Strawberries for prevention of esophageal cancer: Study

By Dr. Ananya Mandal, MDApr 6 2011

According to a preliminary study released Wednesday, strawberries have the potential to prevent esophageal cancer. Researchers, led by Ohio State University have shown that freeze-dried strawberries slowed the growth of dysplastic, or precancerous, lesions in about 30 people who consumed the fruit for six months. Study's lead researcher, Tong Chen, an assistant professor in the oncology division of Ohio State University, presented the study at the American Association for Cancer Research's annual meeting.

At present esophageal cancer or cancer of the food pipe is the third most common gastrointestinal cancer and the sixth most frequent cause of cancer death in the world, Dr. Chen said. About 16,000 new cases of esophageal cancer a year are diagnosed in the U.S., according to the American Cancer Society. Dr. Chen and colleagues are studying esophageal squamous cell carcinoma, the dominant type of esophageal cancer world-wide. They are looking at whether food or other substances might prevent cancer. Previous work showed that freeze-dried strawberries were able to significantly inhibit tumor development in rats.

For the present study the team designed a small study in humans and approached the California Strawberry Commission, which agreed to fund the study and make available the freeze-dried strawberries. The commission is a state agency funded by the strawberry industry. The team recruited 38 people in China who had mild-to-moderate dysplasia in the esophagus; 36 people completed the study. Biopsies of the esophagus were taken before and after the study. On average, patients were about 55 years old. Each participant consumed 30 grams of freeze-dried strawberries dissolved in a glass of water twice daily for a total of 60 grams a day for six months. Dr. Chen said the freeze-dried substance is about 10 times as concentrated as fresh strawberries, but suggested people could still benefit from eating whole strawberries on a daily basis.

Results showed that 29 out of 36 participants experienced a decrease in histological grade of the precancerous lesion, or a slowing in the growth of the lesion during the study. Overall, six had no change and one had an increase in lesion development.

Dr. Chen said larger, randomized placebo-controlled studies are needed to confirm the results. She said it isn't clear exactly what the anti-cancer agent in strawberries might be. But she noted that strawberries contain a variety of vitamins, minerals and other substances known as phytochemicals, which are also found in some other types of berries. 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 explained.

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. 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.