What Causes Constant Heartburn: Conditions and Triggers

Constant heartburn almost always traces back to stomach acid reaching the lining of your esophagus too often, staying there too long, or your esophagus reacting more strongly to even small amounts of acid. The medical umbrella for this is gastroesophageal reflux disease (GERD), but the reasons it becomes a daily problem vary widely from person to person. Anatomy, body composition, medications, habits, hormones, and even your emotional state can each push reflux from occasional annoyance to persistent misery.

How Reflux Actually Happens

Your esophagus and stomach meet at a muscular ring called the lower esophageal sphincter (LES). Under normal conditions, the LES stays closed except when you swallow. But it also opens briefly on its own in events called transient lower esophageal sphincter relaxations, or TLESRs. These momentary openings are the single biggest route for acid to splash upward into the esophagus. They are a normal part of digestion and happen in healthy people too, but in people with GERD they tend to happen more frequently and are more likely to carry acidic stomach contents with them.¹

After a meal, a layer of unbuffered acid collects on top of your stomach contents, sitting just below or right at the junction where the esophagus meets the stomach. Researchers call this the “acid pocket.” In healthy people the pocket usually sits below the diaphragm, where it’s less likely to cause trouble. But in people with GERD, the pocket tends to migrate upward. When it sits above the diaphragm, each TLESR is far more likely to send acid into the esophagus. One study found that the acid pocket was positioned above the diaphragm before more than three-quarters of TLESRs in patients with large hiatal hernias, compared with roughly one in five in healthy volunteers.² The stronger the acidity of this pocket and the bigger it is, the more reflux episodes people experience and the worse their symptom scores tend to be.³

Hiatal Hernia and Why It Matters So Much

A hiatal hernia occurs when part of the upper stomach pushes through the opening in the diaphragm that the esophagus passes through. This anatomical shift weakens the barrier between stomach and esophagus in several ways at once: it lowers the resting pressure of the LES, increases the frequency of TLESRs, and slows the esophagus’s ability to clear acid once it arrives.⁴ The bigger the hernia, the worse these effects become. Patients with larger hernias have weaker and shorter LES segments, less effective esophageal muscle contractions to push acid back down, and measurably greater acid exposure in the esophagus.⁵

Many people have a small hiatal hernia and never know it. A small one by itself doesn’t doom you to constant heartburn. But when a hernia is present alongside other risk factors, it acts as a multiplier. The esophageal junction becomes incompetent, acid clearance is impaired, and GERD develops more readily.⁶

Body Weight and Abdominal Pressure

Carrying extra weight around your midsection is one of the strongest and most modifiable risk factors for persistent heartburn. The mechanism is straightforward: abdominal fat increases the pressure inside your abdomen, which pushes against the stomach and forces its contents upward toward a junction that may already be under strain. The association between body mass index (BMI) and acid exposure in the esophagus is remarkably linear. Research measuring pressures in real time showed that higher BMI correlated strongly with higher intra-gastric pressure, and that mechanically mimicking abdominal compression with a belt produced the same reflux-promoting changes seen in people with elevated BMI.⁷

Central obesity in particular disrupts the esophagogastric junction.⁸ Beyond the mechanical squeeze, abdominal fat may also weaken the esophageal mucosal barrier through inflammatory pathways.⁹ This is why weight loss frequently reduces heartburn more effectively than many dietary changes, and why tightfitting clothing around the waist can worsen symptoms in people who are otherwise managing their reflux.

When the Esophagus Is Too Sensitive, Not Too Acidic

Not everyone with persistent heartburn has unusually high acid exposure. In fact, a large share of people with chronic heartburn symptoms have what clinicians call nonerosive reflux disease (NERD), meaning their esophagus looks normal on endoscopy with no visible damage. Studies using pH monitoring found that only about 45% of NERD patients had abnormally high acid exposure, compared with 75% of patients with visible erosions and over 90% of those with Barrett’s esophagus. NERD patients also had fewer total acid reflux episodes and lower overall acid contact time.¹⁰

So why do these patients feel heartburn if their acid exposure is near-normal? Some of them have what is now classified as reflux hypersensitivity: their esophagus is genuinely more reactive to even small amounts of acid that would go unnoticed in someone else. Others have functional heartburn, where the sensation occurs without any measurable connection to reflux events at all. Together, reflux hypersensitivity and functional heartburn account for more than 90% of heartburn patients who don’t improve on twice-daily acid-suppressing medication.¹¹ This distinction matters because adding more acid suppression won’t help if the problem is nerve sensitivity rather than excess acid.

Conditions That Mimic or Overlap With GERD

Several conditions produce symptoms that feel exactly like chronic heartburn but require completely different treatment. Eosinophilic esophagitis is an immune-mediated inflammation of the esophageal lining that often shows up as difficulty swallowing and chest pain. Achalasia, a rare motility disorder where the LES fails to relax properly, can cause a burning sensation and food regurgitation. Gastroparesis, where the stomach empties too slowly, keeps food and acid sitting in the stomach longer than normal, increasing reflux. Even a gastrinoma, a hormone-secreting tumor that drives the stomach to overproduce acid, can present as stubborn heartburn.¹² If your heartburn hasn’t responded to standard treatment, the issue may not be ordinary reflux at all, and the diagnostic workup changes significantly.

Dietary Triggers and a Few Myths

Certain foods are routinely blamed for heartburn, and some of those claims hold up better than others. Fat is the most commonly accused trigger, and there is a physiological basis for the concern: fat in the gut releases cholecystokinin (CCK), a hormone that relaxes the LES somewhat. Infusion studies showed that CCK reduced LES pressure by roughly a third at higher doses.¹³ However, when researchers actually fed people high-fat and low-fat meals of comparable size and measured reflux parameters afterward, they found no meaningful difference in LES pressure or acid exposure between the two.¹⁴ The total volume of a meal may matter more than its fat content.

Mint is another classic on the “avoid” list for heartburn sufferers. The reasoning was that menthol relaxes the LES. But when researchers directly infused menthol into the esophagus and measured motility with modern high-resolution equipment, they found no appreciable effect on LES pressure or esophageal contractions in either healthy volunteers or GERD patients. The older studies suggesting a connection were done with less precise instruments, and the recommendation to avoid mint may be outdated for most people.¹⁵

Large meals, alcohol, carbonated drinks, citrus, and tomato-based foods remain commonly reported personal triggers. The evidence for these varies, and individual responses differ a lot. Keeping a food diary to identify your own triggers tends to be more useful than following a generic avoidance list.

Medications That Worsen Heartburn

Several widely used medication classes can promote or worsen reflux. Calcium channel blockers, commonly prescribed for high blood pressure and heart conditions, work by blocking calcium from entering smooth muscle cells. Since the LES is smooth muscle, the same mechanism that relaxes blood vessels also relaxes the sphincter meant to keep acid out of the esophagus.¹⁶ Other drugs that relax the LES include benzodiazepines, nitrates, asthma-related beta-2 agonists, and theophylline-type medications.¹⁷

NSAIDs like ibuprofen and naproxen are a separate concern. They reduce the protective prostaglandins that help maintain the stomach and esophageal lining, making tissue more vulnerable to acid damage.¹⁸ Beyond LES relaxation and mucosal damage, some pills can directly injure the esophagus if they dissolve too slowly during their trip down. Capsules or tablets commonly get delayed in the esophagus, and if their caustic contents linger against the tissue, they produce localized inflammation or ulceration.¹⁹ Taking pills with plenty of water and staying upright for at least 30 minutes afterward helps prevent this kind of damage.

Smoking and the LES

Smoking promotes reflux through multiple routes. Nicotine lowers resting LES pressure, reducing the barrier’s effectiveness. Smoking also slows saliva production, which matters because saliva is mildly alkaline and helps neutralize acid that reaches the esophagus. On top of that, the physical act of coughing or deep inhalation during smoking spikes intra-abdominal pressure, creating the same kind of upward push that excess body weight does.²⁰ Quitting doesn’t fix reflux overnight, but over time it removes several stacked contributors at once.

Sleep Position Makes a Measurable Difference

How you lie down at night has a surprisingly large effect on nighttime acid exposure. Sleeping on your left side consistently outperforms both right-side and back sleeping in studies measuring esophageal acid contact. One study using simultaneous position tracking and pH monitoring found that acid exposure time was essentially zero for many left-side sleepers, while right-side and supine sleepers had measurably higher acid contact. Acid clearance time was also fastest on the left, at roughly half the time compared to lying on your back or right side.²¹ A meta-analysis confirmed that left-side sleeping reduced both acid exposure time and acid clearance time compared with right-side and supine positions.²²

The anatomy explains this nicely. When you lie on your left, the stomach hangs below the esophageal junction, and the acid pocket pools away from the opening. On your right, gravity positions the stomach contents right at the junction. Elevating the head of the bed by about 15 to 20 centimeters also helps by using gravity to keep acid in the stomach, and some clinicians recommend combining head elevation with left-side positioning for the best results.

Stress and Symptom Perception

Stress doesn’t appear to increase the amount of acid your stomach produces, but it does change how intensely you perceive the acid that’s already there. An experiment using controlled acid infusion into the esophagus while subjects listened to a stressful audio stimulus found that stressed patients felt the burn faster and rated the sensation as more intense. The acid dose was the same, but the experience of it was amplified.²³ This helps explain why heartburn often flares during high-stress periods even when diet and other habits haven’t changed. For people whose reflux falls into the hypersensitivity or functional heartburn categories, stress management can sometimes make a bigger difference than adding another medication.

Pregnancy and Hormonal Shifts

Heartburn during pregnancy is extremely common, especially in the second and third trimesters. The primary driver is progesterone, which relaxes smooth muscle throughout the body, including the LES. As pregnancy progresses, the growing uterus also increases intra-abdominal pressure, compounding the hormonal effect.²⁴ The combination of a weaker sphincter and higher abdominal pressure is essentially the same recipe that makes obesity a risk factor, just driven by different causes. For most women, heartburn resolves after delivery as progesterone levels drop and abdominal pressure normalizes.

Genetic Susceptibility

GERD tends to run in families, and research has identified specific genetic variations that influence risk. Variations in genes involved in inflammation, DNA repair, and the development of the esophageal-gastric junction have all been linked to higher GERD susceptibility.²⁵ This doesn’t mean heartburn is “genetic” in the way that eye color is. Rather, some people inherit a slightly weaker LES, a tendency toward more visceral nerve sensitivity, or connective tissue characteristics that make a hiatal hernia more likely. Genetics loads the gun, and lifestyle and environment pull the trigger.

When Chronic Heartburn Causes Lasting Damage

If acid exposure continues uncontrolled over years, the esophageal lining can undergo a change called Barrett’s esophagus, where the normal flat cells are replaced by a type of columnar cell more typically found in the intestine. This transformation is the body’s attempt to protect itself from ongoing acid and bile exposure, but the new tissue carries an increased risk of developing esophageal adenocarcinoma, a type of cancer.²⁶ Barrett’s develops specifically in the setting of severe, long-standing disruption of the barrier between the stomach and esophagus, and involves exposure not just to acid but also to bile salts that reflux from the small intestine into the stomach and then upward.²⁷

The absolute risk of Barrett’s progressing to cancer is low in any given year, but the cumulative risk is why gastroenterologists recommend surveillance endoscopy for people diagnosed with it. The more immediate consequences of uncontrolled reflux are esophageal strictures (narrowing from scar tissue), erosive esophagitis, and chronic cough or hoarseness from acid reaching the throat and airways. These complications tend to develop gradually, which is part of why constant heartburn gets dismissed as a nuisance rather than treated as the warning sign it can be.

Helicobacter Pylori and a Complicated Relationship

You might expect that the bacterium H. pylori, famous for causing stomach ulcers and gastritis, would also drive heartburn. The real relationship is more tangled. H. pylori infection causes a range of effects on gastric acid secretion that depend on where in the stomach the infection settles. In some patterns of infection, it actually reduces acid production over time by damaging the acid-producing cells, which might paradoxically protect against reflux. In other patterns it increases acid output. The relationship between H. pylori and GERD remains genuinely debated among researchers, and eradicating the infection does not reliably improve or worsen reflux symptoms.²⁸ This is one area where the science is messier than you’d hope, and a simple “treat the infection, fix the heartburn” story doesn’t hold up.

Getting the Right Diagnosis

Standard acid-suppressing medication works well for many people, but when heartburn persists despite treatment, the diagnostic pathway gets more involved. The current gold standard for measuring reflux objectively is 24-hour impedance-pH monitoring, a test where a thin catheter in the esophagus tracks both acid and non-acid reflux events around the clock. Newer metrics extracted from this test, including baseline impedance levels overnight and how well swallowing clears reflux afterward, have further improved its accuracy.²² The test is especially useful for distinguishing between true excess reflux, reflux hypersensitivity, and functional heartburn, which each point toward different treatment strategies. High-resolution manometry, upper endoscopy with biopsies, and gastric emptying studies round out the toolkit when the basic picture doesn’t add up.

If you’ve been living with daily heartburn and over-the-counter antacids are your main strategy, it’s worth understanding that the causes are more varied and more treatable than most people assume. The same symptom can arise from a mechanical problem like a hiatal hernia, a nerve sensitivity issue, a medication side effect, or a condition that isn’t reflux at all. Matching the treatment to the actual cause is what separates people who manage their heartburn successfully from those who just endure it.