Stomach acid is powerful enough to dissolve stainless steel.

The human stomach contains gastric juice with a pH level typically between 1.5 and 3.5. This extreme acidity comes primarily from hydrochloric acid (HCl), secreted by parietal cells in the stomach lining. In a 1997 study published in Gastrointestinal Endoscopy, researchers tested gastric juice on various materials and found that a single-edged stainless steel razor blade corroded significantly after just 24 hours of exposure.This corrosive power is crucial for breaking down proteins and activating digestive enzymes like pepsin. Yet the same acid that dissolves metal would quickly destroy human tissue if unprotected. The stomach survives by producing a mucosal barrier—a layer of bicarbonate-rich mucus that neutralizes acid before it reaches the stomach's cells. This protective layer is so vital that any breakdown in its production leads to painful gastric ulcers.The stomach also relies on rapid cell renewal. The body replaces the entire stomach lining every three to five days, shedding damaged cells before acid can cause permanent damage. This is one of the fastest cell-regeneration processes in the human body. Without this constant cycle of protection and renewal, the stomach would digest itself within hours.