The vagus nerve has anti-inflammatory properties through its afferents (activating HPA) and its efferents (the cholinergic anti-inflammatory pathway, CAP). The CAP inhibits pro-inflammatory cytokine release (especially TNFα) from splenic and intestinal macrophages.
Vagus nerve stimulation has been shown to alleviate damage to the intestinal epithelial glycocalyx, reduce intestinal permeability and gut/lung injury — mediated through CAP.
Contemplative practice has measurable effects on this system. A systematic review of 18 studies across 11 years found that mind-body interventions including mindfulness, meditation, yoga, tai chi, and Qigong downregulate genetic expression of inflammatory cytokines and NF-κB target genes — effectively reversing the molecular signature of chronic stress.
Activities with documented vagal effect: slow abdominal breathing (4-6 breaths/min, especially extended exhalation); brief cold exposure; singing, chanting, mantra (vibrating the larynx); yoga, especially restorative; mindfulness meditation; adequate sleep (vagal tone follows circadian rhythm).
Emerging: non-invasive transcutaneous vagus nerve stimulators (auricular VNS — Gammacore, Nemos) are being studied in IBD protocols. Used in some centers for refractory cases.