Read a magazine story about an earlier stage of this research (June 2000).

Souped-Up Broccoli, Broccoli Sprouts Deter Cancers in Rats

Specially grown broccoli--containing hundreds of times more selenium than grocery store varieties--protected laboratory rats against mammary tumors in a Roswell Park Cancer Institute laboratory at Buffalo, N.Y.

And high-selenium broccoli sprouts protected rats against precancerous lesions in the colon in an Agricultural Research Service laboratory in Grand Forks, N.D. Whether the findings translate to humans, either for efficacy or safety, will require further study.

John W. Finley, a nutritionist at ARS' Grand Forks Human Nutrition Research Center, and colleagues recently reported the findings together with Clement Ip at Roswell Park, Buffalo; Phil D. Whanger at Oregon State University, Corvallis, and others.

The broccoli heads and sprouts used in these studies were produced for experimental purposes and are not available commercially. The rats were given enough to approximate a human dose of about 200 micrograms daily. Several human studies have shown that taking a 200 mcg-selenium supplement--that’s about three times the Reference Daily Intake--can reduce the incidence of several types of cancer. But it will not reverse tumors once they develop.

The researchers enriched broccoli because it stores selenium in a unique form, called SeMSC for short. It’s easy for people and animals to convert SeMSC into the active anticancer agent compared to a much longer process for other selenium compounds. In earlier studies, when Finley and co-workers challenged rats with known carcinogens, the animals that had eaten the high-selenium broccoli had far fewer precancerous colon lesions than the groups given selenium salts--selenate or selenite.

In the latest studies, Ip and coworkers at the Buffalo lab found a similar protective effect of high-selenium broccoli against mammary tumors, using a rat model for such tumors. The rats got about 30 times more selenium from the specially grown broccoli than they would in a standard diet.

Meanwhile, Finley and coworkers at the Grand Forks lab tested high-selenium broccoli sprouts in a rat model for colon cancer and saw the same protective effect they had earlier gotten with high-selenium broccoli. Found in many health food stores, broccoli sprouts are known to be rich in other anticancer compounds, but commercially available broccoli sprouts are not enriched in selenium.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.