Gastrin

Gastrin is a peptide hormone secreted by G cells in the stomach and duodenum. Its main function is to stimulate gastric acid (HCl) secretion from parietal cells, aiding protein digestion. It also enhances gastric motility, stimulates pepsinogen release, promotes growth of the gastric mucosa, and increases gastric blood flow—supporting effective digestion and mucosal maintenance.

Gastrin rises in response to food (especially proteins), gastric distension and vagal stimulation (via gastrin-releasing peptide). Low stomach acidity — from atrophic gastritis, proton pump inhibitors or antacids — removes negative feedback and increases gastrin. Pathologic causes include gastrin-secreting tumors (gastrinomas/Zollinger–Ellison syndrome), H. pylori–related antral gastritis, hypercalcemia and chronic renal failure, which can also elevate gastrin levels.

Low gastrin reduces stomach acid production and weakens gastric mucosal maintenance. Consequences include impaired protein digestion, poorer absorption of iron and vitamin B12, bacterial overgrowth, bloating, indigestion, and higher risk of certain GI infections; it can also slow gastric motility and lead to nutrient deficiencies and weight loss if prolonged. Clinical evaluation is needed to identify the cause and treat deficiencies.

Excess gastrin (as in gastrinoma/Zollinger–Ellison) causes symptoms from stomach acid overproduction: severe, recurrent peptic ulcers, intense abdominal pain, persistent heartburn/acid reflux, chronic diarrhea, nausea, vomiting, weight loss, gastrointestinal bleeding and anemia. Less commonly, esophagitis and steatorrhea occur. Symptoms arise from gastric acid hypersecretion and warrant medical evaluation and testing for gastrin levels and acid-related complications.

Gastrin is increased by signals during meals: protein/peptides and certain amino acids, stomach distension, vagal stimulation, calcium, and reduced gastric acidity. Practical steps: eat protein-rich meals, chew thoroughly to promote gastric distension, maintain adequate dietary calcium, and be aware that acid-suppressing drugs (antacids/PPIs) raise gastrin via feedback. Discuss any medication or dietary changes with your clinician.

Diet influences gastrin: protein-rich meals, amino acids or peptides, large meal volume, and stimulants like coffee or alcohol increase gastrin release. Low stomach acid (for example after proton-pump inhibitors or with H. pylori infection) can raise gastrin by removing acid feedback. High acidity and fasting lower gastrin. Overall meal composition, size, and certain beverages modulate gastrin secretion.