Wasabi Science

The Science of Wasabi — Why the Leaf?

Most people meet wasabi on a sushi plate: the sharp green paste made from the plant's root (rhizome). WasaFit is built on a different part of the same plant — the leaf of Japanese wasabi (Wasabia japonica, also classified as Eutrema japonicum), a plant that grows in the cold, clear mountain streams of Japan.

That choice is deliberate. For most of wasabi's history, the leaves were the part left over — even discarded — while the root took the value. But the leaves carry a different chemistry: where the root is famous for its pungent heat compounds, the leaves are rich in flavonoids, the plant compounds researchers study for skin care. For an athlete's skin — stretched, dried out, and stressed by training, sweating, and body transformation — that leaf chemistry is the interesting part.

This page explains what the research actually says, in plain language, and where its limits are. It is the same philosophy behind ATHLYDŌ — Athlete X Bushidō: no magic, no quick fixes. Discipline, evidence, and consistency.

Researched in Japan: Our Work with Wasa-Lab

Athlydō works closely with Wasa-Lab, the research platform of Kinjirushi Co., Ltd. — a Japanese company that has specialised in wasabi since 1929 and has researched wasabi's functional components since 1996. Kinjirushi's researchers developed the leaf as a cosmetic ingredient under the name Wasabi Flavone® (INCI: Wasabi Leaf Extract) — and, as you'll see below, they authored some of the key scientific papers on it themselves. When we cite research "from Japan" on this page, much of it comes from the people who know this plant best.

The Key Compound: Isosaponarin

The most studied compound in wasabi leaf is isosaponarin, a flavone glycoside (a type of flavonoid) concentrated from the leaf's flavonoids. It matters because of one job that decides how firm skin looks and feels: collagen production.

Collagen is the structural protein that gives skin its firmness and elasticity. It is made by cells called fibroblasts in the deeper layer of the skin. As we age — and as skin is repeatedly stretched by muscle gain, fat loss, and intense training — collagen production slows and existing collagen breaks down, which shows up as sagging, dryness, and loss of tone.

What the Research Found

1. Isosaponarin and collagen synthesis (2010)

In a laboratory study published in 2010, researchers Nagai, Akita, Yamada, and Okunishi — all researchers at Kinjirushi, the company behind Wasa-Lab — investigated wasabi leaf extract and isosaponarin on human fibroblasts. They found that:

• Wasabi leaf extract increased the production of type I collagen in human fibroblasts.
• Isosaponarin was the key compound behind this effect among the leaf's ingredients, and it increased type I collagen production at the gene (mRNA) level.
• It worked by up-regulating the TGF-β type II receptor (TβR-II) — part of the signalling pathway that tells fibroblasts to make collagen — and prolyl 4-hydroxylase (P4H), an enzyme collagen cannot be built without.

Reference: Nagai M., Akita K., Yamada K., Okunishi I. (2010). "The effect of isosaponarin isolated from wasabi leaf on collagen synthesis in human fibroblasts and its underlying mechanism." Journal of Natural Medicines, 64(3), 305–312. View on PubMed.

2. Wasabi extracts and the enzymes that break skin down (2021)

A 2021 study in the International Journal of Molecular Sciences analysed wasabi (Eutrema japonicum) grown in Poland, measuring the flavonoid and phenolic acid content of its flower, root, and leaf extracts and testing their cosmetic potential in the laboratory. The extracts showed antioxidant activity and inhibited collagenase, elastase, and hyaluronidase — the enzymes that break down collagen, elastin, and hyaluronic acid — with no cytotoxicity toward normal human skin fibroblasts. In the interest of accuracy: the strongest results in this study came from the flower extract; leaf and root extracts were also active, and it is the leaf that WasaFit uses. The study also confirms wasabi leaf extract is an established cosmetic ingredient, listed in the International Nomenclature of Cosmetic Ingredients (INCI).

Reference: Szewczyk K. et al. (2021). "Flavonoid and Phenolic Acids Content and In Vitro Study of the Potential Anti-Aging Properties of Eutrema japonicum." International Journal of Molecular Sciences, 22(12), 6219. View on PubMed.

3. Manufacturer clinical testing (Kinjirushi)

Beyond the published papers, Kinjirushi has run its own clinical testing on the leaf ingredient (Wasabi Flavone®) as it is used in cosmetics. In company-run tests, a formula with 1% wasabi leaf extract improved stratum-corneum moisture after 2 weeks compared with placebo, and in a 12-week test with 17 subjects, wrinkle volume decreased while skin texture and moisture indices improved. We label this honestly: this is manufacturer testing, not peer-reviewed research — promising, and part of why we chose this ingredient, but a different level of evidence from the published studies above.

4. Wasabi leaf and skin — human research on intake (2023)

In a clinical trial, participants took a wasabi leaf extract drink daily for 8 weeks. Compared with the placebo group, the wasabi leaf group showed increased total antioxidant capacity, reduced advanced glycation end products (AGEs — compounds associated with skin ageing), reduced skin melanin and spots, and increased skin moisture (+6.6%). Please note: this study used wasabi leaf taken as a drink, not applied to the skin. We include it because it shows the leaf's activity in the body — not as proof of what a topical gel does.

Reference: Chiang H-M. et al. (2023). "Wasabi leaf supplementation had antioxidant, anti-glycation, and improved skin melanin, spot and moisture." Journal of Functional Foods, 100, 105398. Read the study (DOI).

5. Emerging research: wasabi leaf and fat metabolism

One more line of research is worth knowing about, precisely because it is early. In a 2016 study co-authored by Kinjirushi researchers, rats fed a high-fat diet with wasabi leaf extract finished lighter than the control group — with no difference in how much they ate — alongside up-regulation of β3-adrenergic receptors in brown fat, a pathway involved in heat production and fat burning. Related cell studies point in a similar direction. All of this evidence is oral and pre-clinical. We present it as active, emerging science on the leaf — never as a claim that a gel burns fat.

Reference: Yamada-Kato T. et al. (2016). "Anti-obesity Effects of Wasabi Leaf Extract on Rats Fed a High-fat Diet." Food Science and Technology Research, 22(5), 665–671.

The Warmth: Capsicum and the Body's Own Sensors

The warming feeling of a pre-workout gel is not a trick of fragrance — it is physiology. Wasabi's own pungent compounds are known to activate TRPA1, one of the body's temperature-and-irritation sensor channels (Uchida et al., 2012). WasaFit pairs wasabi leaf extract with capsicum, whose compounds act on the related warmth sensor TRPV1; in human studies, topical application of such warming agents measurably increases blood flow in the skin. That gentle warmth is the signal: the session has started, and the skin is being prepared for movement, sweat, and change alongside the muscles underneath it.

From the Laboratory to Your Training Routine

Research describes what an ingredient can do. A routine is what turns that potential into a result you can see. WasaFit is designed to be used the way athletes train:

• Before training: apply the gel to the areas you are working — or the areas changing most — as part of your pre-workout ritual.
• Daily: skin does not transform in one session, and neither does a body. The formula is built for consistent, daily use.
• Over months, not days: based on the skin's own renewal cycle, we recommend a minimum of 3 months of consistent use, combined with regular training, proper hydration, and balanced nutrition.

See how WasaFit Body Booster Gel works →

An Honest Note on Evidence

We would rather show you the studies than ask you to trust adjectives. So, plainly: much of the research above was done on isolated ingredients in laboratory settings; some of it was carried out by researchers at Kinjirushi, our ingredient partner; and no published study has yet tested a wasabi leaf gel on human body skin directly. Ingredient research is not the same as proof that a finished cosmetic product will produce a specific result for a specific person. WasaFit is a cosmetic, not a medicine. It does not diagnose, treat, or prevent any condition, and individual results vary.

What we can say — and what the research supports — is that wasabi leaf is a genuinely studied Japanese botanical, that its key flavonoid has a documented effect on collagen synthesis in human skin cells, and that we built WasaFit around it on purpose, with the company that researched it. The rest is discipline: yours, applied daily.

Embrace the Path. — ATHLYDŌ・Athlete X Bushidō