Age-related hearing loss is the most common type of hearing impairment. A number of factors may contribute to hearing loss due to aging. Some observational studies have suggested that there may be a connection between low levels of folic acid (a B vitamin) and hearing loss .
A study in the January 2, 2007 Annals of Internal Medicine found that older adults who took a daily folic acid supplement experienced less hearing loss than those who took a placebo. This study took place in the Netherlands, however, so its results may apply less to older adults living in countries such as the United States, where the food supply is fortified with folic acid.
About the Study
This study included 728 Dutch men and women ages 50-70 years who had high homocysteine levels (homocysteine levels increase as folic acid levels decrease). The researchers randomly assigned the participants to take either an 800-microgram folic acid supplement or a placebo pill daily for three years. The participants had hearing tests before the study began and after three years, and the researchers compared hearing changes between the folic acid and placebo groups.
After three years, hearing thresholds increased significantly—indicating hearing loss—in both groups of participants. But in the folic acid group, low-frequency thresholds increased by 1.0 decibel (dB), compared to a 1.7-dB increase in the placebo group. Folic acid supplementation did not affect the decline in high-frequency hearing.
Folic acid fortification of foods is prohibited in the Netherlands. As expected, therefore, the folic acid levels of the participants in this study were about half of those found in the United States population, where fortification of flour with folic acid is mandatory.
How Does This Affect You?
This study suggests that folic acid supplementation may help reduce hearing loss in older adults, at least in a country where foods are not fortified with folic acid. Although the 0.7 dB decrease in hearing loss observed in this study was small and probably would not be noticed, it is possible that longer term supplementation could have a larger impact on preventing or slowing age-related hearing loss.
While taking extra folic acid is likely to benefit older adults whose folic acid levels are low, it is not clear from this study that such supplementation would benefit populations with higher levels of folic acid in the diet. More studies are needed to determine if there are hearing-related benefits of folic acid supplementation in these countries. But this study may help justify folic acid fortification of foods in countries that currently do not mandate it.
- Reviewer: Richard Glickman-Simon, MD
- Review Date: 02/2007 -