By Clarissa Brincat — Fact checked by Ferdinand Lali, Ph.D.
Good news for coffee drinkers emerged earlier this year, with studies reporting that drinking coffee is linked to a lower risk of mortality and that moderate daily coffee drinking may reduce kidney injury risk by 23%.
However, historically, more than 75% of medical professionals have advised patients with cardiovascular disease to avoid coffee. Recent observational studies challenged this misconception by discussing the safety and beneficial effects of caffeine consumption concerning arrhythmia and cardiovascular disease.
Little information was available on the impact of different types of coffee on heart health. This prompted researchers at the Baker Heart and Diabetes Research Institute in Melbourne, Australia, to conduct a large observational study that would provide some insights into the role of caffeine on cardiovascular outcomes by comparing the impact of decaffeinated and caffeinated coffee.
The newly published findings indicate that instant, ground, and decaffeinated coffee, particularly at 2–3 cups a day, is linked to a lower risk of cardiovascular disease and death, and caffeinated coffee significantly reduces the risk of arrhythmia.
Prof. Peter Kistler, Ph.D., study author and head of the Baker Heart and Diabetes Research Institute in Melbourne, Australia, explained:
“The real-world implications are that coffee should be considered part of a healthy diet. People should NOT stop drinking coffee if they develop any form of heart disease, including heart rhythm disorders, unless they notice a specific personal association between coffee drinking and their symptoms.
The study does not show that if you have heart disease you should start drinking coffee but rather if you are already a coffee drinker you should feel reassured that it is not only safe but somewhat protective.”
The study was published in the European Journal of Preventive Cardiology.
Coffee and cardiovascular disease
Between January 1, 2006, and December 31, 2010, the study recruited participants from the UK Biobank ages 40 to 69.
The study included 449,563 participants who were not diagnosed with cardiovascular problems at enrollment. The participants had a median age of 58, and 55.3% were females.
The researchers asked the participants to self-report how many cups of coffee they drank each day and the type of coffee they usually drank via a touchscreen questionnaire. The different coffee types, in order of popularity, were:
- instant coffee (44.1% of participants)
- ground coffee (18.4%)
- decaffeinated coffee (15.2%)
22.4% of the study population did not drink coffee and served as the comparator group. For each type of coffee, the researchers divided the study participants into 6 categories, depending on daily intake: 0, 1, 1, 2-3, 4-5, and >5 cups/day.
The researchers followed up on the participants’ health status for 12.5 years and determined their health outcomes by looking at the ICD (International Classification of Diseases) codes on medical and death records.
The study adjusted for factors that influence the risk of cardiovascular problems, including age, gender, alcohol intake, tea intake, obesity, diabetes, high blood pressure, obstructive sleep apnea, and smoking status. The researchers then found that people who habitually drank ground, instant, or decaffeinated coffee had significantly lower risks of cardiovascular disease and death from any cause than non-coffee drinkers.
The researchers observed that consumption of 2-3 cups of coffee a day, regardless of the type of coffee, was consistently associated with the largest risk reduction in cardiovascular disease, coronary heart disease, congestive cardiac failure, and death from any cause.
Caffeinated coffee lowers arrhythmias risk
An arrhythmia is when the heart beats too slowly, too fast, or irregularly. According to the Centers for Disease Control and Prevention (CDC), atrial fibrillation is the most common type of treated heart arrhythmia.
The researchers found that ground and instant coffee, but not decaffeinated coffee, was associated with a lower risk of arrhythmia, including atrial fibrillation. They saw a “U-shaped” relationship between caffeinated coffee intake and the risk of arrhythmia, with the lowest risk observed in those who consumed 2-3 cups of coffee daily.
“This study is novel in identifying specific benefits of caffeinated coffee on atrial fibrillation which are biologically plausible given caffeine’s effects on adenosine receptors on heart cells,” Pro. Kistler told MNT.
The heart needs to beat rhythmically to circulate blood to the entire body. The period in which the heart relaxes between beats is the refractory period. Adenosine produced by the body shortens the refractory period, which raises the risk of arrhythmias.
Previous studies have suggested that caffeine blocks adenosine receptors, effectively protecting the heart against the effects of adenosine. This antiarrhythmic property of caffeine may therefore explain the different effects of caffeinated and decaffeinated coffee on the arrhythmia risk reported in this study.
Dr. Eric Topol, cardiologist, professor, and Founder and Director of the Scripps Research Translational Institute, expressed enthusiasm about the new study’s findings on Twitter:
— Eric Topol (@EricTopol) September 27, 2022
In their paper, the researchers identified several study limitations to keep in mind when interpreting their findings. Firstly, some participants had to be omitted from the analysis due to missing data.
Coffee consumption by the study participants was self-reported, which carries the potential risk of reporting bias. Participants could only select one type of coffee on the questionnaire, but some participants may have possibly drunk more than one type of coffee daily. Additionally, the researchers assumed that the participants’ coffee consumption did not change from baseline to follow-up. Yet, it is possible that some participants drank more than one type of coffee over time.
The researchers also acknowledged that the system used to track the participants’ health (ICD-10 codes) is susceptible to measurement and reporting errors. Furthermore, certain arrhythmias, particularly atrial/ventricular ectopy, may have gone undetected.
The participants’ alcohol and tea intakes were considered in the analysis, but other components of the participants’ diets may have impacted their health outcomes.
Finally, since most of the UK Biobank population is Caucasian, the study conclusions may not entirely apply to people of other ethnic groups.
This article originally appeared here and was republished with permission.