June 18, 2010 (Utrecht, the Netherlands) — The latest look at the effects of tea and coffee consumption on cardiovascular morbidity and mortality suggests that moderate intake of either reduces coronary heart disease risk but has little effect on stroke and no effect on all-cause mortality . Tea, however, does seem to reduce CHD deaths.
Dr J Margot de Koning Gans (University Medical Center, Utrecht, the Netherlands) and colleagues prospectively studied more than 35 000 participants in the Dutch portion of the EPIC study, EPIC-NL. They report their findings online June 18, 2010 in Arteriosclerosis, Thrombosis, and Vascular Biology.
Coauthor Dr Yvonne T van der Schouw (University Medical Center) told heartwire the relationship between CHD morbidity and coffee was U-shaped: "We saw a significant protective effect with around two to four cups of coffee a day," whereas for tea, it was a linear and inverse association, with the lowest hazard ratio seen for more than six cups a day. But three to six cups of tea a day was associated with an almost 50% reduction in CHD deaths, although the number of events was small.
She stressed, however, that the findings are applicable only to filter coffee prepared as it is in the Netherlands and primarily to black tea, which is the type of tea consumed by around 80% of Dutch people. And she warned that the results do not indicate that people who have never drunk coffee or tea should start to do so, "because that is not what we studied."
No Association Between Coffee and Tea Intake and Stroke
The Dutch researchers assessed tea and coffee consumption with a validated food-frequency questionnaire and observed the 37 514 participants for 13 years for the occurrence of CVD morbidity and mortality.
For CHD, the lowest hazard ratio was seen for 2.1 to 3.0 cups of coffee per day (0.79; p=0.01) and for tea this was observed for more than six cups per day (0.64; p=0.02). No associations between coffee or tea and stroke were found.
Tea consumption did significantly reduce CHD mortality, however, with a hazard ratio of 0.55 (p=0.03) for 3.1 to 6.0 cups per day. Coffee also reduced CHD mortality, but the effect was not significant. Neither beverage had an effect on all-cause death.
Discussing possible mechanisms for these observed effects, the investigators point out that coffee contains several biologically active substances that could increase CVD risk by increasing cholesterol and decreasing insulin sensitivity, but it also contains other compounds with antioxidant properties that could reduce risk. Tea contains flavonoids, which are antioxidant, but the underlying mechanisms of their effects are still not entirely clear, they note.
They also mention some limitations of their study. Relatively few patients died of CHD or stroke, so there was limited power to detect associations for these end points. Also, they relied on self-reported data on tea and coffee intake.
Evidence Strengthened on Lower CHD Risk With Tea and Coffee
Previous studies have also shown U-shaped association between coffee consumption and CHD morbidity, the investigators note, and modest benefits on CV mortality. Taken together with this study, the findings overall "suggest a modest risk reduction of CV mortality with moderate coffee consumption," they state.
For tea, only prior studies in continental Europe have suggested a decrease in the rate of CHD with increasing tea consumption, and most previous research on tea intake and CHD mortality has been in specific subgroups, such as hypertensive or postmenopausal subjects, they note.
In conclusion, they say, "With this large prospective study, we showed that tea consumption was associated with a reduced risk of CHD mortality. We strengthen the evidence on the lower risk of CHD associated with coffee and tea consumption; however neither . . . was associated with the risk of stroke or all-cause mortality."
The authors declare that they have no conflicts of interest.
Heartwire from Medscape © 2010 Medscape, LLC
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