- Published on 23 May 2019
A possible otoprotective effect from one of our favourite foodstuffs has been highlighted by the results of the first large cohort study of the effect of chocolate on hearing loss in middle-aged people.
This mouth-watering research by a team led by Sang-Yeon Lee of the Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, surveyed a total of 3575 subjects from 40 to 64 years of age, concluding that "the rate of any hearing loss (unilateral or bilateral hearing loss) was significantly lower in the subjects who consumed chocolate (26.78%) than in those who did not (35.97%). In addition, chocolate consumption decreased the risk of bilateral hearing loss (13.31% vs. 20.32%) and high-tone hearing loss (51.58% vs. 63.60%), respectively.
The study, published in the journal Nutrients on March 30 this year, also showed an inverse correlation between the severity of hearing loss and the frequency of chocolate consumption.
It falls short, however, of defining causal mechanisms or to linking results to any particular type of chocolate. Its limitations also include that it offers no information on chocolate consumption among participants over 65. "Given the protective effect of chocolate on age-related hearing loss, the association might have been significant if older persons had been included," the authors say.
Another hypothesis of the researchers, that chocolate would protect against tinnitus, was unexpectedly not borne out by results. "Chocolate intake was not associated with tinnitus or tinnitus-related annoyance," say the researchers.
Earlier animal studies have already pointed to various compounds in chocolate protecting against hearing loss. Chocolate exerts antioxidant and anti-inflammatory effects, which may provide some protection to the cochlea, which is especially susceptible to oxidative stress. Meanwhile, several studies have shown the causal relationship between vascular risk and hearing loss; cocoa, a major ingredient of chocolate, attenuates these risks by reducing blood pressure and improving endothelium-dependent vasodilation.
So, specifically which chocolate might be involved? Unfortunately, the researchers did not control the type of chocolate, dose, and duration of consumption. They point out, however, that milk chocolate and chocolate drinks reportedly do not exert a significant effect on health.
A randomized controlled study of the functional properties of chocolate is needed to establish causality, the authors comment.