Heartburn happens when stomach acid flows backward into your esophagus, the tube that connects your throat to your stomach. At the bottom of that tube sits a ring of muscle that normally opens to let food pass into your stomach, then closes tight. When that muscle relaxes at the wrong time or becomes weak, acid escapes upward and irritates the esophageal lining, producing that familiar burning sensation behind your breastbone. The reasons this happens range from what you ate for dinner to pregnancy, medications, or a structural change in your anatomy.
How the Valve Between Your Stomach and Esophagus Fails
That ring of muscle at the base of your esophagus, called the lower esophageal sphincter, is the gatekeeper. It relaxes briefly every time you swallow, then snaps shut to keep acid where it belongs. Heartburn is fundamentally a problem with this valve. If it relaxes too often, stays open too long, or loses strength over time, acid creeps upward.
Several things weaken or disrupt this valve. Excess body weight puts pressure on your abdomen and pushes stomach contents upward. A hiatal hernia, where the upper part of your stomach bulges through the diaphragm into your chest cavity, physically displaces the valve and makes reflux far more likely. Small hiatal hernias often cause no symptoms at all, but larger ones allow food and acid to back up easily. Delayed stomach emptying, where food sits in the stomach longer than it should, also increases the odds.
Foods and Drinks That Set It Off
Certain foods relax that esophageal valve directly, while others ramp up acid production or irritate the lining on contact. The most common culprits include fatty and fried foods, chocolate, citrus fruits, garlic, onions, spicy foods, and peppermint or spearmint. Large meals are worse than small ones because a full stomach puts more pressure on the valve.
Caffeine deserves special attention because it can relax the esophageal sphincter. Coffee, tea, and soda are all potential triggers. Even some herbal teas that seem gentle, particularly those containing peppermint or spearmint, can aggravate symptoms. Alcohol does the same thing, both relaxing the valve and increasing acid production. Eating late at night compounds the problem because lying down removes gravity’s help in keeping acid in your stomach.
Medications That Cause or Worsen Heartburn
If your heartburn started or worsened after beginning a new medication, the drug itself may be the reason. Common over-the-counter pain relievers like ibuprofen (Advil, Motrin) and aspirin can irritate the esophageal lining directly. Antibiotics like tetracycline can do the same.
Other medications don’t irritate the lining but instead relax the esophageal valve or increase acid reflux. These include certain blood pressure medications (calcium channel blockers, ACE inhibitors, nitrates), some antidepressants, opioid pain medications, overactive bladder drugs, potassium supplements, and statins. If you suspect a medication is involved, talk to your prescriber about alternatives rather than stopping on your own.
Why Pregnancy Makes Heartburn So Common
Heartburn during pregnancy is extremely common, and two things drive it. First, progesterone levels rise significantly, and this hormone relaxes smooth muscle throughout the body, including the esophageal sphincter. With a looser valve, acid refluxes more easily. Progesterone also slows digestion overall, keeping food in your stomach longer and giving acid more opportunity to escape upward.
Second, as the uterus grows, it physically pushes the stomach upward, compressing it and forcing contents toward the esophagus. This mechanical pressure gets worse in the second and third trimesters, which is why heartburn often intensifies as pregnancy progresses. Food simply doesn’t move through the digestive system as quickly during pregnancy.
When Heartburn Feels Like Something Worse
Heartburn and a heart attack can both produce chest pain, and it’s worth knowing the difference. Heartburn typically causes a burning sensation in the chest and upper abdomen that responds to antacids. Heart-related chest pain feels more like pressure, tightness, or squeezing, and it may spread to your neck, jaw, arms, or back. Both can come and go, so duration alone isn’t a reliable way to tell them apart. If you feel pressure or tightness rather than burning, especially with shortness of breath, lightheadedness, or pain radiating to your arm or jaw, treat it as a medical emergency.
What Happens If Heartburn Becomes Chronic
Occasional heartburn after a big meal is normal. But when it happens twice a week or more, it may qualify as gastroesophageal reflux disease, or GERD. Persistent acid exposure damages the esophageal lining over time. Scar tissue can form and narrow the esophagus, making swallowing difficult. Between 10% and 15% of people with GERD develop a condition called Barrett’s esophagus, where the cells lining the lower esophagus change in response to chronic acid damage. Barrett’s esophagus carries a small but real risk of progressing to esophageal cancer, which is why chronic heartburn warrants more than just reaching for antacids.
Practical Ways to Reduce Symptoms
Small changes in timing and positioning make a measurable difference. Eating your last meal at least two to three hours before bed gives your stomach time to empty before you lie down. Smaller, more frequent meals put less pressure on the esophageal valve than large ones.
Sleep position matters more than most people realize. Elevating your upper body with a wedge pillow helps gravity keep acid in your stomach. Sleeping on your left side also helps. A study of 57 people with chronic heartburn found that while the number of reflux episodes was similar regardless of position, acid cleared from the esophagus much faster when participants slept on their left side compared to their right side or back. Faster clearance means less time for acid to irritate the lining, which means less pain.
Losing weight, if you carry extra pounds around your midsection, reduces the abdominal pressure that pushes acid upward. Quitting smoking helps too, since nicotine relaxes the esophageal sphincter. Avoiding your personal trigger foods (keeping a food diary for a week or two can help you identify them) is more effective than following a generic list, since triggers vary from person to person.
Over-the-counter antacids neutralize acid that’s already in the esophagus and provide quick relief. Acid-reducing medications work differently by decreasing the amount of acid your stomach produces, which is more useful for frequent heartburn. If you find yourself relying on these regularly, that’s a signal the underlying cause needs attention rather than just symptom management.