Medical uses for Wasabia japonica
Wasabia japonica is one of the worlds’ rarest and least understood perennial crops.
A few facts about Wasabia japonica
• Wasabia japonica is a member of the plant family called the Brassicaceae, formerly Cruciferae. This family includes broccoli, cabbage and cauliflower.
• Wasabia japonica is believed to be native to Japan and Sakhalin Island, north of Japan, although China now claims that it is also a native.
• It grows naturally in the gravel beds of mountain streams and requires a specific environment to thrive naturally in this habitat. There is another Wasabia japonica species that grows in swampy ground, but produces inferior quality stems.
• Wasabia japonica is traditionally cultivated in either water or soil. This gives the plant different characteristics, and affects the level of active ingredients contained within the plant. In this article we are only referring to the water grown variety which is known as Sawa, as this produces the best Wasabia japonica plants with the highest level of bioactive components. We shall use Sawa Wasabi throughout this article to differentiate it from common horseradish sushi wasabi.
• Outside of Japan (and even in Japan), the spicy green paste served with sushi or Sashimi is commonly called Wasabi. However, typically, this Wasabi paste is in fact European Horseradish root (Armoracia rusticana) and colouring, and contains very little or no part of the true Wasabia japonica plant.
• True Wasabi (Sawa Wasabi) is expensive and considered a rare delicacy around the world. It is traditionally grated fresh onto food, since it can lose its flavour in as little as 10-15 minutes.
• In Japan, Sawa Wasabi has not only been considered a food delicacy that adds a pungent flavour to food, but it is also believed to have powerful medicinal action.
Like many aspects of a healthy traditional Japanese diet, regular use of Sawa Wasabi may be partially responsible for the longevity and health of the Japanese people. Currently, scientific research is investigating the folklore surrounding why Sawa Wasabi is regarded as both a super food and a powerful herbal medicine.
Fresh Sawa Wasabi contains protein, fibre, vitamins B6 and C, and the minerals calcium, magnesium, potassium and manganese. Sawa Wasabi also contains a stable group of compounds called glucosinolates. These compounds are changed by enzymes to the bioactive unstable isothiocyanates (ITCs) if water is present when the cells are torn apart by being chewed or ground up.
Sawa Wasabi differs from other brassicas in that it has significantly higher concentrations of ITCs, especially long-chain ITCs. These long-chain ITCs (6-methylsulfinylhexyl isothiocyanate or 6-MITC, 7-methylsulfinylheptyl isothiocyanate and 8-methylsulfinyloctyl isothiocyanate) also give Sawa Wasabi its unique flavour. These long chain ITCs are not found in other plants.
The enzyme responsible for converting the inert glucosinolates to ITC is myrosinase, a very unstable molecule.
If Sawa Wasabi is air-dried, its myrosinase breaks down, and the ITCs that produce the characteristic heat, flavour and biomedical activity of Wasabia are not formed. This is why traditionally only fresh rhizomes and leaves were used. A process pioneered by Michel Van Mellaerts in New Zealand, of freeze-drying Sawa Wasabi to stabilise the activity of the myrosinase until exposed to water or digestive fluids, has removed this requirement for using fresh product. It is also the basis of the Wasabi based Nutraceutical products that are becoming common on the health food shop shelves.
There is a tremendous amount of ongoing research, especially in Asian countries, on Sawa Wasabi and its medicinal and health benefits.
Current research is focused on the ITCs that provide the majority of activity. Many scientists have concentrated on 6-MITC, of which Wasabia japonica contains a high concentration. It has been found to be 40 times more effective than other ITCs found in other Brassicas. However, all of Sawa Wasabi’s many ITCs (20 or more) likely contribute to the medicinal action in a symbiotic manner. Isolating one particular ITC without the others is likely to cause more harm than good. Combined with traditional knowledge, new research on Wasabia japonica is providing insights into the actions of Sawa Wasabi in the body. Scientific evidence suggests that there are many potential biomedical and health applications for the natural components found in Sawa Wasabi.
The following is a research summary of Wasabia japonica and its ITCs.
Sawa Wasabi may be useful for controlling seasonal allergies and asthma. ITCs are effective agents for inflammation based on their rapid action and the low levels needed.
6-MITC can inhibit lipoxygenase, cyclooxygenase and cAMP phosphodiesterases that are involved in inflammation.
Isothiocyanates of Sawa Wasabi and other crucifers are anti-inflammatory (Depree et al., 1998) and anti-asthmatic (Dorsch et al., 1984) agents. Depree et al. (1998) were so impressed with results when testing ITCs that they made the following statements: “The anti-inflammatory effects and inhibition of platelet aggregation by omega-methylthioalkyl isothiocyanates is perhaps of more interest given the rapid action of the compounds and the low levels at which they are effective.” This could potentially be used to counter inflammatory conditions such as allergies, asthma, eczema or even anaphylaxis.
The ability of the Sawa Wasabi isothiocyanates to inhibit platelet aggregation (blood clotting) could also have medical and health applications, particularly in the treatment of heart attacks. Further work on the pharmacology of these compounds and their possible medicinal use, as well as other medicinal properties of Sawa Wasabi, seems warranted. A growing experience from natural health practitioners suggests that Sawa Wasabi can be an effective treatment for seasonal allergies as well as asthma and eczema.
ITCs have an inhibitory effect on several strains of bacteria, yeast and mould. It is believed that Wasabia japonica was first introduced into the raw fish diet of the Japanese for its anti-microbial properties. Isothiocyanate vapours inhibit the growth of several strains of bacteria, yeast and mould (Depree et al., 1998). Several scientific studies (Ono et al., 1998; Shin and Lee, 1999) have shown that 6-MITC from Sawa Wasabi extracts have potent anti-bacterial properties against Staphylococcus aureus (Golden Staph) and Escherichia coli (E.coli).
Isothiocyanates in Sawa Wasabi have demonstrated an inhibitory effect against Streptococcus mutans, the bacterium responsible for dental cavities (Masuda et al., 2000). These results may lead to Sawa Wasabi extracts being used in a variety of products (i.e., toothpastes and mouthwashes) for cavity prevention.
More recent research has proven Sawa Wasabi extracts inhibit mutant strains of the Staphylococcus bacterium. Another biomedically important bacterium that Sawa Wasabi and ITCs inhibit is Helicobacter pylori (Masuda et al., 2001; Shin et al., 2004; Haristoy et al., 2005). This bacterium is known to be responsible for gastric ulcers and ensuing stomach cancers. Sawa Wasabi extracts kill the bacterium, even if it has entered cells lining the stomach.
The inhibition of blood clots forming in the bloodstream is important for protection against heart attacks and strokes. The 6-MITC of Sawa Wasabi has been found to inhibit platelet aggregation (Kumagai et al., 1994; Morimitsu et al., 2000; Morimitsu et al., 2002), a property useful in the elderly, where preventing excessive clotting is vital. Platelet aggregation is a major factor in cardiovascular diseases. 6-MITC inhibits platelet aggregation by a number of different mechanisms, including the inhibition of lipoxygenase, cyclooxygenase, cAMP phosopodiesterases and cGMP phosphodiesterase.
There is a growing base of evidence on how ITCs work against cancerous cells. Isothiocyanates act to inhibit enzymes that cause pre-carcinogenic compounds to turn into carcinogenic ones (Phase I enzymes). They also can induce detoxifying Phase II enzymes (Yu et al., 1996; Hecht, 1999; Kirlin et al., 1999), like glutathione S-transferase (Morimitsu et al., 2000), possibly through gene expression (Yu et al., 1996; Gao and Talalay, 2004), and inhibit initiation of cancerous growths (Yano et al., 2000).
6-MITC has also been shown to block the cell cycle of cancerous cells (Hashimoto et al., 2004) and to affect protein production in cancerous cells (Hou et al., 2000).
Metastasis, a critical stage in spreading cancer beyond the local site, can be blocked by ITCs and in particular 6-MITC. Fuke and her co-workers (1997, 2000, 2006) and Manesh and Kuttan (2003) have shown that 6-MITC from Sawa Wasabi suppressed dissemination or metastasis of certain tumour cells.
In numerous cases, the ITCs from Sawa Wasabi have been shown to cause cancerous cells to undergo apoptosis or cell death. This has been shown in leukemia cells (Nakamura et al., 2001; Fimognari et al., 2004), breast cancer cells (Nomura et al., 2005), lung cancer (Kuang and Chen, 2004), colorectal cancer (Lund et al., 2001) and cancerous cells of other types (Watanabe et al., 2003; Fimognari et al., 2005).
An important point is that ITCs are effective against the cancerous cells but do no harm to healthy cells. No side effects have been encountered!
Musk and co-workers (1993, 1995) showed that allyl isothiocyanates (AITC), another ITC in Sawa Wasabi, was selectively toxic toward colorectal tumor cells. Nakamura et al. (2001) found in the case of leukemia that the ITCs from Sawa Wasabi inhibit the growth of leukemia cells but do not inhibit normal cells.
Other Health Effects
In addition to the above health benefits, there is now evidence showing that Sawa Wasabi and its isothiocyanates provide other medical effects: It reduces diarrhea (Nakayama et al., 1998); protects nephrons in diabetes patients (Fukuchi et al., 2004); acts as antioxidants (Gao et al., 2001; Lee et al., n.d.); provides immune modulation (Manesh and Kuttan, 2003); inhibits cancer and lessens treatment toxicities (Manesh and Kuttan, 2005); and protects cardiovascular function (Wu et al., 2004).
Wasabia japonica contains another potentially exciting compound. Suzuki and his co-authors (Suzuki et al., 1997; Suzuki and Yamaguchi, 1999) found that a compound in Wasabia japonica leaf stalk extract has a significant stimulatory effect on bone calcification in vitro and in vivo. The authors’ findings revealed that the compound was easily extracted from the plant tissue, is of small molecular weight and functions at low concentrations.
It is likely that Sawa Wasabi will become a useful adjunct for many of the chronic health conditions that plague our world. These include asthma, seasonal allergies, arthritis, IBS, Crohn’s disease, allergic reactions, food poisoning, dental carries, gingivitis, H. pylori-caused infection and ulcers, heart disease, stroke, blood clots, protection against certain cancers (breast, prostate, colon, lung, pancreas, throat, bladder, leukemia and more), toxicity from chemotherapy and radiation treatment, and osteoporosis. Hopefully, Wasabia and the ITCs found in the whole plant will eventually prove effective against diseases that kill millions of people yearly, like heart disease, cancer, chronic inflammatory diseases and infections.
Recent advances in herbal processing have made the active glucosinolates in Sawa Wasabi stable until mixed with digestive juices, allowing the full spectrum of fresh Sawa Wasabi rhizome ITCs to be available. This is indeed an exciting time to be discovering the ancient wisdom of medicinal plants. Sawa Wasabi has a long traditional use in the East and the potential to become a useful food, supplement and/or medicine for the rest of the world.
A scientific paper published in January 2011 has found that one of the unique Isothiocyanates (6MITC) found in Wasabia japonica is of significant benefit to those suffering from Type 2 diabetes. The article can be found here, at long last maybe diabetes sufferers can move away from the insulin injections.