Soy and Tomato Combined May Be Effective in Preventing Prostate Cancer

A new study among researchers from the University of Illinois indicates that tomatoes and soy foods may be more effective in preventing prostate cancer when they are eaten together than when either is eaten alone.

"In our study, we used mice that were genetically engineered to develop an aggressive form of prostate cancer. Even so, half the animals that had consumed tomato and soy had no cancerous lesions in the prostate at study's end. All the mice in the control group--no soy, no tomato--developed the disease," said John Erdman, a U of I professor of food science and nutrition, according to a press release.

From the time they were 4 to 18 weeks old, the animals were fed one of four diets: (1) 10 percent whole tomato powder; (2) 2 percent soy germ; (3) tomato powder plus soy germ; and (4) a control group that ate neither tomato nor soy.

The 4- to 18-week time frame modeled an early and lifelong exposure to the bioactive components in these foods, he said.

"Eating tomato, soy, and the combination all significantly reduced prostate cancer incidence. But the combination gave us the best results. Only 45 percent of mice fed both foods developed the disease compared to 61 percent in the tomato group, and 66 percent in the soy group," he said.

Prostate cancer is the most frequently diagnosed cancer in men, but the disease has nearly a 100 percent survival rate if it's caught early. In older men, it is often a slow-growing cancer, and these men often choose watchful waiting over radiation and surgical treatments that have unwelcome side effects, said Krystle Zuniga, co-author of the paper.

Soy isoflavone serum and prostate levels in the mice are similar to those found in Asian men who consume one to two servings of soy daily. In countries where soy is eaten regularly, prostate cancer occurs at significantly lower levels, according to Erdman.