When it comes to preventing prostate cancer, the benefits of tomatoes and soy may be more powerful when they're combined than when they're eaten alone, according to a new study published in Cancer Prevention Research by researchers at the University of Illinois at Urbana-Champaign and Ohio State University.

Using mice genetically engineered to develop an aggressive form of prostate cancer, the team fed them one of four diets: one composed of 10 percent tomato powder, one composed of 2 percent soy germ, one containing both tomato powder and soy germ, and a control diet that contained neither tomato nor soy. In the group of mice fed both tomato and soy, 45 percent developed prostate cancer, compared to 61 percent of the mice in the tomato group, 66 percent of the mice in the soy group, and all of the control mice.

These results would translate to three to four servings of tomato per week, and one to two servings of soy foods daily for an adult human male, the researchers said in a University of Illinois press release. It may also be more beneficial to eat tomatoes and drink soy milk than take lycopene or soy supplements, as compounds in the whole foods could be adding to the anti-cancer benefits.