P&S Journal: Fall 1997, Vol.17, No.3
Two Cancer Studies: Tomatoes, Green Tea, and Cancer
Tomatoes may help reduce the risk of certain types of cancer, according to a study presented at the annual meeting of the American Association for Cancer Research.
P&S and Harlem Hospital researchers evaluated the association between lycopene and lung cancer. Lycopene, an antioxidant, has been linked to a reduced risk of cancers of the prostate and digestive tract. Tomatoes are the only major dietary source of lycopene.
In a case-control study, investigators at Harlem Hospital Center and P&S collected blood samples from 93 individuals with non-small cell lung cancer and from 102 matched controls. The researchers tested the samples for levels of certain micronutrients, including lycopene, retinol, and beta-carotene.
They found no significant differences between subjects with lung cancer and control subjects in most of the micronutrients for which they tested. However, they found that lung cancer patients had significantly lower concentrations of lycopene concentrations.
After adjusting for age, sex, race, smoking, drinking, occupational exposure, vitamin supplements, and season, the investigators found that the group with the lowest lycopene levels had nearly a three-fold increased risk for cancer compared with the group with the highest lycopene levels. In African-Americans, subjects with the lowest level of lycopene had an eight times greater risk for cancer.
When the investigators evaluated current smokers, they found that the group with the lowest blood levels of lycopene had four times the risk of cancer than the group with the highest lycopene levels.
According to principal investigator Dr. Jean G. Ford, assistant professor of medicine: "We concluded from our findings that low intake of lycopene may be a risk factor for lung cancer, especially for smokers. Even though our findings are preliminary, they add to the growing body of evidence that diets rich in tomatoes and tomato products are strongly linked to a reduced risk of certain types of cancer."
Green tea and cancer
In another study presented at the same meeting, dermatology researchers presented evidence that green tea protects against UVA-induced skin damage in mice.
PUVA photochemotherapy is widely used in the treatment of various skin diseases. However, epidemiologic studies have indicated that PUVA enhances the risk of squamous cell carcinoma and perhaps melanoma. Dr. David R. Bickers, the Carl Truman Nelson Professor and Chairman of Dermatology, and colleagues conducted a study to determine whether extracts of green tea protect against PUVA-induced skin photodamage in mice.
In the experiment, a green tea polyphenol fraction was topically applied to mice 10 minutes before PUVA photochemotherapy (which consists of 8-methoxypsoralen plus UVA irradiation). Typically, this therapy causes skin photodamage in mice, including redness and swelling after two to three days and hyperplasia and hyperkeratosis (skin thickening and lesions) after one to two weeks. However, the application of the green tea polyphenol fraction resulted in a statistically significant 78.1 percent inhibition of the PUVA-induced net increase in skin thickness. The treatment also resulted in a 98.6 percent inhibition of the PUVA-induced net increase in lesion severity. Applying the green tea polyphenol fraction five minutes after PUVA also significantly protected against skin photodamage. Administration of a 0.6 percent extract of green tea in the drinking water seven days before PUVA treatment protected against skin photodamage in the mice.