Zinc as a possible treatment for tinnitus
Zinc is an essential trace element present in all organs, tissues, fluids, and secretions of the body and it is widely distributed in the central nervous system, including the auditory pathway in synapses of the VIII nerve and in the cochlea. Zinc is an essential component of Cu/Zn superoxide dismutase (SOD) and in certain enzymes and it is important for proper function of the immune system. Three possible mechanisms have linked zinc to tinnitus; cochlear Cu/Zn SOD activity, synaptic transmission, and depression. Evidences in the literature suggest prevalence rates of zinc deficiency in individuals with tinnitus from 2 to 69%, affecting elderly individuals more frequently. Four among five small studies indicate that administration of zinc has a beneficial effect on tinnitus but these results still have to be confirmed in clinical trials with larger samples using a cross-over design, validated tinnitus handicap questionnaires, measurements of tinnitus magnitude, and accessing the coexistence of other symptoms such as depression, phonophobia, and hyperacusis.