It is now becoming clear that scientific research went through a dark-ages period that will forever taint its history. This period lasted from the end of the 1960’s all the way to the end of the 1990’s, and was characterised by an arrogant and unscientific corporatist agenda that had the single-minded goal of proving that cholesterol and saturated fat in the diet was the cause of cardiovascular disease. Throughout this period any data that contradicted the a priori assumption that dietary lipids were the cause of cardiovascular disease was ridiculed, ignored or attacked vehemently. A plethora of ad hoc hypotheses were created to defend the theory from observational data contradicting the new diet heart religion. While the diet heart hypothesis is still ingrained in the minds of mainstream medicine, the nutritional sciences have abandoned the theory. However, remnants of the diet heart hypothesis still remain today.
One such remnant is the notion that coffee is detrimental to the cardiovascular system. For example, a handful of studies reported an association between coffee consumption and elevated level of low density lipoprotein (LDL). Despite no proof of a causal relationship, coffee became part of the diet heart hypothesis axis of evil. This belief was easy to disseminate to the public using the usual propaganda outlets pretending to be serious scientific endeavours, and government guidelines were adjusted to recommended a reduction in coffee consumption. When used to justify the coffee theory of cardiovascular disease, this data was often supported by citations showing that coffee could cause an acute elevation in systolic blood pressure. However, this effect is common to all drinks containing methylxanthines, including tea, and only occurs in those unaccustomed their effects. Despite this the blood pressure raising effects of coffee were determined to be real.
However, as with the diet heart hypothesis, the weight of evidence now disproves the coffee cardiovascular disease hypothesis. For example, it is known that coffee contains the hydroxycinnamic acids caffeic acid and its (-)-quinic acid ester chlorogenic acid (figure 1). Hydroxycinnamic acids are thought to be protective of oxidative stress and may reduce the risk of cardiovascular disease. In addition, unfiltered coffee contains the diterpene molecules cafestol and kahweol (figure 2) which may have beneficial anti-cancer and bone health effects. It is these molecules that are thought to raise LDL concentrations. However, they are removed during the filtration of coffee and meta-analysis of studies to date shows that only unfiltered coffee raises LDL concentrations. In addition, studies using subjects unaccustomed to coffee consumption have been questioned for their relevance as it is known that habitual coffee consumers do not show many of the effects reported in these studies.
Figure 1. The structures of caffeic acid and chlorogenic acid. Chlorogenic acid is a quinic acid ester of caffeic acid.
Figure 2. The structure of cafestol and kahweol. Cafestol has a similar structure to kahweol but is missing a double bond.
Recently, researchers1 have published results from analysis of a prospective study investigating the association between coffee consumption and disease. The data included observation of 42,659 participants in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Germany study. Food frequency questionnaires were used to assess the intakes of coffee in the subjects and medial records were used to assess the incidence of chronic diseases. The results showed that during a 8.9 year follow-up, caffeinated coffee consumption of between 1 and 4 cups/d (1 cup = 150mL serving) was not associated with any diseases, when compared to less than 1 cup/d. In addition, the authors analysed consumption of decaffeinated coffee and also found no association with disease. However, the authors reported a reduced risk of type 2 diabetes with consumption of between 1 and 4 cups/d caffeinated or decaffeinated coffee, compared to consumption of just 1 cup/d.
These results support the growing body of evidence that coffee consumption is not associated with chronic disease. This suggests that a number of authors have misinterpreted previous observations to fit the a priori assumption that coffee is a contributory factor in cardiovascular disease. That coffee might be protective of diabetes could be explainable by the weight loss effects of caffeine, as caffeine consumption is associated with weight loss and lower body weights. However the observation that decaffeinated coffee is also associated with a reduced risk suggests that other components may be responsible. Care should always be taken when interpreting results from epidemiological data because cause and effects cannot be inferred from associations. That coffee consumption is associated with other disease causing variables like a stressful lifestyle, type A personality or poor general nutrition, should never be ignored. However, the weight of evidence suggests that coffee consumption is not detrimental to health.
RdB
