A study has found that people with symptoms of cardiovascular health issues, such as angina and heart palpitations, tend to drink less coffee, avoid coffee altogether, or drink decaf. The scientists used a genetic technique to show that these symptoms determine how much coffee people drink, rather than the other way round.
There is observational evidence that drinking moderate amounts of coffee can benefit cardiovascular health; and prospective studies, which follow people over time, have provided evidence that drinking coffee is safe for most people and is associated with lower mortality rates. However, this study suggests that some of the supposed health benefits of coffee for cardiovascular health may have been overblown. As a result of the caffeine that coffee contains, excessive consumption can cause unpleasant symptoms such as tachycardia (a fast resting heart rate) and palpitations. Drinking coffee can also lead to a moderate, temporary increase in blood pressure. So, it may come as a surprise that regular coffee drinkers either have normal or reduced blood pressure compared with people who do not drink coffee.
One explanation may be that coffee drinkers develop a physiological tolerance for the effects of caffeine. But this study suggests that people with a high genetic risk of cardiovascular disease unconsciously reduce how much they drink to avoid unpleasant cardiovascular symptoms. The research found that individuals with high blood pressure, angina, or arrhythmia drank less caffeinated coffee and were more likely to drink decaffeinated coffee.
Crucially, there was substantial evidence that their genetic vulnerability to cardiovascular disease led to their reduced consumption of coffee. This rules out the alternative explanation: that consuming less coffee made them more vulnerable to cardiovascular disease. In reality, people vulnerable to high blood pressure may avoid drinking coffee because, for them, caffeine is more likely to cause unpleasant symptoms.
Researchers at the University of South Australia in Adelaide conducted the study, which appears in The American Journal of Clinical Nutrition.