2.2. Study Design
This was a randomized, double-blind, and placebo-controlled trial. The PRO group were given three soft capsules containing 227 mg/3 capsules of propolis twice per day, i.e., after breakfast and dinner (total intake: 454 mg/6 capsules/day) for 12 weeks. Meanwhile, the PLA group were given placebo capsules at the same dosage and frequency for 12 weeks. The participants were instructed to take the capsules with water or tea. Furthermore, all participants were required to not alter their lifestyle habits, such as diet and exercise, during the study period. To assess compliance, the participants were instructed to record changes in their lifestyle and health status and daily capsule intake.The study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Review Board (or Ethics Committee) of the Prefectural University of Hiroshima (15MH064) and Kobe University Graduate School of Health Sciences (277-2). Furthermore, the trial was registered at the University Hospital Medical Information Network (UMIN) Center (ID: UMIN000020459). Informed consent was obtained from all subjects involved in the study.