Can caffeine increase sympathetic activity and trigger palpitations or reflux symptoms?

Caffeine’s influence on the body is characterized by its role as an adenosine receptor antagonist, which can trigger physiological changes across the nervous, cardiovascular, and digestive systems. While individual responses vary significantly based on habituation and genetics, the link between caffeine and sympathetic activation, heart palpitations, and reflux symptoms is supported by established mechanistic pathways.

Clinical evidence and mechanisms

The physiological effects of caffeine are largely driven by its ability to block adenosine receptors, which normally inhibit neuronal activity.

• Sympathetic activation: Caffeine stimulates the locus coeruleus, increasing neuronal firing and the release of catecholamines like norepinephrine. Studies have shown that caffeine can increase plasma norepinephrine by nearly 97% in some populations, leading to heightened sympathetic markers such as sudomotor (sweat) activity and peripheral vasoconstriction.
• Palpitations: While moderate caffeine intake (under 400 mg) is generally not linked to serious arrhythmias like atrial fibrillation, it can trigger subjective palpitations. In trials like the CRAVE study, caffeine did not significantly increase premature ventricular contractions (PVCs), but higher doses—particularly from energy drinks containing other stimulants—have been shown to increase supraventricular extrasystoles (SVES) and alter hemodynamic stability.
• Gastroesophageal Reflux (GERD): Caffeine is a known stimulant of gastric acid secretion. This occurs via bitter taste receptor (TAS2R) signaling in the stomach's parietal cells. Additionally, it is traditionally thought to relax the lower esophageal sphincter (LES), allowing acid to enter the esophagus, though large-scale clinical trials have found inconsistent results regarding the severity of erosive esophagitis in regular coffee drinkers.

Practical considerations

The impact of caffeine is highly personalized. For many, the sympathetic surge is mitigated by baroreflex buffering or caffeine tolerance. Similarly, while medical guidelines from the ACG and AGA recommend limiting caffeine for those with GERD, these recommendations are often based on patient-reported symptom relief rather than universal physiological data.

Bottom line

Caffeine acts as a physiological stimulant that can plausibly increase sympathetic activity and trigger heart palpitations or GERD symptoms in sensitive individuals. While not a universal trigger for serious cardiac or digestive disease, its role in symptom exacerbation is well-recognized in clinical practice.