High-Selenium Broccoli Vs. Colon
By Judy McBride
June 9, 2000
Agricultural Research Service scientists
dramatically reduced early stages of colon cancer in rats by feeding the
animals broccoli grown in a high-selenium medium.
ARS nutritionists John Finley and Cindy Davis drew on reports that the form
of selenium in broccoli is more potent against cancer than other food forms or
selenium salts. The broccoli form is known as selenium methyl selenocysteine,
or SeMSC. The body simply snips the end off this amino acid to produce the
anticancer agent called methyl selenol.
The form of selenium prevalent in grains and some meats requires several
chemical conversions to produce methyl selenol. Selenium salts--the forms used
in some supplements--convert more readily. But its only one step for the
form in broccoli to get there.
To test its efficacy, the researchers grew broccoli having several thousand
times the selenium normally found in the vegetable. They grew the broccoli at
the Grand Forks Human Nutrition
Research Center in North Dakota.
Then, in a series of rat studies, they confirmed that differences in
selenium metabolism translated to differences in risk of colon cancer. First,
they pitted high-selenium broccoli against the selenium salt selenate. And they
made sure to control for any beneficial effects of broccoli itself, for the
vegetable scores high in antioxidants and contains other substances shown to be
active against cancer.
After beefing up the rats selenium levels for several weeks, they
injected the animals with a potent carcinogen. High-selenium broccoli always
resulted in fewer precancerous lesions than selenate. And the number of
precancerous lesions decreased as the dose increased.
Then they confirmed the findings using a different salt--selenite--and a
higher dose of selenium. They also challenged the animals with a much more
potent carcinogen. Although many more precancerous lesions occurred, the rats
fed high-selenium broccoli had half as many as the animals getting selenite.
More details about these studies appear in the June issue of Agricultural Research magazine.
ARS is USDAs chief scientific agency.
Scientific contact: John W. Finley
and Cindy D.
Davis, ARS Grand Forks Human Nutrition Research Center, Grand Forks, N.D.;
phone (701) 795-8353, fax (701) 798-8395,