Antioxidant-rich supplements may reduce noise-induced and perhaps even age-related hearing loss in humans, if human trials can echo promising results from animal studies.
Studies using guinea pigs and mice found that supplements of beta carotene and vitamins C and E, and the mineral magnesium consumed prior to exposure to loud noise could prevent both temporary and permanent hearing loss in the animals.
Researchers from the universities of Florida, Michigan, and Washington, and OtoMedicine reported their findings yesterday at the Association for Research in Otolaryngology's annual conference in Baltimore.
"What is appealing about this vitamin 'cocktail' is that previous studies in humans, including those demonstrating successful use of these supplements in protecting eye health, have shown that supplements of these particular vitamins are safe for long-term use," said researcher Colleen Le Prel, an associate professor in Florida.
According to the National Institute on Deafness and Other Communication Disorders, about 26 million Americans have noise-induced hearing loss.
Previously, researchers from the Netherlands reported that folic acid may prevent age-related hearing loss in older men and women (Annals of Internal Medicine, 2007, Vol. 146, pp.1-9).
Guinea pigs and mice
The first study used guinea pigs and after consumption of the vitamin supplements the animals were exposed to four-hours of 110 decibel (dB) noise. Such levels are similar to those reached at a loud concert. Animals who consumed the vitamins did not suffer from temporary hearing loss, reported the researchers.
In the second study, the researchers looked at the effects of a single loud sound exposure which would lead to permanent noise-induced hearing loss. In this case, the vitamin supplements are reported to prevent cell loss in an inner ear structure called the lateral wall. This structure is linked to age-related hearing loss, and the researchers suggest this has implications for protecting against age-related changes in hearing in humans.
The findings appear to fit with earlier findings that noise-induced hearing loss is linked to the production of free radicals.
"The free radicals literally punch holes in the membrane of the cells," explained Miller, from t the University of Michigan.
Vitamins and iPods
Research is ongoing in the area, confirmed the scientists, with a clinical trial funded by the National Institutes of Health investigating the effects of vitamin supplements in Florida college students who wear MP3 music players, and noise-exposed military troops and factory workers in Sweden and Spain.
Assuming positive results from these trials, the researchers stated that concert goers could soon be taking a supplement before heading out, a daily supplement for factory workers or a nutritional bar for soldiers.
"Ear protection, such as ear plugs, is always the best practice for the prevention of noise-induced hearing loss, but in those populations who don't or can't wear hearing protection, for people in which mechanical devices just aren't enough, and for people who may experience unexpected noise insult, these supplements could provide an opportunity for additional protection," said Le Prell.