True wasabi - Wasabia japonica- is a member of the Brassicaceae family of vegetables which includes cabbages, horseradish and mustard.

Packed with powerful cancer-fighters called isothiocyanates, wasabi helps to stimulate the detoxification enzymes in your liver that disarm free-radicals and carcinogens.

Be sure to look for real wasabi, which comes powdered in a can or fresh in root form. Most wasabi in sushi restaurants is colored horseradish.  

Wasabi is generally sold either in the form of a root (real wasabi), which must be very finely grated before use, or as a ready-to-use paste (horseradish, mustard and food coloring), usually in tubes. Once the paste is prepared it should remain covered until served to protect the flavor from evaporation.