Osmanthus fragrans extracts for preventing noise induced hearing loss in brewery workers: A randomized, double-blind, controlled study

This studies whether the water extract of Osmanthus fragrans can prevent noise-induced hearing loss (NIHL) after exposure to a noisy environment. Twenty-four healthy factory workers in southern Taiwan were recruited. The hearing threshold was determined before and after each dosing period. Measurements of oxygen radical absorbance capacity (ORAC), glutathione (GSH), oxidized glutathione disulfide (GSSG), GSH/GSSG ratio, superoxide dismutase (SOD) and glutathione peroxidase (GPx) in plasma as well as audiometric measurements were made before and after the extract was ingested for 270 days. The results demonstrate that consuming single Osmanthus fragrans extract (SOFE) during continuous exposure to noise levels that exceed 85 dB for 270 days reduced temporary hearing loss (TTS) from 6.4 ± 2.3 dB HL to 2.8 ± 1.6 dB HL. The values of ORAC, GSH, GSH/GSSG ratio and GPx activity were significantly increased whereas those of GSSG and SOD were significantly reduced by the ingestion of Osmanthus fragrans extract. Furthermore, the complex Osmanthus fragrans extract (COFE) group exhibited a perceptible improvement in hearing threshold and antioxidant activity. The results herein showed that the correlation coefficients of ORAC, GSH, GSH/GSSG ratio, GPx, GSSG and SOD with the TTS at 4000Hz exceeded 0.90. After taking Osmanthus fragrans extract (OFE), workers at a factory with a high-noise environment exhibited increased antioxidant capacity, which ultimately mitigated TTS.