A Slice of Pizza Cuts Prostate Cancer Risk
Antioxidant in tomatoes reduces DNA damage, says study
WEDNESDAY, Dec. 19, 2001 (HealthDayNews) -- Men with a taste for ketchup, tomato juice or pasta sauce may have an extra edge against prostate cancer, suggests a new study.
Researchers in Chicago suspect that lycopene, the pigment that gives tomatoes their red color, may reduce damage to DNA linked to prostate cancer, raising its potential as a therapy for this type of tumor.
The findings, which appear in the Dec. 19 issue of the Journal of the National Cancer Institute, add to a growing body of evidence about lycopene's effects against conditions that include cancer and cardiovascular disease.
Lycopene is part of a family of pigments called carotenoids, which occur naturally in fruits and vegetables.
Venketeshwer Rao, a professor of nutritional sciences who studies lycopene and health at the University of Toronto, says that North Americans get between 85 percent and 90 percent of their dietary lycopene from tomatoes, although it can also be found in foods like watermelon and pink grapefruit.
The chemical form of lycopene found in processed tomato-based foods, like pasta sauces and ketchup, is absorbed more efficiently than the lycopene found in fresh tomatoes, says Rao. Lycopene is also a powerful antioxidant that neutralizes harmful oxygen radicals that have been linked to various forms of cancer, including prostate cancer.
More than 198,000 American men develop prostate cancer every year and about 31,500 men will die of the disease. Prostate cancer is most common in men over the age of 55, and in the United States, it's roughly twice as common among black men as it is among white men.
Early signs include frequent or painful urination or weak urine flow. The disease is detected either by a rectal exam or a blood test showing high levels of prostate-specific antigen (PSA), and confirmed by tests including ultrasound or biopsy.
In the latest study, Phyllis Bowen and her colleagues at the University of Illinois in Chicago followed 32 men recruited between May 1998 and July 1999. All were between the ages of 57 and 69, had been diagnosed with prostate cancer and were scheduled for a radical prostatectomy, or removal of the entire prostate.
For the three weeks prior to the surgery, Bowen had the men eat a tomato-based pasta dish, containing three-quarters of a cup of tomato sauce or roughly 30 milligrams of lycopene, once a day. Fullerton, Calif.-based Hunt-Wesson, Inc., which partially funded the study, provided the tomato sauce.
The men's blood and prostate lycopene concentrations and PSA were measured before and after the sauce regimen was put in place. The researchers also measured levels of oxidative DNA damage in each man.
The men experienced a threefold increase in lycopene levels during the diet and surgery, and the researchers found that oxidative DNA damage was reduced by an average of 28 percent after the men started the sauce diet.
"Lycopene is a good antioxidant," says Bowen, adding that one theory suggests that the prostate is prone to cancer because it's under more oxidative stress than other tissues. "Therefore, an antioxidant might prevent the DNA damage -- which is necessary for all cancers to get started -- that might occur in an oxidatively stressed prostate."
PSA levels were also reduced by 17.5 percent, but it's less clear whether lycopene was directly responsible for that effect, says Bowen. Other substances in tomatoes, including phenolic compounds, vitamin C and salicylic acid, could be responsible, she says.
"Levels of lycopene are significantly lower in prostate cancer patients," says the University of Toronto's Rao. "We're finding, actually, the same thing with breast cancer patients."
"Lycopene seems to be, in fact, the first level of defense for these patients," says Rao. Because a prostate cancer patient is fighting more oxidative damage, his body uses up his normal dietary intake of lycopene to protect his DNA from oxidative damage.
"In that sense, [lycopene] protects the DNA against the reactive oxygen species that would otherwise react with the DNA and caused oxydative lesions," he says. "Only when lycopene is depleted are vitamin E and other [antioxidants] called upon."
Rao says this suggests that supplementing lycopene to maintain normal levels in prostate cancer patients may slow the progression of the disease. "Lycopene, perhaps, can not only prevent it from growth but also be responsible for the regression of the tumor," Rao says.
Exactly how much lycopene is required to have this effect in cancer patients is still a subject of debate. However, Rao says that some of his research has suggested that between five milligrams and 10 milligrams daily may be sufficient for healthy people.
Bowen says that these findings call for a larger scientific trial of lycopene or tomato products.
"We don't have definitive answers that translate into advice to men who are at high risk for prostate cancer or who have prostate cancer," she says. "However, since one of the important pieces of dietary advice is to eat at least five servings of fruits and vegetables a day, tomato products should be part of this mix. I think a lot of people overlook tomato sauce on their pizza or pasta as counting for a serving of vegetables."
What To Do
Read about lycopene and prostate cancer from Lycopene.org.uk.