Circadian Rhythm
Plain-English definitions of microbiome research vocabulary — the terms you'll see across articles, testing services, and probiotic claims.
The approximately 24-hour biological cycle that governs sleep-wake patterns, hormone release, and metabolism. The gut microbiome exhibits its own circadian fluctuations in composition and function, influenced by meal timing, light exposure, and host circadian clock genes.
Related terms
Melatonin
A hormone primarily associated with sleep regulation, produced by the pineal gland and — in much larger quantities — by enterochromaffin cells in the gut. Gut-derived melatonin influences intestinal motility, inflammation, and epithelial barrier function, and its production is influenced by the microbiome.
Gut-Brain Axis
The bidirectional communication system between the gastrointestinal tract and the central nervous system, involving neural, hormonal, and immune pathways. The microbiome plays a central role in this communication.