Undesirable Cardiovascular Effects of Hot Drinks

Various estimates suggest that 80-90% of adults in the U.S. and elsewhere consume caffeinated hot coffee. For most nations, no one knows at what ages this habit begins but some suggest as early as childhood (e.g. 4-6 years of age, personal communications). In this physiological investigation college-age young single adults served as volunteer subjects. On separate occasions each consumed approximately 12-16 ounces of hot, caffeinated coffee and equal volumes of hot tap water containing no drugs or other known, harmful contaminants. Data were collected continuously, both while consuming the hot drinks and for 60 minutes after. Data included a standard limb lead electrocardiogram (ECG), estimates of systemic arterial systolic and diastolic blood pressures, cardiac sounds registered from the brachial artery, and estimates of blood flow in a finger (pulse plethysmography). Aphysiological, cardiovascular effects were seen immediately upon consuming the beverages and for at least 60 minutes after (i.e. changes in the ECG, heart rate, and peripheral blood flow). These effects could be divided in two, those due to temperature and others caused by caffeine. We conclude that hot, caffeinated coffee has previously-unreported cardiovascular effects that might be harmful. We also conclude that more physiological and pharmacological investigations are needed, especially in light of the confusing and voluminous literature for behavioral, epidemiological, meta-analytical, nutritional, and social effects of coffee.