Soy and tomato combo may be effective in preventing prostate cancer

Tomatoes and soy foods may be more effective in preventing prostate cancer when they are eaten together than when either is eaten alone, said a University of Illinois study.

"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.

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.

Prostate cancer is the most common cancer for men in Western countries. A man's risk of developing prostate cancer is 35% higher than a woman's risk of getting breast cancer. In 2009, an estimated 192,000 men in America will be diagnosed with prostate cancer, and an estimated 27,000 people will die from this relatively slow-growing cancer this year. If current trends continue, 1 in 6 American men will develop prostate cancer during his lifetime.

Under normal conditions, cells within the prostate grow, divide, and die in a controlled manner. Prostate cancer develops when the cells begin to grow out of control. Instead of dying, these cells outlive normal cells, invade adjacent tissues, and sometimes spread to other parts of the body (process called metastasis). Abnormal cell growths are called tumors. Prostate cancer is usually comprised of several very small tumors within the prostate. Provided it has not metastasized to other parts of the body, prostate cancer can often be successfully treated with surgery or radiation. Unfortunately, as it usually causes no symptoms early on, prostate cancer is often diagnosed only at a later stage when it has already spread to other parts of the body.

People with a family history of prostate cancer have a significantly higher risk of developing the disease than men without close relatives diagnosed with the disease. Men with a single first-degree relative (father, brother or son) with a history of prostate cancer are twice as likely to be diagnosed with the disease, while those with at least two close relatives affected are nearly four times as likely to develop the disease. The risk increases further if the family members were affected at a young age. Although genetics seem to influence a man's risk of developing prostate cancer, lifestyle factors, such as diet, are likely to have an effect as well.