Antioxidant flavonols and ischemic heart disease in a Welsh population of men: the Caerphilly Study

Abstract

Antioxidant flavonols and their major food source, black tea, have been associated with a lower risk of ischemic heart disease (IHD) and stroke in Dutch 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 14 y. 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: 1.6; 95% CI: 0.9, 2.9; P = 0.119; n = 131) and cancer mortality (RR: 1.3; 95% CI: 0.7, 2.3; P = 0.150; n = 104) and strongly related to total mortality (RR: 1.4; 95% CI: 1.0, 2.0; P = 0.014; n = 334). Men with the highest consumption of tea (> 1.2 L, or > 8 cups/d) had an RR of 2.4 (95% CI: 1.5, 3.9) of dying in the follow-up period compared with men consuming < 300 mL/d (< 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.

Bioavailability of catechins from tea: the effect of milk

“…The consumption of black tea in the United Kingdom is high compared with other countries (5±6 cups vs 1±2 cups per day) and yet the incidence of coronary heart disease is not lower. In contrast to earlier epidemiological data from The Netherlands (Hertog et al, 1993;Keli et al, 1996), where plain black tea is consumed, a recent study in the United Kingdom showed that consumption of tea with milk was not inversely associated with mortality of ischemic heart disease (Hertog et al, 1997). A possible explanation may be that the bioavailability of¯avonoids from tea is reduced by the addition of milk to black tea.…”

“…Several epidemiological studies suggest that black tea consumption is associated with a reduced risk of degenerative diseases such as cardiovascular disease (Hertog et al, 1993;Keli et al, 1996). There is increasing evidence from experimental studies that free radical-mediated damage may play a role in the aetiology of cardiovascular disease and that antioxidants may act in preventing this damage (Steinberg et al, 1989;Witztum & Steinberg, 1991;Esterbauer & Ramos, 1995).…”

A single dose of tea with or without milk increases plasma antioxidant activity in humans

“…It has been suggested that addition of milk to tea, which is common practice in the United Kingdom, could explain the increased risk of death from isachemic heart disease associated with tea drinking in a Welsh population of heavy tea drinkers (Hertog et al, 1997b). Addition of milk to tea leads to binding of tea components to milk protein (Siebert et al, 1996) and may thus prevent their uptake by the intestine.…”

“…In a Welsh population (United Kingdom) the consumption of tea was not associated with a lower mortality of ischaemic heart disease (Hertog et al, 1997b). Among heavy tea drinkers tea drinking was even related to an increased risk of death from ischaemic heart disease.…”

“…Among heavy tea drinkers tea drinking was even related to an increased risk of death from ischaemic heart disease. Hertog et al (1997b) suggested that addition of milk to tea could be an explanation for this increased risk due to the¯avonoid binding capacity of milk proteins resulting in a reduced absorption of¯avonoids from the gastrointestinal tract. This is, however, not consistent with recent ®ndings that adding milk to black tea had no effect on the plasma concentration of catechins (Van het Hof et al, 1998).…”