Supplements of folic acid may prevent age-related hearing loss in older men and women, says a new double-blind, randomised, placebo-controlled trial from the Netherlands. The study, published in the new issue of the Annals of Internal Medicine, followed 728 men and women between the ages of 50 and 70 randomly assigned to receive either a folic acid supplement (800 micrograms per day) or placebo for three years.

Lead author Jane Durga and her colleagues from Wageningen University and Wageningen Centre for Food Sciences, and University Hospital Maastricht, reported that the folic acid-supplemented group exhibited lower age-related hearing loss in the low frequency region.

“Considering that the folate status of older adults is generally low in countries without folic acid fortification programs, our findings suggest a possible way to diminish the public health burden of hearing loss in those countries,” wrote Durga.

However, it is not known if such benefits would be observable in countries like the US and Canada where mandatory fortification occurs.

Folate is found in foods such as green leafy vegetables, peanuts, 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.

The researchers suggest that hearing loss may be linked to homocysteine levels, which could be reduced by folic acid supplementation. However the focus of the study on people with lower homocysteine levels limited the researchers from extending the findings to a general population. The authors also note that no mandatory folic acid fortification was present in the Netherlands during the study, and that the baseline levels of folate in the blood was about 50 per cent that of the US population, where mandatory folic acid fortification is present.

“Folic acid supplementation slowed the decline in hearing of the speech frequencies associated with aging in a population from a country without folic acid fortification of food. The effect requires confirmation, especially in populations from countries with folic acid fortification programs,” concluded the researchers.

In an accompanying editorial, Robert Dobie from the University of California, Davis said that if such a benefit could be applied generally then a five-decibel decrease in age-related hearing loss might be observed over a 20-year period. This would lead to a subsequent significant reduction in the need for hearing aids.

The research was supported by grants from the Netherlands Organisation for Health Research and Development, Wageningen University, and Wageningen Centre for Food Sciences.

Source: Annals of Internal Medicine
2 January 2007, Volume 146, Issue 1, Pages 1-9
“Effects of Folic Acid Supplementation on Hearing in Older Adults - A Randomized, Controlled Trial”
Authors: J. Durga, P. Verhoef, L.J.C. Anteunis, E. Schouten, and F.J. Kok