The process of digestion is more of a mental process than you might think.
Believe it or not, digestion starts before anything even enters our mouths. Merely the smell, sight, or even thought of a tasty morsel sends signals throughout our nervous system, preparing our entire digestive system to process food.
Stimulation of the parasympathetic nervous system—that which we activate to rest and digest—promotes salivation in the mouth (where carbohydrate digestion begins), secretion of gastric juices in the stomach, release of digestive enzymes in the small intestine, gastrointestinal motility, relaxation of the various sphincters of the GI tract, and so much more.
Promoting healthy digestion and thus a healthy gut-brain axis can be achieved through meal hygiene.
Being mentally present at your meal and showing gratitude, setting electronic devices aside while you eat, taking a few controlled breaths before beginning, eating with others if possible, and chewing your food well before swallowing ensures your food is processed adequately for the bacterial processing step.
As we have learned, the microbes in your gut produce metabolites, stimulating the vagus nerve, connecting the enteric nervous system to the central nervous system.
Furthermore, when you’re stressed, vagus nerve function is compromised and can lead to unfavorable changes in microbiota composition, encouraging the incidence of GI issues such as IBS.
Bonaz B, Bazin T, Pellissier S. The Vagus Nerve at the Interface of the Microbiota-Gut-Brain Axis. Front Neurosci. 2018 Feb 7;12:49. doi: 10.3389/fnins.2018.00049. PMID: 29467611; PMCID: PMC5808284.