The Popular Japanese Diet Ingredient: Kurozu ‘Black Vinegar’

Kurozu – Black Vinegar

Made from Fermented Rice

The ‘Kurozu Diet’ is one of the most popular diets in Japan

A diet based on consuming black vinegar called kurozu (koo-row-zoo) may sound strange and unknown in Western countries but is an effective, commonly used method of losing a few pounds for Japanese. Black vinegar supplements, salad dressing, and added vinegar to drinks is the method sworn by to see excess weight disappear. This black vinegar has been produced in the country and a part of the Japanese diet since before 300 BCE, or the Jomon Period. Rather than a condiment, it is more often used in ‘Kanpo’, or traditional Chinese medicine.

How is Japanese Black Vinegar made?

There are 3 ways:

  • Deep Fermentation Method (Aeration)

This method requires air pumped into a tank containing the raw materials in order to start the fermentation process. Within 24 hours, mass-production is efficiently achieved, however, the smell easily evaporates causing a bland taste resulting in a relatively low amount of nutrients.

  • Standing Fermentation Method (Surface-modified)

This method has the materials sit in still or slowly flowing liquid. This is the commonly utilized method for making black vinegar. An acetic acid bacterium membrane is formed on the surface, and fermentation and aging are done over a period of about 3-6 months. The scent is difficult to evaporate which allows the black vinegar to have a rich flavor and mellow acidity. The ripening of the materials causes the nutrients to condense and develops ‘umami’ flavor.

  • Traditional Method

The traditional method manufactures black vinegar in a special way called the “tortoise pot preparation”. Nowadays, vinegar making uses a metal container, but this way uses tortoise looking pots outdoors.
tortoise pot
The creation of black vinegar requires three steps: (1) saccharification (breakdown of starches into sugars) (2) alcohol fermentation and (3) acetic acid fermentation. With the tortoise pot method, these steps occur all at once. Microorganisms that promote fermentation are inside the pot and play an important role in the manufacturing process. Since this fermentation method requires at least 1 year, the nutrients, taste, and fragrance are condensed into high-grade quality.

What are the Benefits of Consuming Black Vinegar?

Extensive research is being done in Japan on the health benefits of Kurozu in the body. (click on the title to see more information about the research)


  • Extract of Kurozu has been found to inhibit the growth of all tested cancer cell lines, possibly through cell cycle arrest and apoptosis. The cancer cell lines included colon and breast adenocarcinoma and lung, bladder, and prostate carcinoma cells. These findings lead to the belief Kurozu can be used in cancer prevention in future treatments.


  • The anti-oxidative activity from acids isolated from Kurozu, suggesting that is is a more beneficial antioxidant food item compared to other kinds of rice vinegar. The research showed the vinegar to have strong radical scavenging activity, necessary to kill unstable molecules that cause cell damage linked to cancer and heart disease.


  • Another research study linked the anti-oxidation activity to the anti-tumor activity. The research tested Kurozu on mouse skin and showed to strongly inhibit lipid peroxidation. This shows the vinegar to be an effective strategy for preventing several lifestyle diseases.

Blood Pressure

  • The acetic acid within Kurozu is one of the main components in reducing blood pressure. The research conducted a long-term administration of the vinegar and found the vinegar does not only reduce blood pressure but also renin activity. It then suggests Kurozu to possibly be helpful if included in the diet to prevent hypertension.


  • One research study found the overall adipocyte size, or fat cell, in the subcutaneous and perirenal adipose tissues, significantly decreased among the test groups of rats given concentrated Kurozu. The rate of fatty acid excretion also increased, which are acids that help form healthy cell membranes, block some tumor and breast cancer cell formations, prevent blood clots, and more. The Kurozu-given group showed significant inhibition of fat accumulation and pancreatic lipase activity. This can be thought to be a very effective aspect of incorporating into the diet of someone who wants to lose weight and at risk for diseases caused by excess amount of fat tissue in the body.

Kurozu is all over Japan today and consumed by many people on a diet or wanting to improve their health. It is an ingredient hard to find in the western world and not commonly found in stores. Have you ever tried it?

*Avoid drinking large amounts of black vinegar, as it is a strong acid which may strain the stomach and stomach lining. It is recommended to dilute the vinegar or drink a small amount after a meal. Over-consumption of any particular food can bring about negative effects, so in the case of Kurozu, less is more.

additional sources:

黒田, 愛美. “黒酢の作り方・製造方法 | ヘルスケア大学”. ヘルスケア大学. N.p., 2016. Web. 21 Apr. 2017.

“黒酢の歴史 | 黒酢 | 株式会社えがお公式通販”. 株式会社えがお すべての人々に健康と笑顔を. Web. 21 Apr. 2017.

* The statements contained herein have not been evaluated by the Food and Drug Administration. The information contained in this website is intended for education, entertainment and information purposes only. This information is not intended to be used to diagnose, prescribe or replace proper medical care. The plant described herein is not intended to treat, cure, diagnose, mitigate or prevent any disease.