Research Under The Microscope Series

The aim of “Research Under The Microscope” series is to translate research papers that are quite often technically complicated, extremely lengthy and contain large amounts of data into simple everyday language making it quicker and easier to understand the research findings.

What is the problem and what is known so far?

Age-related hearing loss affects approximately 37% of older adults. Many factors contribute to age-related hearing loss, such as long-term exposure to loud noises.

Noise-induced hearing loss (NIHL) from prolonged loud noise exposure, causes permanent hearing loss with disturbances such as tinnitus. This severely impacts a person’s quality of life.

NIHL is an injury and degeneration of hair cells in the organ of Corti’s located in the cochlea portion of the inner ear and can manifest tinnitus due to spontaneous depolarization of auditory fibres which creates noise without an external stimulus.

What is the background to this research?

This research investigated the effectiveness of zinc supplementation on tinnitus associated with noise-induced hearing loss.

As NIHL develops, there is a close relationship between a reduction in blood flow and an increase in free radical (toxic molecules) production in the damaged part of the cochlea. There is little research to evaluate the effectiveness of nutritional compounds such as zinc supplementation as a potential therapy for NIHL-associated tinnitus. The interest in zinc is due to its antioxidant properties which are thought to protect the cochlea from an oxidative stress injury due to the production of free radicals.

What was studied in this research?

In total 40 participants were included in the study—twenty patients with NIHL-induced tinnitus and 20 healthy control subjects.

How was the research performed?

The treatment group received 40 milligrams of elemental zinc gluconate per day split into two doses daily of 2 x 10 milligrams tablets for 2 months.

The primary measure was to determine improvements in auditory function, serum zinc levels and the patient’s overall quality of life by measuring their perceived tinnitus handicap. All measures were taken before the commencement of the trial and after two months of treatment.

What did the study researchers find?

Zinc supplementation successfully elevated plasma zinc levels as well as significantly improved tinnitus handicap inventory scores for patients with NIHL associate tinnitus.

What is the take home message?

• Zinc is a mineral that is required to help over 100 enzymes carry out chemical reactions within the human body.
• Zinc is especially abundant in the synapses of the auditory nerve system. Low zinc levels have been associated with auditory function loss such as sensorineural hearing loss, imbalance, and tinnitus.
• In previous studies conducted on patients with tinnitus, there is a significant association between hypozincemia (low levels of zinc) and tinnitus.
• In patients suffering from NIHL with tinnitus, oral zinc supplementation may help improve a patient’s quality of life by decreasing their overall emotional and functional response reaction to tinnitus.
• The highest forms of zinc for absorbency include zinc picolinate, zinc citrate, zinc acetate, zinc glycerate, and zinc mono-methionine.
• Zinc sulphate has the lowest absorbency factor.

What You Can Do Now

• If you are experiencing hearing loss or tinnitus, then please see your doctor.
• Ensure that you are eating food that contains zinc. Zinc is a biological essential mineral for humans. Over 300 enzymes in the body require zinc to function normally. Zinc is found in a variety of food sources such as pumpkin seeds, beef and egg yolks. Protein helps with the absorption of zinc so ensure that you are eating adequate protein in your diet each day.
• Zinc is absorbed in the small intestines however, absorption can be greatly disrupted due to diet, illness and various inhibitors such as phytic acid found in food sources such as grains and legumes. Again, please speak with a qualified health practitioner if you are affected by anything that may impact zinc absorption.
• Be mindful of symptoms of zinc deficiency including hair loss, changes in nails, an increase in infections, loss of appetite, eye problems, lack of taste and smell and skin changes that may present as eczema.
• Testing for zinc deficiency can be unreliable, therefore usually the best cause of action if zinc deficiency is suspected is to start zinc supplementation and monitor symptoms to see if there is an improvement.

If you need assistance, changes to your diet or nutrition to manage a health condition should only be undertaken with advice from a suitably qualified nutritional health professional.

This factsheet is for general information only.

Please contact me to discuss your individual needs.

References:

1. Yeh, Chun-Wei, Leng-Hsuan Tseng, Chao-Hui Yang, and Chung-Feng Hwang. 2019. ‘Effects of Oral Zinc Supplementation on Patients with Noise-Induced Hearing Loss Associated Tinnitus: A Clinical Trial’. Biomedical Journal 42 (1): 46–52. https://doi.org/10.1016/j.bj.2018.10.009.