Under the assumptions required for Mendelian randomization and assuming a linear-logistic relationship between difference of circulating IL-10 level and odds of gastric cancer, the predicted ORs for 5 and 10 pg/mL IL-10 increment were 1.07 (95% CI: 1.01–4.12) and 1.14 (95% CI: 1.01–16.99), respectively. The gene discussed is IL10; the disease is gastric cancer.