By Janet Colston
Wasabi Japonica is not a name that trips off the tongue when you think of medicinal plants but this ancient Japanese herb is full of functional metabolites with a proven ability to heal disease. The Japanese have known for centuries that Wasabi bestows a remarkable array of medicinal properties with benefits to human health including significant anticancer and antimicrobial functions. Even the heart shaped leaves that grow out of the crown suggest it has cardiovascular benefits as Japanese herbalists used the plant as a vasodilator to improve blood circulation. We delve into these properties and how to grow it successfully to reveal a plant that should be on every health conscious person’s plate.
Botanically it is a member of the Brassica family and thrives in humid mountain river beds in Japan where it is known as SAWA Wasabi. Alternative soil grown methods (OKA) favouring leaf and petiole production are popular in China, Korea and Taiwan. Wasabi contains similar glucosinolates to broccoli and produces highly bioactive metabolites when enzymes are released during grinding of plant tissue causing its cells to rupture. Hydrolysis of the glucosinolate precursor Sinigrin by the enzyme myrosinase releases a range of volatile Allyl isothiocyanates (AITCs). Wasabi uniquely contains a higher concentration of the long chain isothiocyanate 6-MITC or 6-MSITC . This reaction to produce 6-MITC reaches maximal effect 5mins after grinding and dissipates again after 15mins as it undergoes further reactions and the effect is reduced. Wasabi like the other crucifers evolved this protective mechanism to prevent predator attack, warning off insects and animals that bite once not to try again .
If you have never seen Wasabi grated right in front of you, we almost guarantee you have never experienced real wasabi. This is most likely fake wasabi, common with pre-packed sushi and consists of horseradish, food colouring and mustard. If you still feel a sensation after 15mins then you know it’s not the real deal.
What effect does it have on our body?
The taste of real ground Wasabi is sweet but then it generates heat and pain in nasal passages as the isothiocyanates bind to the Wasabi receptor. That’s right, the Wasabi receptor, technically known as the transient receptor potential ankyrin 1 (TRPA1) channel located on sensory nerve endings in highly innervated areas at the tip of the tongue and nasal passages . It’s a mouthful but TRP channels are a very important defence mechanism adapting the bodies response to a wide variety of stimuli including temperature, nociceptive stimuli, touch, osmolarity and pheromones .The TRPA1 channel is well known to be activated by AITC, more commonly known as mustard oil which allows sodium and calcium ions to flood into cells. This induces pain and neurogenic inflammatory responses in expressing sensory nerves resulting in the noxious sensation in the sinuses .
Anti-Cancer, Anti-Microbial, Anti-Inflammatory, Cardioprotectant
Japan’s oldest botanical script, the Honzowamyou compiled in 918 is thought to be the first description of Wasabi being cultivated as a medicinal plant . Wooden plant labels with the inscription ‘Wasabi Sansho’ were also excavated in what was thought to be one of the first medicinal herb gardens .
Historically the Japanese used ground Wasabi to prevent food poisoning from raw fish and although they were most likely unaware of the mechanism, Wasabi soon caught on and was reserved for the higher classes. We know these early herbalists used Wasabi to treat rheumatic arthralgia, poor blood circulation and as an effective pain reliever . The fresh plant is high in protein, fibre, vitamins B6 and C, and the minerals calcium, magnesium, potassium and manganese. However the main scientific interest lies in the bioactive compounds in Wasabi, the isothiocyanates and p-hydroxycinnamic acid properties .
Overwhelming evidence demonstrates 6-MITC and other phytochemicals in Wasabi extracts are highly efficient in killing cancer cells albeit in the lab and these include lung, breast, colon, pancreatic, oral, blood, skin cancers and bone metastasis [10,11,12,13,14,15,16,17,18,9]. Tumour killing mechanisms involve complex cellular pathways that researchers continue to study in an effort to only kill malignant cells while not disrupting healthy tissue.
According to the World Health Organisation, antibiotics around the world are increasingly resistant (AMR) to infections caused by bacteria, viruses, parasites and fungi and there is a desperate need to look for alternatives . Wasabi may provide an opportunity to exploit its ancient antimicrobial activity. Extracts have shown inhibitory effects on bacteria that cause food poisoning (E Coli, Vibrio), respiratory disease (S Aureus), dental caries ( S Mutans), duodenal ulcers (H Pylori), as well as preventing yeasts, fungi and molds spreading [20,21,22,23,24,25].
Amongst the many other functional effects, Wasabi extracts were found to inhibit platelet aggregation protecting against heart attack and stroke providing a good reason for researchers to examine effects it may have on SARS-CoV2 . Indeed AITC is a potent agonist at the site specific TRA1 channel  which elicits peripheral vasodilation and induces a biphasic blood pressure response potentially playing an important role in prevention of cardiovascular disease .
As if all these functional properties were not enough, 6-MITC has also been reported as a neuroprotectant , preventing a range of inflammatory conditions  and as a potential weight loss promoter . Even more incredible, researchers have found high levels of Isosaponarin in Wasabi which promotes collagen synthesis and stimulates papilla cells in the scalp to promote hair growth .
Although there is no direct evidence of Wasabi fighting Coronavirus, previous studies did find extracts had antiviral activity on influenza . Researchers in Thailand are currently working on computational molecular docking data of the SARS-Cov2 genome examining two major active phytochemicals in Wasabi in an attempt to develop a blended tea for treatment of long covid conditions .
Is Wasabi really that hard to grow – can CEA enable farmers to grow it with confidence?
Wasabi Japonica may have a built up a reputation as ‘hard to grow’ in traditional farms or commercial polytunnels but we believe Controlled Environment Agriculture (CEA) and careful monitoring holds the key to eliminating most problems suffered by growers.
Wasabi can take up to two years to mature and care must be taken to ensure the conditions are just right. Thousands of years of evolution, growing in the shady humid river beds in the shadow of Mount Fuji in its native Japan can be difficult to replicate. But it is possible despite one of the biggest challenges scaling from pilot to commercial farm.
Manipulating the growing environment of Wasabi throughout the growing cycle with a combination of micro-propagation, LED lights and hydroponics can lead to enhanced plant yields. A range of fertilisers can be applied at different periods of growth through early stages, petiole, flower and stem production in a variety of substrates to optimise biomass.
High value crop
With a surge in recent years of Sushi bars and restaurants in the US there has been a rise in demand for real Wasabi to accompany fine dining. This has resulted in a relatively high value for fresh Wasabi (circa $250 per kg) due to the low supply in the west and because commercial production is still relatively uncommon outside of Asia.
Some of the prohibitive reasons are a 2 year growing cycle and the risk of crop loss during this time due to disease. Professionally modelled greenhouse production, continual review of IPM and beginning with clean plant material can help overcome these issues.
Outside of Japan and Asia, growers employ a range of production methods including spring water beds, recirculating gravel beds or soil/coir grown in protective environments or a combination approach to either maximise stem size or increase leaf and petiole production rates. Both SAWA and OKA production lend themselves well to CEA. Size is not everything though as discerning sushi chefs look for colour, stickiness and long lasting flavour and this requires a degree of understanding of different cultivar properties. The two main types of Wasabi cultivated are Daruma and Mazuma although breeders ensure there are many derivatives of these developed for different commercially viable traits.
Daio Wasabi Farm, Nagano, Japan
In North America, the Pacific Northwest region has one of the most conducive climates outside of Japan for growing Wasabi where many have based their operations. So the question of which method you employ comes back to Chris Higgins saying ‘it all depends’. Whether you aim to grow in shaded river banks, spring water terraces, polytunnels, glasshouses or indoors, all must take into account geographical location of the farm, capital investment, environment monitoring, labor management and long term maintenance protocols.
Start Clean Stay Clean
This phrase is most associated with integrated pest management (IPM) but here we associate it with fungal endophytes abundant in vascular plant tissue. This can lead to poor growth and disease spread in both hydroponic tanks and soil grown plants if not tightly controlled. Wasabi produces multiple semi mature offshoots that can be harvested and replanted but these will have inherent problems carrying any fungal disease onto the next generation. The way to start clean is to micropropagate new plants via meristem tip culture. The meristem (left image) in pale yellow is just a few millimetres in size and sits proud above swollen basal cells located inside the primordial leaves (middle image). Excising this actively growing area excludes any disease as it is outside the plant phloem bundles that carry viruses. Active meristem tissue can then be promoted in sterile culture to produce a new clean clone (right image).
Wasabi grows well in tissue culture and this can be a fast efficient way to scale large numbers of identical clones for commercial production. Ultimately, integrating a good IPM will alleviate issues with viral transmission, as Wasabi is especially vulnerable to aphid attack in the flowering season. Reducing nitrogen levels in fertilisers during this period is advised.
Can Wasabi ever be mainstream?
Wasabi not only looks good in the greenhouse, but every part of the plant is edible, including the flower, petiole, leaf and stem.
The taste is much sweeter and more subtle than fake Wasabi most people know as the lurid green paste in tubes. Powdered wasabi certainly can prolong the shelf-life but this has not caught on and the taste cannot replace the fresh product experience. Fresh leaves have a spicy taste that pep up salads and the stems can be added for crunch or pickled as they do in Japan into Zuki, popular in Shizuoka Prefecture . Sushi, Sashimi and Soba noodles are well established in western diets, and seen as a healthy option. As consumers become increasingly aware of fake condiments it is likely to increase high global demand for fresh grown Wasabi.
Get together with friends and share homemade sushi, it’s one of the healthiest things to eat and we guarantee it’s outstanding when combined with Loch Fyne Scottish Salmon! If you are not too sure then you can learn how to make perfect sushi at the Californian Sushi Chef Institute.
The future of metabolite Research needs Controlled Environmental Agriculture
Speed breeding Wasabi via controlled environmental agriculture can accelerate production of metabolites. This is a technique being employed by blueberry breeders  and can cut down the growing cycle of plants like Wasabi that normally take 2 years to reach maturity. Modelling of glucosinolates in plants grown under different environmental conditions can push our understanding of how Wasabi distributes bioactive metabolites, literally shining a light on the biological mechanisms that cure disease. Below is a series of wasabi root images in our early studies, left shows healthy root growth under RB LEDs, middle is a newly emerged root and right is a RGB confocal overlay image of increased secondary metabolites  autofluorescence signal in a root slice indicating cellular fluorophore production potentially due to flavonoids.
This leads to new research pushing scientific understanding of metabolite production and has proved a successful model for those who grow Wasabi in Asia for large scale powder production for the health and wellness market.
Our genuine wish is to see diversification of CEA crops to include more complex plants like Wasabi, ensuring this way of growing complements any unique selling points of farmers in what is a very niche market. We have many years experience with Wasabi so if you’re Interested in learning more about growing in a controlled environment, get in touch.
All images unless otherwise stated are courtesy of The Functional Plant Company.
Janet Colston PhD is pharmacologist with an interest in growing ‘functional’ foods that have additional phytonutrients and display medicinal qualities that are beneficial to human health. She grows these using a range of techniques including plant tissue micropropagation and controlled environmental agriculture to ensure the highest quality control.