The studies were presented Sunday in Chicago at the American Chemical Society's national meeting.
Both studies included tests on rats, not people.
The first study comes from scientists including Gary Stoner, Ph.D., of Ohio State University's internal medicine department.
In a lab, they prepared an extract made from black raspberries and added it to the diet of rats that had been exposed to a cancer-causing substance.
Those rats developed up to 80 percent fewer colon tumors and 40 percent to 60 percent fewer esophageal tumors than rats exposed to the same carcinogen that hadn't received the raspberry extract.
Based on the findings, the scientists have begun tests in people with Barrett's esophagus (a condition of the esophagus that increases risk of esophageal cancer) and precancerous colon polyps. The results of those tests aren't yet available.
Blueberries vs. Colon Cancer
The second study focused on pterostilbene, a compound found in blueberries, cranberries, lingonberries, and grapes.
The researchers included Bandaru Reddy, Ph.D., research professor of chemical biology at Rutgers, the State University of New Jersey.
They added pterostilbene to the diets of rats exposed to a cancer-causing substance. Pterostilbene reduced the formation of precancerous colon growths in those rats.
"This study underscores the need to include more berries in the diet, especially blueberries," Reddy says in an American Chemical Society news release.
The amount of pterostilbene in berries varies, Reddy notes.
Berries can be part of a healthy diet. But it's too soon to count on berries to prevent colon cancer.
The studies don't prove that berries prevent colon cancer or esophageal cancer in people, and the researchers aren't blaming cancer on diet. A mix of genetic and environmental factors likely affects cancer risk.
By Miranda Hitti
Reviewed by Louise Chang, M.D.
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