Question explored with the scientific record
What causes heartburn?
Heartburn is stomach acid flowing backward into the esophagus, but the real problem is often a weak or improperly timed valve, not just too much acid.
The burning sensation happens when the lower esophageal sphincter (LES) relaxes at the wrong time, letting acid splash up. This is called a transient LES relaxation (TLESR), and it is the main mechanism behind most reflux episodes [6]. A hiatal hernia, where part of the stomach slides above the diaphragm, makes this much worse by physically breaking the barrier [3]. In one study of 405 people with reflux-related throat symptoms, about 26% had a hiatal hernia [4]. Obesity adds pressure on the stomach, and a 2022 study of 174 adults found that higher BMI correlated with more frequent heartburn symptoms, though it did not predict how much damage was seen on endoscopy [5].
Not all heartburn is from acid. In a 2014 study of 100 patients who still had symptoms despite taking acid-blocking proton pump inhibitors (PPIs), only 14% had acid reflux alone. The majority, 55%, had non-acid reflux, and 30% had a mix of both [1]. Another 2016 study of 39 PPI-resistant patients found that over half had functional heartburn, meaning their pain came from a sensitized esophagus, not from actual reflux [2]. This matters because PPIs only reduce acid; they do not fix a weak valve or stop non-acid reflux.
The evidence here is mostly about mechanisms and treatment comparisons, not about long-term safety of any single intervention. The studies are small and many are funded by device or drug makers. The bottom line: heartburn is a mechanical problem of the valve and diaphragm, often made worse by weight and hiatal hernia, and acid is only part of the story.
My call: heartburn is primarily a mechanical barrier failure, not an acid disease. Confidence: moderate — the mechanism is well-established, but the evidence on what works long-term for the mechanical problem is thin and industry-funded.
Sources used 6
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Survey of findings in patients having persistent heartburn on proton pump inhibitor therapy
This study investigates the etiology of persistent heartburn in patients on proton pump inhibitor therapy, revealing that a significant proportion of these patients experience nonacid reflux and other disorders, rather than solely acid reflux.
DOI: 10.1111/dote.12293 -
Tailored therapy for the refractory GERD patients by combined multichannel intraluminal impedance–pH monitoring
This study investigates the reasons for proton pump inhibitor (PPI) failure in refractory gastroesophageal reflux disease (GERD) patients and demonstrates that tailored therapy guided by multichannel intraluminal impedance-pH monitoring can lead to symptom relief in a significan…
DOI: 10.1111/jgh.13049 -
Contribution of hiatal hernia to asthma in patients with gastroesophageal reflux disease
This study investigates the correlation between hiatal hernia and asthma in patients with gastroesophageal reflux disease, revealing that patients with hiatal hernia experience more severe symptoms and better outcomes following laparoscopic anti-reflux surgery compared to those …
DOI: 10.1111/crj.12748 -
The Yield of Upper Gastrointestinal Endoscopy in Patients with Suspected Reflux-Related Chronic Ear, Nose, and Throat Symptoms
A prospective study evaluating the yield of upper gastrointestinal endoscopy in 405 patients with suspected reflux-related chronic ENT symptoms, comparing findings with 545 heartburn patients, and assessing response to proton pump inhibitor therapy, revealing a high prevalence o…
DOI: 10.1111/j.1572-0241.2004.30066.x -
GERD and Its Association with BMI in Adult Patients Undergoing Upper GI Endoscopy at the Kenyatta National Hospital
A cross-sectional analysis of 174 adults with GERD undergoing upper GI endoscopy at Kenyatta National Hospital in Kenya shows overweight/obesity are common; BMI correlates with GERD symptom frequency but does not significantly predict endoscopic esophagitis or hiatal hernia.
DOI: 10.23880/ghij-16000191 -
Overview of the mechanisms of gastroesophageal reflux
This review synthesizes mechanisms of gastroesophageal reflux, emphasizing transient lower esophageal sphincter relaxations as the dominant mechanism of reflux events, with esophagogastric junction barrier impairment, hiatal hernia, and esophagitis as contributing factors.
DOI: 10.1016/S0002-9343(01)00828-2