- Irritable bowel syndrome (IBS) may be caused by gravity, one new theory suggests.
- Brennan Spiegel, MD, a gastroenterologist at Cedars-Sinai Medical Center in Los Angeles is behind the new theory.
- Though it may seem controversial, the theory is meant to unify different ideas—including motility abnormalities, and gut microbiome health—for what causes IBS.
Irritable bowel syndrome—a condition that affects as much as 10% of the world’s population—continues to puzzle researchers, physicians, and patients alike. But one new theory suggests that the root cause may be closer to home than once thought: gravity.
In a December paper published in the American Journal of Gastroenterology, Brennan Spiegel, MD, a gastroenterologist at Cedars-Sinai Medical Center in Los Angeles, suggests that IBS—along with many other conditions—may be due to the body’s inability to manage gravity.
“Our body systems are constantly pulled downward,” Dr. Spiegel said in a news release. “If these systems cannot manage the drag of gravity, then it can cause issues like pain, cramping, lightheadedness, 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.”
The theory may seem controversial, but it’s actually meant to unify different theories as to what causes IBS, including abnormalities in motility, the health of one’s microbiome, and gut hypersensitivities.
“At first glance, it seems like a large departure from our current understanding,” said Gregory S. Sayuk, MD, MPH, a gastroenterologist at Washington University, who was not involved with the new paper. “But what [Dr. Spiegel] is trying to do is incorporate a lot of the theories we already have and show how gravity could be a common thread.”
How Gravity May Affect the Intestines
From the moment we’re born to the moment we die, gravity is weighing on us—it can compress the spine, decrease flexibility, and even cause organs to shift downward. According to Dr. Spiegel, the contents of the abdomen are heavy, and we carry it around our entire lives.
Some people can carry their abdominal contents around just fine, but others—particularly those with “stretchy” ligaments and tendons, likely due to the way collagen is distributed throughout their bodies—aren’t able to carry the weight as well. This can cause the intestines to drop or the belly to protrude, among other things and these changes might lead to motility problems or bacterial overgrowth in the gut, Dr. Spiegel theorized.
He points to people with Ehlers-Danlos syndrome (EDS) as an example. The syndrome, technically a group of connective tissue disorders, causes overly flexible joints and stretchy, fragile skin; but it can also lead to gastrointestinal issues that are similar to IBS. A 2015 study found that nearly 40% of people with unexplained gastrointestinal symptoms may also have joint hypermobility, or extra-stretchy joints.
“Our gut is almost like a marionette puppet,” Dr. Spiegel told Health. “It’s not just smashed in there, it’s held together in a very specific way.” If the mesentery—the membrane that holds the abdominal contents in place—is extra elastic, the pull of gravity can cause it to stretch enough to allow the organs in the gastrointestinal tract to twist or move out of place, he added.
Because people who are assigned female at birth (AFAB) tend to naturally have more elastic tendons than people who are assigned male at birth (AMAB), this theory could also explain why IBS is more common in females, Dr Spiegel said.
The Gut-Brain Axis May Be Impacted Too
Dr. Spiegel theorized that it’s not just the intestines that are potentially affected by gravity, but the nervous system too—and in a few different ways.
“The nerves in the gut are like an ancient G-force detector that warns us when we’re experiencing—or about to experience—a dangerous fall,” Dr. Spiegel said in the news release. “It’s just a hypothesis, but people with IBS might be prone to over-predicting G-force threats that never occur.”
What Is a G-Force?
A G-force—or the gravitational force equivalent—is the force of gravity or acceleration on a body. It can be most easily explained as the feeling of being pushed back into your seat while on a rollercoaster or a plane during takeoff.
Some people may be more sensitive to G-forces than others—Dr. Spiegel said this reveals a person’s “G-force vigilance.”
Serotonin, too—or more specifically the dysregulation of serotonin—may also play a role. Serotonin is a neurotransmitter responsible for regulating numerous bodily functions including mood, digestion, blood flow, and sleep. The gut produces nearly all of the body’s serotonin supply.
“Dysregulated serotonin may be a form of gravity failure,” Dr. Spiegel said. “When serotonin biology is abnormal, people can develop IBS, anxiety, depression, fibromyalgia, and chronic fatigue. These may be forms of gravity intolerance.”
A Theory That Needs Further Testing
Currently, Dr. Spiegel’s theory is just that—and further testing is necessary to help determine the true impact of gravity on gut health and any potential treatments.
“These are all anecdotal observations and the paper is pulling together the things we do know about IBS and saying gravity could be an explanation for why these seemingly very different mechanisms could all be related to the problem,” Dr. Sayuk said.
The theory, however, is a testable one. “The first step is to determine whether or not people with IBS react differently to changes in gravity,” Dr. Sayuk said. “Then we can get into serotonin, the microbiota, these things that are subsets of the theory.”
And if Dr. Spiegel’s theory is proven to be true, it could be hugely beneficial to IBS research and to anyone with the condition.
“If proved correct, it is a major paradigm shift in the way we think about IBS and possibly treatment as well,” Shelly Lu, MD, the Women’s Guild Chair in gastroenterology and director of the division of digestive and liver Diseases at Cedars-Sinai, said in the press release.
For now, the theory itself also bodes well for the scientific community.
“I’m excited about work like this when it comes out because these types of things push the envelope forward and get scientists and clinicians and patients all thinking and working together to advance our understanding beyond where we currently are,” Dr. Sayuk said. “That is the purpose of hypothesis, to generate ideas and then go about studying them.”
Spiegel B. Gravity and the gut: a hypothesis of irritable bowel syndrome. Am J Gastroenterol. 2022;117(12):1933-1947. doi:10.14309/ajg.0000000000002066
The Ehlers-Danlos Society. Gastrointestinal Involvement in the Ehlers-Danlos Syndromes (for Non-Experts).
Fikree A, Aktar R, Grahame R, et al. Functional gastrointestinal disorders are associated with the joint hypermobility syndrome in secondary care: a case-control study. Neurogastroenterol Motil. 2015;27(4):569-579. doi:10.1111/nmo.12535
Terry N, Margolis KG. Serotonergic mechanisms regulating the GI tract: experimental evidence and therapeutic relevance. Handb Exp Pharmacol. 2017;239:319-342. doi:10.1007/164_2016_103