Diet and cancer prevention: New evidence for the protective effects of fruits and veggies

The age-old refrain, “Eat your vegetables!” gets scientific support as researchers present the latest findings on cancer prevention at the American Association for Cancer Research’s Sixth Annual International Conference on Frontiers in Cancer Prevention, being held December 5 – 8 in Philadelphia, Pennsylvania.

Today, researchers present new data that demonstrate how diets full of raw vegetables -particularly broccoli sprouts - and black raspberries could prevent or slow the growth of some common forms of cancer.

Dietary administration of black raspberries modulates markers of oxidative stress in patients with Barrett’s esophagus. Abstract no. B34

Black raspberries may protect against esophageal cancer by reducing oxidative stress in patients with Barrett’s esophagus (BE), a pre-cancerous condition that usually arises due to gastroesophageal reflux disease, report researchers at The Ohio State University.

According to the researchers, BE patients have a 30- to 40-fold increased risk of developing esophageal adenocarcinoma (EAC), the fastest growing cancer in terms of incidence in the United States. EAC is a deadly cancer with a 15 percent five-year survival rate; an estimated 14,000 people will die from esophageal cancer in the U.S. in 2007. Moreover, a number of treatment options are available to BE patients for symptom relief, researchers say, but none has proven curative or eliminated the risk of cancer progression.

“In addition to gastroesophageal reflux disease, increasing body mass index or body fatness is strongly associated with EAC development; whereas, plant-based diets and particularly increased fruit consumption has been associated with decreased risk for EAC,” said Laura A. Kresty, Ph.D., assistant professor of at Ohio State University.

According to Kresty, research using animal models of BE showed that black raspberries inhibited chemically induced oral, esophageal and colon cancers. The studies showed that berries reduced measures of oxidative stress (the destruction done to cells by oxygen ions or small reactive molecules containing oxygen), decreased DNA damage, inhibited cellular proliferation rates, and reduced the number of pre-cancerous cells in the esophagus and colon.

“We can give black raspberries before we have any initiated cells, or we can administer after we already know we have initiated cells,” Kresty said. “What’s promising about the berries is that they work in both cases, and in multiple models. There aren’t nearly as many agents that work in the latter scenario.”

In this study, BE patients ate 32 or 45 grams (female and male, respectively) of freeze-dried black raspberries daily for 26 weeks. After 26 weeks, patients experienced a statistically significantly decline in the mean urinary levels of 8-Isoprostane, an indicator of global oxidative stress and DNA damage - both processes linked to the development of BE and EAC. According to Kresty, 58 percent of patients experienced marked individual level declines of 8-Isoprostane. Among 37 percent of BE patients, the black raspberry regimen also resulted in the increased expression of tissue levels of GSTpi. GSTpi is an enzyme that detoxifies carcinogens and reactive oxidants and is typically reduced in Barrett’s epithelium compared to normal esophageal epithelium.