It depends on the residual sugar. A kombucha with more than 2 g of carbohydrates per 100 ml activates sugar metabolism and breaks the fast. Mūn Kombucha varieties are between 0.1 and 1.8 g/100 ml: the glycaemic impact is minimal and allows most people to continue intermittent fasting.
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Open sugar calculator →What is intermittent fasting?
Intermittent fasting consists of alternating periods of fasting and periods of eating. The most common practices are:
- 12:12 — 12 hours of fasting + 12 hours of eating window (the mildest).
- 16:8 — 16 hours of fasting + 8 hours of window (the most popular).
- 18:6 and 20:4 — more restrictive variants.
- OMAD (One Meal a Day) — one meal a day (~23:1).
- 5:2 — two days a week only one meal is consumed daily.
- Prolonged fasts of 24, 48 or 72 hours, usually with supervision.
Its documented benefits are associated with the activation of metabolic switching: when cells deplete glucose reserves, they begin to use fats as an energy source. Studies point to improvements in glycaemic regulation, resistance to oxidative stress, and reduction of inflammation. Dr. Mark Mattson, a neuroscientist at Johns Hopkins, published in The New England Journal of Medicine that intermittent fasting "may become another healthy habit in people's lives".
Does kombucha break a fast?
Infusions (water, black coffee, unsweetened tea) do not break a fast or interfere with autophagy. Kombucha is fermented tea, but with an important nuance: for it to ferment, sugar is needed as fuel for the yeasts and bacteria of the SCOBY. The key question is how much sugar remains in the final product:
- Kombuchas with fast fermentation (10-14 days) usually contain 3-5 g or more of sugar per 100 ml: a 250 ml bottle provides between 8 and 12 g of sugar. They activate sugar metabolism and break the fast.
- Kombuchas with long fermentation, such as Mūn Kombucha (30 days), have between 0.1 and 1.8 g of sugar per 100 ml. The glycaemic impact is minimal and allows fasting to continue.
Practical rule: if kombucha has less than 2 g of carbohydrates per 100 ml, the impact on fasting is negligible. All Mūn varieties meet this criterion. Exact comparison by variety.
Sugar per Mūn variety
Table with the sugar content of the main varieties:
| Variety | Sugar (g/100 ml) | Per 250 ml bottle |
|---|---|---|
| Hibiscus | 0,10 | 0,25 g |
| Not-Birra Lemon | 0,16 | 0,40 g |
| Not-Birra | 0,20 | 0,50 g |
| Verbena | 0,50 | 1,25 g |
| Isotonic | 0,60 | 1,50 g |
| Ginger | 1,60 | 4,00 g |
| Natural | 1,80 | 4,50 g |
For strict fasts, the Hibiscus, Not-Birra, and Not-Birra Lemon varieties are the most suitable (all below 0.2 g/100 ml).
What science says: kombucha and glycaemia
A study by the Glycaemic Index Research Service at the University of Sydney involved 11 healthy adults with normal glucose tolerance and normal BMI. They underwent a crossover, randomised, placebo-controlled study (sparkling water) that examined the responses of the glycaemic index (GI) and insulin index (II) after a standardised high-carbohydrate meal, accompanied by three drinks: sparkling water, diet lemonade soft drink, and unpasteurised kombucha.
Results: kombucha and glycaemic response
With sparkling water or sugar-free soft drink, there was no significant difference in glycaemia and insulin. With kombucha, acute postprandial glycaemic and insulin responses were significantly reduced.
The mechanisms are not entirely clear. The study suggests that several processes may be involved: improvements in gut microbiota, islet beta-cell function, inhibition of inflammation and insulin resistance, and reduction of damage to the intestinal barrier. Polyphenols, organic acids (acetic, gluconic), and live microorganisms in kombucha may slow down the rate of digestion and carbohydrate absorption.
It is a small sample study, but it is the first in humans (until then, effects had only been observed in animal models). The authors suggest expanding the research with larger samples and different populations.
Not all kombuchas are the same
The authors also point out that the results cannot be extrapolated to all kombucha: the tea used, the species of bacteria and yeasts in the starter culture, and the fermentation conditions vary. A kombucha with a lot of residual sugar will not produce the same effects.
OMAD, autophagy and kombucha
OMAD (One Meal a Day)
OMAD is a restrictive variant of intermittent fasting: a single meal a day, with a very short eating window. Combined with a low-carbohydrate or keto diet, it seeks to maximise ketosis and the effect on insulin sensitivity. Compatibility with kombucha follows the same principle: only kombuchas with very low residual sugar.
Autophagy
The term autophagy derives from the Greek "self-eating". Periods of fasting, high-intensity exercise, and carbohydrate restriction activate a cellular recycling mechanism: cells degrade disused components to regenerate themselves. The Japanese Yoshinori Ohsumi won the Nobel Prize in Medicine in 2016 for his research on this process.
Autophagy is one of the mechanisms by which intermittent fasting is associated with benefits for cellular health and longevity.
Practical tips for drinking kombucha during fasting
- Check the label. Before buying, check carbohydrates per 100 ml. If it exceeds 2 g, it's better for outside the fasting window.
- Start with low-carbohydrate Mūn. Hibiscus, Not-Birra, or Verbena are the best options for strict fasting.
- Hydrate with water first. Kombucha complements, it does not replace water during fasting.
- Serve cold. It improves flavour and the feeling of satiety.
- One bottle is enough. You don't need more than 250 ml to complement your fast.
- Consult a professional if you have any medical condition or are taking medication.
Frequently asked questions
Does kombucha break a fast?
It depends on the residual sugar. A kombucha with 3-4 g of carbohydrates per 100 ml provides about 8-12 g of sugar per bottle and breaks the fast. A kombucha below 2 g (like all Mūn varieties) has a minimal impact and allows most people to continue fasting.
Which is the best Mūn variety for intermittent fasting?
Hibiscus (0.10 g/100 ml), Not-Birra Lemon (0.16 g/100 ml), and Not-Birra (0.20 g/100 ml) are the lowest in carbohydrates and the most suitable for strict fasting.
Does kombucha activate fasting?
Not directly. Fasting is activated by the absence of significant calories. Kombucha with very low sugar (like Mūn) provides few calories and does not interfere; kombuchas with a lot of sugar do break the fast.
What about autophagy? Does kombucha interrupt it?
Autophagy is activated after several hours of fasting and is maintained as long as there is no significant caloric intake. Kombuchas with very low sugar (like Mūn, 0.1-1.8 g/100 ml) provide few calories and are unlikely to interrupt it during typical 16-20 hour fasts.
How much kombucha can I drink during my fasting window?
250-500 ml throughout the window, without replacing water. It is enough to complement hydration without affecting the fasting state.
Can I drink kombucha during long fasts (48-72h)?
For prolonged fasts, it is advisable to consult a professional. In these cases, water, pure infusions, and broths are usually recommended. If kombucha is included, choose varieties with the least sugar (below 0.5 g/100 ml).
Does kombucha on an empty stomach improve digestion?
Live probiotics and organic acids can contribute to the balance of the gut microbiota. Starting the day with kombucha on an empty stomach is a common practice among those who consume it regularly.
Is intermittent fasting the same as the keto diet?
No, they are distinct but compatible approaches. Intermittent fasting regulates when you eat; the keto diet regulates what you eat (minimum carbohydrates). Mūn Kombucha is compatible with both. More on kombucha and keto diet.
Delve deeper into each topic
Compatible with your fast
Mūn Kombucha: all varieties below 1.8 g of sugar per 100 ml. Hibiscus and Not-Birra, below 0.2 g/100 ml. Since 2015.
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