Tea Flavonoids May Protect Against Atherosclerosis
JM Geleijnse, L J Launer, A Hofman, HAP Pols & JCM Witteman, Arch Intern Med, 1999; 159: 2170-2174

Background: Epidemiological studies have indicated a protective role of dietary flavonoids in cardiovascular disease, but evidence is still conflicting. Tea is a major dietary source of flavonoids in Western populations. We studied the association of tea intake with aortic atherosclerosis in a general population.

Methods: The present analysis formed part of the Rotterdam study, a prospective study of men and women 55 years and older. Dietary intakes were assessed at base line by a trained dietician who used a semiquantitative food frequency questionnaire. Calcified plaques in the abdominal aorta were radiographically detected after 2 to 3 years of follow-up. Aortic atherosclerosis was classified as 'mild,' 'moderate,' or 'severe,' according to the length of the calcified area. The association of tea intake with severity of aortic atherosclerosis was studied in 3454 subjects who were free of cardiovascular disease at baseline. Data were analysed by logistic regression, adjusting for age, sex, body mass index, smoking, education, and intake of alcohol, coffee, vitamin antioxidants, total fat, and total energy. Results: Multivariable analyses showed a significant, inverse association of tea intake with severe aortic atherosclerosis. Odds ratio decreased from 0.54 for drinking 125 to 250 ml (1-2 cups) of tea to 0.31 for drinking more than 500 ml/d (4 cups per day). The associations were stronger in women than in men. The association of tea intake with mild and moderate atherosclerosis was not statistically significant.

Conclusion: This study indicates a protective effect of tea drinking against ischemic heart disease.

Tea and coronary heart disease: protection through estrogenlike activity?
Geleijnse JM, Witteman JC, Launer LJ, Lamberts SW, Pols HA, Arch Intern Med 2000 Nov 27; 160(21): 3328-9.

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 favourable 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.

Serum prolactin concentrations are influenced by (remaining) estrogenic activity and can be considered a "bioassay" for such activity.6 To explore the hypothesis of an estrogenlike activity of tea, we determined serum prolactin levels in a random sample of 577 female participants in the Rotterdam Study who had different levels of tea intake. We deliberately oversampled women from both extremes of the tea intake distribution (0 and >500 ml/d, respectively) to generate a contrast. Three women with elevated prolactin levels (37.6, 46.7, and 48.6 µg/L) were excluded from the analysis because of underlying disease. Furthermore, 37 women who were currently being treated with anticholinergic drugs, sex hormones, and psycholeptics were excluded because of the influence these drugs may have on prolactin secretion. The asymmetric serum prolactin distribution was converted into a normal distribution by log transformation. The mean log prolactin values in women with daily tea intakes of 0 ml (n = 175), 0 to 250 ml (n = 73), 250 to 500 ml (n = 74), and more than 500 ml (n = 215) were obtained by analysis of covariance and adjusted for age. After back-transformation, serum prolactin concentrations in consecutive strata of tea intake were 2.46, 2.75, 2.86, and 2.86 µg/L, respectively (P = .03). The increase in serum prolactin concentration associated with tea drinking was on average 0.38 µg/L (P = .003). Additional adjustment for body mass index (calculated as weight in kilograms divided by the square of height in meters), hormonal substitution therapy (ever in life), menopausal age, and number of offspring did not change the association. When examining for age-adjusted tea intake continuously in a linear regression model, using log prolactin as the dependent variable, similar results were obtained (P = .02).
From our findings, using serum prolactin measurements as a bioassay, we hypothesise that phytoestrogens in tea may account for (part of) the beneficial effects of tea drinking against coronary heart disease.

Effects of Black Tea Polyphenols in Cholesterol Fed Rats
N Matsumoto, Food Research Laboratories, Mitsui Norin Co, Ltd, J-NUTR-SCI-VITAMINOL, 1998, Vol./Issue/Pg. 44/2 (337-342), ISSN: 0301-4800,

The influence of black tea polyphenols on plasma lipid levels was investigated in rats fed 15% lard and 1% cholesterol diet. The diet was supplemented with 1% black tea polyphenols extracted and condensed from black tea. Rats fed the lard-cholesterol diet showed an increase in plasma cholesterol and liver lipids compared to rats fed a basal diet. The supplementation of black tea polyphenols in this lard-cholesterol diet decreased the lipid levels in the plasma and increased the faecal excretion of total lipids and cholesterol. On the other hands, 1% supplementation of either instant black tea with a 20% polyphenol content or 0.2% supplementation of EGCG in the lard-cholesterol diet had no effect on plasma cholesterol and phospholipid levels. These results suggest that a high dose of black tea polyphenols exert a hypocholesterolemic effect in cholesterol- fed rats.

Antioxidant flavonols and ischemic heart disease in a Welsh population of men: the Caerphilly Study
Michaël Hertog, peter M Sweetnam, Ann M Fehily, Peter C Elwood and Daan Kromhout. Am J Clin Nutr 1997; 65:1489-94

Antioxidant flavonols and their major food source, black tea, have been associated with a lower risk of ischemic heart disease (IHD) and stroke in Welsh men. We investigated whether flavonol intake predicted a lower rate of IHD in 1900 Welsh men aged 45-59 y, who were followed up for 14y. Flavonol intake, mainly from tea to which milk is customarily added, was not related to IHD incidence [relative risk (RR), highest compared with lowest quartile: 1.0; 95% CI: 0.6, 1.6;P for trend = 0.996; n - 186] but was weakly positively related to IHD mortality (RR: 1.4; 95% CI: 1.0, 2.0; P - 0.014; n = 334). Men with the highest consumption of tea (>1.2L, or <2 cups/d). We conclude that intake of antioxidant flavonols is not inversely associated with IHD risk in the United Kingdom. Possibly, flavonols from tea to which milk is added are not absorbed; experimental evidence suggests that adding milk to tea abolishes the plasma antioxidant-raising capacity of tea. The apparent association between tea consumption and increased mortality in this population merits further investigation.