“One of the useful things about age is realizing conventional wisdom is often simply inertia with a candy coating of conformity.”
— Anna Quindlen
No doubt you have heard that caffeine increases your risk of certain cardiac dysrhythmias like atrial fibrillation or atrial flutter. Perhaps you even heard that from healthcare professionals like doctors and nurses. It is one of those accepted truisms within the healthcare community that has existed for so long that nobody questions from whence it came and if it is even true. It seems to make logical sense, and since everybody agrees, well then, it must simply be so. But like so much conventional wisdom, when put to the test, we find that it is neither.
As this week’s Study Spotlight observes, atrial fibrillation (AF) is the most common heart rhythm disorder, affecting one in three people during their lifetime. Currently in the US, over 10.5 million people have been diagnosed with atrial fibrillation. Coffee, with its caffeine content, is often targeted as something to avoid to reduce the burden of AF. Yet despite the commonly prescribed recommendation to avoid that cup of morning Joe in an effort to reduce episodes of atrial fibrillation, the evidence behind such conventional wisdom, as is often the case, is lacking.
- This study was a prospective, open-label, randomized clinical trial enrolling 200 current or previous (within the past 5 years) coffee-drinking adults (71% male with a mean age of 69 years) with persistent AF, or atrial flutter with a history of AF.
- The participants were scheduled for planned elective cardioversion.
- The study group was randomized in a 1:1 ratio to regular caffeinated coffee consumption vs coffee and caffeine abstinence for 6 months.
- Participants in the coffee consumption group were encouraged to drink at least 1 cup of caffeinated coffee daily. During follow-up, the average consumption in this group was 7 cups per week.
- Participants in the abstinence group were encouraged to completely abstain from both caffeinated and decaffeinated coffee and other caffeine-containing products. During follow-up, the average consumption of this group was 0 cups per week.
- The recurrence rate in the coffee-drinking group was 47%, compared with 64% in the group abstaining from coffee and caffeine; a 39% risk reduction.
The Caveat:
As the study noted, the patients with atrial fibrillation who continued to drink coffee after successful cardioversion suffered less recurrence of AF or atrial flutter compared with abstinence from coffee and caffeinated products. A finding 180° from the prevailing conventional wisdom.
Caffeinated coffee has traditionally been considered to be an instigator of abnormal heart rhythms. And as the current study also notes, “physicians continue to advise that coffee reduction may minimize the effects of AF.” This practice continues despite evidence from the recent Coffee and Real-time Atrial and Ventricular Ectopy (CRAVE) randomized trial, which found that caffeinated coffee consumption did not increase premature atrial contractions, which are known to trigger AF episodes. Other observational studies have also reported no effect or even a protective effect (lower risk of AF) among coffee consumers.
Regular coffee contains caffeine. However, coffee also contains many other biological compounds. Many of these appear to have anti-inflammatory properties. Because systemic inflammation is a risk factor for atrial fibrillation, coffee may reduce AF risk by reducing inflammation. Atrial fibrillation can also be induced, in some instances, through stimulation of the vagus nerve. The caffeine found in coffee may counteract that; caffeine is also a diuretic, potentially reducing blood pressure and AF risk.
Whatever the mechanism in this instance, the general practice of selecting a particular nutrient or ingredient in food and either deifying or demonizing it is, unfortunately, a widespread practice. Like this example of caffeine in coffee, recommendations are often promoted by various healthcare professionals—and by other “self-proclaimed” experts—to the point that they become accepted as conventional wisdom. And herein lies the danger and confusion. A book is often more than just its cover, and a whole food is often more than just the sum of its ingredients.
Additional references:
