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Catechins are bioactive flavonoids present in tea, fruits, and vegetables. Previous epidemiological studies regarding tea and cancer risk were inconclusive, possibly because catechins are also present in other plant foods. We investigated whether a high intake of catechins are associated with cancer incidence among postmenopausal women. Methods: A cohort of 34,651 postmenopausal cancer-free women aged 55–69 years were followed from 1986 to 1998. At baseline, data on diet, medical history, and lifestyle were collected. Incident cancers were obtained through linkage with a cancer registry. Cox proportional hazards analysis was used to estimate risk ratios. Results: After adjustment for potential confounders, catechin intake was inversely associated with rectal cancer incidence only (risk ratios from lowest to highest quartile: 1.00, 0.93, 0.73, and 0.55; p for trend 0.02). Non-significant inverse trends were found for cancer of the upper digestive tract, pancreas, and for hematopoietic cancers. Catechins derived primarily from fruits, ( )-catechin and (-)-epicatechin, tended to be inversely associated with upper digestive tract cancer, whereas catechins derived from tea were inversely associated with rectal cancer. Conclusions: Among several cancers studied, our data suggest that catechin intake may protect against rectal cancer. The distinct effects found for catechins derived from solid foods (fruits) and beverages (tea) may be due to differences in bioavailability or metabolism of the catechins, or to their interactions with other dietary components.

Catechins are polyphenolic compounds in plant foods that belong to the family of flavonoids. Due to their strong antioxidant activity and their capacity to influence mammalian enzyme systems, catechins were hypothesized to affect risk of cardiovascular diseases and cancer in humans. After optimizing the extraction and quantification of six major catechins from foods, a database containing catechin contents of more than 130 commonly consumed plant foods and beverages was created. Catechin levels varied between 5 and 610 mg/kg and were particularly high in tea, chocolate, fruits and red wine. Among 6,200 participants of the Dutch National Food Consumption Survey 1998, the average catechin intake was 50 mg/day. Catechin intake increased with age, and the intake was higher in women (60 mg/day) than in men (40 mg/day). Tea was the main catechin source in all age groups. The role of catechins in chronic disease prevention was studied in two prospective cohort studies: the Zutphen Elderly Study (~800 Dutch men, 65-84 years old, followed since 1985) and the Iowa Women's Health Study (~34,000 postmenopausal American women, 55-69 years old, followed since 1986). In Zutphen, a high intake of catechins was associated with a 51% lower risk of coronary heart disease (CHD) mortality, but not with myocardial infarction incidence or stroke. In Iowa, a 24% lower risk of CHD mortality was found in the highest quintile of intake of (+)-catechin and (-)-epicatechin, catechins typical of foods other than tea. Catechins derived from tea were not associated with CHD mortality. Lung cancer incidence was studied in both the Zutphen Elderly Study and the Iowa Women's Health Study. Whereas in Zutphen a borderline significant inverse association with lung cancer was found for catechins from foods other than tea, particularly apple, catechins were not associated with lung cancer in Iowa. The incidence of other cancers studied in Zutphen - total epithelial cancer and epithelial cancers other that those of the lung - was not associated with catechin intake. In Iowa, among several cancers studied, total catechin intake and the intake of catechins from tea were inversely associated with rectal cancer risk only. Thus, catechins are quantitatively important minor constituents of the diet. Major catechin sources in both the Netherlands and the USA are tea, apples, and chocolate. Overall, our data do not support a strong protective effect of the studied catechins against myocardial infarction, stroke and cancer incidence. However, certain catechins may lower the risk of CHD mortality and possibly certain cancers.