Why is kombucha so low in calories?

January 2, 2026 •

5 min read

A standard 8-ounce serving of kombucha typically contains only 30-50 calories. This surprisingly low-calorie count often raises questions, especially since sugar is a key ingredient used to start the fermented tea. The answer to why is kombucha so low in calories lies in the fascinating science of fermentation.

Quick Summary

Kombucha's low calorie content is a direct result of its fermentation process. A symbiotic culture of bacteria and yeast consumes most of the sugar, converting it into organic acids and carbon dioxide.

Key Points

SCOBY's Consumption: The primary reason for kombucha's low-calorie count is the SCOBY, which consumes most of the sugar during the fermentation process.
Sugar-to-Acid Conversion: The SCOBY's bacteria and yeast convert sugar into organic acids and carbon dioxide, significantly reducing the beverage's sweetness and calorie content.
Fermentation Time Matters: The longer kombucha ferments, the more sugar the SCOBY consumes, resulting in a lower calorie count and a tarter flavor.
Flavorings Increase Calories: Added ingredients like fruit juices or purees during the second fermentation will increase the final calorie and sugar content.
Healthier Than Alternatives: Kombucha serves as a significantly lower-calorie and lower-sugar alternative to many sodas and sweetened juices.
Residual Sugar is Intentional: The incomplete fermentation process leaves a small amount of residual sugar to balance the tangy flavor, preventing it from becoming overly acidic.

The Fermentation Process: How a SCOBY Works

At the heart of every batch of kombucha is the SCOBY, a Symbiotic Culture of Bacteria and Yeast. This living culture is the engine of the fermentation process, consuming the sugar that is added to brewed black or green tea. Without this vital ingredient, the entire process would fail. While homebrewers can choose various sugar sources like white, brown, or raw sugar, the SCOBY is non-discriminatory and will utilize whatever is provided, as long as it is fermentable.

The SCOBY's Role in Consuming Sugar

When the SCOBY is introduced to the sweetened tea, its yeast component goes to work first. The yeast consumes the sugar, primarily sucrose, breaking it down into glucose and fructose and converting it into alcohol and carbon dioxide. Then, the bacteria in the SCOBY take over. These acetobacter consume the alcohol and convert it into beneficial organic acids, most notably acetic acid. This two-step process is crucial for creating kombucha's distinct tangy flavor and is the primary reason for the low sugar and calorie count in the finished beverage.

The Sugar Transformation: From Sweet to Tangy

The initial brew is quite sweet, as it must contain enough sugar to feed the SCOBY. However, the longer the fermentation process continues, the more sugar is consumed and converted. A shorter fermentation might leave a sweeter, less tart flavor profile with more residual sugar, while a longer ferment will produce a tangier, more acidic drink with fewer remaining sugars and, therefore, fewer calories. This incomplete fermentation, where not all the sugar is converted, is what allows kombucha to remain a pleasant, palatable beverage rather than a fully alcoholic or vinegary one.

Factors Influencing Kombucha's Calorie Count

The final calorie count of a bottle of kombucha is not a fixed number and can be influenced by several factors. The duration of fermentation, the amount of sugar used at the start, and the addition of other ingredients after the initial fermentation (known as the second fermentation or F2) all play a role.

Common factors include:

Fermentation Duration: A longer fermentation period results in more sugar being consumed by the SCOBY, leading to a lower final calorie count.
Added Ingredients: Many commercial kombuchas add fruit juices, purees, or extra sugar during the second fermentation to enhance flavor. These additions will increase the total calories and sugar.
Sugar Type: Different types of sugar, such as white sugar versus fruit juice, can affect the speed and efficiency of the SCOBY's consumption, though the end result will still be low in calories due to the process.
SCOBY Health: A healthier, more robust SCOBY will ferment more efficiently, leading to a more consistent calorie reduction. A weak SCOBY might leave more sugar behind.

Kombucha vs. Other Popular Beverages

Comparing kombucha's nutritional profile to other common drinks highlights why it is often seen as a healthier alternative.


Beverage (approx. 8 oz / 240 ml)	Calories	Sugar (grams)	Notes
Kombucha	30-50	7-10	Varies by fermentation time and added flavorings.
Regular Soda	~150	~39	A 12oz can is often higher, around 150 calories and 39g sugar.
Fruit Juice	Varies, often >100	Varies, can be >20g	While natural, often high in sugar and calories without the fiber of whole fruit.
Sweetened Iced Tea	Varies, often >80	Varies, can be >20g	Many commercially sweetened teas are calorie and sugar-dense.
Flavored Sports Drink	Varies, often >50	Varies, can be >15g	Contains carbs for energy, but often higher in sugar than kombucha.

What About the Sugar That's Left?

Because kombucha is an incomplete fermentation, some sugar always remains. This residual sugar is what gives kombucha its characteristic flavor balance, preventing it from tasting like straight vinegar. For those concerned about sugar intake, choosing a longer-fermented kombucha or a less-sweet flavor can help. Homebrewers have complete control over this variable and can simply let the brew ferment for longer to achieve a lower sugar content. While the residual sugar contributes to the overall calorie count, the amount is minimal compared to the sugar-rich alternatives kombucha often replaces.

The Health Benefits of a Low-Calorie Fermented Drink

The low-calorie nature of kombucha is only one piece of its appeal. The beverage also offers several potential health benefits, largely due to the fermentation process and its probiotic content.

Probiotics for Gut Health: Kombucha is rich in beneficial bacteria, or probiotics, which can help balance the gut microbiome. A healthy gut is linked to improved digestion, enhanced nutrient absorption, and stronger immune function.
Source of Antioxidants: As a fermented tea, kombucha contains antioxidants that can neutralize free radicals in the body, potentially reducing inflammation and protecting against cellular damage.
Supports Hydration: Kombucha is an excellent way to stay hydrated, offering a flavorful and fizzy alternative to plain water without the high sugar content of most commercial sodas.
Aides Digestion: The organic acids and enzymes produced during fermentation may support digestive health by promoting a balanced gut environment and easing discomfort.
Potential Antimicrobial Properties: The acetic acid in kombucha has shown antimicrobial properties that can help inhibit the growth of harmful bacteria.

Conclusion: The Science Behind the Sip

In conclusion, the primary reason why kombucha is so low in calories is the metabolic action of the SCOBY during fermentation. The symbiotic culture consumes the majority of the added sugar, transforming it into organic acids and carbonation. This process leaves behind a tangy, naturally effervescent beverage with significantly fewer calories and less sugar than its unfermented counterparts, like sweetened tea or soda. While the exact calorie and sugar content can vary based on fermentation time and added flavorings, kombucha offers a refreshing and potentially beneficial alternative for those seeking a lower-calorie drink. Understanding this process demystifies the low-calorie nature of kombucha and highlights the powerful, natural magic of fermentation. To learn more about the science behind fermentation, explore informative resources like those on Kombucha Kamp, where experts discuss the intricate process in detail.

To discover the role of sugar in fermentation, explore expert resources like this FAQ from Kombucha Kamp: Does Kombucha really need sugar to make kombucha?.

Frequently Asked Questions

No, kombucha does not have a lot of sugar in its final form. Although sugar is a necessary ingredient to begin fermentation, the SCOBY consumes most of it during the process, resulting in a low-sugar beverage.

An average 8-ounce serving of kombucha typically contains between 30 and 50 calories. The exact amount depends on the brand, fermentation time, and any added flavorings.

No, you cannot make kombucha without sugar. Sugar is the essential food source that powers the fermentation process carried out by the SCOBY. Without it, the yeast and bacteria cannot thrive, and the kombucha will not ferment.

No, the calorie content varies. Factors like the duration of fermentation, the amount of initial sugar used, and whether flavorings or extra sugar were added during the second fermentation all influence the final calorie count.

Yes, fermentation is the key mechanism that reduces the calorie content. The SCOBY metabolizes the sugar, turning it into organic acids, thereby lowering the overall sugar and calorie load.

Some kombucha brands add extra sweeteners, like fruit juices or flavorings, after the initial fermentation to create a sweeter, more palatable product. This will increase the final sugar and calorie content compared to unsweetened varieties.

Kombucha is significantly lower in calories than soda. A typical 12-ounce can of soda can have around 150 calories, while a kombucha of the same size would be much lower, often around 45-75 calories, depending on the variety.

Residual sugar is the small amount of sugar that remains in the kombucha after fermentation is complete. It contributes to the flavor and is necessary to prevent the drink from tasting too acidic, as the fermentation process is incomplete.