Despite occasional claims that spicy foods can “irritate” the stomach, thereby promoting stomach ulcer development, there is no human evidence linking spicy foods to a higher risk of ulcers, nor is there good reason to think that capsaicin causes damage to the stomach lining.[1] Eating spicy food might cause abdominal pain in people with an existing ulcer, but this doesn’t mean spicy food is actually making the problem worse.[2]
A clinical trial from 1987 is sometimes cited as evidence that spicy food can damage the stomach. The study administered various doses of chili pepper powder to a group of 8 participants, reporting a small increase in stomach bleeding after ingestion of 100 milligrams of chili pepper powder.[3] However, there are a few reasons to be skeptical of this finding. For one thing, no clear increase in stomach bleeding was observed following consumption of higher doses of chili pepper powder (0.5 grams, 1 gram, or 1.5 grams). It seems fairly implausible that higher doses would have no observable effect on stomach bleeding, yet a low dose would have such an effect. Additionally, the study measured stomach bleeding using a chemical technique that appears not especially reliable.[4]
Some research even suggests that spicy food might protect against the development of stomach ulcers. A few small studies found that people with ulcers eat spicy food less often, not more often (as would be expected if spicy foods cause ulcers).[5][6] And while this could just be because spicy foods aggravate ulcers (leading people with ulcers to avoid them), a few clinical trials have found that capsaicin seems to protect the stomach’s mucous membrane from damage caused by alcohol and certain nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin.[7][8]
Still, there is limited evidence looking at how capsaicin interacts with H. pylori infection, which is believed to be responsible for most cases of stomach ulcers. Although some evidence suggests capsaicin might actually inhibit H. pylori growth,[6][9] more research is needed to determine whether capsaicin has an effect, positive or negative, on ulcer development related to H. pylori infection.