Does Kefir Have Lactobacillus Reuteri? What You Need to Know

January 1, 2026 •

4 min read

According to a 2021 study, the microbiome of kefir can contain hundreds of bacterial and yeast species, but whether it contains Lactobacillus reuteri is not guaranteed. The presence of L. reuteri depends heavily on the specific kefir grains, the fermentation process, and whether it is a homemade or commercial product.

Quick Summary

The inclusion of Lactobacillus reuteri in kefir varies greatly depending on its origin, with homemade versions being highly variable and some commercial brands specifically adding it. Kefir contains a wide array of other beneficial microbes, offering broad probiotic support that differs from single-strain products.

Key Points

Source Matters: The presence of Lactobacillus reuteri in kefir depends on whether it's a homemade ferment or a commercially produced item with added specific strains.
Homemade Inconsistency: Traditional kefir made with grains has a highly diverse and variable microbial makeup, so L. reuteri is not a consistent component.
Commercial Specificity: Many store-bought kefir brands and specialty starter powders explicitly include L. reuteri in their formulations, which is listed on the label.
Unique Benefits: Specialized L. reuteri products, such as 36-hour fermented yogurts, are optimized to produce very high, therapeutic counts of this specific strain, yielding distinct health benefits.
Broad Spectrum Probiotics: Even without L. reuteri, general kefir provides a wide array of other beneficial bacteria and yeasts, supporting overall gut and immune health through its diverse microbial community.
Compatibility Issues: Adding L. reuteri to a traditional kefir ferment is not a reliable way to incorporate it, as the existing competitive culture can prevent the added strain from establishing.

The Variable Microbiome of Kefir

Kefir is a complex fermented beverage produced using kefir grains, which are a symbiotic culture of bacteria and yeasts (SCOBY). Unlike single-strain fermented products like certain yogurts, the microbial composition of kefir is diverse and can fluctuate significantly. The final bacterial makeup is influenced by several factors, including the geographical origin of the grains, the type of milk used, fermentation time, and temperature. For this reason, you can't assume that any given batch of kefir, particularly homemade versions, will contain Lactobacillus reuteri. The unpredictable nature of wild fermentation means that while L. reuteri might occasionally be present, it is not a consistent component.

Homemade vs. Commercial Kefir

When considering whether your kefir has Lactobacillus reuteri, it's critical to distinguish between homemade kefir made with traditional grains and commercially produced kefir. Homemade kefir is made from grains that can contain a wide variety of microorganisms, which makes the presence of specific strains like L. reuteri inconsistent. The microbial content is a reflection of the unique, diverse ecosystem within your kefir grains. Commercial kefir, however, offers more predictability.

Some commercial brands explicitly list Lactobacillus reuteri on their ingredient labels, meaning they've added this specific probiotic strain to their product. For example, a search of ingredients on certain commercial products confirms they include Lactobacillus reuteri as one of their listed cultures. Similarly, some ready-to-use kefir starter powders are specifically formulated with L. reuteri to ensure its presence in your homemade ferment. Therefore, if you are seeking a specific strain, checking the label of a store-bought product or purchasing a specialized starter culture is the most reliable method.

Other Probiotic Strains in Kefir

While L. reuteri is not a universal ingredient, kefir is a rich source of many other beneficial probiotic strains. The exact composition varies, but a comprehensive list of species found in milk kefir includes:

Lactobacillus Species: Lactobacillus kefiranofaciens, Lactobacillus kefiri, Lactobacillus plantarum, Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus acidophilus
Lactococcus Species: Lactococcus lactis
Streptococcus Species: Streptococcus thermophilus
Leuconostoc Species: Leuconostoc mesenteroides
Bifidobacterium Species: Bifidobacterium longum, Bifidobacterium breve
Yeasts: Saccharomyces florentinus, Saccharomyces cerevisiae, Candida kefyr

This broad spectrum of microorganisms is what provides kefir with its wide range of health benefits, such as improving digestion, fighting infections, and supporting the immune system. The synergistic relationship between the bacteria and yeasts within the kefir grains is a key feature of its potency.

Benefits of Lactobacillus reuteri vs. General Kefir Benefits

It's important to differentiate the unique benefits of consuming L. reuteri from the overall health advantages of drinking kefir. While there is some overlap, specialized L. reuteri products and kefir offer distinct advantages.


Aspect	Lactobacillus reuteri	General Kefir Benefits
Microbial Content	Often contains high, concentrated amounts of specific L. reuteri strains (e.g., DSM 17938 or ATCC PTA 6475).	Contains a broad, diverse, and variable mix of bacteria and yeasts.
Fermentation Process	Many high-dose L. reuteri products, such as specialty yogurts, are fermented for a specific, longer duration (e.g., 36 hours) under controlled conditions to maximize bacterial counts.	Traditional kefir fermentation is typically 12-48 hours and is a "wild" fermentation process, resulting in a more diverse and less predictable probiotic profile.
Key Mechanisms	Known to produce reuterin, an antimicrobial compound, and influence specific immune markers. Promotes beneficial hormones like oxytocin.	Produces a wide range of beneficial compounds, including organic acids, antimicrobial peptides (bacteriocins), and the polysaccharide kefiran.
Health Focus	Strong evidence for treating conditions like H. pylori, SIBO, and infant colic. Also linked to mood, skin health, and dental health.	Broad digestive support, immune system modulation, anti-inflammatory effects, and potential anti-cancer properties. Excellent source of calcium and other nutrients.

Can You Add Lactobacillus reuteri to Kefir?

Yes, it is possible, though the outcome is not predictable. Some fermentation hobbyists experiment with adding L. reuteri probiotic capsules to their kefir while fermenting, hoping to enrich the final product. However, kefir grains contain a very competitive and robust microbial community that may outcompete and overwhelm the added strains. The mixed culture nature of kefir means it may not create the ideal environment for the added L. reuteri to proliferate effectively and reach the high concentrations found in specialized L. reuteri yogurts. For consistent, high-dose L. reuteri counts, making a separate batch of yogurt specifically with a dedicated L. reuteri starter culture is more reliable.

Conclusion

In summary, whether kefir has Lactobacillus reuteri is not a simple yes or no answer; it depends on the source and production method. Most traditional homemade kefir is not guaranteed to contain L. reuteri due to the variable nature of its microbial composition. However, some commercial brands and specialized starter cultures are formulated with this specific probiotic, providing a reliable way to get it. Both general kefir and specialized L. reuteri products offer unique and complementary benefits for gut health and overall wellness, catering to different dietary needs and health goals.

Frequently Asked Questions

For general gut health and a wide variety of probiotic strains, regular kefir is excellent. If you are targeting specific health concerns that are addressed by L. reuteri (such as H. pylori or SIBO), a dedicated, high-dose L. reuteri yogurt is likely a more potent option.

Kefir grains are a reusable symbiotic culture of bacteria and yeast (SCOBY) that creates a diverse, unpredictable ferment. A direct-set starter is a single-use powder containing specific, measured strains, offering consistent results, but it cannot be reused indefinitely.

The most reliable way is to purchase a commercially prepared kefir that lists Lactobacillus reuteri as an ingredient or use a specific starter culture powder formulated with this strain to make your own.

Accurately testing your homemade kefir for specific strains would require microbiological analysis in a lab using techniques like PCR, which is not feasible for the average home fermenter. It is generally understood to have a variable composition.

Yes, L. reuteri can be found in some other fermented foods like sourdough bread, kimchi, sauerkraut, and pickles. It is also widely available as a probiotic supplement in capsule or liquid form.

In specialized high-dose L. reuteri yogurts, a longer fermentation time (e.g., 36 hours) at a specific temperature is critical for maximizing bacterial counts. In traditional kefir, the general fermentation time does not guarantee the presence or concentration of this specific strain.

L. reuteri is known for producing the antimicrobial compound reuterin and for its immune-modulating and anti-inflammatory properties. It has been extensively studied for its positive effects on gut health, skin, and mental wellness.