April 6, 2011 -- Eating freeze-dried strawberries may help prevent esophageal cancer, according to new but preliminary research.
''Eating strawberries may be a way for people at high risk for esophageal cancer to protect themselves from the disease," says researcher Tong Chen, MD, PhD, assistant professor of medicine at The Ohio State University Comprehensive Cancer Center, Columbus.
She presented the results of her small study at the American Association for Cancer Research meeting in Orlando, Fla. The study was funded by the California Strawberry Commission.
After an animal study showed strawberries might have some cancer-fighting benefits for esophageal cancer, Chen decided to study their effect in people.
She evaluated the use of freeze-dried strawberries in 36 men and women who had precancerous lesions of the esophagus.
Their average age was about 54. All were at high risk for cancer of the esophagus, the tube that connects the throat to the stomach. It allows food to enter the stomach for digestion.
In 2010, 16,640 new cases of esophageal cancer were diagnosed in the U.S. and 14,500 people died of it, according to the American Cancer Society. Risk factors for esophageal cancer include tobacco use and the combination of smoking and drinking alcohol heavily. A diet low in fruits and vegetables may also increase risk.
Chen instructed the men and women in the study to eat about 2 ounces of freeze-dried strawberries a day. The freeze-dried form was used to boost the potential cancer-fighting ingredients, she says.
"By removing the water from the strawberries we concentrated the components by tenfold," Chen says.
Participants kept records daily of their strawberry intake. They were not instructed to change anything else in their diet or lifestyle. Most participants smoked, Chen says.
All had a biopsy of the esophagus before and after the study. At the study start, 31 had the precancerous condition known as mild dysplasia and five had moderate dysplasia.
Doctors can predict the chances that precancerous lesions will develop into cancer, Chen says. "If they have mild dysplasia, about 25% will develop cancer in about 15 to 20 years. If they have moderate, 50% will develop cancer over the next 15 or 20 years."
The strawberries appeared to slow progression of the lesions in most. "Twenty nine of the 36 experienced a decreased level of precancerous lesions," Chen tells WebMD.
Overall, six had no change and one had an increase in lesion development.
A cancer-causing agent known as N-NMBA (nitrosomethylbenzylamine) is linked with esophageal cancer, Chen says.
It's found in some pickled vegetables, fried bacon, and other foods, she says. Tobacco smoke also contains nitrosamine cancer-causing agents.
''We think the strawberries can inhibit the activation of the NMBA," she says.
Among the substances in the strawberries that may help, she says, are vitamins, folic acid, and minerals.
The new research is interesting but preliminary, according to Stephen Shibata, MD, clinical professor of medical oncology at the City of Hope Comprehensive Cancer Center in Duarte, Calif. He reviewed the study findings for WebMD.
Many questions remain to be answered, he tells WebMD. "The basic idea [for future study] would be to make sure this isn't chance -- to observe a number of patients who did not get strawberries but got medical advice."
It's possible, he says, that the patients in the study made other lifestyle changes once they joined the study.
Other questions to be answered, he says, are figuring out the best dose of strawberries and for how long they should be eaten.
"I would not recommend people go out and eat a lot of strawberries based on this," he says.
More research is needed, including studies that compare eating strawberries with not eating strawberries, says Marji McCullough, RD, ScD, an epidemiologist with the American Cancer Society. Meanwhile, including plenty of fruits and vegetables in your diet is a good idea, she says.
"Studies show that eating a wide variety of non-starchy fruits and vegetables, and avoiding tobacco, alcohol, and obesity, are important ways to reduce the risk of esophageal cancer," McCullough says.
This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.