"We set out to look at the effect of digestion, subjecting tea extracts to simulated digestion in the lab setting and looking for changes in biological activity between digested and undigested samples exposed to cancer cell lines," Bomser said.
In the laboratory study, they found that whether the extracts were digested or not and the type of tea affected the anticancer activity, as did the type of cancer cell.
"For the black tea, digestion didn't have much of an impact on colon cancer activity," he said. However, the anticancer effect of the green tea on the colon cancer cells was about 50 percent less when the extracts were digested. And the gastric cancer cells, overall, were less sensitive to the anticancer effects than were the colon cancer cells.
More study is needed, Bomser said, but, "If catechins [such as EGCG] are in fact the primary compounds responsible for anticancer activity rather than the breakdown products, you want to maintain and absorb as many catechins [as possible]," he said.
In a previous study, one researcher on the current team found that one way to protect the catechins from breaking down was to add lemon or vitamin C to tea.
The tea research is interesting, and the results not unexpected, said Tom Gasiewicz, chairman of the department of environmental medicine at the University of Rochester Medical Center, who has studied tea's health benefits extensively.
"To me, it's not unexpected that digestion would be accompanied by loss of [anticancer] activity," he said. "The bottom line is, we still don't know what concentrations are effective and have anticancer activity in other organs besides the GI tract."
Yet another team of researchers found in animal studies that tart cherries help reduce inflammation, in turn potentially reducing the risk of getting heart disease and type 2 diabetes. Inflammation is a normal process that fights infection or injury, but when it's chronic, it increases the risk for heart problems and diabetes.
The cherries contain antioxidants called anthocyanins, believed to give them their anti-inflammatory powers. The cherry study was funded by the Cherry Marketing Institute, but the institute had no other role in the study, conducted at the University of Michigan.
Compounds in the cherries, said Gasiewicz, may work in similar ways as the tea extracts.
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SOURCES: Margaret Bynoe, Ph.D., assistant professor, microbiology and immunology, Cornell University School of Veterinary Medicine, Ithaca, N.Y.; John Richert, M.D., executive vice president, research and clinical programs, National Multiple Sclerosis Society, New York City, Tom Gasiewicz, Ph.D., professor and chairman, department of environmental medicine, University of Rochester Medical Center, Rochester, N.Y.; Joshua Bomser, Ph.D., associate professor, nutrition, Ohio State University, Columbus; April 6-7, 2008, presentations, Experimental Biology annual meeting, San Diego