimer. This article is for information purposes only and does not replace a consultation with a doctor or pharmacist. Food supplements are not intended to treat or prevent diseases and are not a substitute for a varied diet and a healthy lifestyle. Before taking supplements, especially during pregnancy or breastfeeding, if you have a chronic condition or if you are taking medicines, consult a healthcare professional.
