Some epidemiologic studies indicate that drinking tea may reduce the risk of cardiovascular disease. Catechins, which are members of the flavonoid family and are found in tea, are thought to be the responsible substances. To further evaluate their alleged protective effect, Dutch scientists compared heart disease incidence and catechin intake in elderly men.

Researchers analyzed data from the Zutphen Elderly Study, a prospective cohort study of over 800 men, 65-84 years old, beginning in 1985. Health, lifestyle, and diet histories were recorded and dietary intakes were analyzed for flavonoid content, specifically for catechins. Physicians, hospital records, and the Central Bureau of Statistics were used to verify the prevalence of ischemic heart disease (IHD), stroke, and myocardial infarction (MI) at baseline and throughout the study.

The health benefits of tea

After 10 years of follow-up, IHD was the primary or secondary cause of death for 90 men, while stroke was the cause of death for 47 of the men. Those with the highest dietary intakes of catechins showed a statistically significant inverse association with the risk of death from IHD (relative risk, or RR, = 0.48; 95% CI: 0.28, 0.82). This relationship remained, even after adjusting for disease state at baseline, age, physical activity, caloric intake, body mass index, alcohol consumption, smoking status, and dietary factors.

When catechin intake was modeled as a continuous variable, an increase in intake of 1 standard deviation (50 mg) was associated with a 25% decrease in IHD risk (95% CI: 0.56, 0.99). Fifty milligrams of catechins are contained in one cup of black tea, 20 grams of dark chocolate, or two large apples.

The association between catechins and MI incidence was not as strong as for IHD mortality (RR = 0.54; 95% CI: 0.32, 0.93) and after adjusting for potential confounders, was not statistically significant. Catechin intake was not associated with stroke morbidity or mortality.

Catechins from foods other than tea

Tea - and particularly green tea - is rich in catechins as well as other flavonoids. To determine whether catechins are the protective agent in tea, the researchers looked at the health effects of catechins from foods other than tea. However, since catechins from other food sources accounted for only 13% of the volunteer's total catechin intake, any effect was difficult to discern.

Questions still remain

Scientists theorize that catechins may prevent cardiovascular disease by protecting LDL from oxidative damage or by interfering with the inflammatory process of atherosclerosis. This study was unique because it looked at catechin intake specifically and not just at tea consumption, even though tea is a primary catechin source. This may explain some of the different findings of other studies that have looked at only tea drinking habits, since catechin content can vary by tea type and preparation method. Further research is needed to determine if catechins from foods other than tea can contribute to heart health.