Without enough stomach acid the Lower Esophageal Sphincter (LES)
tone may weaken or relax inappropriately allowing
stomach acid
to flow back into the esophagus.
Causes of low stomach acid include stress, aging, gastritis, poor diet, nutrient deficiencies - iron, zinc, B vitamins, smoking, alcohol, H. Pylori infection, acid blockers, stomach surgery.
In my case it’s autoimmune gastritis.