“Butterflies in the stomach” is that fluttery, nervous feeling you might have before a job interview, giving a speech or at the start of a romance.
It’s a cute description for one part of the fight-or-flight response that can kick in if you’re excited or afraid.
But what exactly are these butterflies? Why can we feel them in our stomach? And is there anything we can do about them?
Threat alert
These “butterflies” – along with a raised heart rate, sweating and feeling “jumpy” – are part of your survival mode. That’s when the part of your body known as the autonomic nervous system gets involved.
When you sense a possible threat – whether it’s physical or social, real or imagined – information is sent to the brain’s amygdala region for emotional processing. If the amygdala perceives danger, it sends a distress signal to another part of the brain, the hypothalamus, which kick-starts a cascade of changes to help the body prepare.
The adrenal glands on top of each kidney send the chemical messengers adrenaline and noradrenaline into the bloodstream, activating receptors in the blood vessels, muscles, lungs and heart. The heart rate and blood flow increase, blood sugar levels go up, and muscles are primed for strength (fight) and speed (flight).
Digestion can wait
Digestion can wait until after you have escaped from the tiger (or the job interview). So while all this is happening, your body reduces blood flow to your stomach and intestines, and pauses the constant digestive pulsing of the gut (known as peristalsis).
The autonomic nervous system also stimulates the stomach (and other organs) via the vagus nerve, the nerve that runs down from the brainstem alongside the vertebra, sending signals back and forth between the brain, heart and digestive system.
There isn’t direct evidence to explain which part of this cascade leads to the feeling of butterflies. But it is likely to be related to how the autonomic nervous system pauses the pulsing of the gut, and the vagus nerve sends signals about this change up to the brain.
The feeling of butterflies is technically a “gut feeling” but it’s just one of the signs of the gut communicating back and forth with the brain, along the so-called gut-brain axis. This is the system of communication pathways that shares signals about stress and mood, as well as digestion and appetite.
Read more:
Our vagus nerves help us rest, digest and restore. Can you really reset them to feel better?
Could our gut microbes be involved?
Gut microbes are one part of this complex communication system. It’s tempting to think that the action of microbes is what causes the fluttery, butterfly feeling, but it’s unlikely to be that simple.
Microbes are, well, microscopic, as are the actions and changes they undergo from moment to moment. There would need to be coordinated microbial movements en masse to explain the sudden onset of that anxious feeling,