Lupus and the Biology of Digestion

More than 50% of those with lupus experience some kind of digestive system disorder.  Here is an overview of this complex part of the human body and how it can be affected by lupus, lupus medications and other conditions associated with SLE.


Lupus is an autoimmune disease that can attack almost any part of the body, such the kidneys, skin, joints, muscles, lungs, blood and even the brain. However, one part of the body that often gets overlooked is the digestive system – even though it is one of the most commonly affected by SLE.  Though digestive issues tend to be less publicized than conditions like lupus nephritis, the symptoms associated with it can also lead to life-threatening situations if not properly treated. Moreover, recent research has shown how critical nutrition and gut health can be to the quality of life for those with lupus, and increasingly the digestive system is being found to have real effects on possibly triggering flares or causing the disease itself. So, it is important to have a basic awareness of your digestive system, and to understand how lupus and your medications can both affect your digestive health and be affected by it.

Fact:  Approximately half of the digestive symptoms that are common to those with SLE are caused by adverse reactions to medications or viral and bacterial infections.

Basics of the Digestive System

The digestive system itself has several names:  the gastrointestinal (GI) tract, the alimentary canal, the digestive tube, and of course, “the gut.”  Whatever name you use, its primarily role, of course, is to get food nutrients from the outside world into our bodies. For this to happen, the digestive tract must be able to take food in whatever form we give it (ingestion), process as much of it as possible with strong acids and enzymes to get those nutrients broken down to the molecular level (digestion) so that we can bring them into our blood stream (absorption) and get rid of the stuff that we don’t need (defecation).

One amazing thing about the GI tract is its ability to be delicate and permeable enough to absorb so many kinds of chemicals – from sugars and fats, to vitamins and all those medications, and yet be strong enough to keep out harmful pathogens like bacteria, viruses, parasites and other bad things that we consume every day.

Yet, there is so much more to the digestive system!  Here is just a brief list of facts that may help you the next time digestion is the theme of your next trivia night!

  • Digestion (and absorption) takes time! On average, it takes 46 hours to make the trip from mouth to the anus, though as we have all experienced, this “transit time” can happen considerably faster or slower than that.
  • Digestion (and absorption) takes room! The average length of the entire digestive tract in an adult is 30 feet and the surface area is approximately
  • Your GI tract is out of your control … mostly. Your digestive system runs almost entirely on the work of smooth muscles. Unlike the skeletal muscles with which you normally use to move around, smooth muscle is  This means that our brain cannot directly control it, and so our digestive tract pretty much runs on its own.  As a matter of fact, even without the brain, the intestinal muscles will continue to move on their own – though without much coordination.
  • Digestion runs on emotion … so stay calm! Though you can’t consciously control the smooth muscles of your digestive system, you can influence them through what is called the autonomic nervous system.  Not to get into too much detail, but this system is divided into sympathetic (“fight or flight”) and parasympathetic (“rest and digest”) systems.  Each of which is significantly driven by emotions.  As it turns out, these can also be affected by medications. So, your emotional state as well as your use of pharmaceuticals can affect how your digestive system, as a whole, works.

When you are under stress, the sympathetic system interferes with healthy digestion because that part of your brain wants you to focus all of your energy on getting out of the stressful situation.  So, you stop producing saliva (you get dry mouth), you may have difficulty swallowing (you have a “frog in your throat”), your stomach stops churning and it feels either too acidic or bloated, and your intestines slow down dramatically and stop absorbing nutrients. Suffice it to say that chronic stress, like the kind you might get from chronic diseases like lupus, can be rough on your digestive system – even beyond the symptoms of the disease itself.

  • “Gut feelings” are real! Not only does the digestive system have the brain giving it emotional signals through autonomic nerves, it also has its very own nervous system – called the enteric nervous system.  The enteric nerves connect and surround all parts of the digestive system with each other and operate independently of the brain and spinal cord.  These nerves are also organized around “mini-brains” called All of this together means that the enteric nervous system is often described as a “second brain.”  So, there actually is a neurological reason for what we call “gut feelings.”
  • Our own gut bacteria outnumber us! Your digestive system is not just about you!  It is a complex ecosystem supporting many hundreds of species that live within it, mostly in your large intestines. Though the statistics are up for debate, some estimate that 90% of the cells of the average human are microbial!

As you can see, the digestive system is surprisingly complex and can be affected by lupus and other diseases in all sorts of ways.  It is important to take a look at both the general affects that you feel (nausea, lack of appetite, etc.) as well as symptoms that are specific to areas of damage (focused pain, visible sores, etc.) in order to make an accurate diagnosis of your condition.  This helps your healthcare profession and you to differentiate which issues are causes and which are effects.  A description of some of those general and specific effects are described below.

General Effects of Lupus and Lupus Medications

We all have experienced digestive problems that make us feel sick and yet may not seem to come from any one specific source.  They include feelings of nausea, loss of appetite, loss of taste for food, vomiting, diarrhea, constipation, gas, and more.  Some of these general symptoms are so common and are caused by many things other than lupus. Because of this and the fact that digestive issues can be diffuse and hard to locate, makes getting a diagnosis tricky.  Yet, since lupus can affect any part of the GI tract, these symptoms all need to be taken seriously. For example, one study estimated that approximately 60% of SLE patients that were researched showed evidence of peritonitis, yet only about 10% of these patients were clinically diagnosed with peritonitis before the study.

These symptoms can affect your nutrition, which in turn, can make other symptoms of your lupus condition even worse.  For example, vomiting and diarrhea can cause dehydration, which may make your feelings of pain or fatigue even worse.  Nausea and vomiting can affect your ability to ingest and absorb nutrients and medications.  If you don’t absorb necessary nutrients or your medications that can initiate a downward spiral in your condition, and your ability to deal with all of your other symptoms may be affected.

Specific Effects of Lupus and Lupus Medications

Mouth and Teeth:  Approximately 95% of lupus patients experience symptoms around the mouth and oral cavity.  Each has its own diagnosis and treatment and they include:

  • Sores (lesions, ulcers) that can be red, white or red and white. They can occur on the lips, roof of the mouth and gums; they are usually painless.
  • Dry mouth, which also can be associated with Sjögren’s Syndrome
  • Yeast infections (thrush, oral candidiasis)
  • An itchy rash on the mouth called lichen planus
  • Gum disease, where they become red, puffy and may bleed easily.

Note:  It is vital for those with lupus to practice good dental hygiene because periodontal disease can trigger many other inflammation reactions throughout the rest of the body.

Esophagus: Inflammation of the esophagus can weaken the smooth muscle tissue that controls the movement of food to your stomach.  A weakened esophagus, or actually a weakened sphincter muscle between the esophagus and the stomach, can allow stomach acid to move back up into the esophagus as temporary acid reflux or long-term (beyond two weeks) gastroesophageal reflux disease (GERD). Treatments may begin with antacids, but GERD may require other medications and changes in diet.

Stomach: Peptic ulcers also occur with lupus, though they are often due to mediations, especially NSAIDs and steroids.  Peptic ulcers usually present as undefined abdominal pain and so can be a challenge to diagnose.  The actual cause of the ulcer is commonly the Helicobacter pylori bacteria.  Unless surgery is needed, most treatments include medications like Zantac and Prilosec.

Small and Large Intestines:  The two most common complaints of the intestines or bowel, come from abdominal pain (diffuse or acute) and a slowdown in the speed at which food moves through them (motility).  Abdominal pain is quite common though studies vary in estimating between 8% and 40% of all SLE patients having these symptoms. There are several conditions, though some quite rare, that produce abdominal pain and they include:

  • Inflammatory bowel diseases (IBD): There are several conditions that are associated with lupus that fall under this category, including:
    • ulcerative colitis (UC), which causes lesions in the large intestine and rectum. It can result in persistent diarrhea and pain.
    • Crohn’s disease with SLE is quite rare, but some drugs used to treat Crohn’s may cause drug-induced lupus.
  • Vasculitis: Other names include lupus mesenteric vasculitis, or lupus enteritis.  It is uncommon, but serious and can cause vomiting and fever.  It may produce blood clots in the small intestines or chronic ulcers in the colon.  It can be triggered by bacterial infections or NSAIDs and other environmental factors and may require a CT scan or ultrasonogram for clear diagnosis.
  • Bacterial overgrowth: As a result of several factors, lupus may slow down the ability for the gut to move food quickly enough.  If this happens, the natural bacteria within the gut has a greater chance of growing too much and cause bloating, nausea and other issues.  Antibiotics may be used for treatment.

Peritoneum:  Peritonitis is the serious inflammation of the peritoneum, the thin connective tissue membrane that covers the organs of your abdomen.  Peritonitis is usually caused by a bacterial or fungal infection, but it can also be a complication from lupus.  Peritonitis can also lead to ascites, a build-up of fluid in the abdominal cavity.

Pancreas: Acute pancreatitis is not very common; yet it can be life-threatening.  It might be caused by vasculitis (inflammation of the blood vessels) of the pancreas or from inflammation of the pancreas itself.  These can be caused by lupus itself or by some medications, though there are conflicting opinions on this.  Symptoms include abdominal pain, vomiting and nausea.  Diagnosis usually requires blood tests that show elevated pancreatic enzymes like amylase and lipase; CT scans and ultrasonagrams are less helpful than for many other GI tract issues.

Liver:  This large and very complicated organ provides many functions such as producing bile for digestion of fats, filtering old red blood cells, storing iron and modifying nutrients or toxins (like medications) that are absorbed by the intestines.  All of these functions mean that anything that might damage or inflame the liver can have major effects on your health and the effectiveness of drugs. Many diseases that damage liver function produce jaundice, the yellow coloring of the skin by abnormally high levels of bilirubin in the blood.  More detail about lupus and your liver can be found at our blog article, The Elusive Liver.

A 2015 study estimated that liver problems can occur in 19% – 60%, of those with SLE, at some point in their lives. Two of the most common include:

  • Lupus hepatitis: Hepatitis is the general term for inflammation of the liver caused by lupus.  It is primarily a result of hepatic vasculitis. Small blood clots caused by the autoimmune response cut off the blood supply to parts of the liver and they are damaged.
  • Autoimmune hepatitis (AIH): This condition is very similar to lupus hepatitis but has no known cause.

Rectum and Anus: Lupus rarely involves the rectum or anus and is usually limited to ulcers caused by vasculitis as occurs in other parts of the GI tract.  However, scleroderma patients are more commonly affected in this area.


In Conclusion

The digestive system is a very complex system of many integrated parts that all must work together to digest and absorb an incredible variety of nutrients and to eliminate everything else.  While each part of this system can be affected by lupus in different ways, the majority of the problems are due to vascular damage from the same autoimmune responses that can affect other parts of the body.  However, it is important to remember that some of this damage can come from the very medications that are used to reduce other symptoms of SLE.  Make sure you take any chronic digestive discomfort seriously and check with your healthcare practitioner if you feel that it may be caused by your lupus.



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Author: Greg Dardis, MS

Professor Dardis was formerly the Chair of the Science Department at Marylhurst University and is currently an Assistant Professor at Portland State University.  His focus has been human biology and physiology with an interest in autoimmunity.

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