by J. Raloff
There's good news for George Bush and others who detest broccoli. Without ever downing another forkful of the green veggie, they can naturally enrich their diets with its most potent anticancer constituent. All they need to do is sprinkle a few tablespoons of sprouts on a salad -- broccoli sprouts, that is.
Paul Talalay and his coworkers at Johns Hopkins Medical Institutions in Baltimore surprised cancer researchers in 1992 when they isolated sulforaphane, a compound in broccoli and its botanical kin that inhibits the development of cancer (SN: 3/21/92, p. 183). The compound works by turning on detoxifying phase-2 enzymes.
The hoopla over sulforaphane soon died down, however. Researchers realized that to get enough of the compound even from broccoli, its richest source, a diner would have to consume unrealistic amounts each week -- about 2 pounds of the brassica, which some people find bitter (SN: 7/12/97, p. 24).
Undeterred, Talalay's team began testing broccoli throughout its life cycle to find how sulforaphane forms and when. "To our surprise," Talalay says, "we found that the seeds were extraordinarily high in [phase-2] enzyme activity." So were 3-day-old broccoli sprouts, which he says are considerably more edible than the seeds. "The sprouts aren't bitter and don't taste like broccoli," he says, though they do possess "a little zing."
Both seeds and sprouts contain a compound that is turned into sulforaphane when their cells are crushed during chewing. As the plants grow, this initial store of sulforaphane's precursor becomes diluted. Indeed, mature plants contain only 2 to 5 percent as much per gram as sprouts do. Even the sulforaphane precursor dramatically inhibits chemically induced cancers in rats, Talalay's team reports in the Sept. 16 Proceedings of the National Academy of Sciences.
Though diets rich in vegetables inhibit cancer development, Talalay's group is one of the few to execute "the very difficult, nitty-gritty studies" of the mechanisms, says Lee W. Wattenberg of the University of Minnesota in Minneapolis. Such work raises the prospect of mining broccoli for extracts that might be administered as cancer-fighting dietary supplements, he says.
Talalay is developing a center to certify that any sprouts ultimately marketed contain high quantities of the sulforaphane precursor.
Each dish contains the same amount of anticancer compound.
Fahey, J.W., Y. Zhang, and P. Talalay. 1997. Broccoli sprouts: An exceptionally rich source of inducers of enzymes that protect against chemical carcinogens. Proceedings of the National Academy of Sciences 94(Sept. 16):10367.
Fackelmann, K. 1997. The bitter truth. Science News 152(July 12):24.
Gerhauser, C., et al. 1997. Cancer chemopreventive potential of sulforamate, a novel analogue of sulforaphane that induces phase 2 drug-metabolizing enzymes. Cancer Research 57(Jan. 15):272.
Monastersky, R. 1994. Broccoli inhibits cancer--mostly. Science News 146(Dec. 24&31):442.
Prochaska, H.J., A.B. Santamaria, and P. Talalay. 1992. Rapid detection of inducers of enzymes that protect against carcinogens. Proceedings of the National Academy of Sciences 89:2394.
Raloff, J. 1990. Another reason to eat your broccoli raw. Science News 137(June 9):367.
______. 1989. To stymie cancer, eat broccoli raw. Science News 136(Nov. 25):351.
Stroh, M. 1992. Inside broccoli: A weapon against cancer. Science News 141(March 21):183.
Zhang, Y., et al. 1992. A major inducer of anticarcinogenic protective enzymes from broccoli: Isolation and elucidation of structure. Proceedings of the National Academy of Sciences 89:2399.
Zhang, Y., et al. 1994. Anticarcinogenic activities of sulforaphane and structurally related synthetic norbornyl isothiocyanates. Proceedings of the National Academy of Sciences 91:3147.
Department of Pharmacology and Molecular Sciences
Johns Hopkins School of Medicine
725 North Wolfe Street
Wood Basic Science, Room 406
Baltimore, MD 21205
Department of Laboratory Medicine
University of Minnesota
6133 Jackson Hall
Minneapolis, MN 55455
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Table of Contents - September 20, 1997
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