Black vinegar, known in Japan as kurozu, is a rice vinegar with a long history as a traditional fermented food. Brands abroad ask for it because the story is strong — a centuries-old Japanese ferment, a dark colour, a tangy taste — and because acetic acid, the acid common to all vinegar, has actual human trial data behind it.
This guide is for brand owners planning a black vinegar or acetic acid product made in Japan. It covers what the human trials show, how Japanese products frame the ingredient, the drink-versus-capsule decision, and what to fix before asking for a quotation.
Health supplements are foods, not medicines, and are not a substitute for medical treatment. Nothing here is a claim that any product prevents, treats or cures a disease.
💬 Planning a black vinegar product made in Japan? We check the full formula against Japanese food law first. See Japan-made supplement OEM.
What the research shows
A 12-week placebo-controlled trial in obese Japanese adults found lower body weight, BMI, visceral fat area and waist circumference with daily vinegar intake, while a smaller kurozu-specific trial found a more modest, largely female-only effect.
| Study | Design | Reported result |
|---|---|---|
| Randomised, double-blind, placebo-controlled trial, Bioscience, Biotechnology, and Biochemistry 2009, 73(8):1837–1843 (doi 10.1271/bbb.90231) | Obese Japanese subjects, 12 weeks, daily drink with 15 ml vinegar (750 mg acetic acid), 30 ml vinegar (1,500 mg acetic acid), or placebo | Body weight, BMI, visceral fat area, waist circumference and serum triglycerides were significantly lower in both vinegar groups than placebo |
| Randomised, double-blind, placebo-controlled trial, Functional Foods in Health and Disease 2013, 3(8):310–322 (doi 10.31989/ffhd.v3i8.45) | 48 obese Japanese adults (28 men, 20 women), 12 weeks, kurozu concentrate supplement (870 mg/day, 480 mg/day as kurozu concentrate) or placebo | Body weight was significantly lower and BMI nearly significantly lower in the kurozu group than placebo; fat area on abdominal CT scans increased less in the kurozu group than placebo, an effect driven mainly by female participants; the authors called the results not definitive |
Three points to keep in view:
- The two trials are not interchangeable. The 2009 trial used plain vinegar drinks dosed by acetic acid content. The 2013 trial used a kurozu-specific concentrate; its 480 mg daily figure is the amount of kurozu concentrate, not of acetic acid, so the two doses cannot be compared directly. Match your claim to the study behind your specific material.
- Population. Both trials were run in obese Japanese adults, not a general healthy population.
- Size and sex. The kurozu-specific trial is small, and its authors described the benefit as concentrated in female participants and the overall result as not definitive.
- Author affiliation. The authors of the 2009 vinegar trial worked at the research institute of a food manufacturer.
Checked against the published abstracts on 12 October 2026.
What Japanese products say
Acetic acid is a recognised functional ingredient in Japan’s Foods with Function Claims system, notified for reducing visceral fat in people with a tendency toward obesity.
Under this system, the business that notifies a product is responsible for the scientific evidence behind the stated function, and submits it to the Consumer Affairs Agency before sale. Vinegar drinks notified this way typically state the acetic acid content per serving and describe an everyday-tendency function, not a medical outcome.
Two lessons for a brand abroad:
- The Japanese wording stays narrow. It refers to visceral fat in people with an obesity tendency, tied to a stated acetic acid amount — not to weight loss in general or to any disease.
- A Japanese notification is not a global endorsement. It is a Japanese regulatory mechanism for products sold in Japan. Your label abroad follows your own market’s rules.
💬 Need an evidence summary for your regulatory adviser that separates the two trials and matches your exact dose? We prepare it with the manufacturing documents. Tell us your market.
Wording that stays on safe ground
Describe black vinegar by the acetic acid amount and the trial population it was studied in, not as a general weight-loss product.
| Safer wording | Wording to avoid |
|---|---|
| ”Contains [X] mg acetic acid per serving, studied in obese adults over 12 weeks" | "Burns fat” or “melts belly fat" |
| "Studied for body weight and visceral fat markers” | Naming obesity as a disease being treated |
| Citing the specific trial and its population | ”Clinically proven” without naming the study and its limits |
How black vinegar is formulated
Vinegar’s sharp acid taste is easy to dilute in a drink and easy to mask in a capsule, so the choice usually comes down to daily routine and dose rather than technical limits.
| Dosage form | Why brands choose it | What to weigh up |
|---|---|---|
| Drink or concentrate diluted with water | Matches the trial format most directly; familiar routine in Japan | Needs dilution guidance; undiluted acidic drinks are commonly flagged by dentists as a risk to tooth enamel, so labels usually recommend diluting and rinsing after drinking |
| Hard capsule or tablet | No acid taste to manage; easy daily dosing | Powdered or concentrated material to reach an equivalent acetic acid amount; check the supplier’s acetic acid content per gram |
| Powder stick | Portable, mixed into water before drinking | Same dilution guidance as a ready-to-drink format |
Decisions that shape the specification:
- Source and acetic acid content. Confirm whether the material is plain rice or fruit vinegar, or a kurozu-specific concentrate, and ask the supplier for the acetic acid content per serving.
- Daily amount. Match the amount to the trial you intend to cite — for example around 750–1,500 mg acetic acid a day in the 2009 trial, or 480 mg a day of kurozu concentrate (870 mg of the supplement) in the 2013 trial.
- Dilution and labelling. A drink or powder format needs clear dilution instructions; this is standard practice for acidic Japanese vinegar drinks.
- Companion ingredients. Black vinegar is sometimes combined with other metabolism-themed ingredients. Each companion needs its own check against Japanese food law and your market’s rules.
The check that comes first
Every ingredient must be permitted in foods in Japan, or a Japanese factory cannot make the product.
Vinegar itself is a long-established Japanese food and presents no issue on this point. The risk usually sits in companion botanicals added to “metabolism” or “detox” formulas, some of which Japan treats as medicines. See the Japan-made supplement OEM page, and compare with our MCT oil and dietary fibre guides for other weight-and-metabolism ingredients.
Before you ask for a quotation
A factory can quote accurately once the material, the acetic acid amount, the form and the packaging are fixed.
- Vinegar source (plain vinegar or kurozu-specific concentrate) and acetic acid content
- Daily amount and servings per pack
- Dosage form, and dilution instructions if a drink or powder
- Companion ingredients and their amounts
- Packaging
- Countries you will sell in, and first order and annual volume
💬 Ready to design a Japan-made black vinegar product? Send us the concept — material, daily amount, form and the countries you will sell in.
Frequently asked questions
1. Does black vinegar reduce body fat?
A 2009 placebo-controlled trial in obese Japanese adults found lower body weight, BMI, visceral fat area and waist circumference with daily vinegar intake over 12 weeks. A smaller, kurozu-specific trial found a more modest effect, concentrated in women, and its authors called the result not definitive. Describe the ingredient as studied for body weight and visceral fat markers, not as a proven fat-loss product.
2. Is black vinegar the same as the vinegar used in the main clinical trial?
Not exactly. The larger, more positive trial used plain vinegar dosed by acetic acid content. Kurozu-specific concentrate was tested separately, dosed as concentrate rather than by acetic acid, with a smaller and less definitive result. Match your claim to the material and study behind your product.
3. Why do Japanese vinegar drinks list an acetic acid amount?
Because Japan’s Foods with Function Claims system notifies acetic acid for a visceral fat function tied to a specific amount per serving. The notifying business is responsible for the evidence behind that claim.
4. Should a black vinegar product be a drink or a capsule?
Either works. A drink or powder format matches the clinical trials most directly but needs dilution instructions, since undiluted acidic drinks are commonly flagged as a risk to tooth enamel. A capsule avoids the acid taste and dilution question but needs a concentrated material to reach an equivalent acetic acid amount.
5. What can stop a Japanese factory making my black vinegar product?
Usually a companion botanical in a metabolism or detox formula. Every ingredient must be permitted in foods in Japan, so we check the full formula first.
Sources: “Vinegar Intake Reduces Body Weight, Body Fat Mass, and Serum Triglyceride Levels in Obese Japanese Subjects”, Bioscience, Biotechnology, and Biochemistry 2009, 73(8):1837–1843 (PubMed 19661687; doi 10.1271/bbb.90231); “Effect of a Dietary Supplement Containing Kurozu (a Japanese Traditional Health Drink) Concentrate on Several Obesity-Related Parameters in Obese Japanese Adults: A Randomized, Double-Blind, Placebo-Controlled Trial”, Functional Foods in Health and Disease 2013, 3(8):310–322 (doi 10.31989/ffhd.v3i8.45); Consumer Affairs Agency notifications for Foods with Function Claims. Checked on 12 October 2026.