Tea drinking appears to be protective against coronary heart disease in a number of epidemiologic studies. It has been suggested that tea flavonols with antioxidative activity, including quercetin, kaempferol, and myricetin,1 could account for the favorable effect on cardiovascular health.
In the older cohort of the Rotterdam Study, we observed an inverse association of tea drinking with severe aortic atherosclerosis.2 Interestingly, the relationship was most pronounced in women, which raised the hypothesis that an estrogen-related mechanism could be involved. Tea drinking in another population-based study of older women appeared protective against bone mineral loss, which may also indicate estrogenicity.3 Tea flavonoids such as kaempferol have indeed been shown to exhibit estrogenic activity in vitro.4 Daily kaempferol intake is almost doubled in regular tea drinkers compared with nondrinkers (a 6-mg increase for 3 to 4 cups of tea). In addition, tea contains lignan polyphenols, such as secoisolaracinol, which have been considered phytoestrogens.5 At present, however, it is not known whether the estrogenic activity of tea substances is biologically important.
Geleijnse JM, Witteman JCM, Launer LJ, Lamberts SWJ, Pols HAP. Tea and Coronary Heart Disease: Protection Through Estrogenlike Activity?. Arch Intern Med. 2000;160(21):3328–3329. doi: