Of all the archnemeses to choose from, gravity wouldn’t necessarily be high on anyone’s list. Unfortunately, there’s really not much we can do against gravity here on Earth. This natural phenomenon not only keeps us within a comfortable distance of the sun and prevents our atmosphere and air from floating away, but it’s also critical to the development of life, literally shaping human evolution.
In fact, it could have some bearing on our bodies, at least for some folks. In a paper published Thursday in the American Journal of Gastroenterology, one hypothesis suggests that irritable bowel syndrome (IBS), a gastrointestinal disease with multiple subtypes affecting up to 15 percent of the U.S. population, could be caused by an intolerance, in a sense, to the natural force.
“It’s not surprising to say that [humans] evolved in some manner to manage gravity … [and] some bodies are better equipped to do that than others, Brennan Spiegel, a gastroenterologist at Cedars-Sinai Hospital and sole author of the paper, tells Inverse. “Although [this idea of gravity causing IBS] may seem unconventional, the paper is not meant to replace any of the many existing theories of IBS, but rather to explain how those seemingly disparate theories may all be simultaneously true.”
Here’s the background – While IBS is characterized by abdominal pain in conjunction with changes in bowel habits, there is a constellation of theories as to what exactly causes and drives the condition. These theories include an overgrowth of certain gut bacteria or shifts in the gut microbiome, food allergies, heightened sensitivity of nerves in the intestines, and abnormal, irregular movement of muscles in the gastrointestinal system.
People with IBS often also have concurrent overlapping conditions ranging from psychiatric conditions such as generalized anxiety disorder or bipolar disorder to musculoskeletal issues like fibromyalgia and Ehler-Danlos syndrome (or EDS), a hereditary connective tissue disorder believed to affect around one in 5,000 people worldwide.
“People talk about all these mechanisms for being the cause of IBS and we really don’t know which one dominates,” David Levinthal, director of the University of Pittsburgh School of Medicine’s Neurogastroenterology and Motility Center, who was not involved in the paper, tells Inverse. “The answer is that it’s probably a common complaint paradigm that may be arising for lots of different reasons [but] it’s the least understood.”
For Spiegel, who has been researching IBS for many years, the idea that gravity may be the common denominator arose when a family member living in an assisted living started having intestinal issues.
“She has recently been spending a lot of time bedbound, and of course, we’re not really designed to be bedbound. We’re designed to be an upright organism,” says Spiegel. “It turned out that almost coincident with starting to lie down, she was developing all sorts of [gastrointestinal] issues, abdominal distress, bloating and constipation, and some really significant issues that required medications.”
This experience led Spiegel down a rabbit hole of exploring the role of gravity in human health and disease — of which he says there’s a vast literature — and to hone in on three categories or domains that could explain how gravity could influence IBS.
The first category is called g-force resistance. “It’s the how well can your body resist this ever-present force of nature that’s constantly pulling it down,” says Spiegel. “And [that encompasses] how strong are your muscles, bones, joints, [and] tendons? How are they physically arrayed to support the viscera [the soft internal organs of the body]?
Spiegel says there’s evidence to suggest that people with IBS may not have the strongest “suspension systems” (i.e., the muscles, bones, joints, and tendons). One example of that are studies that found a significant overlap in patients with EDS having IBS symptoms.
Next is g-force detection, which Spiegel defines as the nervous system’s ability to receive and detect input from the body that is potentially due to gravity causing anatomical structures to shift around. This can be understood if you’ve ever had the sensation of “butterflies” in your stomach, which Spiegel explains is caused by falling, whether actually physically falling or dropping on a roller coaster.
“It could be that IBS is a neuro-visceral fear of falling with a g-force accelerometer in your gut telling you that you’re either falling or about to fall,” says Spiegel. “[In IBS], it gets to the point where you always feel like you’re going to fall when in fact, you’re not falling, which is why cognitive behavioral therapy is so effective.”
The last is g-force vigilance, which is also based in the nervous system but instead makes it ready to predict or respond to potential threats.
“If you look at functional MRI scans in people with IBS, it looks an awful lot like people with chronic fatigue syndrome, anxiety, or fibromyalgia,” says Spiegel. “There is a hypervigilance to threat detection because your body at some point needs to protect itself because it's so sensitized.”
While this hypervigilance leads to behaviors that are meant to protect the organism (or person with IBS, in this case), it can also lead to maladaptive behaviors that can cut into one’s quality of life, as many with IBS often experience.
Digging into the details – While Spiegel’s gravity hypothesis provides a new way of looking and potentially better understanding IBS, Levinthal and Harmony Allison, a gastroenterologist at Tufts Medical Center, aren’t sure it’s the be-all and end-all.
“[Spiegel] is totally right to highlight this increasing appreciation that connective tissue does seem to have an outsized impact on gastrointestinal tract function,” acknowledges Levinthal. “[But] patients don’t have symptoms all the time, which is another problem that [this paper] doesn’t discuss. It’s well-known patients with IBS go through periods where their symptoms are not as bad. Gravity doesn’t change, so it seems like it can’t fully explain the patterning.”
“IBS is a bit of a mystery and I think this idea about gravity is interesting,” Allison tells Inverse. “I’m not sure if [this theory] explains everything… we’ve been dealing with gravity for all of humanity and IBS seems to be a little bit more of a new phenomenon.”
However, this theory does seem to suggest that exercises that improve the body’s physical ability to resist gravity (aka strengthen the suspension systems), should be recommended more often to IBS patients alongside traditional pharmaceutical therapies and cognitive-based therapies.
“Exercise improves the movement of [stool] through the GI system, and it also decreases stress,” says Allison. “I think that’s a large component of everyone’s bag of tricks, to help [IBS patients] with these symptoms.
Spiegel makes no bold claims that his gravity-IBS hypothesis is anything but a hypothesis that would need to be held up to the lens of research for scrutiny. He says he hopes his paper will get more people to start thinking about gravity’s effect on IBS. “It has implications for how we communicate with people and how we treat this condition.”