In this post I will summarize a series of two interesting interviews I came across from 2012 with Gus Mueller, PhD, Contributing Editor of Audiology Online interviewing Christopher Spankovich, PhD, Research Assistant Professor and Colleen Le Prell, PhD, Associate Professor, both at the University of Florida.
It’s well known that nutrition is relevant to many aspects of health, and it seems likely that our diets influence susceptibility to hearing loss. Most data evaluating the relationship between nutrition and hearing loss come from animal models, with only a handful of studies that examined the influence of diet on hearing in humans.
Studies with calorie restriction of individual nutrients (protein, carbohydrates, or fat intake) found that reduced levels of protein may increase vulnerability to noise-induced hearing loss and ototoxicity (ear poisoning) in guinea pigs (4, 5). Several studies also suggested that long-term (12 month) increased fat intake (6) and high-cholesterol, high-triglyceride diets (7) increase risk for noise-induced hearing loss in rats.
Most micronutrient (vitamins and minerals) studies involve either supplementing the animal’s diet or looking at nutrient deficiency and the effects of either age, noise, or a drug that’s toxic to the ear. Specific nutrients such as vitamin A (8, 9) B-vitamins (10, 11), vitamin C (1, 12), vitamin E (13, 14, 15), and magnesium (16, 17) have been shown to provide protective effects when individually supplemented, and there are also benefits when dietary nutrient supplements were combined (18, 19).
Findings with humans as related to hearing and diet are currently mostly limited to retrospective (looking backward) epidemiological studies that look at relationships between the foods people eat and measures of auditory function.
In a classic study (20) that manipulated fat intake among patients in two Finnish mental institutes over a 5 year period, subjects placed on a low-fat diet showed reduced levels of cholesterol and significantly better hearing thresholds. The researchers switched the diets at the two institutions for a 3.5 year period and found a reverse in the results, where the patients moved to the low-fat diet had reduced cholesterol and less progression in hearing loss compared to the group that was switched back on to the high saturated fat diet.
Most human nutritional epidemiology studies track the impact of a single nutrient on hearing. This approach has several limitations: 1) we don’t eat isolated nutrients, we eat meals consisting of foods with a variety of complex combinations of nutrients; 2) nutrients interact and impact each other’s relationship with the outcome measure; 3) the effect of a single nutrient may be too small to detect; 4) you increase your odds of finding a significant relationship by chance if you are looking at 25 separate nutrients.
To date there have only been a few human studies, most of which have been conducted in the past few years, and are fairly consistent with the animal literature. Some work (21) demonstrated a relationship between vitamin C, vitamin E, magnesium, and lycopene with better auditory function and higher cholesterol and fat with poorer auditory function. There also is research data showing increased odds of hearing loss with higher carbohydrate and sugar intake (22).
Colleen Le Prell and her colleagues at other institutions have identified benefits for a micronutrient supplement of vitamin A (delivered as beta-carotene), vitamin C, vitamin E, and magnesium (ACEMg). Each of these nutrients were shown to confer protection against hearing loss, in animal models. Le Prell and colleagues are ramping up to begin a clinical trial that will test vitamin A, vitamin C, vitamin E, and magnesium in human subjects.
While supplements may have beneficial effects on hearing, it seems unlikely that any supplement could “replace” a healthy diet given the variety of different vitamins, minerals, and macronutrients that need to come from our diet. You can’t just take a multivitamin supplement and get all of the benefits that might come from a healthy diet. Nutrients derived from food sources represent the full spectrum of nutrients and phytochemicals associated with that specific food, including the numerous chemical forms, and there are implications for how food is digested and metabolized compared to a supplement.
Spankovich believes that the greatest impact of a healthy diet will likely be in reducing age-related hearing loss, which includes noise history, health history, diet, genetics, and ear-damaging drugs. We have some data that we are working on that suggest that diet may have its’ greatest impact in older age groups, but early adoption of healthy eating practices is recommended. In his opinion, hearing loss is not an inevitable outcome.
The human studies to date on diet and hearing define a healthy diet as one that includes the amounts of fruits, vegetables, grains, meats, and dairy recommended by the U.S. Department of Agriculture (USDA). It is my opinion that given what is known about the health benefits of a plant-based diet, a diet that is rich in whole, plant-based foods (especially leafy green vegetables) has the potential to provide significantly more protection against hearing loss than what has been observed in previous studies.
I believe that it would be nice to see these studies redesigned to compare hearing loss in subjects that consume a whole, plant-based diet to subjects that consume the standard American diet. I think that would be much more informative.
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- Someya, S., Yamasoba, T., Weindruch, R., Prolla, T.A., & Tanokura, M. (2007). Caloric restriction suppresses apoptotic cell death in the mammalian cochlea and leads to prevention of presbycusis. Neurobiology of Aging, 28, 1613-22.
- Someya, S., Tanokura, M., Weindruch, R., Prolla, T.A., & Yamasoba, T. (2010). Effects of caloric restriction on age-related hearing loss in rodents and rhesus monkeys. Current Aging Science, 3, 20-5.
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- Du, Z., Yang, Y., Hu, Y., Sun, Y., Zhang, S., Peng, W., Kong, W. (2012). A long-term high fat diet increases oxidative stress, mitochondrial damage and apoptosis in the inner ear or D-glactose-induced aging rat. Hearing Research, 287(1-2), 15-24.
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- Scholik, A.R., Lee, U.S., Chow, C.K., & Yan, H.Y. (2004). Dietary vitamin E protects the fathead minnow, Pimephales promelas, against noise exposure. Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology, 137(4), 313-323.
- Hou, F., Wang, S., Zhai, S., Hu, Y., Yang, W., & He, L. (2003). Effects of alpha-tocopherol on noise-induced hearing loss in guinea pigs. Hearing Research, 179, 1-8.
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- Sendowski, I., Raffin, F., & Braillon-Cros, A. (2006). Therapeutic efficacy of magnesium after acoustic trauma caused by gunshot noise in guinea pigs. Acta Otolaryngologica, 126(2), 122-129.
- Heman-Ackah S.E., Juhn S.K., Huang T.C. & Wiedmann T.S. (2010). A combination antioxidant therapy prevents age-related hearing loss in C57BL/6 mice. Otolaryngology - Head and Neck Surgery, 143, 429-434.
- Le Prell, C.G., Hughes, L.F., & Miller, J.M. (2007). Free radical scavengers vitamins A, C, and E plus magnesium reduce noise trauma. Free Radical Biology & Medicine, 42, 1454-1463.
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- Spankovich, C., Hood, L., Silver, H., Lambert, W., Flood, V., Mitchell, P. (2011). Associations between diet and both high and low pure tone averages and transient evoked otoacoustic emissions in an older adult population-based study. Journal of the American Academy of Audiology, 22, 49-58.
- Gopinath, B., Flood, V.M., McMahon, C.M., Burlutsky, G., Brand-Miller, J., & Mitchell, P. (2010). Dietary glycemic load is a predictor of age-related hearing loss in older adults. Journal of Nutrition, 140, 2207-12.