Which factor is described as decreasing the risk of ulcerative colitis?

• A. Smoking
• B. Non-smoking
• C. High-fat diet
• D. Regular exercise

Answer: (A)

Smoking reduces the risk of developing ulcerative colitis. People who smoke have a lower incidence of UC compared with nonsmokers, a protective association thought to involve nicotine and other tobacco components that can modulate mucosal immune responses in the colon. This does not mean smoking is good overall; it increases risks for many other diseases and can worsen outcomes if UC is already present. The other factors don’t have a proven protective effect against UC: not smoking removes the protective influence, a high-fat diet isn’t established to decrease UC risk, and regular exercise, though healthy, isn’t specifically known to lower UC incidence.