News | Drinking kefir yogurt, can it really "regulate the gut"? The latest research offers a more cautious answer
In recent years, as a traditional fermented dairy product, kefir has been sought after globally for its "probiotic-rich" label, and is regarded by many consumers as a natural choice for improving gut health and enhancing immunity. However, a systematic review recently published in the international journal Nutrients points out that although kefir may alter the composition of certain microorganisms in the gut and oral cavity, its true health effects still lack consistent and robust scientific evidence.
This study, completed by multiple scientists, systematically reviewed published human studies, focusing on evaluating the effects of kefir intake on the human gut and oral microbiome. The results show that kefir may indeed cause changes in specific microbial niches, but due to generally small study sizes and considerable differences in study designs, its clinical significance remains to be further clarified.
From a traditional Caucasus beverage to a modern research subject
Kefir originated in the Caucasus mountain region and has a drinking history of more than 3,000 years. It is fermented from "kefir grains," which are complex symbiotic communities composed of lactic acid bacteria, acetic acid bacteria, and yeast, wrapped in a polysaccharide matrix. When the grains are added to milk, they trigger natural fermentation, gradually thickening the milk and producing a mildly sour flavor.
In addition to cow's milk, kefir can also be made from goat's milk, sheep's milk, or even soy milk. In industrial production, the grains are typically added to milk at a ratio of 1:30 to 1:50, fermented at room temperature for up to 24 hours, and then the grains are filtered out before drinking or refrigerated storage.
The researchers point out that a core challenge regarding kefir's health effects is its highly unstable composition. Factors such as the fermentation substrate, the source of the grains, fermentation time, and temperature can all significantly affect the types and proportions of microorganisms in the final beverage, as well as the bioactive metabolites they produce. This also means that the kefir products used in different studies are often not comparable.
Microorganisms in kefir: potential and differences coexist
The most predominant microbial group in kefir is lactic acid bacteria (LAB), including Lentilactobacillus kefiri, Leuconostoc mesenteroides, and Lactococcus lactis. These species produce lactic acid by breaking down lactose, and can also generate bacteriocins, hydrogen peroxide, and other substances that have inhibitory effects on certain intestinal pathogens.
Among them, L. kefiri and L. mesenteroides can survive passage through the gastrointestinal tract and adhere to the intestinal epithelium, and are considered to possess typical probiotic characteristics. Studies have also found that L. kefiri has the ability to bind heavy metals and mycotoxins, showing potential toxicological applications; while L. mesenteroides can produce linoleic acid, which may have anti-inflammatory, anti-atherosclerotic, and anti-cancer effects.
In addition, kefir contains various acetic acid bacteria, such as genera Acetobacter and Gluconobacter, whose metabolic production of acetic acid and related products is considered to help promote intestinal motility, improve colonic blood flow, and maintain intestinal epithelial homeostasis.
Yeasts are also an important component of kefir, including Saccharomyces cerevisiae and various Kluyveromyces species. These yeasts produce small amounts of ethanol and carbon dioxide, giving kefir its unique flavor and slight effervescence. Among them, the Saccharomyces boulardii variant of S. cerevisiae has shown antibacterial, anti-inflammatory, and antioxidant potential in multiple studies, and is considered possibly helpful in the management of irritable bowel syndrome and Crohn's disease.
Effects on gut and oral microorganisms: results are inconsistent
Regarding the gut microbiota, responses to kefir vary markedly among different populations. Some healthy adults showed only a slight, statistically non-significant increase in Lactococcus lactis after consumption; whereas patients with metabolic syndrome and inflammatory bowel disease (IBD) showed increased abundance of Actinobacteria and Lactobacillus, respectively.
In critically ill patients, although gut microbial diversity decreased, kefir intake still improved the "gut microbiota health index." Women with polycystic ovary syndrome (PCOS) showed a significant increase in the abundance of Bacilli after drinking kefir, along with marked improvements in physical and mental health scores compared to before the intervention.
It is worth noting that even when the increase in lactic acid bacteria was not significant, some metabolic syndrome studies still observed within-group improvements in fasting insulin, inflammatory factors (such as TNF-alpha and IFN-gamma), and blood pressure indicators, suggesting that microbial changes may be related to systemic health effects.
Regarding the oral microbiota, the evidence is even more limited. Only 4 studies to date have evaluated the effects of kefir on the oral flora, showing that it may reduce levels of Streptococcus mutans in saliva, a bacterium that is an important causative factor of dental caries in both adults and children.
However, the researchers emphasize that these studies all relied on traditional culture methods, which cannot fully reflect the overall structure of the oral microbiota, and did not use DNA sequencing technology. Therefore, the true impact of kefir on oral microbial diversity remains unknown.
Conclusion: potential exists, but evidence is still insufficient
Overall, existing research suggests that kefir may have some effects on the gut and oral microbiota, but the magnitude, consistency, and clinical significance of these effects remain highly uncertain. Differences in kefir products from various sources, inconsistent study designs, and small sample sizes all limit a clear determination of its long-term health effects.
The research team calls for future clinical studies with larger scale, more rigorous designs, and longer intervention periods, using standardized kefir products and modern sequencing technologies, to truly clarify the role of this traditional fermented beverage in human health.
Story source:
Collected from the internet
Author LinkedIVF TeamPublished 2025-12-17
This article used AI assistance; LinkedIVF has not recorded an editorial review for this item. It is not medical advice.
This content is for informational purposes only and does not constitute medical advice. Please consult a licensed physician. Content guidelines & editorial policy
News | Can Drinking Kefir Really Improve Gut Health? New Research Offers a More Cautious Answer
News | Drinking kefir yogurt, can it really "regulate the gut"? The latest research offers a more cautious answer
In recent years, as a traditional fermented dairy product, kefir has been sought after globally for its "probiotic-rich" label, and is regarded by many consumers as a natural choice for improving gut health and enhancing immunity. However, a systematic review recently published in the international journal Nutrients points out that although kefir may alter the composition of certain microorganisms in the gut and oral cavity, its true health effects still lack consistent and robust scientific evidence.
This study, completed by multiple scientists, systematically reviewed published human studies, focusing on evaluating the effects of kefir intake on the human gut and oral microbiome. The results show that kefir may indeed cause changes in specific microbial niches, but due to generally small study sizes and considerable differences in study designs, its clinical significance remains to be further clarified.
From a traditional Caucasus beverage to a modern research subject
Kefir originated in the Caucasus mountain region and has a drinking history of more than 3,000 years. It is fermented from "kefir grains," which are complex symbiotic communities composed of lactic acid bacteria, acetic acid bacteria, and yeast, wrapped in a polysaccharide matrix. When the grains are added to milk, they trigger natural fermentation, gradually thickening the milk and producing a mildly sour flavor.
In addition to cow's milk, kefir can also be made from goat's milk, sheep's milk, or even soy milk. In industrial production, the grains are typically added to milk at a ratio of 1:30 to 1:50, fermented at room temperature for up to 24 hours, and then the grains are filtered out before drinking or refrigerated storage.
The researchers point out that a core challenge regarding kefir's health effects is its highly unstable composition. Factors such as the fermentation substrate, the source of the grains, fermentation time, and temperature can all significantly affect the types and proportions of microorganisms in the final beverage, as well as the bioactive metabolites they produce. This also means that the kefir products used in different studies are often not comparable.
Microorganisms in kefir: potential and differences coexist
The most predominant microbial group in kefir is lactic acid bacteria (LAB), including Lentilactobacillus kefiri, Leuconostoc mesenteroides, and Lactococcus lactis. These species produce lactic acid by breaking down lactose, and can also generate bacteriocins, hydrogen peroxide, and other substances that have inhibitory effects on certain intestinal pathogens.
Among them, L. kefiri and L. mesenteroides can survive passage through the gastrointestinal tract and adhere to the intestinal epithelium, and are considered to possess typical probiotic characteristics. Studies have also found that L. kefiri has the ability to bind heavy metals and mycotoxins, showing potential toxicological applications; while L. mesenteroides can produce linoleic acid, which may have anti-inflammatory, anti-atherosclerotic, and anti-cancer effects.
In addition, kefir contains various acetic acid bacteria, such as genera Acetobacter and Gluconobacter, whose metabolic production of acetic acid and related products is considered to help promote intestinal motility, improve colonic blood flow, and maintain intestinal epithelial homeostasis.
Yeasts are also an important component of kefir, including Saccharomyces cerevisiae and various Kluyveromyces species. These yeasts produce small amounts of ethanol and carbon dioxide, giving kefir its unique flavor and slight effervescence. Among them, the Saccharomyces boulardii variant of S. cerevisiae has shown antibacterial, anti-inflammatory, and antioxidant potential in multiple studies, and is considered possibly helpful in the management of irritable bowel syndrome and Crohn's disease.
Effects on gut and oral microorganisms: results are inconsistent
Regarding the gut microbiota, responses to kefir vary markedly among different populations. Some healthy adults showed only a slight, statistically non-significant increase in Lactococcus lactis after consumption; whereas patients with metabolic syndrome and inflammatory bowel disease (IBD) showed increased abundance of Actinobacteria and Lactobacillus, respectively.
In critically ill patients, although gut microbial diversity decreased, kefir intake still improved the "gut microbiota health index." Women with polycystic ovary syndrome (PCOS) showed a significant increase in the abundance of Bacilli after drinking kefir, along with marked improvements in physical and mental health scores compared to before the intervention.
It is worth noting that even when the increase in lactic acid bacteria was not significant, some metabolic syndrome studies still observed within-group improvements in fasting insulin, inflammatory factors (such as TNF-alpha and IFN-gamma), and blood pressure indicators, suggesting that microbial changes may be related to systemic health effects.
Regarding the oral microbiota, the evidence is even more limited. Only 4 studies to date have evaluated the effects of kefir on the oral flora, showing that it may reduce levels of Streptococcus mutans in saliva, a bacterium that is an important causative factor of dental caries in both adults and children.
However, the researchers emphasize that these studies all relied on traditional culture methods, which cannot fully reflect the overall structure of the oral microbiota, and did not use DNA sequencing technology. Therefore, the true impact of kefir on oral microbial diversity remains unknown.
Conclusion: potential exists, but evidence is still insufficient
Overall, existing research suggests that kefir may have some effects on the gut and oral microbiota, but the magnitude, consistency, and clinical significance of these effects remain highly uncertain. Differences in kefir products from various sources, inconsistent study designs, and small sample sizes all limit a clear determination of its long-term health effects.
The research team calls for future clinical studies with larger scale, more rigorous designs, and longer intervention periods, using standardized kefir products and modern sequencing technologies, to truly clarify the role of this traditional fermented beverage in human health.
Story source:
Collected from the internet