Coffee consumption and risk of chronic diseases: changing our views

Abstract

The association between coffee consumption and risk of chronic disease is of considerable relevance because coffee is consumed worldwide and any effect on health that it may cause will have public health consequences. These effects, especially on cardiovascular disease (CVD), cancer, and diabetes, have been extensively studied in recent years, and a growing body of evidence suggests that we may need to change our perception of the health effects of this beverage. Traditionally, research on coffee focused on the acute cardiometabolic effects of caffeine. Ingestion of caffeine stimulates the release of adrenaline, an inhibitor of insulin activity, and acutely increases blood pressure and serum homocysteine (1). These effects are consistent with the increased risk of coronary artery disease and stroke in the hours after coffee consumption that has been observed in some studies (2). However, in a seminal work by van Dam and Feskens (3), habitual coffee consumption was associated with a substantial reduction in the risk of type 2 diabetes in a Dutch population. This observation might reflect the long-term effects of coffee manifested in habitual drinkers who developed tolerance to the acute effects of caffeine. Coffee has a very complex chemical composition. In addition to caffeine, other substances have been shown to have biological effects. For example, phenolic compounds in coffee (chlorogenic acid, ferulic acid, p-coumaric acid), magnesium, trigonelline, and quinides have been associated with improved insulin sensitivity (4). Phenolic compounds also have antioxidant activity (5). In addition, diterpenes in coffee (cafestol and kahweol) have anticarcinogenic properties (6). Thus, it is plausible that the harmful effects of caffeine could be offset by the beneficial effects of these other components. In this issue of the Journal, Floegel et al (7) conducted analyses in the 42,659 German participants of the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort to examine the association between coffee consumption and the risk of total chronic disease and of type 2 diabetes, CVD, and cancer. Coffee consumption was assessed at the beginning of the 8.9-y follow-up period. The results showed that neither caffeinated nor decaffeinated coffee consumption was associated with an increased risk of total chronic disease, CVD, or cancer; furthermore, both types of coffee showed an inverse association with the risk of type 2 diabetes. These results are consistent with systematic reviews of randomized controlled trials assessing the effect of coffee on known risk factors of chronic diseases. For instance, Jee et al (8) concluded that filtered coffee (the main type of coffee in the German EPIC) consumed during 20 d does not increase serum cholesterol; in addition, Noordzij et al (9) found that coffee intake for 7 d barely increased blood pressure. Moreover, in a recent randomized controlled trial of 8 wk, caffeinated coffee consumption increased adiponectin and IL-6 in plasma, and decaffeinated coffee decreased fetuin-A concentrations (10). This indicates that coffee improves adipocyte and liver function, which may decrease the risk of type 2 diabetes. Unlike previous studies that specifically examined the effect of coffee on individual diseases (myocardial infarction, stroke, specific tumors), Floegel et al (7) assessed ‘‘overall chronic disease’’ to balance the positive and negative effects of coffee on separate diseases; in this way they summarized the effect of coffee on overall health. In addition, they conducted a competing risk analysis to ensure that the associations estimated for individual diseases were not biased by the fact that the occurrence of a first disease event may preclude the onset of another disease. Finally, this study evaluated the health effects of coffee in a European population, which is important because much of the evidence available proceeds from American cohorts. The work by Floegel et al (7) adds to the evidence on the null association between habitual coffee consumption and CVD, cancer, and total mortality, another indicator of the global effect on health (11), and suggests that this beverage may produce health benefits. However, coffee cannot yet be recommended for health purposes. First, most of the evidence has been obtained from persons without apparent health problems. More research is needed among individuals who are already sick or have high blood pressure, hypercholesterolemia, diabetes, cancer, or CVD. The evidence already available is insufficient to provide clinical recommendation to these individuals. Second, the long-term effects of nonfiltered coffee are not well known. When coffee is made by using a nonfiltered process (boiled, French press, espresso), diterpenes are not removed. In short-term studies, nonfiltered coffee has been shown to increase