Drinks · ~50 kcal per cup (240 ml)
Does kombucha break a fast?
A 240 ml cup of kombucha has about 40 to 60 kcal and 7 to 12 g of sugar. It breaks most fasts and is a grey area for weight loss.
The answer for each goal
Weight loss
Grey areaAutophagy
Breaks fastGut rest
Breaks fastBlood sugar
Breaks fastKombucha is tea fermented with sugar, yeast and bacteria. The culture eats part of the sugar, and regular brands keep about 3 to 5 g per 100 ml. That makes about 40 to 60 kcal and 7 to 12 g of sugar in a 240 ml cup. A 355 to 473 ml bottle has about 50 to 120 kcal, and a large one can hold about 25 g of sugar.
On the site's own four goals, a cup is grey for weight loss, because it sits close to the 50-calorie rule of thumb. That rule is a rough guide that no health body has set. The sugar breaks a blood-sugar fast. Sugar and live cultures reaching the gut break gut rest, and the calories break autophagy.
Some low-sugar brands have about 4 kcal per 100 ml, so a 240 ml glass is about 10 kcal. Fermentation makes a little alcohol and can carry on in the bottle. In the US, kombucha that reaches 0.5% alcohol at any point is regulated as an alcoholic drink.
Watch out
Kombucha labels vary a lot, and the serving size may not be the whole bottle. Read the sugar and calories for the amount you will drink.
Questions people ask
Can I drink kombucha while fasting?
A small glass of a low-sugar brand is a grey area for weight loss. A full bottle of a regular brand adds about 50 to 120 kcal and breaks the fast for most goals. Drink it in your eating window if you fast for gut rest, autophagy or blood sugar.
Is kombucha good for your gut during a fast?
There is little human evidence either way. A 2019 review found only one study of kombucha in people. During a fast, its sugar and live cultures mean the database counts it as breaking gut rest.