What is in probiotics and how do they work?

October 29, 2025 •

2 min read

According to a 2012 survey, probiotic or prebiotic use in adults quadrupled between 2007 and 2012. The ingredients found in probiotics, which are live microorganisms, vary widely and can include beneficial bacteria, yeasts, and food sources to help them thrive.

Quick Summary

This guide details the components found in probiotic products, such as specific bacterial strains and yeasts, the role of prebiotics, and other ingredients that ensure effectiveness and stability. It explores how these elements work together to support a healthy gut microbiome.

Key Points

Microbial diversity: The core of any probiotic is its live microorganisms, which can include bacteria like Lactobacillus and Bifidobacterium, as well as yeasts like Saccharomyces boulardii.
Strain specificity: The health benefits of probiotics are strain-specific, not just species-specific, so looking for products with clinically tested strains is important.
Role of prebiotics: Many probiotic products, especially synbiotics, also contain prebiotics—non-digestible fibers that act as food to help the beneficial microorganisms survive and multiply.
Formulation technology: Supplements use protective measures like encapsulation and cryoprotectants to ensure the live cultures can withstand manufacturing, storage, and stomach acid.
Dietary vs. supplement sources: Probiotics are found in fermented foods like yogurt and kimchi, but supplements offer a more concentrated and targeted dose of specific strains.

Core Ingredients in Probiotics

Probiotic products are defined by the live microorganisms they contain, which, when administered in adequate amounts, confer a health benefit to the host. While the most common ingredients are bacteria, probiotics can also contain yeasts. The specific strains, and their proper identification, are crucial for their targeted effect on health.

Beneficial Microorganisms

The most common bacteria in probiotics belong to the Lactobacillus and Bifidobacterium genera. Labels typically show the genus, species, and often a strain (e.g., Lactobacillus rhamnosus GG). Different strains within a species can have distinct effects.

Lactobacillus: Found in yogurt and fermented foods, strains like L. acidophilus, L. casei, and L. rhamnosus support digestive balance.
Bifidobacterium: Common in the large intestine and included in dairy and supplements. Strains like B. longum and B. breve may help with IBS symptoms and gut health.
Other Bacteria and Yeasts: Streptococcus thermophilus is used in yogurt production, while spore-forming Bacillus strains are known for stability. Saccharomyces boulardii is a probiotic yeast used for diarrhea, especially during antibiotic use.

Prebiotics and Other Additives

Probiotics often include prebiotics, non-digestible fibers that nourish beneficial bacteria, helping them grow in the gut. Synbiotic products combine probiotics and prebiotics.

Common prebiotics include FOS, GOS, inulin, and resistant starch. Additional ingredients like cryoprotectants and encapsulating agents protect the microorganisms during manufacturing, storage, and passage through the stomach.

Comparison of Probiotic Forms

Probiotics come in various forms, each with pros and cons:


Feature	Fermented Foods	Capsules/Powders	Synbiotic Products
Microbial Content	Variable strains and quantity, often lower CFU count	Targeted, high-concentration strains, precise CFU count	Combines specific strains with a food source (prebiotic)
Survival Rate	Viability can be inconsistent due to storage and processing	Often uses protective encapsulation for high survival rates	Prebiotic provides a protective matrix and nourishment for higher viability
Key Additional Ingredients	Naturally occurring prebiotics and nutrients	Stabilizers, cryoprotectants, prebiotics	Specific prebiotic fibers like FOS or inulin
Key Benefit	Adds a diverse mix of cultures and nutrients to diet	Delivers a consistent, targeted dose of specific strains	Boosts probiotic effectiveness by providing a built-in food source
Taste/Format	Found in foods like yogurt, kefir, and kimchi	Tasteless powders or easy-to-swallow capsules	Can be in powder, capsule, or fortified food format

How Probiotic Ingredients Work

Probiotics influence the gut microbiome by restoring balance and supporting health. Their mechanisms include:

Competitive Exclusion: Competing with pathogens for space and nutrients.
Producing Beneficial Compounds: Fermenting fibers into SCFAs that support gut lining health.
Immune System Modulation: Interacting with gut immune cells.
Enhancing the Gut Barrier: Strengthening the intestinal barrier.

Combining active microorganisms with nutrients like prebiotics helps probiotics survive and thrive, exerting positive effects.

Conclusion

Probiotics are complex formulations with specific live microorganisms like Lactobacillus, Bifidobacterium, and Saccharomyces boulardii. They often include prebiotics such as inulin or FOS to serve as a food source. Understanding these ingredients helps in choosing the right product for digestive health. Future research promises even more targeted formulations.

Frequently Asked Questions

Probiotics are the live, beneficial microorganisms, such as bacteria and yeast, that are consumed for health benefits. Prebiotics, on the other hand, are non-digestible fibers that act as a food source to help fuel and sustain these beneficial microbes.

No, probiotic strains are not the same. Even within the same species, different strains can have unique properties and effects on the body. This is why identifying a probiotic product by its full strain designation (e.g., Lactobacillus rhamnosus GG) is important for understanding its potential benefits.

A synbiotic product is a supplement or food that combines both probiotics (live microorganisms) and prebiotics (the food source for the microorganisms). This combination is designed to improve the survival and efficacy of the probiotic cultures.

Yes, many foods are natural sources of probiotics, especially fermented ones like yogurt, kefir, sauerkraut, and kimchi. However, the strains and concentration of microorganisms in foods can be variable compared to targeted supplements.

To identify a high-quality probiotic, look for products that list the full strain names, a specific CFU count, and an expiration date. Reputable brands often use protective encapsulation to ensure viability and may provide clinical research to back their claims.

Probiotics are named by their genus, species, and strain. The genus is the first name (e.g., Lactobacillus), the species is the second (e.g., acidophilus), and the strain is a specific designation (e.g., DDS-1) that indicates a unique subgroup with distinct properties.

Some probiotic strains are sensitive to heat and moisture, which can decrease their viability over time. Refrigeration helps to preserve the live cultures and ensure their potency until the product is consumed.