An invisible force has played a very important role in the evolution of life on Earth. This force has determined the size animals can grow up to, the shapes of body tissues and a sense of direction in plants. The invisible force in question is the the universal force of attraction: gravity.
Now, according to a hypothesis, researchers think that our body’s response to gravity may be the reason for irritable bowel syndrome (IBS).
IBS is one of the most common disorders that affects at least 10% of the world’s population. It affects the stomach and intestines with symptoms that vary from cramping, abdominal pain, bloating gas, diarrhoea or constipation or both.
However, medical professionals and scientists still don’t know what exactly causes IBS. Some theories suggest that it is caused due to abnormalities in the gastrointestinal tract, hypersensitivity in the gut or a disorder in the gut-brain interaction. Some theories also suggest abnormality in serotonin levels or the autonomic nervous system.
“There’s such a variety of explanations that I wondered if they could all be simultaneously true,” said Brennan Spiegel, the director of Health Services Research at Cedars-Sinai, Los Angeles, in a press release.
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“As I thought about each theory, from those involving motility, to bacteria, to the neuropsychology of IBS, I realised they might all point back to gravity as a unifying factor. It seemed pretty strange at first, no doubt, but as I developed the idea and ran it by colleagues, it started to make sense,” he said.
Published in the American Journal of Gastroenterology, Dr Spiegel’s theory suggests how the brain, spine, intestine, heart and nerves have evolved to manage gravity.
Dr Spiegel said that the nerves in the gut are like an “ancient G-force detector” that warns us when we are about to experience a fall. It is the cause for the weird sensation we get in our gut—usually called ‘butterflies’ or ‘gut feeling’—when on a roller coaster or a turbulent plane. “It’s just a hypothesis, but people with IBS might be prone to over-predicting G-force threats that never occur,” Dr Spiegel said.
However, gravity does not only affect our gastrointestinal tract.
“Our body systems are constantly pulled downward,” Dr Spiegel noted. “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.”
Normally, when the intestines fill with gas, the diaphragm relaxes and the anterior abdominal wall contracts to bolster the abdominal cavity. By contrast, abdominal distension results when the diaphragm contracts, the viscera fall with gravity, and the anterior abdominal wall relaxes, leading to outpouching in the upright position. | Photo Credit: The American Journal of Gastroenterology
The effect of gravity on the body can be seen in the spine, which gets compressed due to the pull. Some organs also may move from their proper positions and drift downwards. For instance, some people have ‘stretchy’ suspension systems that make the intestines droop, while others may have a weak spine causing the diaphragm to sag and squish the abdomen.
Though the body has evolved to carry the load of organs, especially the gut, failure of support may result in IBS symptoms such as pain, cramping, lightheadedness, back problems and rapid heartbeat, the paper noted.
Another part of the puzzle is the contribution of serotonin. Produced mainly in our intestinal tract, this neurotransmitter is extremely complex with a number of functions. Serotonin helps with mood regulation, cognition, learning, reward, memory and physiological processes like vomiting, maintaining balance, circulating blood and moving the contents of the gut against gravity.
Dr Spiegel thinks that serotonin may have partly evolved to manage the effects of gravity throughout our bodily systems, although further research is needed to prove this theory. Irregular levels of serotonin are strongly linked to IBS along with anxiety, depression, fibromyalgia and chronic fatigue. Dysregulated serotonin may be a form of gravity failure, Dr Speigel noted.
“Our bodies are affected by gravity from the moment we’re born to the day we die. It’s a force so fundamental that we rarely note its constant influence on our health,” he added.
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