SPECIAL FEATURE
The Link Between Diet and Hearing Loss Summary by John A. Coverstone, AuD
Research into curing hearing loss continues to progress and show promise for restoring some degree of lost hearing. At the same time, many researchers are looking at ways to strengthen our hearing system in the hope that we might prevent hearing loss from occurring in the first place. For many years, the U.S. military has invested in research into such drugs as D-methionine, an amino acid that has been long investigated by Kathleen Campbell, PhD, of Southern Illinois University.1 More recent breakthroughs include the 2018 publication of St. Jude’s researchers’ discovery of an enzyme that protects rats and mice from hearing loss and the 2020 publication of research from the University of Iowa and Washington University showing that a certain type of hearing loss could be prevented by blocking a chemical receptor in the ear.2,3 Other research has shown positive effects of antioxidants and anti-inflammatory agents in reducing the risk of hearing loss from noise exposure. However, while it may sound attractive to take a pill or an injection before attending that rock concert or engaging in a military operation with potential combat, all this research raises questions about the role of diet in hearing loss. D-methionine, for instance, occurs naturally in certain animal products, including meat, eggs, and fish. Other nutrients that affect the resilience of our ears may yet be discovered. 30
TINNITUS TODAY SUMMER 2020
Christopher Spankovich, PhD, at University of Mississippi and Colleen LePrell, PhD, at University of Texas at Dallas recently collaborated to provide a more thorough look at the relationship between diet and noise-induced hearing loss, in the hope of providing guidance on healthy eating habits that support healthy hearing.4 They found that early research on this topic involved the relationship of fat and cholesterol to hearing loss. In animal models, high levels of either were associated with a greater likelihood of damage from noise exposure. Deficiency of necessary nutrients has also been shown to make people more susceptible to hearing loss from noise exposure. These are too many to list but include important vitamins and minerals, such as magnesium and vitamins A, B12, C, and E, among others. Most of these studies came from animal models because it is not ethical to manipulate nutrition in humans. However, some human studies exist to support these findings. One study well known in audiology circles involves the Mabaan tribe of the Sudan, who, in general isolation from modern society, maintained a healthy diet and active lifestyle with very little exposure to loud noise. In a 1962 study by Samuel Rosen of Mount Sinai School of Medicine, tribal members were found to have normal hearing into their 80s. Marcos Goycoolea and others from the
University of Minnesota furthered this study in 1982 by showing that inhabitants of Easter Island who had lived only on the island their entire lives had better hearing than island natives who had lived in modern civilization. This was attributed both to differing diets and greater noise exposure in modern society. Long-term studies of human populations have shown similar results. A notable study published in 2010 followed almost 3,000 inhabitants of the Blue Mountains in Australia for three years, plus follow-up for five additional years to track mortality. This study showed poorer hearing in those with high carbohydrate and sugar intake, estimated by increased glycemic index. In another study, 65,000 women were followed as part of the Nurses’ Health Study II by Brigham and Women’s Hospital, Harvard Medical School, and Harvard T. H. Chan School of Public Health. Researchers found better hearing present in women with higher intake of certain sources of vitamin A. The study also reported that high intake of vitamin C (often termed “megadoses”) was associated with
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