Protecting Your DNA from Lethal MutationsSeptember 2005
By Dave Tuttle
Wasabi Battles Carcinogens
Wasabi japonica is a member of the Brassica, or cruciferous, family of vegetables, which includes cabbage, broccoli, cauliflower, bok choy, horseradish, and 10 other plants. These vegetables add crunch and flavor to meals, and have long been recognized as important parts of a healthy diet because of their fiber content. Recent research has revealed, however, that there is much more to these vegetables than mere fiber. They contain high levels of glucosinolates, a group of compounds that are converted to isothiocyanates by the enzyme myrosinase when the plant cells are damaged by harvesting, cutting, or chewing. It is the isothiocyanates that give these vegetables their sharp flavors. Wasabi, the green, pungent horseradish usually served with sushi, is one of the most potent sources of isothiocyanates among all plant species.
The isothiocyanates do more than add flavor to a meal. A Japanese study found that allyl isothiocyanate has significant antioxidant actions, particularly against the superoxide radical.22 According to the authors, this phytochemical also has an inhibitory effect on the growth of food poisoning bacteria and fungi, and showed anti-mutagenic activity against a common carcinogen found in broiled fish and meat.
Three other Japanese studies discovered dramatic benefits from 6-methylsulfinyhexyl isothiocyanate, or 6-MITC. Researchers at Japan’s Nagoya University found 6-MITC to be a potent inducer of glutathione S-transferase, one of the most important Phase II detoxification enzymes, due to its high reactivity.23 6-MITC has also been shown to inhibit cell proliferation in human leukemia and stomach cancer cells in vitro by promoting apoptosis within 24 hours.24,25 This may suppress the growth of pre-clinical tumors and contribute to a decreased incidence of cancer. Scientists at Japan’s Kanazawa Gakuin College learned that 6-MITC has similar properties against breast cancer and melanoma cells, influencing not only cell growth but also the cells’ survival.26 The authors concluded that because of the low dosages required, 6-MITC has the potential to control cancer cells of all types.
The importance of 6-MITC has also been demonstrated in experiments with rats and mice. Japanese researchers discovered that oral 6-MITC is easily absorbed and rapidly enters the circulatory system, reaching a maximum level within 30 minutes.27 Blood levels then decrease relatively slowly, allowing it to stimulate higher glutathione S-transferase levels for extended periods. Additional experiments have found that isothiocyanates inhibit rat lung, esophagus, mammary gland, liver, small intestine, colon, and bladder tumorigenesis.28-30 These results have led researchers to consider isothiocyanates to be readily available cancer chemopreventive agents.
Because cultivating wasabi is complex and time consuming, and fresh Wasabi japonica rhizomes (roots) are very expensive, most restaurants substitute less expensive European horseradish, adding green color and a touch of real wasabi for flavor. European horseradish, however, does not contain wasabi’s diversity of isothiocyanates. While it shares many of the short-chain isothiocyanates, European horseradish lacks longer-chain isothiocyanates, including 6-MITC. Most other vegetables in the Brassica family are also deficient in these longer-chain isothiocyanates, so it is hard to attain all the potential benefits of these phytochemicals from dietary sources. In addition, cooking these vegetables results in substantial degradation of the myrosinase conversion enzyme. This makes wasabi supplementation an attractive option.
Broccoli Extract: Rich in Anti-Mutagens
Broccoli is a plentiful source of glucosinolates, which are converted enzymatically into isothiocyanates. In the body, the isothiocyanates in broccoli boost production of several Phase II detoxification enzymes, enhance antioxidant status, and protect animals against chemically induced cancer.31 As a result, nutritionists recommend consuming broccoli and similar vegetables at least three times a week. Concentrated extracts of broccoli enable you to boost your intake of these beneficial compounds even more.
One of the primary isothiocyanates in broccoli is sulforaphane. In numerous studies, this plant chemical has demonstrated anti-carcinogenic actions. In an in-vitro experiment with mouse liver cancer cells, sulforaphane raised levels of two Phase II detoxification enzymes, glutathione S-transferase and quinone reductase.32 The authors concluded that sulforaphane’s ability to elevate these enzymes may be a significant component of broccoli’s anti-cancer action.
A study at Johns Hopkins University examined oral sulforaphane’s effects on chemically induced mammary cancers in rats.33 When given around the time of exposure to the carcinogen, sulforaphane significantly reduced the incidence, multiplicity, and weight of mammary tumors, and their development was delayed. An in-vitro experiment shows that sulforaphane can also help fight prostate cancer,34 a disease characterized by early and near-universal loss of expression of the glutathione S-transferase enzyme. However, when sulforaphane was added to several human prostate cancer cell lines in vitro, Phase II enzyme expression increased dramatically, bolstering cell defenses. This finding helps to explain the observed correlation between increased consumption of cruciferous vegetables and reduced risk of prostate cancer.
Broccoli’s benefits do not end there. A study of vegetables found that broccoli produced the greatest protective effect against several mutagenic chemicals,35 and also stimulated the proliferation of non-cancerous cells. Another experiment at Johns Hopkins found that the sulforaphane in broccoli is a potent agent against three reference strains and 45 clinical isolates of the H. pylori bacterium.36 A study performed at the same time showed that sulforaphane also blocked stomach tumors in mice exposed to mutagenic chemicals. According to the researchers, these multiple benefits resulted from increased production of Phase II detoxification and antioxidant enzymes.
Maximizing Protection Against Mutagens
It has become increasingly difficult to protect our health from the encroachment of carcinogenic chemicals, including pesticides, that are part of the air we breathe, the water we drink, and the food we eat. Providing the body with defensive agents such as curcumin, chlorophyllin, wasabi, and broccoli extract can maximize protection against DNA damage, thus making an important contribution to optimal health and longevity.
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