Gastric cancer thus joins a long list of malignancies for which studies have shown a reduced risk associated with a diet that contains broccoli—including cancer of the esophagus, bladder, skin and lung, among others.
“I have to be careful about how enthusiastically I state the case,” said Jed W. Fahey, the faculty research associate at Johns Hopkins School of Medicine whose research led to the Japanese study. “This was a small trial. But the evidence is all pointing toward broccoli or broccoli sprouts being able to prevent cancer in humans.”
The chemical in broccoli responsible for the protective effect is sulforaphane, Fahey said. His group first described it as a potent antibiotic against Helicobacter pylori in 2002. The Japanese study, reported in the April issue of Cancer Prevention Research, was designed to show whether eating broccoli sprouts, which are rich in sulforaphane, resulted in lower levels of H. pylori, a bacterium that is closely associated with the risk of stomach damage and gastric cancer.
The study was done in Japan because the rate of H. pylori infection there is high. Though about 25 percent to 30 percent of Americans are infected, “in Japan there is infection at levels approaching 90 percent because of crowding and poor economic conditions,” Fahey said. The bacterium is spread by person-to-person contact.
The study included 48 infected people. Half ate 70 grams a day of broccoli sprouts, and the others ate alfalfa sprouts, which do not contain sulforaphane. After eight weeks, tests showed significantly lower levels of H. pylori infection in those who ate broccoli sprouts, with no reduction among the alfalfa sprout eaters.
“H. pylori is a known carcinogen,” Fahey said. “The fact that we were able to reduce the effects of an infectious agent that is also a carcinogen gives us hope that if someone were to eat broccoli sprouts or broccoli regularly, it would reduce levels of H. pylori and, over a period of many years, reduce the chance that they would get that cancer. It is not proven, but the results are highly suggestive.”
Fahey is a co-founder of a company licensed by Hopkins to produce broccoli sprouts. He has no equity in the company.
Broccoli and sprouts are both important, said Dr. Steven H. Zeisel, director of the Nutrition Research Institute at the University of North Carolina.
“Specifically, the sprouts before broccoli becomes a plant are rich in sulforaphane,” Zeisel said. “It is formed only when broccoli or sprouts are macerated, chewed on. When you break the cell, the chemical is formed.”
Sulforaphane then causes the liver to produce an enzyme that is important in deactivating cancer-causing agents, Zeisel said. “People who eat more broccoli tune up their liver and other cells to destroy cancer-causing agents,” he said.
Garlic has the same effect, he said, and so “increasing the amount of plants in the diet—broccoli is good, broccoli sprouts even better — causes production of a valuable bioactive chemical.”
That is good advice, Fahey said, but inevitably some people will try a shortcut, taking a sulforaphane pill rather than eating what’s good for them.
“I have come to the resigned conclusion that we will not be able to persuade everybody to change their diet,” Fahey said. “A pill would be better than nothing, but that doesn’t mean that I’m advocating it or promoting massive pill-taking.”
Just two or three ounces a day of cooked broccoli would have a protective effect, he said.
Zeisel added that people who try the pill-taking shortcut might well lose any benefit.
“It’s probably a combination of ingredients in the plant that is responsible,” he said. “When you try to extract them out to make a pill, it usually doesn’t work.”
The U.S. National Cancer Institute has information on diet and cancer.
SOURCES: Jed W. Fahey, Sc.D., faculty research assistant, Johns Hopkins School of Medicine, Baltimore; Steven H. Zeisel, M.D., director, Nutrition Research Institute, University of North Carolina, Chapel Hill, N.C.; March 6, 2009, Cancer Prevention Research
By Ed Edelson
Last Updated: April 06, 2009
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