2.2. Study Design
throat
RECRUITMENT
This randomized, double-blind, two-sequence, two-treatment, and two-period placebo-controlled crossover trial was conducted at Tamagawa University (Tokyo, Japan) between September and October 2022. The alleviation of oral and throat discomforts was expected to be derived from the direct effects of bLF, mucin, and water complexes on oral and throat mucosa. Therefore, we considered that carryover effects were negligible and chose a crossover design with a 1-week washout period. The test had four periods: recruitment, assessment of eligibility, and randomization (1 month); treatment period 1 (1 day); washout (1 week); and treatment period 2 (1 day). The participants were randomly assigned (1:1) to ingest bLF in treatment period 1, followed by a placebo in treatment period 2 (Sequence A), or placebo in treatment period 1, followed by bLF in treatment period 2 (Sequence B). The intervention was conducted once during each treatment period.