Q. Can wasabi prevent food poisoning?

A. Lately, we have been bombarded with headlines of illnesses caused by foods contaminated with E. coli bacteria. A few months ago, it was spinach, and a few weeks ago, it was lettuce at several Mainland Taco Bell restaurants. It would be great if there was a magic substance that could protect us from these nasty germs.

Well, there sort of is. In the 10th century, a Japanese medical encyclopedia describes germ-fighting properties of the Wasabia japonica plant, from which "real" wasabi is derived. Because raw fish may be prone to bacterial contamination, it is thought that this was one reason that wasabi was eaten with raw fish by the Japanese in the old days.

Recent studies have shown that substances called allylisothiocyanates found in the roots, stems and leaves of the W. japonica plant inhibit the growth of several types of food poisoning bacteria. They are especially effective against E. coli and staphyloccocus bacteria, common culprits in contaminated food.

Unfortunately, the green paste we see on our plates when we order sushi is usually not "real" wasabi. Neither are the tubes of green paste or powder we get from the grocery store. They are usually made of horseradish, starch binders, green food coloring, and possibly mustard. They don't contain any part of the W. japonica plant, which is difficult to grow. It is quite expensive compared to the European horseradish that is used as a substitute.

Although horseradish comes from a different plant than wasabi, it may still offer some protection against food poisoning. Horseradish contains bacteria-killing allylisothiocyanates but in different amounts than wasabi. Results of a Japanese study discussed in the journal Biofactors showed that both European horseradish and wasabi inhibit food poisoning bacteria.

The best protection from food poisoning is to avoid eating contaminated food. Unfortunately, we don't always know when food has pathogens until we become sick. They're not usually detectable by smell or taste.

As for wasabi, fresh wasabi root grown in Oregon and New Zealand is available on the Web. Big Island farmer Lance Yamashiro also grows it. It may be available at some Japanese markets. It is served in some upscale restaurants on the Neighbor Islands and at Alan Wong's on O'ahu.

Because of the high cost of real wasabi, I will probably continue to enjoy the rush of heat in my nostrils provided by faux wasabi for now.

Amy Tousman is a registered dietitian and certified diabetes educator. Hawai'i experts in traditional medicine, naturopathic medicine and diet take turns writing the Prescriptions column. Send questions to: Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; islandlife@honoluluadvertiser.com; or fax 535-8170. This column is not intended to provide medical advice.