Gastric secretion is stimulated by the act of eating (cephalic phase) and the arrival of food in the stomach (gastric phase). Arrival of the food in the intestine also controls gastric secretion (intestinal phase). The secreted fluid contains hydrochloric acid, pepsinogen, intrinsic factor, bicarbonate, and mucus.

When does the stomach release acid?

Acid secretion is stimulated by distension of the stomach and by amino acids present in the food. The intestinal phase: The remaining 10% of acid is secreted when chyme enters the small intestine, and is stimulated by small intestine distension and by amino acids.

What time of day is stomach acid the highest?

Acid secretion is highly variable from night to night, yet peaks in a circadian fashion between 10 pm and 2 am, suggesting a circadian component ( Figure 1).