Berries: Sweetening Cancer Prevention
When it comes to cancer prevention, berries are among the more diverse and powerful members of the fruit family. AICR’s expert report and its updates show that eating a diet high in fruit reduces the risk of cancers of the esophagus, lung, stomach, mouth, pharynx and larynx. Research is providing new evidence that berries are not only strong antioxidants, but affect the expression of a vast range of genes and molecular pathways associated with the development of cancer.
According to Gary Stoner, PhD, a Professor of Medicine at the Medical College of Wisconsin who has studied berries' potential link to cancer prevention for more than two decades, berries contain two particularly active classes of compounds that may make them tough anti-cancer contenders: anthocyanins, flavonoids that give berries their dark color, and ellagitannins, the source of the polyphenol ellagic acid.
Anthocyanins are probably the key cancer preventive agents in most berries because they are present in high concentrations. Berries also contain vitamin C and fiber, along with trace amounts of vitamins A and E, calcium and selenium.
What the Studies Show
Berries' anthocyanins and ellagic acid are poorly absorbed in our blood, says Stoner. This has led scientists to focus primarily on cancers that come into direct contact with berry’s phytochemicals, such as cancers of the mouth, esophagus and colon. Recent evidence suggests our gut bacteria metabolizes berries’ anthocyanins into metabolites that are better absorbed than the anthocyanins themselves, suggesting the metabolites may be the ultimate cancer preventive agents.
Animal studies conducted by Stoner found that a diet of freeze-dried black raspberries or strawberries can inhibit esophageal cancer in rats by 30 to 70 percent and colon cancer by up to 80 percent. In these studies, researchers ground freeze-dried berries into a powder to make a concentrated formulation
In early phase clinical studies, Stoner and his colleagues have found that black raspberry and strawberry powder is safe and well tolerated. Current pilot studies are focusing on berries acing as chemoprevention agents for individuals at high risk for cancer.
Berries and Breast Cancer
AICR grantee Harini Aiyer, PhD
In animal studies investigating the effect of blueberries and black raspberries on estrogen-receptor (ER) positive breast tumors, Harini Aiyer, PhD, Postdoctoral Research Fellow at Lombardi Cancer Center, Georgetown University School of Medicine, found that a six-month diet of black raspberries reduced tumor volume in rats by 70 percent.
The same diet length of blueberries had similar results, says Aiyer, who conducted this research in graduate school. In later cell studies, Aiyer also found that adding ellagic acid to ER positive cells treated with tamoxifen made them less likely to become resistant to the effects of the drug. Although promising, the data is preliminary and further studies are needed.
“If we look at estrogen as the fuel for some breast cancers that guides the car forward, we may be able to use ellagic acid, which acts like an anti-estrogen, to cut off the fuel supply or even stop the engine," said Aiyer, an AICR grantee.
Incorporating Berries into the Day
Research with berries and cancer prevention often includes different berries, and there may be a lot of merit to mixing berry types, said Stoner. “In animal models of esophageal cancer, we have found that at least seven berry types are effective in preventing cancer irrespective of their chemical composition.”
According to Stoner, one possible concern with eating berries is that some people may experience mild gastrointestinal disturbances, but these are usually transitory. He suggests people get about four to five helpings of berries per week.
Likewise, Aiyer suggest people try to eat berries every day, also stressing the whole food approach. It’s the combination of berry’s compounds that appears most effective for cancer prevention. Aiyer’s animal studies, for example, found that a black raspberry diet was more effective in reducing mammary tumors than a pure ellagic acid diet. “This was due to the berries’ anthocyanins that synergize with ellagic acid to provide greater benefit,” she said.
Excerpted from ScienceNow.