Large trials should be held to see if kombucha can help reduce blood sugar levels for people with Type 2 diabetes, scientists say.
The ancient fermented tea drink has grown in popularity in recent years due to a range of purported health and energy benefits, though evidence to support many of the claims is thin.
Kombucha’s basic ingredients are black tea, yeast and sugar.
A small “feasibility” study – designed to see if a bigger project is worthwhile – has now linked it to lower blood sugar levels.
Twelve people with Type 2 diabetes were involved, with half drinking eight ounces (236ml) of kombucha daily for four weeks and the others given a placebo drink.
Researchers then swapped what the groups consumed – with the placebo sample getting kombucha and vice versa.
The US-based scientists found that after a month the drink appeared to lower average fasting blood glucose levels, while those having a placebo showed no difference.
A larger project is now being called for to see if the results hold true over a bigger sample size.
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Author Professor Dan Merenstein, from Georgetown University School of Medicine in Washington DC, said: “Some laboratory and rodent studies of kombucha have shown promise and one small study in people without diabetes showed kombucha lowered blood sugar, but to our knowledge this is the first clinical trial examining effects of kombucha in people with diabetes.
“A lot more research needs to be done but this is very promising.
“A strength of our trial was that we didn’t tell people what to eat because we used a crossover design that limited the effects of any variability in a person’s diet.”
The study is published in the journal Frontiers in Nutrition.