I started eating a few chilis a day to man up when it came to spicy foods. Someone saw this and said that I'm probably going to get an ulcer or another stomach problem from it. Is there any truth to this?
Most ulcers are caused by bacterial infections (in particular, "Helicobacter pylori" infections are known to lead to ulcers, for which antibiotics are available), some others by aspirin and similar drugs and the rest by smoking or without clear cause. Spicy food does not cause ulcers.
Peptic ulcers were formerly thought to be caused by stress, coffee consumption, or spicy foods. Now it is clear that about 60% of peptic ulcers are caused by a bacterial infection that can usually be cured. Another 20% are caused by nonsteroidal antiinflammatory drugs (NSAIDs) such as aspirin and ibuprofen (Advil, Nuprin, etc.), and another 20% have miscellaneous causes such as cigarettes or no clear cause. (medicinenet.com, medscape.com)
On the contrary, a 1995 study by the National University of Singapore even suggests chili actually protects against ulcers, at least if you're Chinese.
The odds ratio of having peptic ulcer disease, adjusted for age, sex, analgesic use, and smoking by multiple logistic regression, was 0.47 (95% confidence intervals: 0.25-0.89) for subjects who had a higher intake of chili both in terms of frequency as well as amount used compared to those who took less chili. Our data support the hypothesis that chili use has a protective effect against peptic ulcer disease.