GERD and the Pressure Differential

By Steven Sandberg-Lewis, ND, DHANP

I admit that I am a GERD nerd. I am in the process of writing a book I am calling Let’s Be Real About Reflux. This blog post will take a little bite out of the subject of gastroesophageal reflux (GERD) by introducing one of the most significant underlying factors leading to heartburn and reflux.

There are many mechanisms that lead to GERD. Most people - including some physicians - assume it is always due to excess acid production in the stomach. This is actually a minor component in most cases. A major mechanism has to do with relative pressure between the chest and the abdomen. To explain this, I will start with a short explanation of the structures involved – the esophagus, esophageal sphincters and the diaphragm.

The esophagus is a tube that measures about ¾ of an inch (2 centimeters) in diameter and is 11-13 inches (28-33 centimeters) long. It carries everything you swallow (saliva, other liquids, food, pills and capsules, bacteria and other organisms) from the mouth to the stomach. The esophagus is not known to have any role in digesting food, but with its muscles and nerves, by a process called peristalsis, it elegantly moves everything ingested down into the stomach.

The lower esophageal sphincter (LES) is a specialized area of muscle at the very bottom of the esophagus. Surrounded by the diaphragm (also a muscle) these two muscle layers have the function of preventing stomach contents from flowing upward (refluxing) into the esophagus. There is also an upper esophageal sphincter (UES) that protects air from getting into the stomach (to be discussed in a different blog post).

Pressure differentials between the abdomen and chest

The respiratory diaphragm divides the trunk of the body into the chest and the abdomen. Everything above is thoracic (referring to the chest) and everything below is abdominal (referring to the abdomen or belly. 

People commonly refer to the entire abdomen as the “stomach”, but the term stomach actually refers to the organ just below the esophagus. The adjective referring to the stomach is “gastric” as in the word gastroesophageal (stomach and esophagus).

Reflux can occur when increases in intra-abdominal pressure (pressure levels below the diaphragm) overpower the LES. Increased abdominal pressure may occur with: 

• Obesity (“apple fat”)

• Pregnancy

• Slowed emptying of the stomach into the small intestine (delayed gastric emptying/gastroparesis)

• Increased stomach volumes (eg. overeating)

• Constipation and build-up of stool in the large intestine

• Breath holding

Breath holding is a common but ill-advised tendency which significantly increases abdominal pressure if done while straining during a bowel movement, lifting a weight or contracting the abdominal muscles. Inhaling and then holding the breath during exertion seems to create the highest pressures in the abdomen.  The medical term for this is the Valsalva maneuver. It also increases the risk of hiatal hernia. Hiatal hernia is a common condition in which the upper inch or two of the stomach protrudes through the diaphragm into the chest. Either lax LES tone or the presence of a hiatal hernia heightens the risk of reflux episodes during periods of increased intra-abdominal pressure.

Another common cause of increased pressure is excessive gas and distention in the small intestine. Most intestinal gas, such as hydrogen, hydrogen sulfide or methane, is produced when carbohydrate foods are processed by bacteria and related microorganisms. The term “fermentation” refers to this process of gas production (just as in the production of alcohol and carbon dioxide gas in the fermentation of beer or wine). When the diet has more food for these organisms to turn into gas, it is called a high fermentation diet. Certain foods are more fermentable such as whole milk, wheat, beans, onions, garlic, etc. [For more on fermentation, please see my post from March, 2019] Besides a high fermentation diet, an overgrowth of the microorganisms in the small intestine will also create more gas and pressure. This is called small intestine bacterial overgrowth (SIBO) or intestinal methanogen overgrowth (IMO). SIBO and IMO have many associated diseases. One of these diseases is erosive esophagitis, which is almost always caused by GERD.

If you’d like to learn more about sliding hiatal hernia, look for my next blog post here in January.

To learn more about proton pump inhibitors, the standard treatment for reflux, see my blog post entitled Proton Pump Inhibitors-For Better or Worse. Additionally, if you want to learn how the much maligned key gastrobiome bacteria called Helicobacter pylori protects against developing reflux and its complications, see my blog post entitled Helicobacter pylori - Friend or (and) Foe? 

Reflux is complex, but understanding the true causes can allow for resolution in many cases.

Steven Sandberg-Lewis, ND, DHANP, has been in clinical practice for 44 years, with a focus on functional gastroenterology. He has been a professor since 1985, teaching a variety of courses but primarily focusing on gastroenterology and GI physical medicine. In 2019, Dr. Sandberg-Lewis co-founded Hive Mind Medicine, continuing his specialization in gastroenterology with a focus on reflux, SIBO, inflammatory bowel disease and functional GI disorders. He is currently working on his latest book, Let's Be Real About Reflux: Getting to the Heart of Heartburn, written to help non-medical and medical professionals alike develop a better understanding of diseases affecting the gastrointestinal tract.

Hive Mind Medicine blog posts are for educational purposes only and are not intended as medical advice. Please consult with your health care practitioner for personalized guidance.