Higher Fish and Omega-3 Intakes Associated with Lower Risk of Hearing Loss
Curhan, S.G. et al., American J. Clinical Nutrition, 100: 1371-1377, 2014
Department of Medicine, Brigham and Women’s Hospital, Boston, MA, USA
The ‘cochlea’ is the auditory portion of the inner ear. Impairment of blood supply to the cochlea has been implicated in a reduction of auditory sensitivities and hearing loss. Since DHA/EPA omega-3 fatty acids as found in fish/seafood have been associated with a lower risk of cardiovascular and cerebrovascular disease and may maintain cochlear blood flow, the relationship of fish and DHA/EPA intakes to hearing loss in women was studied. The population of 65,215 women who were followed for 18 years and analyzed were from the Nurses’ Health Study II. The ages ranged from 27-44 years having an average age at baseline of 36 years. On follow-up, 11,606 cases of self-reported hearing loss of varying degrees developed based on questionnaires. At various times over the study interval, a validated food-frequency assessment was made which, together with omega-3 nutrient composition tables, provided an estimate of omega-3 PUFA (polyunsaturated fatty acid) intakes.
After adjusting for multiple variables (age , physical activity, intakes of other nutrients, body mass index, other factors), those women who consumed 2 or more fish servings/week had a significantly lower risk (by 20 %) for developing a hearing loss as compared to those women who consumed fish less than one serving/month. The overall risk of hearing loss with 2-4 fish servings/week was 15 % less as compared to one serving/week. The more frequent intake of any type of fish was inversely associated with a lessened risk. Those women with the highest intake of total omega-3 fatty acids (top 20 % of intakes) had a 12 % lower risk for developing hearing loss as compared to those in the lowest 20 % of intakes. Interestingly, higher intakes of the short-chain omega-3 fatty acid (as LNA, alpha-linolenic acid, mainly from plant sources) did not show any protective influence against hearing loss. In contrast, a significantly lower risk of hearing loss was associated with the higher intake of the long-chain omega-3 fatty acids (mainly from fish sources) as DHA (docosahexaenoic acid) plus EPA (eicosapentaenoic acid). Those women in the top 20 % with respect to DHA/EPA intakes were found to have a 15 % lower risk for developing hearing loss as compared to those in the bottom 20 % with respect to DHA/EPA intakes. The authors concluded that ‘regular fish consumption and higher intake of long-chain omega-3 PUFAs are associated with lower hearing loss in women’.
Dr. Holub's Comments:
Regarding the mechanisms for the beneficial effect of fish and DHA/EHA intakes observed in this study, the reported effects of DHA/EPA in improving blood lipid profiles (particularly triglyceride-lowering), reducing thrombosis and inflammation , improving vascular reactivity , plus others may contribute to maintain healthy cochlear blood flow thereby reducing the risk of hearing loss. It is noted that the women with the lowest risk of hearing loss had typical intakes of DHA plus EPA of approximately 400 milligrams (mg) per day throughout the study period. Such intakes are near triple that of current intakes (120 -130 mg/day) in North America. Target intakes of 400 mg/day (or 2800 mg/week) can be easily met by consuming 2 servings/week of various fish (salmon, herring, mackerel, others) and/or via supplementation with quality DHA/EPA sources.