What's the difference between heartburn and acid reflux?

If this is how you feel after lunch, we have a problem.
If this is how you feel after lunch, we have a problem.

Sometimes after you eat, you might experience a painful, burning sensation in your chest. It feels like someone has run a knife through you just beneath the sternum and is taking their time twisting it around.

Although it can feel like your heart is being squeezed in the palm of a giant, what you're feeling is actually the result of what happens when contents of the stomach -- recently swallowed foods and liquids, bile and stomach acid -- climb up the esophagus.


When food enters your mouth, digestion begins. Saliva begins to break down the starch contained in your food into smaller molecules. Food is then carried down the esophagus into the stomach, where glands in the lining of the stomach create more digestive products, one of which is stomach acid.

The esophagus is a long tube (about 10 inches (25.4 centimeters) long for adults) that connects your throat to your stomach. When you swallow food, you start a wavelike motion in the muscles that line the esophagus, and this motion carries food down toward your stomach. When food reaches the end of your esophagus, it must pass through a ring of muscle -- the lower esophageal sphincter (LES) -- in order to reach the stomach. When objects approach the LES from above, this valve opens inward to allow entry into the stomach. Once the objects have passed through the valve, the valve closes, and pressure exerted on the valve from the stomach only further seals the one-way valve. However, not all valves function perfectly all the time (or, in some cases, at all).

Sometimes, due to a malfunctioning LES, acid reflux and heartburn occur. How does this happen? And aren't acid reflux and heartburn the same thing? (No.)


Heartburn and Acid Reflux: Like Fire and Smoke

Some LESs don't form a tight seal when closed, and others will relax randomly when there is still work to be done. When the LES relaxes with food still in the stomach, pressure from the fullness of the stomach, physical movement or even tight-fitting clothes can force the contents back up through the relaxed valve into your esophagus.

Although used interchangeably, there is a difference between heartburn and acid reflux. So let's clear this up:


  • Acid reflux occurs when stomach acid regurgitates up into the esophagus. Reflux is the cause of heartburn. However, you may feel no pain at all when reflux occurs.
  • Heartburn is a sensation of tightness, pain or discomfort in the middle of the chest that can -- but doesn't always -- follow an occurrence of acid reflux. Heartburn is exactly what it would feel like if acid ate away at the lining of your esophagus, because that's what's happening.

While you can and do likely have occasional bouts of acid reflux without heartburn, you can't have heartburn without acid reflux. Acid reflux is the cause, and heartburn is a potential sensation. Reflux: the fire; heartburn: the smoke. The pain of heartburn is the irritation or damage taking place to your esophagus by the refluxed stomach acid.

If you have frequent acid reflux, you may have acid reflux disease. Acid reflux disease and gastroesophageal reflux disease (GERD) are the same thing. Both terms refer to a chronic condition relating to the LES and exacerbated by lifestyle factors, such as obesity, consumption of acidic foods, smoking and eating large portions during a single meal.

Have more questions about heartburn, GERD and the digestive system? See the next page for answers.


Lots More Information

Related HowStuffWorks Articles

  • American Gastroenterological Association. "Heartburn." April 2008. (June 18, 2009) http://www.gastro.org/wmspage.cfm?parm1=848
  • Bowen, R.A., Ph.D. "Pregastric Digestion: The Esophagus." Department of Biomedical Sciences, Colorado State University. July 31, 2006. (June 26, 2009) http://www.vivo.colostate.edu/hbooks/pathphys/digestion/pregastric/esophagus.html
  • Jackson Siegelbaum Gastroenterology. "Gastro Esophageal Reflux Disease." (June 19, 2009) http://www.gicare.com/diseases/GERD.aspx
  • Marks, Jay W. "Gastroesophageal Reflux Disease (GERD, Acid Reflux, Heartburn)." (June 17, 2009)http://www.medicinenet.com/gastroesophageal_reflux_disease_gerd/article.htm
  • Mayo Foundation for Medical Education and Research. "GERD." May 23, 2009. (June 16, 2009) http://www.mayoclinic.com/health/gerd/ds00967
  • Mayo Foundation for Medical Education and Research. "Heartburn." May 23, 2009. (June 16, 2009) http://www.mayoclinic.com/health/heartburn-gerd/DS00095
  • MedlinePlus. "Esophagus Disorders." June 17, 2009. (June 27, 2009) http://www.nlm.nih.gov/medlineplus/esophagusdisorders.html
  • National Digestive Diseases Information Clearinghouse. "Heartburn, Gastroesophageal Reflux (GER), and Gastroesophageal Reflux Disease (GERD)." May 2007. (June 17, 2009)http://digestive.niddk.nih.gov/ddiseases/pubs/gerd/
  • National Digestive Diseases Information Clearinghouse. "Your Digestive System and How It Works." National Institute of Diabetes and Digestive and Kidney Diseases. April 2008. (June 27, 2009) http://digestive.niddk.nih.gov/ddiseases/pubs/yrdd/