Water kefir benefits: 5 things the science actually says

6 min readBy our founder and head brewerLast reviewed

Water kefir benefits: 5 things the science actually says

The short answer

Water kefir is a fermented drink made with a diverse community of live bacteria and yeasts. Scientists around the world are researching it, and fermented foods more widely, with interesting early results from laboratory, animal and diet studies. But there are no clinical trials of water kefir in people yet, so it’s too early to say exactly what it does for health. Here are five things the science does tell us, with links to every source.

Search for “water kefir benefits” and you’ll find long lists of bold promises. We make water kefir and we love it, but we think you deserve the honest picture. We’ve read the research so you don’t have to: here’s what it says, where it’s still unclear, and where to read more.

1. Most of the sugar is transformed during fermentation

Water kefir starts as sugar water, but it doesn’t stay that way. In a study at Vrije Universiteit Brussel in Belgium, the sucrose (table sugar) in a water kefir ferment was completely broken down within the first 24 hours. The microbes turned it into simpler sugars, natural acids, carbon dioxide (the gentle fizz) and the gel that makes up the grains themselves (Laureys & De Vuyst, 2014).

That’s why water kefir tastes tangy rather than sugary. How much sugar is left in a finished drink depends on the recipe and how long it’s fermented, so check the label.

2. It contains a diverse community of live microbes

Water kefir grains aren’t grains at all. They’re living clusters of microbes. When the same Belgian researchers analysed a water kefir fermentation, they identified several species of lactic acid bacteria, acetic acid bacteria, bifidobacteria and yeasts. They found millions of live lactic acid bacteria and yeasts in every millilitre (Applied and Environmental Microbiology, 2014).

The exact mix varies with the grains, the ingredients, and the time and temperature of fermentation (International Journal of Food Microbiology, 2021). Because PiQi is raw and never pasteurised, the cultures in every bottle are alive.

3. Scientists are studying how fermented foods interact with the gut

This is the most active area of research, and the most often overstated, so here’s what’s actually been found:

  • A diet study in people (US): at Stanford University in 2021, 36 healthy adults increased either fibre or fermented foods (such as yoghurt, kefir, kombucha and fermented vegetables) for ten weeks. The fermented-food group ended up with a more varied mix of gut microbes and lower levels of some inflammation-related markers in their blood. It was small and short, and it tested a whole diet, not water kefir on its own (Stanford Medicine, 2021).
  • A laboratory gut model (Belgium and Switzerland): researchers added water kefir to a simulated colon using gut bacteria from three volunteers. They measured more short-chain fatty acids (compounds gut bacteria produce) and more bifidobacteria. They stress that the results “will require validation in clinical settings” (Nutrients, 2021; the study was funded by Nestlé).
  • Trials of milk kefir (international): most human kefir trials have used milk kefir. A 2025 analysis of seven trials found no significant overall difference in blood pressure or C-reactive protein (CRP, a blood marker of inflammation), though results varied with how long people drank it (Endocrinology, Diabetes & Metabolism, 2025). Milk kefir and water kefir are different drinks, so these results can’t simply be applied to water kefir.

An international panel of scientists from the International Scientific Association for Probiotics and Prebiotics (ISAPP) has also made an important distinction. “Fermented food” describes how a food is made. “Probiotic” is reserved for specific live microbes that have been shown in studies to provide a health benefit (ISAPP consensus statement, 2021).

4. Fermentation creates natural acids and compounds researchers are investigating

As water kefir ferments, its microbes produce organic acids and other compounds. A 2024 review from Democritus University of Thrace in Greece gathered studies on these compounds and the microbes that make them. The studies reported antioxidant and anti-inflammatory activity in laboratory and animal studies, and in one lab study, fig-based water kefir showed higher antioxidant activity than versions made with sugar alone (AIMS Microbiology, 2024).

The authors are careful to say that because each study used different grains and conditions, you can’t conclude that any particular water kefir has all these properties, and that more research is needed. A second 2024 review reached the same conclusion: clinical studies in people are still needed (Heliyon, 2024).

5. It suits dairy-free and vegan diets

This one’s simple. Water kefir is made with water, not milk, so it’s naturally dairy-free and lactose-free. PiQi is certified vegan and organic. Four of our five flavours are caffeine-free; Matcha & Mint contains caffeine from the matcha. Natural fermentation leaves PiQi at under 0.5% ABV.

What isn’t proven yet

You’ll see water kefir credited online with everything from clearer skin and weight loss to stronger immunity and “detox”. There isn’t reliable evidence from studies in people for any of these. The UK’s leading health bodies are cautious too:

  • The NHS says there’s some evidence that probiotics may help in some specific cases, but little evidence to support many of the health claims made for them.
  • The British Dietetic Association notes that kefir and kombucha may contain beneficial microorganisms. It doesn’t yet class them as probiotics, because there isn’t enough scientific evidence about their health effects.

Why we don’t make health claims

In the UK, food brands can only make health claims that have been officially approved, and none have been approved for live cultures yet. So we won’t promise that PiQi will do anything for your health. Instead, we’ll share the research honestly and let you read it for yourself.

Good to know

If you have a health condition or a weakened immune system, or you’re pregnant, check with your GP before adding fermented foods or drinks to your diet. Read our guide to fermented drinks in pregnancy.

Sources and further reading

Why we love it anyway

We drink water kefir because it’s delicious: lightly sparkling, gently tangy and endlessly versatile. Ours is organic, vegan, raw and hand-brewed in small batches in Devon, with organic figs in every first ferment. Read what water kefir is, learn how to make it at home, or try our organic water kefir.

Keep reading

All articles