Aojiru — literally “green juice” — is a Japanese category built around powdered green vegetables mixed into water: usually barley grass, kale or ashitaba, sometimes blended together. Brands abroad ask for an aojiru-style product because the format is instantly recognisable as Japanese and the powder-stick format travels well.
“Aojiru” is a category name, not one ingredient. Barley grass, kale and ashitaba are three different plants with different published evidence, and a brand should know which plant its evidence actually comes from before it writes any copy. This guide explains what has been studied for each, and what to decide before a Japan-made product.
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 an aojiru-style product made in Japan? We check the full formula against Japanese food law first. See Japan-made supplement OEM.
What the research shows
Evidence is small in scale and belongs to the specific plant and preparation tested, not to “aojiru” as a category.
| Study | Design/What was analysed | Reported result |
|---|---|---|
| Randomised, double-blind, placebo-controlled crossover trial, Antioxidants (Basel) 2018 (PMID 29883433) | 10 men, 7 days of barley-wheat grass juice at 70 mL or 140 mL/day, before a bout of high-intensity exercise; DNA damage and antioxidant markers | Superoxide dismutase activity rose 44.7% with supplementation, but the juice did not reduce the exercise-induced rise in DNA damage compared with placebo |
| Randomised, double-blind, placebo-controlled crossover trial, Biomedical Reports 2016 (PMID 27882216) | 42 Japanese adults with non-diabetic but elevated post-meal glucose response, single test meal with 7 g or 14 g of kale-containing food | Both kale doses significantly reduced the peak and area-under-curve of post-meal blood glucose versus placebo, with no difference between the two doses |
| Randomised, double-blind, placebo-controlled trial, International Journal of Food Sciences and Nutrition 2024 (PMID 38557440) | 42 overweight adults, 16 mg/day encapsulated ashitaba chalcone extract for 12 weeks | Waist circumference and visceral fat area significantly decreased versus placebo |
| Randomised controlled trial, Biomedical and Environmental Science 2008 (PMID 18548846) | 32 men with hypercholesterolemia, 150 mL/day kale juice for 12 weeks | HDL-cholesterol and the HDL-to-LDL ratio increased, LDL-cholesterol and the atherogenic index decreased |
| Single-group before-and-after study without a control group, Metabolites 2021 (PMID 34436500) | 18 healthy adults, granola containing a high-fibre whole-grain barley variety, once daily for 4 weeks | Butyric-acid-producing gut bacteria and faecal butyric acid concentration increased; both fell back one month after stopping |
These trials are small (10 to 42 people), short (single meals to 12 weeks), and each tested one plant, one preparation and one dose — the ashitaba trial used a concentrated chalcone extract rather than whole-leaf powder, and the barley fibre study used a whole-grain barley variety in granola rather than young barley leaf juice and had no control group, so neither result should be assumed to transfer to a typical aojiru powder. The barley-wheat grass exercise trial is a reminder that not every outcome moves together: an antioxidant enzyme rose while DNA damage was unaffected. None of these findings support a disease-related claim, and the kale-cholesterol trial studied a population with a diagnosed lipid condition.
Checked against the published abstracts on 25 September 2026.
What Japanese products say
Aojiru is mostly sold in Japan as a general food, with some products separately notified as Foods with Function Claims for a specific ingredient inside the blend rather than for the green-juice blend as a whole.
Barley grass, kale and ashitaba each appear widely in Japanese green-juice products sold as ordinary foods. Some notified Foods with Function Claims products use barley-grass-derived dietary fibre or a named plant extract as the specific functional component, evidenced and dosed on its own terms. That is different from claiming a benefit for the finished green-juice blend, and a brand should check the current notification database for the specific component it plans to use, rather than assume the category carries a notification.
💬 Need help separating what one plant’s trial actually supports from a category-wide claim? We prepare the evidence summary with the manufacturing documents. Tell us your market.
Wording that stays on safe ground
Name the plant that was actually studied, and never round “aojiru” evidence up to a category-wide claim.
| Safer wording | Wording to avoid |
|---|---|
| ”Contains kale powder, with the plant studied for post-meal glucose response in a small trial" | "Aojiru improves digestion” without naming which plant or study |
| ”Contains barley grass powder” with the amount per serving | Cholesterol, blood-sugar or disease-related claims for the product |
| ”A source of dietary fibre" | "Detoxifies” or “cleanses” |
How aojiru is formulated
Aojiru’s defining format is a freeze-dried or spray-dried vegetable powder in a single-serve stick, dissolved in water or a drink.
| Dosage form | Why brands choose it | What to weigh up |
|---|---|---|
| Powder stick (single-serve sachet) | The standard Japanese aojiru format; easy portioning and travel | Colour, bitterness and solubility of the plant powder |
| Loose powder in a tub | Lower packaging cost per serving | Measuring consistency for the customer |
| Ready-to-drink bottle or pouch | Convenience, no mixing | Stability of colour and nutrients through the shelf life |
Decisions that shape the specification:
- Plant selection and blend ratio. Barley grass, kale and ashitaba have different tastes, colours and evidence bases; a blend needs its ratio fixed and disclosed.
- Amount per serving. Match the amount of each plant to any study you intend to cite for that specific plant.
- Vitamin K disclosure. Barley grass, kale and other leafy green powders are naturally rich in vitamin K; a caution for people taking anticoagulant medicines such as warfarin is a standard, honest addition to the label regardless of destination-market rules.
- Companion ingredients. Fruit powders, sweeteners and other botanicals are common in aojiru blends; each needs its own check against Japanese food law.
- Solubility and taste masking. Green vegetable powders vary widely in bitterness; ask the supplier for processing options that affect taste without changing the declared plant content.
The check that comes first
Every ingredient must be permitted in foods in Japan, or a Japanese factory cannot make the product.
Barley grass, kale and ashitaba are all long-used as foods in Japan. Fruit powders and other botanicals sometimes added to a green-juice blend need their own check, since some botanicals sold freely elsewhere are treated as medicines in Japan. See the Japan-made supplement OEM page, and our dietary fibre guide for a related gut-focused ingredient.
Before you ask for a quotation
A factory can quote accurately once the plant blend, the amount, the form and the packaging are fixed.
- Plant or plant blend (barley grass, kale, ashitaba) and the ratio
- Amount per serving and servings per pack
- Dosage form (powder stick, loose powder, ready-to-drink)
- Companion ingredients and their amounts
- Packaging
- Countries you will sell in, and each plant’s status there
- First order and annual volume
💬 Ready to design a Japan-made aojiru product? Send us the concept — plant blend, amount, form and the countries you will sell in.
Frequently asked questions
1. Is “aojiru” one ingredient with its own evidence base?
No. Aojiru is a category name for green-juice powders that can contain barley grass, kale, ashitaba or a blend. Evidence belongs to the specific plant and preparation tested — for example, a kale trial does not support a claim about a barley grass product.
2. What has actually been studied for these plants?
Small trials report post-meal glucose reduction from kale, lipid changes from kale juice, and waist-circumference reduction from a concentrated ashitaba chalcone extract. All are small studies (10 to 42 people); none supports a disease-related claim for a finished product.
3. Does aojiru help with gut regularity?
The direct evidence is limited. A small fibre-focused study without a control group, using a high-fibre whole-grain barley product (not the barley leaf powder typically used in aojiru) increased gut butyric-acid-producing bacteria, but this result should not be assumed to transfer to a barley grass leaf powder.
4. Why does the vitamin K content matter?
Barley grass, kale and other leafy green powders are naturally rich in vitamin K, which can interact with anticoagulant medicines such as warfarin. A caution statement for customers on such medicines is good practice regardless of your market’s label rules.
5. Which format suits an aojiru product?
The single-serve powder stick is the standard Japanese format, chosen for portioning and travel convenience. Loose powder and ready-to-drink formats are also used, each with its own trade-offs in cost and shelf stability.
Sources: “Exogenous Plant-Based Nutraceutical Supplementation and Peripheral Cell Mononuclear DNA Damage Following High Intensity Exercise”, Antioxidants (Basel) 2018 (PMID 29883433); “Intake of kale suppresses postprandial increases in plasma glucose: A randomized, double-blind, placebo-controlled, crossover study”, Biomedical Reports 2016 (PMID 27882216); “Randomised, double-blind, parallel group comparison of Ashitaba (Angelica Keiskei) chalcone effects on visceral fat areas and waist circumference of overweight persons”, International Journal of Food Sciences and Nutrition 2024 (PMID 38557440); “Kale Juice Improves Coronary Artery Disease Risk Factors in Hypercholesterolemic Men”, Biomedical and Environmental Science 2008 (PMID 18548846); “Fiber-Rich Barley Increases Butyric Acid-Producing Bacteria in the Human Gut Microbiota”, Metabolites 2021 (PMID 34436500). Checked on 25 September 2026.