2.2. Study Design
MAY, OXIDATIVE STRESS
The Idaho State University Institutional Review Board, Human Subjects Committee approved the study protocol IRB-FY2021-264. Participants provided written informed consent. Enrollment occurred between September 2021 and May 2022. The study’s clinical trials registry identification is IRB-FY2021-264 at ClinicalTrials.gov (The investigation followed a 2 × 2 factorial randomized controlled design. The independent variables were time (morning vs. evening) and treatment (grape vs. placebo). The dependent variable was the urine concentration of F-2 isoprostane, a biomarker of oxidative stress. Secondary outcomes included urine levels of grape metabolites. Briefly, fasted participants attended a laboratory visit where they consumed a high-fat meal with a grape or placebo drink in the morning or evening. Urine samples were collected at baseline and 1 h post-meal in the laboratory and 1–6 h post-meal outside the laboratory. The schedule of study activities is shown in 