Acid reflux happens when stomach acid flows backward into your esophagus, the tube connecting your mouth to your stomach. Roughly 10% of the global population experiences this regularly, with over 825 million people affected worldwide as of 2021. The causes range from what you ate for dinner to how your body is built, and most people have more than one factor working against them at the same time.
How the Anti-Reflux Barrier Works
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, then squeezes shut to keep acid where it belongs. This muscle doesn’t work alone. Your diaphragm wraps around the same junction, adding a second layer of defense, and the angle at which your esophagus meets your stomach creates a natural flap. When any of these components weaken or malfunction, acid escapes upward.
Most causes of acid reflux ultimately come back to this barrier. Something is either relaxing the sphincter when it should be closed, increasing the pressure inside your stomach until it overwhelms the barrier, or physically distorting the junction so it can’t seal properly.
Foods and Drinks That Trigger Reflux
Certain foods directly relax the sphincter muscle. Alcohol loosens the LES and irritates the esophageal lining at the same time, a double hit. Coffee and other caffeinated drinks do the same, and they also stimulate your stomach to produce more acid. Tea, cocoa, and cola drinks are all powerful stimulants of acid production, so even switching from coffee to tea may not help if caffeine is your trigger.
High-fat and fried foods are another common cause. Fat slows stomach emptying, meaning food sits in your stomach longer and generates more acid before moving on. Large meals create the same problem simply through volume: the more your stomach stretches, the more pressure pushes against that sphincter. Spicy foods, citrus, tomato-based sauces, and chocolate round out the usual list of offenders, though triggers vary from person to person.
Body Weight and Abdominal Pressure
Carrying extra weight, particularly around your midsection, is one of the strongest risk factors for reflux. The mechanism is straightforward: abdominal fat increases the pressure inside your stomach, physically pushing contents upward. It also pulls apart the two components of the anti-reflux barrier (the sphincter and the diaphragm), creating a gap that acid can slip through.
Research published in the New England Journal of Medicine found that visceral fat, the fat packed around your organs rather than just under your skin, correlates with the severity of reflux symptoms. Waist circumference may actually be a better predictor of reflux than BMI alone. This explains why some people at a “normal” weight still develop reflux if they carry fat around the middle, and why even modest weight loss often brings noticeable relief.
Timing, Posture, and Sleep
Gravity is your ally when you’re upright and your enemy when you lie down. Eating within two to three hours of bedtime is one of the most common reasons people wake up with a burning throat or sour taste. When you’re horizontal, acid doesn’t have to fight gravity to reach your esophagus.
Elevating the head of your bed can help. Clinical guidelines suggest starting at about 10 centimeters (roughly 4 inches) using blocks under the bed legs or a wedge pillow. If that doesn’t improve things after a few weeks, increasing to 20 centimeters (about 8 inches) has been shown to reduce the total time acid sits in the esophagus. Stacking regular pillows doesn’t achieve the same effect because it bends your body at the waist rather than tilting your entire torso.
Hiatal Hernia
A hiatal hernia occurs when part of your stomach pushes up through the opening in your diaphragm where the esophagus passes through. This opening is only about 2 centimeters long and is formed by muscle fibers from either side of the spine. When the stomach slides upward through it, the entire anti-reflux barrier is compromised. The sphincter loses pressure, the diaphragm can no longer reinforce it, and acid clearance from the esophagus slows down.
Small hiatal hernias are extremely common and often cause no symptoms at all. Larger ones are a different story. If you’ve been told you have a hiatal hernia, it doesn’t necessarily mean surgery is in your future, but it does explain why lifestyle changes alone may not fully control your symptoms.
Pregnancy
If you’re pregnant and suddenly dealing with reflux for the first time, you’re in the majority. Progesterone, a hormone that rises dramatically during pregnancy, relaxes the esophageal sphincter. It also slows digestion, keeping food in your stomach longer and giving acid more opportunity to escape. As pregnancy progresses, the growing uterus adds upward pressure on the stomach, compounding the problem. Reflux typically worsens in the third trimester and resolves after delivery.
Stress, Smoking, and Tight Clothing
Stress doesn’t directly produce more stomach acid, but it makes your esophagus more sensitive to the acid that’s already there. People under chronic stress report more severe reflux symptoms even when their actual acid exposure hasn’t changed. Smoking weakens the sphincter and reduces saliva production (saliva naturally neutralizes acid in the esophagus). Tight belts, waistbands, and shapewear increase abdominal pressure the same way excess weight does, physically squeezing acid upward.
Medications That Can Cause Reflux
Several common medications relax the lower esophageal sphincter as a side effect. Blood pressure medications in the calcium channel blocker class, certain heart medications containing nitrates, some asthma inhalers, sedatives, and anti-anxiety medications can all contribute. Anti-inflammatory painkillers like ibuprofen and aspirin irritate the stomach lining directly. If your reflux started or worsened around the same time you began a new medication, that connection is worth exploring with whoever prescribed it.
When Reflux Becomes GERD
Everyone gets occasional acid reflux. It crosses into gastroesophageal reflux disease (GERD) when symptoms occur two or more times per week, or when acid exposure has started damaging the tissue lining your esophagus. Using over-the-counter antacids more than twice a week is another signal that something beyond occasional heartburn is going on.
GERD progresses through stages. Early on, the esophageal lining becomes inflamed. Over time, repeated acid exposure can cause narrowing of the esophagus or changes to the cells lining it. Pay attention to symptoms beyond the typical burning sensation: difficulty swallowing, food feeling stuck in your chest, a chronically hoarse voice, a persistent cough that doesn’t respond to cold or allergy treatments, or regurgitation of food or liquid. These suggest the condition has advanced and needs evaluation, typically with an endoscopy to look directly at the tissue.
What You Can Do Now
Start by identifying your personal triggers. Keep a simple log of what you eat and drink, when symptoms appear, and how severe they are. Patterns usually emerge within a week or two. Eat smaller meals, finish eating at least three hours before lying down, and avoid the common trigger foods listed above to see if symptoms improve.
If you carry extra weight around your midsection, even a 5 to 10 percent reduction in body weight often produces meaningful improvement. Sleep on a wedge or elevate the head of your bed. Avoid eating while slouched or lying on the couch. Wear looser clothing around your waist.
Over-the-counter antacids neutralize acid that’s already in your esophagus and work within minutes but wear off quickly. Acid-reducing medications work longer by decreasing how much acid your stomach produces in the first place. These are reasonable for short-term use, but if you find yourself relying on them regularly, that’s your body telling you the underlying cause still needs attention.