MONDAY, Dec. 12 (FoodConsumer.org News) - Drinking tea daily may reduce risk of ovarian cancer by 50 percent, suggests a Swiss study appearing in the Dec. 26 issue of Archives of Internal Medicine.
A growing body of evidence from laboratory studies indicates that green and black tea preparations may possess anticancer properties and chemo-preventive acivity. The epidemiological study was meant to examine the relationship between drinking tea and the risk of ovarian cancer.
The study, by Susanna C. Larsson, M.Sc., and Alicja Wolk, D.M.Sc., of Karolinska Institute (Stockholm, Sweden) involved 61,057 women aged 40 to 76, who took part in the population-based Swedish Mammography Cohort.
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AusmusParticipants were asked to complete a validated 67-item food frequency questionnaire when they entered the study between 1987 and 1990. They were followed for cancer incidence through Dec. 2004. 68 percent of the participants reported drinking tea (mainly black) at least once per month. During the 15-year follow-up, 301 women contracted invasive epithelial ovarian cancer.
"We observed a 46 percent lower risk of ovarian cancer in women who drank two or more cups of tea per day compared with non-drinkers," the authors write. "Each additional cup of tea per day was associated with an 18 percent lower risk of ovarian cancer."
The ovarian cancer risk for those who drank less than one cup per day was 18 percent lower than non-drinkers. Those who drank one cup of tea a day experienced 24 percent lower risk of the disease compared with non-drinkers.
"This association does not depend on lower coffee consumption among women with high tea consumption; coffee is not associated with ovarian cancer risk in this cohort," the authors report, suggesting that the active ingredient(s), if any, may not be caffeine.
"In summary, our results from a large population-based cohort of Swedish women suggest that tea consumption may lower the risk of ovarian cancer," the authors conclude.
Although the study could not suggest that drinking tea is responsible for lowering the risk of ovarian cancer, it cannot exclude the possibility either.
Previous laboratory studies have consistently revealed inhibitory effects against carcinogenesis in a variety of organs in rodents.
"Because prospective data on this relationship are scarce, our findings need confirmation by future studies," said the authors.
In a similar Australian case-control study of 254 Chinese patients with histologically confirmed epithelial ovarian cancer, conducted during 1999 to 2000, Zhang Min and colleagues of Curtin University of Technology, Australia, determined the association between drinking tea (mainly Chinese green tea) and the incidence of the disease.
The results, published in the Aug. 2002 issue of Cancer Epidemiology Biomarkers & Prevention, showed the risk of ovarian cancer declined with increasing frequency and duration of overall tea consumption.
Those who drank green tea daily had a 60 percent lower risk compared with those who did not. 30-year tea consumption was correlated to a 75 percent reduction of the risk of ovarian cancer. Similar to the current study, the dose response relationships were significant.
If teas do prevent or inhibit ovarian cancer in humans, it is generally believed that polyphenols in teas may be responsible for the activity. The polyphenols as antioxidants can neutralize harmful free radials, which could damage cells leading to all types of cancer.
Ovarian cancer is the seventh common cancer and the fourth leading cause of death after lung and bronchus, breast, and colorectal in US women, states the Centers for Disease Control and Prevention.
A woman's risk of getting ovarian cancer during her lifetime is about 1 in 58 and the risk of dying from it is 1 in 98, according to the American Cancer Society.
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