Do Lactic Acid Bacteria in Doburoku Really Reach the Gut? A Brewer Provides a Thorough Explanation with Scientific Evidence

Doburoku is sometimes described as "drinking yogurt."

Its milky white, viscous appearance and the refreshing sourness that spreads in your mouth the moment you taste it certainly make it a drink with many commonalities to yogurt.

However, not many people truly understand the "source of that sourness" or "why it's said to be good for the gut."

Especially recently, with the common dairy product slogan "lactic acid bacteria reach the gut alive," we at Craft Brews frequently receive questions like, "Do the lactic acid bacteria in Doburoku also reach the gut?"

In this article, we will honestly address whether Doburoku's lactic acid bacteria truly reach the gut and if gut health benefits can truly be expected, referencing materials from the National Tax Agency and public research data.

What is Doburoku? Its Official Classification under the National Tax Agency

First, let's clarify what kind of alcoholic beverage Doburoku is.

According to the National Tax Agency's "Classification and Definition of Alcoholic Beverages under the Liquor Tax Law," Doburoku is classified as "other brewed alcoholic beverages."

Specifically, it refers to alcoholic beverages made from rice, rice koji, and water, fermented and finished without filtering the mash, with an alcohol content of less than 20% and an extract content of 2% or more (from the National Tax Agency's "Sake Guide").

While sake (Japanese sake) is defined as "filtered mash," Doburoku's main characteristic is that by not filtering it, all components involved in fermentation, such as rice, rice koji, yeast, and lactic acid bacteria, remain in the liquid.

Is Doburoku's Sourness Truly Derived from Lactic Acid Bacteria?

In short, Yes.

In Doburoku brewing, natural lactic acid bacteria become active before or in parallel with yeast beginning alcohol fermentation.

Lactic acid bacteria break down rice-derived sugars to produce lactic acid, making the mash acidic. This suppresses the growth of unwanted bacteria and creates an optimal environment for yeast.

Traditional sake brewing methods like "Kimoto" and "Yamahai" intentionally incorporate the natural activity of these lactic acid bacteria, and their bacterial flora has been analyzed in detail through research by various breweries.

For example, research by Kiku-Masamune Sake Brewing has reported that in Kimoto brewing, lactic acid bacteria form the foundation for yeast proliferation and play a role in creating sourness and complex flavors.

The pleasant sourness of Doburoku is due to lactic acid fermentation, which is exactly the same as the sourness of yogurt.

While the raw materials differ (milk vs. rice), in terms of microbial activity, they are extremely closely related.

Reference: Ministry of Education, Culture, Sports, Science and Technology "Standard Tables of Food Composition in Japan (8th Edition) Supplement 2023" Food Composition Database

Main Topic: Do Doburoku's Lactic Acid Bacteria Truly "Reach the Gut Alive"?

This is the core of this article.

While it is widely known that "lactic acid bacteria are good for the gut," it's also true that their effects are often discussed under the premise that lactic acid bacteria "reach the gut alive."

So, what about Doburoku?

Challenge ①: The Barrier of Stomach Acid and Bile Acid

Lactic acid bacteria ingested orally must first pass through the formidable barrier of stomach acid.

The Japan Dairy Council also clearly states that "most lactic acid bacteria in yogurt are killed by stomach acid and bile acid," and that it is mainly strains guaranteed to be resistant in Foods for Specified Health Uses (FOSHU) or Foods with Function Claims that reach the gut alive.

Challenge ②: Doburoku's Own Alcohol Content

Furthermore, a specific characteristic of Doburoku is that the product itself contains alcohol.

In fact, it is known in sake brewing that as yeast ferments and alcohol concentration increases, lactic acid bacteria in the shubo (sake starter) gradually die off.

Research by the Nagano Prefectural General Industrial Technology Center also reports that many lactic acid bacteria cannot grow in environments with over 10% alcohol content.

This means that in finished Doburoku (with an alcohol content of 6-15%), most lactic acid bacteria are likely already weakened or dead.

Reference: Hiroshima University Press Release "Discovery of the effect of live plant lactic acid bacteria to alleviate alcohol intoxication symptoms" (2020)

Exception: High Resistance of Plant-Based Lactic Acid Bacteria

However, not all of them perish.

It has been reported in multiple studies that plant-based lactic acid bacteria found in rice-derived fermented products have higher resistance to stomach acid, bile acid, and alcohol compared to animal-based lactic acid bacteria (lactic acid bacteria in yogurt).

A presentation by Hiroshima University Graduate School of Biomedical & Health Sciences indicated the possibility that live cells of the plant lactic acid bacterium Lactobacillus plantarum SN13T can survive in an alcohol environment and improve disturbances in the gut microbiota (International Journal of Molecular Sciences, 2020).

Furthermore, in unpasteurized (nama) Doburoku, some yeast and lactic acid bacteria may remain alive.

The Concept of Postbiotics: Value in "Dead Lactic Acid Bacteria"

This is the most important point.

In recent gut microbiota research, the old notion that "only live bacteria are meaningful" is being overturned.

The new concept of postbiotics, proposed by international academic organizations (ISAPP), refers to "inactivated microbial cells or their components that confer a health benefit on the host."

Simply put, even dead lactic acid bacteria (inactive cells) have cellular components that serve as food for beneficial bacteria in the gut and moderately stimulate immune cells.

A fact repeatedly verified in current gut microbiota research, as pointed out by Russian researcher Metchnikoff over 100 years ago, is that "there is no significant difference in the efficacy of live and dead lactic acid bacteria."

This means that whether Doburoku's lactic acid bacteria are alive or dead, their cell components reach the gut and indeed serve as material to improve the gut environment.

"Non-Lactic Acid Bacteria" Gut-Health Components in Doburoku

In addition, Doburoku is rich in the following mash-derived components:

• Resistant proteins: Indigestible proteins that function similarly to dietary fiber, adsorbing and expelling fats.
• Oligosaccharides and rice-derived dietary fiber: Prebiotics that serve as food for beneficial bacteria.
• Enzymes and amino acids from rice koji: Aid in digestion and absorption.

Therefore, it is more accurate to view Doburoku not just as a source of lactic acid bacteria, but as a "comprehensive fermented food" that supports gut health from multiple angles.

Calories: An Honest Comparison with Shochu

Let's accurately examine the statement, "Doburoku has fewer calories than shochu."

Based on the Ministry of Education, Culture, Sports, Science and Technology's "Standard Tables of Food Composition in Japan (8th Edition) Supplement 2023" and various public data, the calorie content per 100ml is roughly as follows:

When comparing 100ml servings, Doburoku is clearly lower in calories than shochu, and roughly equivalent to sake.

However, there's an important caveat. Shochu is rarely consumed straight in 100ml portions; it's typically diluted with water or hot water.

On the other hand, Doburoku is often poured straight into a glass and consumed as is, so the calorie difference can narrow when comparing actual consumption amounts.

Please be honest with yourself that "low calorie per 100ml does not mean you won't gain weight."

Overdrinking Leads to Calorie Excess: Recommended Intake

While Doburoku offers gut-health benefits and the appeal of fermented foods, overdrinking will ultimately lead to excessive calorie intake.

The Ministry of Health, Labour and Welfare's "Healthy Japan 21" recommends an appropriate daily alcohol intake of approximately 20g for men and 10-13g for women in terms of pure alcohol.

Translated to Doburoku with 15% alcohol content, this is roughly 160ml for men (about 3-4 small sake cups).

Moreover, Doburoku has a mellow taste and sweetness, making it easy to drink too much. If you're consuming it for gut health, it's ideal to enjoy around 100ml slowly with a meal.

Summary: How to Enjoy "Doburoku" as a Craft Brew

Finally, let's summarize the key points:

• Doburoku is a fermented alcoholic beverage made from rice, rice koji, and water, classified under the Liquor Tax Law as "other brewed alcoholic beverages."
• Its sourness is indeed derived from lactic acid bacteria (lactic acid fermentation), following the same fermentation principle as yogurt.
• Whether lactic acid bacteria "reach the gut alive" depends on conditions. However, the effect of dead bacteria (postbiotics) on the gut environment is scientifically supported.
• It's also rich in gut-health components other than lactic acid bacteria, such as resistant proteins, oligosaccharides, and enzymes.
• While its calorie content per 100ml is lower than shochu, overconsumption can lead to excessive calorie intake, so caution is advised.
• A moderate intake is around 100-160ml per day.

As producers of Craft Brews, we want to convey that Doburoku is not just an "alcohol good for the gut," but the very essence of Japan's oldest fermentation culture, with the power of rice and microorganisms condensed into every drop.

Health benefits are predicated on "enjoying it in moderation."

Please try to savor it slowly with your meals.

References

• National Tax Agency "Sake Guide" Classification and Definition of Alcoholic Beverages under the Liquor Tax Law

• Ministry of Health, Labour and Welfare "Healthy Japan 21 (Second Term)" Guidelines for Appropriate Drinking
• Nagano Prefectural General Industrial Technology Center Research Report No. 15 "Evaluation of Lactic Acid Bacteria PP165 for Sake Brewing" (2020)
• Kiku-Masamune Sake Brewing Research Institute "Microbial Flora Analysis of Kimoto and Lactic Acid Bacteria Dynamics"
• International Scientific Association for Probiotics and Prebiotics (ISAPP) Statement on Postbiotics