Your Appendix May Not Be Useless After All


The appendix, known for becoming inflamed and possibly rupturing, has long been thought to have no real function for human anatomy. However, new research shows the appendix may serve a purpose after all – to protect healthy bacteria living in the gut.

Heather F. Smith, PhD and associate professor at Midwestern University Arizona College of Osteopathic Medicine, examined the evolution of gastrointestinal traits of different species. This included the presence or absence of the appendix in 533 different mammals.

Illustration of appendix removal.

Her findings, published in the journal Comptes Rendus Palevo, showed that once introduced into mammalian bodies, the appendix rarely disappeared from a lineage. The organ’s persistence throughout time suggests that it did, and still does, serve a purpose.

Smith’s research team included professionals from Duke University Medical Center, the University of Stellenbosch in South Africa and the Muséum National d’Histoire Naturelle in France. Their research debunked previous hypotheses that the appendix may be related to dietary or environmental factors.


Furthermore, researchers found that species with an appendix tend to have higher levels of lymphoid in the cecum, a pouch that connects the large and small intestines. Lymphoid tissue plays a role in immunity and can also stimulate the growth of healthy gut bacteria. According to Smith, it makes sense to suggest that the appendix serves as a “safe house” for these microorganisms.   

Related: Bad Gut Bacteria Could Sabotage Your Weight Loss Resolution

Had your appendix removed? Don’t sweat it.

“In general, people who have had an appendectomy tend to be relatively healthy and not have any major detrimental effects,” Smith says.

CAT scan showing acute appendicitis. Credit: James Heilman, MD/Wikimedia Commons, CC BY-SA 3.0

However, studies have shown that people without an appendix may be slightly more susceptible to infection than those who have the organ intact. Smith adds it could also take them a bit longer to recover from illnesses, particularly those where beneficial gut bacteria has been flushed from the body.

Smith notes that because the appendix is full of immune tissue, poorly developed immunity is a leading cause of the organ becoming inflamed.

“Exposure to pathogens and infectious agents, like bacteria and viruses, is important for the normal development processes of the immune system,” she says.

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Without this exposure, the immune system may be underdeveloped and become hypersensitive, the same idea used to explain conditions like asthma and allergies.

While this new research suggests the appendix is not as useless as once thought, we’re still unclear as to why it is so susceptible to inflammation, also known as appendicitis.

“As treatments are developed for other autoimmune disorders and responses, it’s certainly possible that something similar may be developed for treating appendicitis,” Smith says.