Antioxidants such as vitamins C and E, and beta-carotene were not associated with any benefits, researchers have told the 2009 American Academy of Otolaryngology-Head and Neck Surgery Foundation (AAO-HNSF) Annual Meeting in San Diego.
Researchers led by Boston-based Josef Shargorodsky used the most recent figures from the Health Professionals Follow-up Study cohort from years 1986 to 2004, a group consisting of 51,529 male health professionals.
The study identified 3,559 cases of men with hearing loss. When the nutritional data was analysed, men over the age of 60 with high folate intake from foods and supplements had a 20 per cent decrease in risk of developing hearing loss.
This is not the first time the B vitamin has been linked to the prevention of hearing loss, the most common sensory disorder in the United States, affecting more than 36 million people. In 2007 scientists from Wageningen University reported that folic acid supplements delayed age-related hearing loss in the low frequency region in a study of 728 men and women between the ages of 50 and 70 (Annals of Internal Medicine, Vol. 146, pp. 1-9).
Another study, published earlier this year indicated a role for beta carotene and vitamins C and E, and the mineral magnesium in preventing prevent both temporary and permanent hearing loss in guinea pigs and mice. The animal study was presented at the Association for Research in Otolaryngology's annual conference in Baltimore in February 2009.
The new study supports the potential of folate from both dietary and supplemental sources, but challenges the findings on antioxidant vitamins – no benefits were observed in people with increased intakes of vitamins C and E, and beta carotene.
Dr Shargorodsky and his co-workers believe theirs in the largest study to delve prospectively into the relation between dietary intake and hearing loss. The findings can allow greater education, prevention, and screening efforts for hearing loss, said the researchers.
Folate is found in foods such as green leafy vegetables, chick peas and lentils, and an overwhelming body of evidence links has linked folate deficiency in early pregnancy to increased risk of neural tube defects (NTD) - most commonly spina bifida and anencephaly - in infants.
This connection led to the 1998 introduction of public health measures in the US and Canada, where all grain products are fortified with folic acid - the synthetic, bioavailable form of folate.
While preliminary evidence indicates that the measure is having an effect with a reported 15 to 50 per cent reduction in NTD incidence, parallel measures in European countries, including the UK and Ireland, are still on the table.
Source: American Academy of Otolaryngology-Head and Neck Surgery Foundation (AAO-HNSF) Annual Meeting
“Vitamin Intake and Risk of Hearing Loss in Men”
Authors: J. Shargorodsky, G. Curhan, S. Curhan, R. Eavey