Our cross sectional study showed a close association between high consumption of green tea and normalisation of serum components, which reflects cardiovascular and liver diseases. Increased consumption of green tea, especially more than 10 cups a day, was associated with decreased serum total cholesterol and triglyceride concentrations; increased high density lipoprotein cholesterol concentrations and decreased low density and very low density lipoprotein cholesterol concentrations, resulting in a reduced atherogenic index; decreased serum concentrations of lipid peroxides among smokers; and decreased aspartate aminotransferase and alanine aminotransferase concentrations, and serum ferritin concentration. The associations between green tea and serum total cholesterol and triglyceride concentrations and between green tea and high and low density lipoprotein cholesterol concentrations are well correlated with experimental observations and the prevalence of heart disease in our cohort, implying that green tea may act preventively against cardiovascular disease. Moreover, this is the first time that an inverse association between consumption of green tea and cell damage of the liver, based on serum markers in humans has been reported.
Advancing age was associated with increased consumption of green tea. This could imply that consumption was also associated with being part of a healthier surviving cohort. If this is the case statistical adjustment for age used in this study could be insufficient to eliminate this effect. A follow up study is needed to clarify this problem.
Increased generation of oxygen radicals and subsequent formation of lipid peroxides were suggested to be cytotoxic and sometimes carcinogenic. Various forms of iron participated in radical reaction in vivo.26 27 Thus high stores of body iron were reported to be associated with increased risk of cancers such as lung, liver, and colon but not stomach.28 29 30 With regard to stores of body iron and lipid peroxidation, our cohort data showed a significant association between serum ferritin concentrations, a stable marker for stores of body iron, and serum concentrations of lipid peroxides (correlation coefficient 0.25, P