Listening to Advice: Who Knew that Antioxidant Vitamins can Affect your Hearing?
If you search google with the term ‘antioxidants’, one of the first links is MedlinePlus which states:
Antioxidants are substances that may protect your cells against the effects of free radicals. Free radicals are molecules produced when your body breaks down food, or by environmental exposures like tobacco smoke and radiation. Free radicals can damage cells, and may play a role in heart disease, cancer and other diseases.
No mention of antioxidants and hearing loss. So it was interesting to see the article by Choi and colleagues linking antioxidants with a risk of hearing loss. They used cross-sectional data from 2,592 participants in the NHANES 2001-2004 survey to examine auditory sensitivity with 24h dietary intake data. Numerous unique statistically-significant nutrient-auditory relationships are reported. The directionality of the associations are consistent. Antioxidant nutrient intakes (beta-carotene, vitamin C, vitamin E and magnesium) show a protective dose-response relationship with maintaining better hearing.
An analysis of Odds Ratios (OR) and quartile cutoffs found in Table 4 with respect to nutrient intakes (Table 1) is insightful. Table 1 shows 2 and 13X greater intakes of vitamin C (91 to 212 mg/d) and vitamin E (3.7 to 49 mg/d) with supplement use. Not the same story for beta-carotene (food = 1931 vs food + supplement = 1931 µg/d). Thus, beta-carotene intake appears to be driven by increased consumption of foods rich in beta-carotene, eg fruit and vegetables. This hypothesis is confirmed by the uniform increases in quartile cutoffs increase uniformly (376, 771, 2034 µg/d) and change in OR found in Table 4. However, there is a significant jump in the highest quartile cutoff for vitamin C (44.6, 107, and 214 mg/d) and vitamin E (0.9, 6.4, 22 mg/d). More importantly, it is only the highest quartile which has a significant reduction in OR. A 38% reduction in OR for vitamin C and 33% reduction for vitamin E. This suggests that to protect hearing, people may need to achieve dietary intakes of vitamins C and E which were only accomplished by supplementation.
The dietary intakes are consistent with NHANES 2003-2006 (Fulgoni et al, 2011). They report that 90% and 37% of Americans have usual intakes of vitamins C and E below the Estimated Average Intake (EAR) unless dietary supplementation is practiced. Of course, people can be educated and encouraged to choose foods that are rich in antioxidants. They should. But what if we don’t?
With 65% of Americans over 70y have hearing loss and a doubling of the number of Americans with hearing loss during the past 30y, Choi and colleagues raise some important questions about the role of antioxidant nutrients in maintaining auditory function.
Choi Y-H, Miller JM, Tucker KL, Hu H, Park SK. Antioxidant vitamins and magnesium and the risk of hearing loss in the US general population. 2013 Am J Clin Nutr doi:10.3945/ajcn.113.068437
Fulgoni III VL, Keast DR, Bailey RL, Dwyer J. Foods, fortificants and supplements: Where do Americans get their nutrients?2011 J Nutr