Excessive alcohol consumption and prolonged administration of non-steroidal anti-inflammatory drugs (NSAIDs) lead to gastritis which affects millions globally, yet safe and effective treatment options remain limited. While a range of nanozymes have been employed in the oral treatment of inflammatory bowel disease (IBD), the research directed toward gastritis therapy remains unexplored. The challenges of rapid gastric emptying, harsh gastric acid erosion, and the non-edible ingredient constitution hinder the practical use of nanozymes in this context. Herein, three types of sub-10 nm ultrasmall iron-polyphenol nanozymes (UIPNs) were synthesized by using fully edible natural active polyphenols, iron ions and PVP. UIPNs rapidly penetrated the gastric mucosa, resided in the stomach for over 12 h, and remained stable in the harsh acidic environment. They exhibited excellent enzyme-like activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD). Compared to omeprazole, all three types of UIPNs showed superior activity, with Fis UIPNs demonstrating the best performance in preventing and protecting against alcohol-induced gastric mucosal injury in mice. The fully food-sourced components, constructed into ultrasmall nanozymes via non-covalent interactions, ensure long-term safety and hold promise for playing significant roles in various gastrointestinal diseases.