Probiotics explained: what it is and side effects
Probiotics are live microorganisms, mostly bacteria and some yeasts, found in some fermented foods such as yogurt and sold as supplements. They are meant to benefit the body when eaten or applied to it and are added to some other foods. One of the products we reviewed lists probiotics, and its label prints an amount of 1 billion CFU per serving.
- Amounts the NIH names
- 1 to 10 billion CFU per dose in many supplements, and 50 billion CFU or more in some
- In the products we reviewed
- 1, its label prints the amount
What probiotics is
- Probiotics are mostly bacteria, and some are yeasts, found in some fermented foods such as yogurt, added to some other foods and sold as supplements.3
- Probiotics are live microorganisms meant to have health benefits when eaten or applied to the body.1
- The most common probiotics are bacteria from the groups Lactobacillus and Bifidobacterium, and other bacteria and yeasts such as Saccharomyces boulardii are used too.1
- Probiotics act mainly in the digestive tract, where they may improve how the digestive system works.2
- Each probiotic is named by its genus, species and strain, as in Lacticaseibacillus rhamnosus GG, where GG is the strain.2
- Many products hold members of the family Lactobacillaceae, which includes several species that were in the Lactobacillus genus until it was restructured in 2020.3
- Many labels list the colony-forming units (CFUs) in a serving, which show how many active microorganisms a product holds better than the total weight does.2
- The number of CFUs in a probiotic can fall over time, so the count when a product was made may not be what it holds when it is bought or used.2
- Some probiotics need to be kept in the refrigerator, and others can be stored at room temperature.2
Foods that have it1
- Yogurt
- Other fermented foods
Works with
- Prebiotics such as inulin. Prebiotics, such as inulin and other fructo-oligosaccharides, are complex carbohydrates that microorganisms in the gut use as fuel.3
Before you take it
Side effects
- In healthy people, probiotics may cause gas, but they rarely cause infections or other health problems.2
- Probiotics have a long history of apparently safe use, mostly in healthy people, but few studies have looked at their safety in detail, so little is known about how often side effects happen or how severe they are.1
- Possible harmful effects include infections, harmful substances made by the probiotic microorganisms, and antibiotic resistance genes passed to other microorganisms in the digestive tract.1
Ask a doctor first
- The risk of harmful effects from probiotics is greater in people with severe illnesses or weakened immune systems.1
- Severe or fatal infections have been reported in premature infants who were given probiotics, and the FDA has warned health care providers about this risk.1
- Some probiotic products have been reported to hold microorganisms other than those on the label, and these contaminants may sometimes pose serious health risks.1
- Talk with a health care provider before taking a probiotic supplement, especially if you have health problems.1
These statements have not been evaluated by the FDA. A supplement is not a medicine.
The product we reviewed that lists probiotics
| Product | Form and serving | Probiotics per serving | Our score | Price a bottle | Buy |
|---|---|---|---|---|---|
 VitaliSlim#4 in weight loss support | Capsules1 capsule | Not printedIn a blend | 9.2 | $49 | Check price |
Questions people ask
What are probiotics?
Probiotics are live microorganisms meant to benefit the body when eaten or applied to it. The NIH says they act mainly in the digestive tract, where they may improve how the digestive system works.
What foods have probiotics?
Yogurt and some other fermented foods contain probiotics. Probiotics are also added to some other foods.
How much probiotics are in a supplement?
Many probiotic supplements contain 1 to 10 billion CFU per dose, and some contain 50 billion CFU or more, according to the NIH. Colony-forming units, or CFUs, show how many active microorganisms a product holds better than total weight does. The CFU count can fall over time.
What are the side effects of probiotics?
Probiotics may cause gas in otherwise well people, but they rarely cause infections or other medical problems. The risk of harmful effects is greater in people with severe illnesses or weakened immune systems. Ask a clinician before starting a probiotic supplement, especially if you have medical concerns.
What's the difference between probiotics and prebiotics?
Probiotics are live microorganisms, while prebiotics are complex carbohydrates that microorganisms in the gut use as fuel. Inulin and other fructo-oligosaccharides are examples of prebiotics.
Which probiotic pills did we review, and how much do they contain?
VitaliSlim is the product we reviewed that lists probiotics. Its label prints 1 billion CFU per serving of 1 capsule.
Sources
The products, amounts and prices come from each product's label and checkout, as its review shows them. AI drafts our pages from listed sources, figures are checked against them, and we have not tried the products.
- 1NIH National Center for Complementary and Integrative Health, Probiotics: Usefulness and Safetynccih.nih.gov/healthchecked
- 2NIH Office of Dietary Supplements, Probiotics Fact Sheet for Consumersods.od.nih.gov/factsheetschecked
- 3NIH Office of Dietary Supplements, Probiotics Fact Sheet for Health Professionalsods.od.nih.gov/factsheetschecked