Q&A: Gravity’s role in IBS pathogenesis, symptoms: A new hypothesis

Irritable bowel syndrome may result from ineffective anatomical, physiological and neuropsychological gravity-management systems, a researcher theorized in an article published in The American Journal of Gastroenterology.

“Our relationship to gravity is not unlike the relationship of a fish to water: We live our entire life in it, are shaped by it, yet hardly notice its ever-present influence on our body,” Brennan Spiegel, MD, MSHS, director of health services research and professor of medicine and public health at Cedars-Sinai Health System in Los Angeles, told Healio.

“Every fiber of our body is affected by gravity every day, including our [gastrointestinal] tract. The abdominal contents are like a sack of potatoes that we are destined to carry around for our entire lives. To meet this demand, our body evolved to support the abdominal load with a set of mechanisms that hoist the viscera in an upright posture.”

Healio spoke with Spiegel about his proposed hypothesis on the pathogenesis of IBS and related diagnostic and therapeutic considerations.

Healio: Describe your hypothesis and how it came about.

Spiegel: In this paper, I discuss how some people are better able to carry the abdominal load than others and how structural variations in GI support systems might lead to IBS. It also reviews how our nervous system evolved its own ways of managing gravity and how gut feelings can arise when our nervous system detects gravity challenges, like getting butterflies when falling on a rollercoaster or in a turbulent airplane.

The paper draws from extensive literature to build a hypothesis that IBS may result from ineffective anatomical, physiological and neuropsychological gravity-management systems designed to optimize GI form and function, protect somatic and visceral integrity, and maximize survival in a gravity-bound world. Although these ideas may seem unconventional, if not a bit strange, the paper is not meant to usurp any of the many existing theories of IBS, but rather to explain how they may all be simultaneously true.

The paper also describes the diagnostic and therapeutic implications of this hypothesis and proposed experiments to test this line of inquiry. It is hoped that the ideas in this thought experiment may help encourage new or different ways of thinking about this common disorder.

The hypothesis is that gravity plays a role in generating and propagating the symptoms of IBS and more specifically, that the existing theories of IBS — which may seem incompatible with one another — can all be mutually consistent when viewed through the lens of gravity.

Healio: In the paper you discuss a “g-force cube.” What is it and how does it relate to IBS?

Spiegel: The “g-force cube” is a concept developed in the paper that describes how IBS susceptibility may be determined by the interplay among three overarching factors: g-force resistance, g-force detection and g-force vigilance. When pictured as a figure, the three dimensions form a 3D cube that describes eight different IBS risk profiles which I discuss in depth in the paper.

The first factor, g-force resistance, refers to our physical ability to manage gravity. The idea here is from the moment of our birth to the day of our demise, gravity is constantly pulling our body systems down toward the earth. Normally we are standing up, and so we evolved a set of support structures to resist the pull of gravity.

Focusing on the GI tract, the abdominal contents are like a sack of heavy potatoes that we are destined to carry around our whole lives. It turns out some people have bodies that appear better designed to hoist that load of potatoes than others. The paper reviews each of the antigravity support systems and discusses what happens when they break down.

As an example, people with Ehlers-Danlos syndrome have a very “stretchy” mesentery which can lead to visceroptosis, in which the abdominal organs sink below their natural position and cause GI distress, bacterial overgrowth and IBS-like symptoms. Other people may have issues with their back, diaphragm or anterior abdominal wall leading to a drooping gut. The paper reviews all these mechanisms in detail.

The second factor is g-force detection, which defines the ability of the peripheral nervous system (PNS) to detect gravity strain on visceral and somatic structures, ranging from normosensitive to hypersensitive. When gravity causes anatomic structures to deflect excessively, indicating a mismatch between expected vs. actual g-force strain on the body, the PNS senses the deviation and transmits signals to the central nervous system where symptoms are perceived.

The nerves in the gut are constantly evaluating whether the intestine is stretching or pulling, which is more likely to occur if gravity pulls and support systems fail. If the effects of gravity strain remain outside the safe range for body integrity, then the sensory neurons begin to discharge more frequently, with a larger magnitude and at a lower threshold than they would in health, a process called peripheral sensitization that is common in IBS.

The third factor is g-force vigilance, which defines CNS readiness to predict and prevent threatening g-force events, ranging from unconcerned to hypervigilant. The CNS is constantly monitoring how our body is moving through space and how well we are standing up, surviving and thriving.

We have developed central mechanisms to oversee our body’s movement, and gut feelings might be an ancient residue of our relationship to gravity. It is curious, for example, that abrupt gravity challenges trigger the sensation of “butterflies” in the belly, like it is a primitive neurovisceral program. This observation suggests that gut feelings can operate like a g-force accelerometer.

For example, on a roller coaster, when you fall, you get butterflies. Why is that? Why do we get butterflies when we are falling, but not when we are rising? This could be a form of g-force vigilance. It is telling you that your body is falling, or you are worried that it is about to fall. This is the vigilance people have to protect themselves against the damage of falling down. The gut may have evolved in part to serve as this sort of g-force alarm system to tell us that we are at risk for falling.

Healio: What have patients with IBS noticed regarding gravity?

Spiegel: It has been really fascinating. I have heard from a lot of patients who have read the paper or read about the paper and have recognized immediate applicability in their lives. For example, one patient said she always feels better when she scuba dives. She initially thought it was because she was distracted and enjoying herself, but she now thinks it may be related to the pressure changes of being underwater bolstering her gut, because when she gets back to sea level her pain returns.

Other people have said they feel better when they go up into the mountains and thought it was because it is so beautiful. When they go down the hill, they feel the symptoms coming back. They now wonder if it has something to do with pressure differences, which is related to gravity from the top of the mountain to the bottom. Others say they get in an airplane and symptoms get worse.

Another example is doing yoga, where someone said when they stand on their head and relax it allows their gut to relax, because it is not straining against gravity. One patient said she has always struggled to swing on swings and still avoids it because the effects of gravity cause GI issues. Others have told me they use tilt tables to alleviate their GI pain. Still others say standing up quickly causes symptoms, or conversely, practicing certain physical activities like abdominal hypopressive exercises reduces IBS symptoms.

These activities appear to involve changing the body’s orientation to gravity and its related pressure effects, including g-force challenges (eg, riding a rollercoaster, swinging), pressure differentials (eg, scuba diving), gravity-related oxygen gradients (eg, altitude) and reorienting the body (eg, inverse yoga, tilt table). There also may be a ”Goldilocks” effect: For some, too much gravity appears to cause problems; for others, too little.

These are just anecdotes, and we cannot prove the gravity hypothesis based on 20 or 30 people emailing me, but it does indicate that a lot of people recognize their relationship to gravity does seem to impact their health. That point is not controversial; it only makes sense, but it also points to many ways to test this hypothesis, such using tilt tables or measuring the effects of altitude, pressure or even effects of riding rollercoasters in IBS patients vs. controls.

Healio: What are the next steps? Do you plan to do a formal study?

Spiegel: I am hoping creative minds can mull over the ideas in the paper and develop their own ways of thinking about tests beyond what I have proposed. The paper itself lists about 30 potential research projects, but there are many others one can imagine. My goal here is to give us a different way of thinking about a condition that needs new scientific advances. But I do intend to pursue some of the questions I have posed.

Starting simply, there are interesting survey studies we can do. We can look at tolerance of roller coasters, for example, and those would be simple, easy questions to ask before we get into more difficult parts, like measuring serotonin expression at different altitudes.

We could study physical structures in the abdominal cavity in IBS vs. controls, like differences in the structure of the mesentery, the anterior abdominal wall or diaphragm. For example, did some children with IBS inherit GI suspension systems that are suboptimized for gravity management? Or perhaps the mesentery did not elongate sufficiently in lockstep with pubertal growth in the abdominal cavity for some teenagers with IBS? These are among the many researchable questions raised by the gravity hypothesis.

It is also notable that astronauts often have GI issues in microgravity, indicating that we have evolved to live in gravity, which is sensible since our entire evolutionary history occurred in its presence. We should continue to follow what NASA is learning about microgravity orbit and GI health.

Back on Earth, it may be that some people struggle to adapt to a particular range of g-forces and may benefit from finding ways to fight the effects of gravity (ie, strength training, dancing, weight loss, cardiovascular fitness, altitude changes, posture changes). These are areas that can be studied and remain largely anecdotal but testable.

Healio: How might this affect patient care?

Spiegel: In the past, we would say, ‘Go out and exercise because it is good for you.’ But we really did not have a specific explanation for why exactly it is going to help IBS other than it just generally lifts your mood and fitness. But now, I show patients a picture of the anatomy of the abdomen and point out how close the spinal column is to the intestines, how the intestines are being pulled up by this system of ligaments that we call the mesentery. Then, how that system attaches right around the middle of the spine, which is like a chassis that holds up the abdominal cavity alongside everything else. Now, they can see that they really have lifted a sack of potatoes their whole life.

You must strengthen your body: You have to work out, do sit ups and back exercises. Then patients really understand the rationale of strengthening their core muscles, improving fitness and basically fighting gravity. Explaining the effects of gravity on the gut provides a different way to think about the benefits of exercise; that alone may be a lasting impact of this paper. It is just a different way to explain why we need to strengthen the body and separately strengthen the mind with cognitive behavioral therapy.

The other implication is that some people have inherited a body that struggles to manage gravity. It may be hard for us to do much about that through medical therapy or exercise. But even if your body is struggling to manage life on this planet, quite literally, you can still change the way your brain experiences that body. You can change the way your brain processes the pain from gravity strain, and this is where cognitive behavioral therapy comes in as an important supplement. We already have evidence that it works for IBS.

Healio: Do you think this hypothesis could be applied to other GI conditions?

Spiegel: I have discussed this with my inflammatory bowel disease colleagues, and they say this hypothesis has implications for IBD. In people with IBD, evidence indicates that immune and inflammatory function changes at the bottom of the mountain vs. the top of the mountain, and IBD is more common at the poles and less common at the equator. That is well-established.

Why is that? We do not know, but we talk about it being related to sun exposure and vitamin D. It could be because there are different gravity forces across the globe — g-forces are lowest at the equator and at the poles.

This is a new way of thinking about this condition and related conditions. It is not at all meant to usurp existing theories: It is giving us a framework to help understand what is already known about IBS. I am hoping it will help reduce some of the debate and provide explanations for many simultaneous theories, which might all lead back to gravity as a singular potential unifying factor.

It is not controversial that gravity has something to do with how we survive and thrive on this planet — it has everything to do with how we survive on this planet. I am taking what is known about IBS and tracking it back to a single potential factor: gravity. Check out the paper for all the details.