When Polish researchers at the Wrocław University of Environmental and Life Sciences and Wroclaw Medical University set out to settle a small, unglamorous question about kombucha, they expected differences between tea types. What they did not expect was how dramatic those differences would be. In a study published in Food Chemistry in April 2026, the team brewed kombucha from five different teas under identical, tightly controlled conditions: black, green, white, oolong, and pu-erh. The kombuchas made from green tea and oolong tea showed antioxidant activity strong enough to leave the other three, including the black-tea brew that dominates grocery store shelves, well behind [1][2].

The result matters because kombucha has spent the last decade graduating from fringe tonic to a multi-billion-dollar beverage category, and most of what is sold commercially is brewed from black or green tea. If the choice of base tea is quietly steering the chemistry, and the antioxidant punch, of every bottle on the shelf, drinkers and home brewers are being asked to make a more consequential decision than they probably realize.

What the study actually did

The Wrocław team, led by Akshay K. Chandran with senior authors Helena Moreira, Anna Szyjka, Ewa Barg, and Joanna Kolniak-Ostek, ran a five-way comparison under conditions designed to isolate the tea as the only meaningful variable. Same SCOBY (a symbiotic culture of bacteria and yeast, the rubbery disc that ferments the tea), same sugar dose, same fermentation temperature, same 7-to-14-day window. Five teas in, five finished kombuchas out [1].

What they measured was unusually comprehensive. Using chromatographic techniques and mass spectrometry, the team tracked hundreds of chemical compounds across each brew, comparing volatile aromatic profiles, polyphenol content, and antioxidant activity (the ability of a substance to neutralise free radicals, the unstable molecules linked to cell damage) in parallel [1][3].

Why the tea acts as a 'matrix'

The word the authors reach for is matrix, and it is the right one. Tea is not just a flavour carrier for kombucha; it is the substrate that shapes how the SCOBY ferments. Green and oolong teas bring high levels of catechins (a class of polyphenols with strong antioxidant activity) and smaller, more reactive polyphenols to the brew. Black tea carries theaflavins and thearubigins, larger, oxidised polyphenols that give black tea its colour and body. Pu-erh and white tea sit further along the oxidation and ageing spectrum, with their own distinct profiles [1][4].

When the SCOBY gets to work, microbial enzymes break some of those larger polyphenols down into smaller, more bioavailable molecules. Other compounds disappear entirely. New ones, including floral and fruity aroma compounds like linalool and 2-phenylethanol, appear where they were not present in the original tea. The end result is a beverage whose chemistry bears only a family resemblance to its starting leaf [1][3][4].

In the Wrocław study, green and oolong teas produced kombuchas with the highest antioxidant activity and the strongest free-radical neutralising ability. Black, white, and pu-erh kombuchas lagged behind, sometimes by a wide margin [1][2][3].

The counterweight the article has to acknowledge

Antioxidant activity in a laboratory assay is not the same thing as a health benefit in a person. The Wrocław authors are clear about this. A 2019 systematic review by Kapp and Sumner in Complementary Therapies in Medicine looked specifically at human-subject studies on kombucha and concluded that the empirical evidence for clinical health benefits is thin. Most positive findings come from test-tube or animal models, which do not reliably predict human outcomes [7].

Registered dietitians at major US hospitals echo the same caveat. Maxine Smith, RD, at the Cleveland Clinic put it bluntly: "There aren't a lot of good quality, robust studies to support a lot of kombucha's hype" [6]. That is not a reason to ignore the Wrocław study. It is a reason to frame it correctly. Stronger in-vitro antioxidant activity is a real, measurable, reproducible finding. It is the necessary first step, not the final word, on whether kombucha is good for you.

Earlier studies sometimes reached different conclusions. A 2023 Food Chemistry paper cited by Healthline found black-tea kombucha had antioxidant activity comparable to or higher than green-tea kombucha, especially at longer fermentation times [5]. The Wrocław team's response, judging by the design of their study, was to standardise conditions across five teas at once and use more detailed compound-level analysis. The newer, more controlled study is the more reliable one to lean on, but the older literature is not wrong so much as narrower.

What this means if you are buying kombucha

Most commercial kombucha is brewed from black or green tea, and on the basis of the Wrocław study, green- and oolong-based brews are the ones most likely to deliver the strongest antioxidant profile. That does not mean black-tea kombucha is bad. It means the same shelf is not full of equivalent products.

A few practical signals to look for on a label:

  • Tea type: green or oolong is preferable to black if you care about antioxidant content. Pu-erh and white teas are interesting but the evidence for them is thinner.
  • Fermentation length: 7 to 14 days is the typical kombucha fermentation window. Shorter ferments taste sweeter; longer ferments taste tarter and more vinegar-forward, and the polyphenol profile continues to shift.
  • Added sugar: kombucha ferments sugar into organic acids, but residual sugar varies a lot between brands. Lower-sugar options exist for those tracking intake.
  • Storage: some commercial kombuchas are pasteurised, which kills the live cultures. Raw, refrigerated kombucha keeps the SCOBY-derived compounds (and the small amount of live bacteria) intact.

Commercial kombucha typically sits below 0.5% alcohol by volume, low enough to be sold as a non-alcoholic beverage in most markets, but worth knowing if you are avoiding alcohol entirely [6].

What this means if you are brewing at home

For home brewers, the lever is straightforward. If your standard recipe calls for black tea, swap it for green or oolong, or a blend weighted toward them, and you are likely to nudge the antioxidant content of every batch upward on the basis of this study. Oolong sits at an interesting midpoint, with a more complex flavour than green tea and a polyphenol profile that the Wrocław study found performs particularly well.

A few caveats that apply specifically to home brewing. Fermentation length still matters: the longer you ferment, the more the polyphenol profile shifts, and the more the flavour moves from sweet-sour to vinegar-forward. Temperature, SCOBY health, and sugar source all also influence the outcome. And the FDA has, in the past, warned about home-brewing in unsanitary conditions, particularly for immunocompromised drinkers. Clean equipment, fresh starter liquid, and a reliable pH check at the end are not optional.

The bigger picture

Kombucha is unusual among functional beverages in that the raw ingredient list is short and the variation in finished product is enormous. Tea type, tea quality, SCOBY composition, sugar source, fermentation time, fermentation temperature, and storage all matter. The Wrocław study isolates one of those variables, the tea, and shows that it matters more than most commercial branding suggests.

That is genuinely useful information. It is also, as the Wrocław authors and the systematic reviewers both stress, only one layer of the story. The next layer, whether these in-vitro antioxidant differences translate into measurable human-health outcomes, has not been answered yet. For now, the practical takeaway is a small, evidence-based adjustment: if you drink kombucha and care about what is in it, the tea on the label is worth reading.