COLUMBUS – A cup of black raspberries a day may help keep esophageal cancer at bay.
Researchers found evidence in rats that black raspberries may both prevent the onset of esophageal cancer as well as inhibit precancerous growth already under way.
Health snack. “Black raspberries are loaded with nutrients and phytochemicals that may prevent the development of cancer,” said Gary Stoner, a study co-author and a professor of public health at Ohio State University.
Stoner, who has also found similar anti-carcinogenic effects with strawberries, said the study results suggest that a daily diet of about 1.4 to 2 cups of fresh berries may be ideal for staving off certain types of cancer.
How many a day? “Although this level is larger than a standard serving size of fruit, it is behaviorally possible,” he said.
“The National Cancer Institute recommends that every American eat at least four to six helpings of fruit and vegetables each day. We suggest that one of these helpings be berries of some sort.”
Cancer statistics. Esophageal cancer is the sixth-leading cause of cancer-related deaths worldwide. The outlook is bleak for those diagnosed with the disease – five-year survival rates range from 8 percent to 12 percent.
In the current study, the researchers looked at black raspberries’ ability to halt the onset of cancer, as well as the fruit’s ability to inhibit the progression of precancerous cells to cancer.
They conducted experiments on two groups of rats. Some of the rats from each group were injected with NMBA, a chemical carcinogen that induces esophageal cancer.
About the study. NMBA is one of a group of chemicals called nitrosamines, compounds that have been linked to cancer. Nitrosamines are found in fried bacon, cured meats, tobacco products, beer and certain industrial products.
Rats in the study received NMBA and their diet in a variety of combinations. Some rats were fed a regular diet without raspberries, while others received diets consisting of 5 percent or 10 percent black raspberries.
Some were fed raspberries only after receiving NMBA, while others were fed the raspberry diet before and after the injection with the carcinogen.
The results. Feeding the rats 5 percent and 10 percent black raspberries before and after NMBA treatment reduced the number of tumors per rat by 39 and 49 percent, respectively, when compared to animals not fed black raspberries.
The fruit also hindered the development of esophageal cancer in individual rats fed black raspberries after NMBA treatment.
By week 15 of the study, diets of 5 percent and 10 percent black raspberries appeared to decrease tumor occurrence and size. At week 25, diets of 5 and 10 percent black raspberries had reduced the number of tumors by an average of 62 percent and 43 percent, respectively.
Consistent finding. “When berries were fed to the rats that had been pretreated with NMBA, the diet containing 5 percent black raspberries seemed to inhibit cancer to a greater degree than did a diet of 10 percent berries, a finding that has also emerged in other studies,” Stoner said.
“There are certain compounds in berries – and other fruits and vegetables – that in very high doses may actually promote the cancer process. This certainly doesn’t mean to stop eating fruits and vegetables, but don’t overdo it.”
Other foods, too. Scientists know that certain foods contain compounds that are likely to protect against specific types of cancer. Past studies suggest that tomatoes help protect against prostate cancer, and that tea consumption may reduce the risk for esophageal cancer.
Raspberries are chock full of compounds with potentially anti-carcinogenic effects, including vitamins, minerals and plant nutrients such as anthocyanins – strong antioxidants that give berries their color.
Looking to the future. “We’re currently looking at berry extracts and testing the ability of these extracts to inhibit the development and progression of cancer,” Stoner said.
“As we identify these extracts, we will then try to pinpoint the specific compounds in them that help inhibit cancer.”