Chronic heartburn happens when the valve between your esophagus and stomach fails to close properly, allowing acid to wash upward repeatedly. Roughly 10% of the global population lives with gastroesophageal reflux disease (GERD), the condition defined by heartburn occurring at least twice a week. The causes range from structural problems with that valve to excess body weight, hormonal shifts, medications, and conditions that slow digestion.
How the Valve Between Your Stomach and Esophagus Fails
At the bottom of your esophagus sits a ring of muscle called the lower esophageal sphincter (LES). It opens to let food into your stomach and closes to keep acid from traveling back up. When this valve malfunctions, acid repeatedly contacts the lining of your esophagus, which isn’t built to withstand it. That contact produces the burning sensation behind your breastbone.
Two patterns of valve failure drive most chronic heartburn. In the first, the sphincter relaxes at the wrong times, opening spontaneously when you haven’t swallowed anything. In the second, the resting pressure of the sphincter is simply too low to hold acid back. Both patterns appear to stem primarily from faulty nerve signaling to the muscle rather than damage to the muscle itself. A section of the diaphragm that wraps around the base of the esophagus also plays a backup role, helping squeeze the valve shut during physical strain. When that support weakens, reflux becomes more likely.
Why Excess Weight Is a Major Driver
Carrying extra weight, particularly around the abdomen, creates a set of mechanical forces that push acid in the wrong direction. Fat tissue around the midsection raises pressure inside the abdominal cavity, which in turn raises pressure inside the stomach itself. That increased pressure pushes against the esophageal valve from below, overwhelming its ability to stay shut.
Obesity also physically separates the two structures that normally work together to prevent reflux: the lower esophageal sphincter and the surrounding diaphragm muscle. When these drift apart, a gap forms that can develop into a hiatal hernia, where the upper portion of the stomach slides above the diaphragm. This disrupts the entire anti-reflux barrier. Research shows that obese patients have higher intragastric pressure, a steeper pressure difference between the stomach and esophagus, and a higher rate of hiatal hernia formation. Together, these create ideal conditions for chronic reflux.
Hormones and Heartburn
Estrogen and progesterone relax smooth muscle throughout the body, including the lower esophageal sphincter. This explains why heartburn is extremely common during pregnancy, when both hormones surge. It also explains a pattern seen outside of pregnancy: women using hormone therapy for menopausal symptoms are 29% more likely to develop GERD. Estrogen-only therapy raises the risk by 41%, progesterone-only therapy by 39%, and combination therapy by 16%. The hormones don’t damage the valve. They simply loosen it enough that acid escapes more easily, and in many cases the effect is ongoing for as long as hormone levels remain elevated.
Medications That Weaken the Valve
Several commonly prescribed drug classes relax the esophageal sphincter as a side effect. If you take any of these and experience persistent heartburn, the medication may be a contributing factor:
- Blood pressure medications (calcium channel blockers) relax smooth muscle throughout the body, including the esophageal valve. These are widely prescribed for high blood pressure and certain heart conditions.
- Nitrate-based heart medications used for chest pain (angina) work by relaxing blood vessels and smooth muscle, which includes the sphincter.
- Anticholinergic drugs used for bladder problems, irritable bowel syndrome, and other conditions block nerve signals that help keep the gut’s muscles contracted, loosening the valve as a result.
If one of these medications is contributing to your heartburn, stopping it without a substitute could be dangerous. The goal is to identify the connection so you and your doctor can weigh alternatives.
Slow Stomach Emptying
In a condition called gastroparesis, the stomach takes far longer than normal to push food into the small intestine. Food and acid accumulate, the stomach distends, and the swollen stomach makes it physically easier for acid to escape through the top. Chronic acid reflux is one of the most common complications of gastroparesis, and it can be severe enough to inflame the esophageal lining. Diabetes is the most frequent known cause of gastroparesis, though in many cases no clear cause is found.
Diet, Habits, and Structural Factors
Certain foods and behaviors don’t damage the valve permanently but trigger relaxation episodes or increase acid production in ways that add up over time. Fatty foods slow stomach emptying and relax the sphincter. Alcohol does the same. Coffee, chocolate, and peppermint can all prompt the valve to open. Eating large meals, eating within two to three hours of lying down, and smoking all increase acid exposure in the esophagus.
Hiatal hernias deserve special mention. When part of the stomach pushes through the opening in the diaphragm, the angle between the esophagus and stomach changes, removing a natural kink that normally helps prevent backflow. Small hiatal hernias are common and often harmless, but larger ones can make reflux significantly worse and harder to control with lifestyle changes alone.
When Chronic Heartburn Changes the Esophagus
Years of acid exposure can cause the cells lining the lower esophagus to change shape, replacing the normal tissue with a type that more closely resembles the intestinal lining. This is called Barrett’s esophagus, and it matters because it slightly raises the long-term risk of esophageal cancer. Screening is typically recommended for people who have had weekly GERD symptoms for five or more years and have additional risk factors such as obesity, smoking history, male sex, or a family history of Barrett’s or esophageal cancer.
Barrett’s esophagus itself doesn’t cause new symptoms. Most people who have it feel exactly the same as they did before. That’s precisely why screening matters: the tissue changes happen silently, and catching them early allows for monitoring or treatment before they progress. Not everyone with chronic heartburn develops Barrett’s, but the longer acid reflux goes unmanaged, the higher the cumulative risk.
Multiple Causes Often Overlap
Chronic heartburn rarely has a single, clean explanation. A person carrying extra abdominal weight who also takes a calcium channel blocker and eats late at night faces three overlapping pressures on the same valve. Pregnancy adds hormonal relaxation of the sphincter on top of the growing uterus pressing upward on the stomach. Understanding which factors are contributing in your case is what makes the difference between chasing symptoms and actually reducing them. Some causes, like medications and meal timing, are modifiable. Others, like a large hiatal hernia, may eventually require a structural fix. Identifying the combination at play is the first step toward relief that lasts.