Despite it being first described more than a century ago and affecting around ten per cent of the population, exactly how irritable bowel syndrome (IBS) develops remains a mystery to doctors.


There are several competing theories for the cause of the disorder including abnormalities in the gut microbiome, miscommunication between the gut and the brain or issues with the movement of muscles within the gastrointestinal tract.

But now, a professor of medicine based at Cedars-Sinai Medical Center in Los Angeles has come up with an entirely different theory – the condition is caused by the body’s inability to cope with gravity.

“As long as there’s been life on Earth, from the earliest organisms to Homo sapiens, gravity has relentlessly shaped everything on the planet,” said Prof Brennan Spiegel, director of Health Services Research at Cedars-Sinai.

“Our body systems are constantly pulled downward. If these systems cannot manage the drag of gravity, then it can cause issues like pain, cramping, light-headedness, sweating, rapid heartbeat and back issues — all symptoms seen with IBS. It can even contribute to bacterial overgrowth in the gut, a problem also linked to IBS.”

Gravity can cause our internal organs to shift downward from their proper position, Spiegel says. Some people are less able to cope with its pull than others due to conditions such as spinal issues that cause the diaphragm to sag down or the belly to bulge.

Issues such as these could potentially trigger problems with the movement of muscles in the gastrointestinal tract or even bacterial growth within the gut. This could also explain why physical therapy and exercise can often help ease the symptoms of IBS by strengthening the body’s support structures.

“The body evolved to hoist this load with a set of support structures. If these systems fail, then IBS symptoms can occur along with musculoskeletal problems,” said Spiegel.

Researchers at Cedars-Sinai now plan to investigate the theory further and look into the development of potential treatments.

“This hypothesis is very provocative, but the best thing about is that it is testable,” said Prof Shelly Lu, the Women's Guild Chair in Gastroenterology and director of the Division of Digestive and Liver Diseases at Cedars-Sinai.

“If proved correct, it is a major paradigm shift in the way we think about IBS and possibly treatment as well.”

Read more about the gut:



Jason Goodyer
Jason GoodyerCommissioning editor, BBC Science Focus

Jason is the commissioning editor for BBC Science Focus. He holds an MSc in physics and was named Section Editor of the Year by the British Society of Magazine Editors in 2019. He has been reporting on science and technology for more than a decade. During this time, he's walked the tunnels of the Large Hadron Collider, watched Stephen Hawking deliver his Reith Lecture on Black Holes and reported on everything from simulation universes to dancing cockatoos. He looks after the magazine’s and website’s news sections and makes regular appearances on the Instant Genius Podcast.