Wednesday, December 1, 2010

Carbohydrates may be linked to hearing loss

Age related hearing loss effected by quality of carbohydrate nutrition.

A new Australian study suggests that age-related hearing loss could potentially be reduced by decreasing the amount of lower quality carbohydrate in the diet and increasing the intake of cereal fibre

Age-related hearing loss is the most prevalent form of hearing loss worldwide. Research suggests that nutrition is a modifiable risk factor that could play a role in the development of age-related hearing loss. The Blue Mountains Hearing Study investigated whether a cross-sectional or longitudinal relationship exists between carbohydrate nutrition, starch, cereal and total fibre, and age-related hearing loss in a large group of adults aged 50 years and older. Of the total 2448 participants 32.1% had hearing loss and more than two thirds (67.9%), had no hearing loss over the 5 year follow up period. Those with hearing loss had a significant change between baseline and the follow up period.

In this group of older adults the higher Glycaemic Index (GI) of foods eaten are associated with an increased risk of hearing loss. However, this association is reduced when there is an increase in dietary intake of cereal fibre. This suggests that the effect of cereal fibre may override the effects of other components of carbohydrate and may have a protective effect on the hearing function, possibly by improving insulin sensitivity or by reducing blood glucose levels after eating.

The incidence of hearing loss in this 5 year period was predicted by a high Glycaemic Load* (GL). A high GL diet at baseline is found to increase the risk of developing age-related hearing loss by 76% among older adults. This is regardless of other potential variables such as education, smoking, previous history of diagnosed stroke and diabetes, family history of hearing loss and exposure to noise at work.

The association with GL and hearing loss suggests that both the quantity and quality of carbohydrate may play a role in the development of age-related hearing loss. The underlying causes for these findings are unknown, however long term higher dietary Glycaemic Load (GL) brings on abnormally high blood sugar levels and excess levels of insulin circulating in the blood. This can lead to diabetes, hypertension, and/or dislipidemia in individuals who are at risk. Other studies show a relationship between hearing and diabetes mellitus, stroke, and vascular risk factors such as high blood pressure and serum lipids. Therefore, dietary GL could potentially influence hearing function through its adverse effects on vascular health. The current study speculates oxidative damage as the underlying mechanism between carbohydrate and hearing loss.

The authors however, conclude that in order to confirm this theory and replicate findings, large high quality randomised controlled trials of long duration are needed to investigate any potential links between carbohydrate nutrition and hearing.

Glycaemic Load* - the product of a food’s glycaemic index and total available carbohydrate content, and represents both the quantity and quality of carbohydrates.


Gopinath B et al. Dietary Glycemic Load is a Predictor of Age-Related Hearing Loss in Older Adults. J. Nutr. 140: 2207-2212, 2010.