By Jonny Lupsha, News Writer

A Taiwanese man who swallowed and passed an Apple AirPod headphone says it still works, according to the Daily Mail. The wireless earphone is the latest in a long line of electronic devices reported by hospitals to wind up in a patient’s bowels. How did it stay intact through its gastrointestinal ordeal?

According to the article in the Daily Mail, Ben Hsu fell asleep listening to music with his wireless Apple AirPod headphones still on. When he awoke, he was unable to locate one of the AirPods, but a tracking system in his phone led him to the unpleasant news. After a panicked visit to the emergency room, Hsu passed the device with the help of a laxative and fished it out of a toilet in a subway station, claiming that it still worked. The article says that while Hsu was excited that the battery still held a 41 percent charge, his doctor reacted more practically, explaining that the plastic casing of the headphone prevented the serious risks associated with swallowing a regular lithium-ion battery. The biology behind this stroke of luck sheds much-needed light on the event.

Stress and Digestion

The plastic casing that comprises the outermost part of the AirPod headphone surely helped prevent its digestion. However, along the way, a number of other factors played a role in saving Ben Hsu’s money—and, ultimately, his life. One of them was stress and how the digestive system reacts to it.

“George Engel, of course, was the founder of the biopsychosocial model,” said Dr. Jason M. Satterfield, Professor of Clinical Medicine at the University of California, San Francisco. “He found that increased levels of stress decreased or turned off the digestive process, and this matches what we know about the sympathetic and the parasympethic nervous system. When you have fight-or-flight response, you don’t want your resources going to digestion.”

Your nervous system releases two chemicals related to stress and digestion: acetylcholine, a neural transmitter, and adrenaline, or epinephrine. “Acetylcholine causes the muscle layer of the digestive organs to squeeze with force and increase the push of food and juice through the digestive tract,” Dr. Satterfield said. “Epinephrine has the opposite effect; it relaxes the muscles of the stomach and intestines and decreases the flow of blood to these organs, slowing or even stopping digestion.”

The Sorting Process

Hsu’s story also begs the question: How does the body know what is food and what isn’t? The stomach uses digestive juices to break down much of what enters it from the esophagus, and different substances take different amounts of time to break down before passing to the duodenum at the top of the small intestines. “Here in the duodenum, enzymes from the pancreas, the liver, and the intestines further break down those food molecules, and what’s used really depends on the kind of food and the composition that’s there,” Dr. Satterfield said. “We’re essentially trying to break down food into its simplest molecular constituents so that we can use whatever nutrients we might need; the rest is just going to pass through.” After the stomach and small intestines break down food and strip it of nutrients, anything that remains—including headphones—continues through the large intestine and is expelled as waste.

The undigested AirPod shows the marvels of the digestive system. Many may simply ponder how it remained functional after its journey, but the real wonder is the human body and its mechanisms of defense and selective absorption.

Professor Jason M. Satterfield contributed to this article. He is Professor of Clinical Medicine, Director of Social and Behavioral Sciences, and Director of Behavioral Medicine in the Division of General Internal Medicine at the University of California, San Francisco (UCSF). He earned his B.S. in Brain Sciences from the Massachusetts Institute of Technology and his Ph.D. in Clinical Psychology from the University of Pennsylvania.