Acid keeps coming up because the muscular valve at the top of your stomach isn’t closing properly, allowing stomach acid to splash back into your esophagus. This valve, called the lower esophageal sphincter (LES), is supposed to open when you swallow and seal shut the rest of the time. When it relaxes at the wrong moment or becomes too weak to hold back pressure from below, you get that burning, rising sensation. Nearly 10% of the global population deals with this problem on a chronic basis.
How the Valve Fails
The LES sits where your esophagus meets your stomach, acting as a one-way gate. Two main patterns of failure cause acid to escape upward. The first and most common is the valve relaxing spontaneously when it shouldn’t. These “transient relaxations” happen without any swallowing trigger, and people with chronic reflux simply have more of them than average. The second pattern is chronically low resting pressure in the valve itself, meaning it never fully seals even between swallows.
Both patterns appear to stem from faulty nerve signaling rather than a problem with the muscle tissue itself. The diaphragm, the large dome-shaped muscle separating your chest from your abdomen, normally wraps around the LES and reinforces it like a second layer of security. When that reinforcement weakens, straining, bending over, or bearing down can push acid past the valve more easily.
Foods and Drinks That Relax the Valve
Certain foods chemically trigger the valve to loosen. Chocolate is a well-studied example: it contains both caffeine and compounds from cacao that directly relax the LES. Coffee and other caffeinated drinks have a similar effect. Peppermint, fatty meals, and alcohol also reduce valve pressure, making acid more likely to escape after eating. Spicy and acidic foods don’t necessarily weaken the valve, but they can irritate an esophagus that’s already inflamed, making each reflux episode feel worse.
Large meals create a separate problem. The more food sitting in your stomach, the greater the upward pressure against the valve. Eating a big dinner and then lying down combines two of the strongest reflux triggers at once.
Why It Gets Worse at Night
When you’re upright, gravity helps keep acid in your stomach. Lying down removes that advantage entirely, so any acid that slips past the valve pools in your esophagus instead of draining back down. Your body also clears acid more slowly at night because you swallow less frequently and produce less saliva during sleep. The result is that nighttime reflux episodes tend to last longer and cause more tissue damage than daytime ones, even if you have fewer of them overall. This is why people with chronic reflux often wake up with a sore throat, a sour taste, or a cough.
Structural Causes: Hiatal Hernia
A hiatal hernia occurs when the upper part of your stomach pushes upward through the diaphragm into the chest cavity. This displaces the LES from its normal position, separating it from the diaphragm’s reinforcing squeeze. The result is a valve that’s weaker, more prone to spontaneous relaxation, and less capable of handling pressure from below. Many people have small hiatal hernias without knowing it, and the condition becomes more common with age. Larger hernias tend to cause more frequent and severe reflux.
Slow Stomach Emptying
If your stomach takes too long to pass food into the small intestine, the extra volume builds up and stretches the stomach wall. That stretching shortens and weakens the LES in much the same way inflating a balloon thins out its neck. With more food and liquid sitting in the stomach for longer, there’s simply more material available to reflux upward. Conditions like gastroparesis (where the stomach’s own muscular contractions are sluggish) and diabetes can both slow emptying and make reflux significantly worse.
Medications That Contribute
Several common medications can trigger or worsen reflux. Anti-inflammatory painkillers like ibuprofen and aspirin damage the protective lining of the esophagus, making it more vulnerable to acid. Some blood pressure medications relax smooth muscle throughout the body, including the LES. If your reflux started or worsened around the same time you began a new medication, that connection is worth exploring with your prescriber.
Pregnancy and Hormonal Changes
Reflux during pregnancy is extremely common and has two overlapping causes. Rising levels of estrogen and progesterone progressively relax the LES throughout pregnancy, with valve pressure reaching its lowest point around 36 weeks. At the same time, the growing uterus pushes upward on the stomach, increasing pressure from below. Most pregnant people first notice symptoms in the first trimester, and they tend to worsen as the pregnancy progresses. The combination of hormonal relaxation and physical compression makes the third trimester the peak period for reflux.
What Happens if Acid Keeps Coming Up
Occasional reflux is uncomfortable but generally harmless. Chronic, repeated acid exposure is a different story. Over time, stomach acid damages the cells lining the lower esophagus. The body sometimes responds by replacing its normal tissue with a tougher, more acid-resistant cell type. This change, known as Barrett’s esophagus, is a precancerous condition. People with Barrett’s have roughly a 0.5% annual risk of developing esophageal cancer. That number sounds small in any given year, but it accumulates over decades of ongoing reflux, which is why persistent symptoms deserve attention rather than just antacids.
The progression from normal tissue to Barrett’s to cancer isn’t inevitable. It moves through stages of increasingly abnormal cell changes, and catching those changes early through endoscopy gives doctors a window to intervene well before cancer develops.
Warning Signs That Need Prompt Attention
Most acid reflux is manageable, but certain symptoms suggest something more serious is happening. According to the American Gastroenterological Association, you should seek care promptly if you experience:
- Difficulty swallowing food or liquids, or a choking sensation while eating
- Unintentional weight loss
- Vomiting blood or material that looks like coffee grounds
- Black or red stools, which can indicate bleeding in the digestive tract
- Chest pain during physical activity like climbing stairs
These signs can point to esophageal damage, ulceration, or narrowing that requires investigation beyond standard reflux treatment.
Practical Steps to Reduce Reflux
Elevating the head of your bed by 6 to 8 inches (using a wedge or blocks under the frame, not just extra pillows) helps gravity keep acid in your stomach overnight. Eating your last meal at least two to three hours before lying down gives your stomach time to empty. Smaller, more frequent meals reduce the volume pressing against the valve at any given time.
Losing weight, even a modest amount, reduces abdominal pressure on the stomach. Tight clothing around the waist has a similar, smaller effect. Identifying your personal trigger foods through trial and elimination is more useful than following a generic restriction list, since triggers vary widely from person to person. If lifestyle changes alone aren’t enough, over-the-counter acid reducers can lower the amount of acid your stomach produces, which doesn’t fix the valve but makes each reflux episode less damaging and less painful.