abstract: Drinking vinegar is a popularly discussed remedy for relieving heartburn symptom, as can be read on many websites; however, there has been no scientific research or theory to support its efficacy. This randomized, placebo-controlled, double-blind, cross-over research study tested the efficacy of the organic apple cider vinegar, with mother, on alleviation of the heartburn symptom related to Gastro-esophageal reflux disease (GERD). A minimum of one week separated the four trial arms: chili (placebo), antacid after chili meal (positive control), vinegar added to chili, and diluted vinegar after chili meal. Twenty grams of vinegar were used in both vinegar treatments, and 10 grams of liquid antacid were used in the antacid trial. A five-point Likert scale and a 10-cm visual analogue scale (VAS) were used to assess heartburn severity during a 120 minutes testing time. Seven of 15 recruited subjects' data was usable for statistical analysis (age: 39.6 ± 12.2 y, body mass index (BMI): 29.4 ± 4.2 kg/m2, waist circumference: 36.4 ± 4.1 inch). There was no statistically significant difference among the mean and incremental area-under-the-curve (iAUC) heartburn scores among different trials (Likert scale questionnaire p= .259, VAS questionnaire p= .659, iAUC Likert scale p= .184, iAUC VAS p= .326). Seven participants were further divided into antacid responder (n=4) and antacid non-responder groups (n=3). Likert scale mean heartburn score and iAUC data in antacid responder group had significant finding (p= .034 and p= .017 respectively). The significance lay between antacid and 'vinegar added to chili' trials. Effect size was also used to interpret data due to the small sample size: Likert scale: mean heartburn score= .444, iAUC= .425; VAS mean heartburn score= .232, iAUC .611. Effect size for antacid responder group was Likert scale: mean heartburn score= .967, iAUC= .936. Future research is needed to examine whether ingesting organic vinegar benefits alleviation of heartburn symptom related to GERD for people who do not respond well to antacid. / Dissertation/Thesis / Masters Thesis Nutrition 2016