Water Kefir May Influence Gut Microbiome Composition, but More Research is Needed

What's new

A recent study investigated how consuming water kefir daily might affect the gut microbiome in healthy adults [1]. Traditionally, kefir is a fermented dairy product known for its potential to alter the gut microbiome and influence metabolic and gut health markers. This study focused on water kefir, a plant-based alternative, to see if it produced similar effects. The researchers observed some changes in the composition of gut bacteria after participants consumed water kefir for 14 days, specifically a decrease in Firmicutes bacteria and an increase in Actinobacteria and Bacteroidetes bacteria. However, no changes were noted in the overall diversity of the microbiome [1].

The science behind it

The study involved 40 healthy adults, aged 18 to 65, who did not have any known health conditions. Participants consumed 200 milliliters of water kefir every day for two weeks. This was a "before-and-after" study design, meaning researchers compared participants' gut microbiome profiles before and after the intervention, without a separate control group receiving a placebo or no intervention [1].

Water kefir is a fermented beverage made by combining water, sugar, and water kefir grains, which are a symbiotic culture of bacteria and yeasts (SCOBY). These microorganisms ferment the sugars, producing lactic acid, ethanol, and carbon dioxide, along with various beneficial compounds. The rationale for studying water kefir stems from the known effects of dairy kefir on gut health, with researchers hypothesizing that the plant-based version might also exert similar influences on the gut microbiota due to its microbial content [1].

The observed shifts in bacterial populations—a decrease in Firmicutes and increases in Actinobacteria and Bacteroidetes—suggest that water kefir could potentially modulate the gut environment. Firmicutes and Bacteroidetes are two of the most abundant phyla in the human gut, and their balance is often associated with various health outcomes. Actinobacteria, while less abundant, also play roles in gut health. However, the study did not find any changes in alpha-diversity, a measure of the variety of microbial species within an individual's gut, which is often considered a key indicator of a healthy and resilient microbiome [1].

What it means in practice

For individuals interested in supporting their gut health through dietary means, water kefir could be considered as part of a varied diet. The study's findings, while preliminary, suggest that regular consumption might lead to some alterations in the gut bacterial landscape. This could be of interest to those seeking plant-based fermented options, especially if they are avoiding dairy products. Given that traditional kefir has shown promise in influencing gut and metabolic health, water kefir might offer a similar avenue, though more robust research is needed to confirm this [1].

However, it's important to approach these findings with caution. The study's design, lacking a control group, means that any observed changes cannot be definitively attributed solely to water kefir consumption. Other factors, such as unmeasured dietary changes or daily variations in the microbiome, could have contributed to the results. Therefore, while intriguing, these results do not yet provide a strong basis for making definitive health recommendations [1].

Caveats

The primary limitation of this study is the absence of a control group [1]. Without a comparison group that did not consume water kefir, it's difficult to ascertain whether the observed changes in the gut microbiome were directly caused by the intervention or by other confounding factors. For instance, natural fluctuations in the gut microbiome can occur over time, and without a control, these cannot be ruled out. Additionally, the study did not standardize or measure the participants' diets, which is a significant oversight given the profound impact of diet on gut microbiota composition [1].

The study's small sample size (40 adults) and short duration (14 days) also limit the generalizability and long-term implications of the findings. Microbial changes can be transient, and a longer intervention period might reveal different or more sustained effects. Furthermore, while changes in bacterial populations were noted, the study did not investigate whether these shifts translated into any measurable health benefits or functional changes in the gut [1].

Future research, ideally a large randomized controlled trial with a placebo group and controlled dietary intake, would be necessary to provide stronger evidence regarding the effects of water kefir on the gut microbiome and, more importantly, on human health outcomes [1].

Source: [1] de Mel R, Al Khafaji AH, Muthusamy S, Xu J, Håkansson Å. Changes in gut microbiota composition following water kefir consumption in healthy adults. Sci Rep. 2026 May 22.