What Are the Three Main Probiotics?

November 21, 2025 •

4 min read

According to the National Institutes of Health, the use of probiotics by adults quadrupled between 2007 and 2012, highlighting their growing popularity. Among the vast universe of microorganisms, the three main probiotics most frequently researched and used in supplements and fermented foods are Lactobacillus, Bifidobacterium, and the yeast Saccharomyces boulardii. These live, beneficial microbes are known for their distinct roles in promoting a healthy gut microbiome and supporting overall wellness.

Quick Summary

This article explores the three major groups of probiotics: Lactobacillus, Bifidobacterium, and Saccharomyces boulardii. It details their specific characteristics, common sources, and the health benefits they offer for digestive and immune system function.

Key Points

Lactobacillus: Known as lactic acid producers, these bacteria are found throughout the digestive and urogenital tracts and are common in yogurt and fermented foods.
Bifidobacterium: A dominant part of the large intestine's microbiome, these bacteria produce short-chain fatty acids from dietary fiber and are crucial for immune support.
Saccharomyces boulardii: A beneficial yeast with high resilience to stomach acid, this probiotic is highly effective for preventing and treating certain types of diarrhea.
Strain Specificity Matters: The health benefits of probiotics are often linked to specific strains (e.g., Lactobacillus rhamnosus GG), not just the general genus.
Diverse Intake is Key: For general health, consuming a variety of probiotic-rich foods, including fermented dairy and vegetables, helps support a more diverse gut microbiome.
CFU Count is Not Everything: The number of colony-forming units (CFUs) is less important than ensuring the microbes are viable and the dose is clinically validated for the intended benefit.
Supplements vs. Food: While food provides a natural source of live cultures, supplements often provide a higher, more targeted dose of specific, clinically studied strains.

The Three Pillars of Probiotic Health

Probiotics are living microorganisms that, when consumed in adequate amounts, confer a health benefit to the host, primarily by influencing the gut microbiota. While there are thousands of different probiotic species, most fall into a few major categories. For consumers, the most relevant and well-documented are the bacterial genera Lactobacillus and Bifidobacterium, along with the beneficial yeast Saccharomyces boulardii. Understanding the differences between these core groups can help you make more informed choices about supplements and probiotic-rich foods.

1. Lactobacillus: The Lactic Acid Producers

Lactobacillus is a diverse genus of bacteria, with many species playing a significant role in human health. These bacteria are particularly known for producing lactic acid, which helps to create a slightly acidic environment in the gut and vagina, inhibiting the growth of harmful bacteria. They are found naturally in the mouth, gut, and urogenital tract and are commonly used in the production of fermented dairy products.

Common Species and Benefits

Lactobacillus rhamnosus GG (LGG): One of the most widely researched strains, LGG is particularly effective for supporting the gut lining, immune balance, and helping to prevent antibiotic-associated diarrhea.
Lactobacillus acidophilus: A well-known probiotic often found in yogurt, it aids digestion and helps balance the microbiome in the gut.
Lacticaseibacillus casei: This species is known for its ability to aid with digestion and support the immune system.

Common Food Sources

Yogurt with live and active cultures
Kefir
Sauerkraut
Kimchi

2. Bifidobacterium: The Colon Colonizers

Bifidobacterium species are a dominant part of the healthy gut flora, especially in the large intestine. These bacteria ferment dietary fibers that we cannot digest, producing beneficial compounds called short-chain fatty acids (SCFAs), such as butyrate, which nourish the cells of the gut lining. Bifidobacterium is also known for its strong immune-modulating properties.

Common Species and Benefits

Bifidobacterium longum: This species is highly researched for promoting regular bowel movements and improving overall digestive comfort.
Bifidobacterium animalis lactis (BB-12): Often used in dairy products, this strain is well-studied for its ability to support immune system function and promote regularity.
Bifidobacterium infantis: Found in the guts of infants, this strain is important for establishing a healthy early-life microbiome.

Common Food Sources

Yogurt
Kefir
Certain aged cheeses like Gouda and aged cheddar

3. Saccharomyces boulardii: The Probiotic Yeast

Unlike Lactobacillus and Bifidobacterium, Saccharomyces boulardii is a beneficial, non-pathogenic yeast, not a bacterium. It is often praised for its resilience and ability to survive harsh stomach acids and bile, making it an excellent probiotic for specific issues like certain forms of diarrhea. It works by competing with pathogenic organisms and helping to reduce inflammation in the gut.

Common Benefits

Prevents Antibiotic-Associated Diarrhea: Studies show it is effective in helping prevent diarrhea caused by antibiotics.
Combats Traveler's Diarrhea: It has been shown to reduce the risk and duration of diarrhea for travelers.
Treats Clostridioides difficile infection: Often used alongside standard antibiotic treatment for C. difficile infections to help prevent recurrence.

Comparison of Main Probiotic Types


Feature	Lactobacillus	Bifidobacterium	Saccharomyces boulardii
Microbe Type	Bacteria	Bacteria	Yeast
Primary Location	Mouth, gut (small intestine), and urogenital tract	Gut (large intestine)	Intestines (transient)
Key Function	Produces lactic acid; maintains healthy pH	Ferments fiber into short-chain fatty acids; supports gut barrier	Competes with pathogens; reduces inflammation
Common Use	General digestive support, vaginal health, antibiotic-associated diarrhea	Digestive regularity, immune support, infant gut health	Specific forms of diarrhea (traveler's, antibiotic), C. difficile
Common Sources	Yogurt, kefir, fermented vegetables	Yogurt, kefir, some cheeses	Supplements; naturally in some fermented foods

How to Choose the Right Probiotic

Choosing the best probiotic for your needs depends on several factors. While these three main groups are excellent starting points, remember that probiotic benefits are often strain-specific, not just species-specific. A product should ideally list the full genus, species, and strain on the label (e.g., Lactobacillus rhamnosus GG). Consulting a healthcare provider is recommended, especially for specific health conditions. For general wellness, incorporating a variety of fermented foods from these different categories can help diversify your microbiome.

Conclusion: Your Gut Health Strategy

The gut microbiome is a complex ecosystem, and the three main probiotics—Lactobacillus, Bifidobacterium, and Saccharomyces boulardii—each offer unique benefits to support it. Whether you are aiming for better digestive regularity with Bifidobacterium, seeking immune support with Lactobacillus, or tackling specific issues like traveler's diarrhea with Saccharomyces boulardii, understanding these foundational probiotic types is key. Incorporating a balanced mix from both food sources and high-quality supplements can be an effective strategy for nurturing your gut and, by extension, your overall health. Always remember to prioritize strain specificity and product quality when making your selections. For more information, the National Institutes of Health provides useful resources on probiotic usefulness and safety.

Frequently Asked Questions

Lactobacillus typically resides in the small intestine and urogenital tract, producing lactic acid. Bifidobacterium is a major resident of the large intestine, where it ferments fiber into short-chain fatty acids.

Saccharomyces boulardii is a beneficial yeast, not a bacterium. This makes it particularly resistant to antibiotics and stomach acid, distinguishing it from most other probiotics.

You can get probiotics from fermented foods like yogurt, kefir, and sauerkraut. However, supplements often contain higher, more targeted doses of specific, clinically studied strains, which may be beneficial for addressing particular health issues.

To choose the right probiotic, identify your specific health goal (e.g., digestive regularity, immune support) and look for a product that clearly lists the full strain (genus, species, and alphanumeric designation) that has been clinically studied for that benefit.

Some probiotic strains are more effective when taken with food, while others may be better on an empty stomach. Always follow the specific instructions on the product label for the best results.

Not necessarily. A higher CFU count does not automatically guarantee greater effectiveness. What is more important is the viability of the specific strains and whether the dosage has been clinically validated for its intended benefit.

Good sources of Lactobacillus include yogurt and fermented vegetables like sauerkraut. Bifidobacterium is found in yogurt and some aged cheeses. Saccharomyces boulardii is primarily available in supplement form.