A prospective study on symptom generation according to spicy food intake and TRPV1 genotypes in functional dyspepsia patients

Background: Capsaicin is an ingredient of red peppers that binds to transient receptor potential vanilloid subtype 1 (TRPV1), and Koreans eat more capsaicin-rich food than do Japanese. This study aimed to compare symptom generation according to TRPV1 genotypes and the intake of spicy foods. Methods: Consecutive functional dyspepsia (FD) patients who were evaluated at Konkuk University Medical Centre (Korea) and Keio University Hospital (Japan) were included. Questionnaires on spicy food intake, patient assessment of gastrointestinal symptoms (PAGI-SYM), patient assessment of quality of life, and hospital anxiety and depression scale were provided. Blood was sampled for the detection of TRPV1 polymorphisms, and upper gastrointestinal endoscopy was performed with biopsies. Key Results: Of 121 included subjects, 35 and 28 carried the TRPV1 CC and GG genotypes, respectively, with the prevalence rates not differing between Japan and Korea. The prevalence of FD subtypes did not differ with the spicy food intake, TRPV1 genotypes, or Helicobacter pylori infection. Neither TRPV1 polymorphisms nor H. pylori infections were related to scores on the PAGI-SYM questionnaires, but spicy food intake was positively correlated with the scores for stomach fullness (p = 0.001) and retching (p = 0.001). Using the linear regression analysis, stomach fullness was associated with spicy food intake (p = 0.007), whereas retching was related to younger age (p < 0.001) and female gender (p = 0.014). Conclusions & Inferences: Upper gastrointestinal symptoms are more common in subjects with a higher consumption of spicy foods, younger age and female gender, regardless of TRPV1 genotypes and the H. pylori infection status. Capsaicin-rich foods may induce stomach fullness.