Effects of a single dose of bovine lactoferrin on mouth and throat moisture under low humidity in healthy adults: a randomized, double-blind, placebo-controlled crossover trial

Abstract Background Low humidity environments induce dryness of the oropharyngeal mucosa, leading to the deterioration of oral health and quality of life. We investigated the effects of a single dose of bovine lactoferrin (LF) on the dry sensation in the mouth and throat caused by low humidity conditions. Methods In a randomized, double-blind, placebo-controlled crossover trial, healthy adults who ingested bovine LF (96.3 mg) or a placebo were exposed to a low humidity environment (20 °C, 20% relative humidity [RH]) for 2 h and underwent clinical assessments over time. The primary outcome was dry sensation in the mouth and throat, assessed using the visual analog scale (VAS). The secondary outcome was the unstimulated whole salivary flow rate (UWSFR). The primary efficacy analysis was performed using a per-protocol set (PPS). Results Of the 40 participants recruited, six who met the exclusion criteria and had protocol violations were excluded, leaving 34 participants in the PPS. The VAS scores for dryness of the mouth and throat were significantly lower in the LF group than in the placebo group at all assessment time points (0.5, 1, and 2 h). The UWSFR was significantly higher in the LF group than that in the placebo group at 2 h. Conclusions A single dose of bovine LF alleviated dry sensations in the mouth and throat of healthy adults in a low humidity environment, possibly through a mechanism involving the maintenance of oral and throat moisture. Registration number University Hospital Medical Information Network Clinical Trials Registry, no. UMIN000056030. Registration date November 4, 2024