The study focuses primarily on black men, who are often underrepresented as clinical subjects. It is also the first to link the effect of tomato sauce consumption to a reduction of human DNA damage, considered a marker for increased cancer risk, according to the researchers.
Researchers at the University of Illinois in Chicago fed 32 volunteers with newly diagnosed prostate cancer three-fourths cup of tomato sauce daily for three weeks. The majority of the subjects (24) were black. In addition to causing significant reductions in DNA damage to prostate cancer cells and leukocytes (white blood cells), the treatment resulted in reduced blood levels of prostate specific antigen (PSA), a protein whose increased levels are strongly linked to a higher prostate cancer risk, according to the researchers.
"This study does not say that tomato sauce reduces cancer," cautions Phyllis E. Bowen, Ph.D., a nutritionist at the university and lead investigator in the study. "It says that it reduces DNA damage that we think is associated with cancer."
Although further studies are needed to determine whether reduced DNA damage is actually protective in healthy individuals who eat tomato sauce, the current study suggests that eating extra tomato sauce — perhaps by consuming more pizza, pasta or spaghetti — may be beneficial to some, especially to those at high risk for prostate cancer, says Bowen.
As a group, African-American men have approximately a 34 percent higher rate of prostate cancer, and are twice as likely to die from it, than white men. The reasons are not clearly understood, but diet and genetics are believed to be factors.
Researchers have known for a few years, based on animal studies and epidemiological data, that diets rich in tomato sauce may reduce the risk of prostate cancer. A lower incidence of prostate cancer has been reported among men in Mediterranean countries, including Italy and Greece, where tomato consumption is considered high.
Researchers believe that lycopene, a red pigment with high antioxidant potential, is the most likely agent involved in this effect. Tomatoes contain more lycopene than any other commonly consumed food, but tomato products vary in lycopene content. Tomatoes cooked in oil, such as tomato sauce, are believed to have the highest benefit, as cooking breaks down cell walls to release more lycopene, while oil is thought to enhance the absorption of the fat-soluble chemical.
Besides tomatoes, other foods contain significant amounts of lycopene, including pink grapefruit and watermelon. In general, diets that are high in fats and low in fruits and vegetables are thought to increase the risk of prostate cancer, while diets that are low in fats and high in fruits and vegetables are thought to lower the risk.
Prostate cancer is the second most common form of cancer in men in the United States, accounting for one-fourth of all newly diagnosed cancer cases among men. The prostate is the walnut-sized gland, located below a man’s bladder, that secretes the seminal fluid.
The exact causes of prostate cancer are not known, although genetic factors have been implicated in its development as have an increase in levels of certain hormones, including the male hormone androgen. Whether it can be prevented or controlled using dietary intervention remains the focus of intense study.
Yearly prostate exams are currently recommended, especially for older men, as the risk increases dramatically with age. Researchers are continuing to work on new ways to screen for prostate cancer in the hope that early detection might save lives.
Hunt-Wesson, Inc., a food manufacturer whose products include tomato-based goods, provided funding for this study.
The paper on this research, AGFD 129, will be presented at 2:00 p.m., Wednesday, August 29, at McCormick Place South, Room S504D, Level 5, during the symposium, "Diet and Prevention of Gender-Related Cancers."
Phyllis E. Bowen, Ph.D., R.D., is an associate professor in the department of nutrition at the University of Illinois at Chicago.
— by Mark Sampson
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