Life Extension Magazine May 2012
Strategies to Protect and Preserve Your Hearing
By Alexander Brookner
Magnesium treatment has been repeatedly shown to reduce the incidence of both temporary and permanent noise-induced hearing loss.38 Magnesium readily penetrates the cochlea from the blood.39 It improves blood flow around the cochlea, and is a vital cofactor in the body’s major antioxidant defense enzyme systems; it may have other mechanisms of action as well.39,40
Laboratory studies show dramatic reduction in noise-induced hearing loss when animals receive magnesium supplements prior to impulse noise such as gunshots.41,42 When human military recruits took 167 mg of magnesium daily during a two-month basic training period, the rate of substantial hearing damage was half that of a control group of soldiers.43 Recruits in this study were exposed to daily mean peak sound levels of 164 dBA, a very high value.
Similar results have been found in other studies in military settings, with magnesium supplements reducing both the frequency and the severity of significant hearing loss.44,45 Recruits with the highest blood magnesium levels had the least severe hearing damage, and effects were similar on both temporary and permanent hearing loss.
N-acetylcysteine (NAC) and Acetyl-L-Carnitine
N-acetylcysteine (NAC) is a potent antioxidant capable of repleting the body’s own antioxidant defenses, and acetyl-L-carnitine is a well-known mitochondrial nutrient that supports cellular energy metabolism. Both nutrients are emerging as leading candidates for hearing protection both before and after exposure to loud noises.
Studies with NAC and acetyl-L-carnitine in combination demonstrate less hair cell loss, lower oxidant levels, and reduced temporary and permanent hearing loss in animals exposed to loud impulse noise.46,47 The effect is so strong that the combination is still effective if used 1-4 hours after the noise exposure.46
Multiple studies demonstrate powerful protection of hair cells and cochlear blood flow in animals treated with NAC alone, resulting in reduced permanent hearing loss, both prior to and following impulse noise.48-50 Human studies using 1,200 mg of NAC daily for two weeks in military recruits exposed to impulse noise at peak levels as high as 165 dB, and in civilian workers exposed to industrial noise at as high as 89 dB, have shown similar protection, with substantial reduction in hearing loss, especially in the higher frequencies where we perceive speech.51,52
Melatonin is an intriguing hormone naturally produced in the pineal gland. Its multiple effects tend to balance out disturbances in the biological environment, including oxidant stress.53 Melatonin also decreases activity of dopamine, an excitatory neurotransmitter.54
Studies with melatonin show potent effects at reducing cochlear damage and preventing hair cell loss in animals, with concomitant protection of hearing thresholds. Melatonin was more effective than either of two powerful steroid anti-inflammatory drugs, methylprednisolone or dexamethasone.55,56
Melatonin may be uniquely effective in reducing both the perception of tinnitus, and the sleep disturbances tinnitus can produce.53 At doses of 3 mg/day, human studies show a 40% reduction in tinnitus perception.54 The same dose also improved sleep quality in a group of patients with chronic tinnitus.57
A variety of other antioxidant vitamins and nutrients have shown promise in reducing noise-induced hearing loss and/or the hair cell damage that produces it. Seventy-nine percent of patients with sudden hearing loss treated with vitamin E had significant hearing gain, compared with just 45% of those in a control group.58 Laboratory studies show less destruction in the cochleae of vitamin E-treated animals than in controls, with concomitant improvement in hearing.59,60
Lipoic acid is an antioxidant nutrient with proven benefit against the oxidant stress induced by impulse noise and blast injury.61,62 Animals treated with lipoic acid have substantially lower levels of oxidant molecules in blood and cochlea, and their hearing is protected significantly compared to untreated ones.63,64
Studies have shown that serum levels of toxic homocysteine are elevated in humans with noise-induced hearing loss or tinnitus, while levels of the anti-homocysteine nutrients folate and vitamin B12 are lowered.65-67 Raising plasma B12 levels to slightly above normal range with oral cyanocobalamin supplements at 1,000 mcg/day resulted in significant improvement in hearing levels in human subjects, compared with placebo recipients.68
Noise-induced hearing loss and tinnitus are major public health problems, and their incidence is rapidly rising in our noise-saturated society. Noise causes dramatic physical changes in the delicate structures of your inner ear, changes driven by oxidant stress.
Previously thought to be irreversible, both noise-induced hearing loss and tinnitus are now showing signs of yielding to prompt treatment with nutrients that can boost your antioxidant levels, including magnesium, N-acetylcysteine, acetyl-L-carnitine, and others.
Using a good, comfortable earplug can also reduce your exposure to hearing-threatening noises—keep a pair handy at all times.
If you have any questions on the scientific content of this article, please call a Life Extension® Health Advisor at 1-866-864-3027.
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