Heartburn happens when stomach acid flows backward into your esophagus, the tube connecting your mouth to your stomach. A ring of muscle at the bottom of that tube, called the lower esophageal sphincter, normally stays closed to keep acid where it belongs. When that muscle relaxes at the wrong time, or when pressure in your abdomen forces acid upward, you feel that familiar burning sensation behind your breastbone. The cause is rarely just one thing. Diet, body position, weight, medications, and underlying anatomy can all play a role.
Foods That Relax the Valve
Certain foods directly cause the muscle at the base of your esophagus to loosen. They also slow digestion, which means food sits in your stomach longer and produces more acid. The main categories are high-fat, high-salt, and heavily spiced foods: fried food, fast food, pizza, bacon, sausage, cheese, and processed snacks like potato chips. These are some of the most reliable heartburn triggers because fat takes longer to digest and relaxes that critical valve.
Other foods cause problems through different mechanisms. Tomato-based sauces and citrus fruits are naturally acidic, which irritates an already-sensitive esophagus. Chocolate and peppermint both relax the sphincter. Carbonated beverages introduce gas that increases stomach pressure and can force acid upward. You don’t necessarily need to eliminate all of these permanently, but identifying which ones consistently trigger your symptoms is one of the fastest ways to get relief.
How Body Weight Affects Reflux
Carrying extra weight, especially around your midsection, physically compresses your stomach. That increased pressure in the abdomen pushes stomach contents upward against the esophageal sphincter, overwhelming its ability to stay closed. This is a mechanical problem: the more abdominal fat, the more constant upward pressure on your stomach. It also disrupts the natural anti-reflux barrier where the esophagus meets the stomach. Even modest weight gain can tip the balance if you were already borderline, which is why heartburn sometimes appears seemingly out of nowhere after a period of weight change.
Medications That Make It Worse
If your heartburn started around the same time as a new prescription, the medication could be the cause. Some drugs directly irritate the esophageal lining, producing a burning pain that feels identical to acid reflux. Common culprits include ibuprofen, aspirin, certain antibiotics, iron supplements, and osteoporosis medications taken by mouth.
A separate group of medications doesn’t irritate the esophagus directly but instead relaxes that lower sphincter or increases acid production. Blood pressure medications (particularly calcium channel blockers), certain antidepressants, sedatives, opioid painkillers, and overactive bladder drugs all fall into this category. If you suspect a medication is involved, don’t stop taking it on your own, but it’s worth a conversation about alternatives or timing adjustments.
Sleeping Position and Nighttime Symptoms
When you lie down, gravity stops helping keep stomach acid in place. That’s why heartburn often feels worse at night or wakes you from sleep. The problem isn’t just being horizontal. Your sleeping side matters too.
Sleeping on your right side is associated with more reflux episodes because of how the stomach sits in your body. In that position, acid pools near the sphincter and flows more easily into the esophagus. Sleeping on your left side does the opposite: the stomach hangs below the esophageal opening, and gravity pulls acid away from the valve. The American Gastroenterological Association recommends left-side sleeping for this reason. Elevating the head of your bed by about six inches (using a wedge pillow or bed risers, not just stacking pillows) also helps by keeping your esophagus above your stomach throughout the night.
Pregnancy and Hormonal Changes
Heartburn affects a large proportion of pregnant women, and it tends to get worse as the pregnancy progresses. Two things are happening at once. First, rising levels of progesterone relax smooth muscle throughout the body, including the esophageal sphincter. As progesterone climbs through each trimester, the sphincter’s resting pressure drops steadily. Second, the growing uterus increases abdominal pressure in the same way excess weight does, pushing stomach contents upward.
The good news is that this type of heartburn resolves after delivery. Sphincter pressure returns to normal once progesterone levels drop.
Hiatal Hernia and Structural Causes
Sometimes the problem is anatomical. A hiatal hernia occurs when the upper part of your stomach pushes up through the opening in the diaphragm where the esophagus passes through. This disrupts the natural anti-reflux barrier and increases acid exposure in the esophagus. Between 50% and 94% of people with reflux-related esophageal inflammation have a hiatal hernia, compared to 13% to 59% in people without reflux symptoms. Small hiatal hernias are common and often cause no trouble, but larger ones can be a major driver of persistent heartburn that doesn’t respond well to diet changes alone.
When Occasional Becomes Chronic
Everyone gets heartburn once in a while. It becomes a concern when it happens frequently, typically two or more times per week, over several weeks. At that point, it’s generally classified as gastroesophageal reflux disease, or GERD, which means the repeated acid exposure is potentially damaging your esophageal lining.
Long-term, untreated GERD carries real risks. Between 10% and 15% of people with GERD develop Barrett’s esophagus, a condition where the cells lining the lower esophagus change in response to chronic acid damage. Barrett’s itself is manageable with monitoring, but it carries roughly a 0.5% per year risk of progressing to esophageal cancer. That number is small in any given year, but it compounds over decades, which is why chronic heartburn is worth addressing rather than just tolerating.
Common Patterns to Watch For
Pinpointing why you’re getting heartburn often comes down to recognizing patterns. A few questions can help narrow it down:
- Timing: Does it happen within an hour of eating? That points to dietary triggers or portion size. Does it hit primarily at night? Sleeping position and late meals are likely factors.
- New variables: Did it start after a medication change, weight gain, or pregnancy? These are the most common non-dietary causes.
- Frequency: Once a month after pizza is normal. Multiple times a week regardless of what you eat suggests a structural issue like a hiatal hernia or a weakened sphincter that needs medical evaluation.
- Response to antacids: If over-the-counter antacids provide quick but short-lived relief, the problem is straightforward acid exposure. If they barely help, the issue may involve bile reflux or esophageal sensitivity, which require different approaches.
Most people with occasional heartburn can manage it by eating smaller meals, avoiding trigger foods within three hours of bedtime, sleeping on their left side with the head elevated, and maintaining a healthy weight. When those changes aren’t enough, or when symptoms are frequent and worsening, the next step is evaluation to check for structural causes and assess whether the esophagus has been damaged.