Wasabi is known as Japanese horseradish and used as a sushi seasoner. The wasabi root is used as a spice and has an extremely strong flavor. Wasabi is a member of the cabbage family. The wasabi you find in sushi restaurants has a deep green color. My understanding is that wasabi root itself is green, but that the wasabi in the sushi restaurants has added green dye to it. I am not sure whether this is a natural or artificial green dye.

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Wasabi and sinus clearing
Many people believe the wasabi clears their sinuses, but new research suggests that the spicy green paste may do the opposite. U.S. researchers found that eating wasabi appeared to increase congestion in a small group of healthy volunteers, despite the fact that participants said they thought that the spice had cleared their nasal passages. "Actually, wasabi is a congestant," says study author Dr. David S. Cameron. "It makes the space of your nasal passages smaller, but it makes you feel more open." Dr. David Cameron explains that wasabi probably clogs up sinuses by increasing blood flow to the lining of the nose. That extra blood takes up space, he said, which constricts the nasal passageway.

Wasabi and Horseradish
Wasabi is often horseradish dyed green, but I have come across a study, see below, that gives wasabi a different species name. At this point I am not sure whether the wasabi in Japanese restaurants is basically horseradish dyed green, or wasabi plant from Japan.

Wasabi Research
Tumor cell proliferation and cyclooxygenase inhibitory constituents in horseradish (Armoracia rusticana) and Wasabi (Wasabia japonica).
J Agric Food Chem. 2005 Mar 9;53(5):1440-4.  Weil MJ, Zhang Y, Nair MG. Bioactive Natural Products and Phytoceuticals, Department of Horticulture and National Food Safety and Toxicology Center, Michigan State University, East Lansing, Michigan
Cyclooxygenase and human tumor cell growth inhibitory extracts of horseradish (Armoracia rusticana) and wasabi (Wasabia japonica) rhizomes upon purification yielded active compounds 1-3 from horseradish and 4 and 5 from wasabi rhizomes. Spectroscopic analyses confirmed the identities of these active compounds as plastoquinone-9 (1), 6-O-acyl-beta-d-glucosyl-beta-sitosterol (2), 1,2-dilinolenoyl-3-galactosylglycerol (3), linolenoyloleoyl-3-beta-galactosylglycerol (4), and 1,2-dipalmitoyl-3-beta-galactosylglycerol (5). 3-Acyl-sitosterols, sinigrin, gluconasturtiin, and phosphatidylcholines isolated from horseradish and alpha-tocopherol and ubiquinone-10 from wasabi rhizomes isolated were inactive in our assays. Compounds 1 through 5 selectively inhibited COX-1 enzyme. In a dose response study, compound 3 inhibited the proliferation of colon cancer cells (HCT-116) and lung cancer cells (NCI-H460). Compound 4 inhibited the growth of colon, lung, and stomach cancer cells. This is the first report of the COX-1 enzyme and cancer cell growth inhibitory monogalactosyl diacylglycerides from wasabi and horseradish rhizomes.

Wasabi product promotional email received in June 2008
At a time when awareness of the benefits of cruciferous vegetables continues to grow, BioCell Technology, LLC has introduced i-Sabi, a proprietary wasabia japonica ingredient. Many epidemiological reviews and prospective studies show various beneficial effects attributable to the isothiocyanates. i-Sabi is unique in that it contains a potent amount of isothiocyanates (15,000 ppm), ready for antioxidative activity. These isothiocyanates are exogenous antioxidants that exhibit very powerful detoxification effects. Experimental evidence reveals that a particular isothiocyanate identified as 6-methylsulfinylhexyl isothiocyanate (6-HITC), as found in i-Sabi?, is a very potent inducer of the family of enzymes collectively known as glutathione S-tranferases (GSTs). GSTs are about 45-55 kilodalton in size and comprise a significant percent of cytosolic protein. GSTs are considered a Phase II enzyme, which is the detoxification pathway that is based on conjugation. Specifically, GSTs conjugate glutathione to toxic substances, thus rendering them water-soluble, polar, and ready for excretion via urine or bile. Isothiocyanates have also been found to be extraordinary in promoting healthy cellular replication.
   BioCell Technology, LLC recently completed clinical research on i-Sabi. Studies demonstrate that i-Sabi has a multitude of health-promoting benefits:
1. High antioxidant activity, including the ability to enter into cells to protect from dangerous oxidative damage in vitro.
2. Immunomodulatroy effects.
3. Strongly inhibits COX-2 expression while allowing the more beneficial COX-1 expression in vitro.
4. Activates the important immune cells called natural killer cells, and acts together with Interleukin-2 to activate these natural killer cells even more in vitro.
5. Protects cells from increased cellular division from the activation of a known mitogen in vitro.