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Source: Sesso HD, et al. Coffee and tea intake and the risk of myocardial infarction. Am J Epidemiol 1999;149:162-167.
We investigated the association of caffeinated coffee, decaffeinated coffee, and tea with myocardial infarction (MI) in a study of 340 cases and age-, sex-, and community-matched controls. The odds ratio (OR) for drinking four or more cups of caffeinated coffee vs. drinking one or less cups per week was 0.84 (95% confidence interval [CI] 0.49-1.42) after adjustment for coronary risk factors (1 cup = 237 ml). The OR for drinking more than one cup per day of decaffeinated coffee vs. nondrinkers was 1.25 (95% CI 0.76-2.04). For tea, the OR for drinking one or more cups per day vs. nondrinkers was 0.56 (95% CI 0.35-0.90). In these data, only tea was associated with a lower risk of MI.
These Harvard-associated investigators analyzed data from the Boston Health Study, collected from healthy Caucasian men and women aged less than 76 years in the early 1980s. The investigators selected a control matched on age, sex, and area of residence, yielding 340 case-control pairs. A self-reported food frequency questionnaire gave them the data from which they draw the conclusions above.
Investigators found that 70.2% of MI cases and 71.5% of controls drank at least one cup of caffeinated coffee daily. The short drink: Coffee had no effect on risk of MI, even when adjustment for coronary risk factors, including lipid levels, was included.
These data are in the middle about coffee and MI. On the one hand, cohort studies have yielded mixed results. On the other hand, most case-control studies have associated caffeine with MI, leading some to speculate about coffee’s effect being acute, like that of saturated fat: It is where the onion ring last lands that the oxidation of atherosclerotic plaque takes place. Maybe the same is true for the caffeine of coffee.
The difficulty in teasing out individual risk factors and their precise association with infarction is daunting. No wonder the public is confused about nutrition. In these data, people who drank caffeinated coffee were more likely to be type A, male, and to smoke more. The decaf drinkers, though, actually had higher rates of hypertension and diabetes, perhaps indicating that someone had already advised them that their morning fuel should come unleaded.
The real interest here is in tea: The methods didn’t identify black, green, or oolong, but the flavonoids in black tea have been touted to inhibit cholesterol oxidation, and green tea has been reported to reduce the incidence of prostate cancer in men, among other benefits.
Problems with this study include a great deal of missing data, from coffee type to brewing method to tea type, to the confounder of smoking, noted above.
Patients who want to know about caffeinated coffee and MI should be told it probably has no direct effect. Tea is probably a healthier choice than decaf. Be especially vigilant for the man whose breakfast is coffee (or tea) and whose midnight snack was alcohol: Beverage choice probably is a marker for lifestyle factors separate and apart from its phytocomponents.