Black raspberries show multiple defenses in thwarting cancer

October 29, 2001

COLUMBUS, Ohio - 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 underway.

"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.

"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."

The research appears in the journal Cancer Research.

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 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. 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.

Feeding the rats 5 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 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.

By week 35 of the study, a diet of 5 percent black raspberries had reduced the number of tumors per animal by 66.5 percent, compared with NMBA-treated control mice fed a regular diet.

"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."

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. But the mechanism of prevention is still somewhat of a mystery.

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.

"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."

In the current study, Stoner and his colleagues tested the effects of ellagic acid - a plant nutrient shown to have protective effects against esophageal cancer. Berries are rich in ellagic acid. But the researchers found that ellagic acid alone could not account for the fruit's ability to inhibit cancer. "One or more additional berry components are undoubtedly contributing to the fruit's anti-cancer effects," Stoner said.

He chose black raspberries for this study because previous studies had shown that ellagic acid inhibited carcinogen-induced esophageal and colon cancer in animals. He and his colleagues then tested a series of fruits for their ellagic acid content, finding that berries contained the highest amount.

"We then decided to take a food-based approach to cancer prevention and began testing the berries' ability to inhibit chemically-induced esophageal and colon cancer," Stoner said. "Sure enough, we found that freeze-dried berries were highly protective in the esophagus and colon. But we also found that they were ineffective in protecting against lung cancer.

"The protective compounds in berries may not be absorbed into the blood stream and delivered to the lungs in high enough amounts to be protective. We do believe that they protect the esophagus and colon because they are absorbed by these organs as the food moves through the digestive tract."
Written by Holly Wagner, 614-292-8310;

The study was funded by a grant from the Ohio Department of Agriculture and the National Cancer Institute.

Stoner co-authored the study with Laura Kresty, Mark Morse, Peter Carlton, Ashok Gupta, Michelle Blackwood and Charlotte Morgan, all of Ohio State, and Jerry Lu of the M.D. Anderson Cancer Center at the University of Texas in Smithville, Texas.

Ohio State University

Related Cancer Articles from Brightsurf:

New blood cancer treatment works by selectively interfering with cancer cell signalling
University of Alberta scientists have identified the mechanism of action behind a new type of precision cancer drug for blood cancers that is set for human trials, according to research published in Nature Communications.

UCI researchers uncover cancer cell vulnerabilities; may lead to better cancer therapies
A new University of California, Irvine-led study reveals a protein responsible for genetic changes resulting in a variety of cancers, may also be the key to more effective, targeted cancer therapy.

Breast cancer treatment costs highest among young women with metastic cancer
In a fight for their lives, young women, age 18-44, spend double the amount of older women to survive metastatic breast cancer, according to a large statewide study by the University of North Carolina at Chapel Hill.

Cancer mortality continues steady decline, driven by progress against lung cancer
The cancer death rate declined by 29% from 1991 to 2017, including a 2.2% drop from 2016 to 2017, the largest single-year drop in cancer mortality ever reported.

Stress in cervical cancer patients associated with higher risk of cancer-specific mortality
Psychological stress was associated with a higher risk of cancer-specific mortality in women diagnosed with cervical cancer.

Cancer-sniffing dogs 97% accurate in identifying lung cancer, according to study in JAOA
The next step will be to further fractionate the samples based on chemical and physical properties, presenting them back to the dogs until the specific biomarkers for each cancer are identified.

Moffitt Cancer Center researchers identify one way T cell function may fail in cancer
Moffitt Cancer Center researchers have discovered a mechanism by which one type of immune cell, CD8+ T cells, can become dysfunctional, impeding its ability to seek and kill cancer cells.

More cancer survivors, fewer cancer specialists point to challenge in meeting care needs
An aging population, a growing number of cancer survivors, and a projected shortage of cancer care providers will result in a challenge in delivering the care for cancer survivors in the United States if systemic changes are not made.

New cancer vaccine platform a potential tool for efficacious targeted cancer therapy
Researchers at the University of Helsinki have discovered a solution in the form of a cancer vaccine platform for improving the efficacy of oncolytic viruses used in cancer treatment.

American Cancer Society outlines blueprint for cancer control in the 21st century
The American Cancer Society is outlining its vision for cancer control in the decades ahead in a series of articles that forms the basis of a national cancer control plan.

Read More: Cancer News and Cancer Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to