Cephalic reflexes: their role in digestion and possible roles in absorption and metabolism.
Level 5 - mechanism / opinion, no new human data
Narrative review and mechanistic animal research
PubMed 3302135 · doi:10.1093/jn/117.7.1191
What was done
This narrative review examines autonomic cephalic phase reflexes triggered by the taste and smell of food that prepare the digestive tract for nutrient processing. It also references experimental findings evaluating intestinal glucose uptake into hepatic portal blood following oropharyngeal sucrose stimulation in conscious, unrestrained rats.
What was found
Cephalic stimulation engages both sympathetic and parasympathetic (predominantly vagal) pathways to trigger salivation, gastric acid secretion, and pancreatic exocrine and endocrine responses independent of postabsorptive nutrient feedback. In conscious, unrestrained rats, oropharyngeal stimulation with sucrose increased the uptake of radioactive glucose from the small intestine into hepatic portal blood. No specific numerical values or statistical metrics were reported in the abstract.
Why it matters
It highlights that anticipatory sensory signals not only regulate digestive secretions but may also modulate downstream intestinal nutrient absorption and metabolism.
Limits
The abstract lacks quantitative effect estimates, sample sizes, and detailed methodology. The evidence describing direct effects on intestinal absorption relies on animal models (rats), which may not directly reflect human physiological responses.
Cited by
- supports The cephalic phase response increases salivation and gastric secretions to prepare the digestive system for incoming food.