Kombucha and keto diet

If you are on a keto diet or intermittent fasting and wonder if kombucha can take you out of ketosis or break your fast, the answer is depends on the residual sugar. Kombuchas with short fermentation contain more than 3 g of carbohydrates per 100 ml, which makes them incompatible. Mūn Kombucha varieties are between 0.1 and 1.8 g/100 ml, below the relevant threshold for maintaining ketosis.

What is the keto diet?

The keto (ketogenic) diet is a low-carbohydrate, high-fat eating plan. Its goal is to put the body into a metabolic state called ketosis, in which the body burns fat instead of carbohydrates for energy.

By drastically reducing carbohydrate intake —typically to a range of 20-50 g net carbohydrates per day— and increasing the consumption of healthy fats, the liver produces ketone bodies that serve as an alternative energy source for the brain and muscles. It is associated with weight loss, greater glycaemic stability, and sustained energy levels.

How much sugar can be consumed on keto?

There is no standard amount: it depends on individual tolerance. Most people following keto keep their daily net carbohydrate intake (total carbohydrates minus fibre) at 20-50 g. Achieving this figure means avoiding added sugars, soft drinks, sweets, and most juices, and obtaining carbohydrates mainly from non-starchy vegetables, nuts, and seeds.

Can kombucha be drunk on keto?

It depends on the kombucha. A typical refrigerated kombucha usually has 3 g or more of carbohydrates per 100 ml: a 330 ml bottle means about 10 g of sugar, almost a third of the daily keto allowance. There are even kombuchas with 5 g/100 ml that easily reach 16 g per bottle.

At Mūn Kombucha, we apply the traditional method with a long fermentation of up to 30 days. Yeasts and bacteria consume almost all the initial sugar and transform it into organic acids. All Mūn varieties are below 1.8 g of sugar per 100 ml — compatible with keto.

Sugar per Mūn variety

Here is the sugar content of the main varieties, ordered from lowest to highest:

The lowest carbohydrate varieties (Hibiscus, Not-Birra, Not-Birra Lemon) are the most suitable for strict keto. The rest are still perfectly compatible within the usual range of 20-50 g/day.

Kombucha and intermittent fasting

Intermittent fasting consists of alternating periods of fasting and eating. The most common variants are 16:8 (16 hours of fasting + 8-hour eating window) or the 5:2 format (two days a week with a single meal).

If the fast is not dry, it allows the intake of water, coffee, and infusions — which in principle do not break the fast or interfere with autophagy. The key issue with kombucha is the amount of residual sugar:

• A kombucha with 3-4 g of carbohydrates per 100 ml provides about 8-12 g of sugar per bottle: it activates sugar metabolism and breaks the fast.
• A kombucha below 2 g of carbohydrates per 100 ml (all Mūn varieties) provides less than 5 g per bottle: the glycaemic impact is minimal and allows most people to continue fasting.

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 body mass index. They underwent a crossover, randomised, placebo-controlled study (sparkling water), which examined the responses of the glycaemic index (GI) and insulin index (II) after a standardised high-carbohydrate meal, accompanied by three different beverages.

Carbohydrate metabolism, easier with kombucha

The results: consuming sparkling water or sugar-free soft drinks showed no statistically significant difference in glycaemia and insulin. When participants consumed kombucha, acute postprandial glycaemic and insulin responses were significantly reduced.

The mechanisms are not entirely clear. The study suggests that several processes could be involved: improvements in gut microbiota, islet beta-cell function, inhibition of inflammation and insulin resistance, and a reduction in intestinal barrier damage. Polyphenols, organic acids (acetic, gluconic), and live microorganisms in kombucha may contribute to slowing down the rate of digestion and carbohydrate absorption.

This is a study with a small sample, but the first in humans (until then, the effects had only been proven in animal models). The authors propose 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 kombuchas: 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.

Keto cramps and kombucha with electrolytes

Muscle cramps are a common complaint among people following a keto diet: the reduction in carbohydrates affects electrolyte levels (sodium, potassium, magnesium), which are essential for muscle function.

At Mūn, we produce a specific variety: Mūn Kombucha Isotonic, which combines kombucha with seawater (from the area between Ibiza and Formentera), rich in magnesium, potassium, and sodium. A natural option for electrolyte replenishment without added sugars.

OMAD, autophagy, and kombucha

OMAD (One Meal a Day) is a restrictive variant of intermittent fasting: a single meal a day, with a very short eating window. Combined with a keto diet, it seeks to maximise ketosis and fat burning.

Autophagy

The term autophagy derives from the Greek "self-eating". Periods of fasting, high-intensity exercise, and carbohydrate restriction activate a cellular recycling and cleaning 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.

Mūn Kombucha, due to its low residual sugar, can be a good alternative to soft drinks and low-alcohol beverages during periods of fasting or OMAD.

Frequently asked questions