L-NAC and hearing loss prevention from loud music

Marshall Chasin
April 24, 2012

This week’s blog is written in the form of a one page information article that can be given to our patients, or in public education materials about hearing loss prevention.  I would suggest leaving out the first paragraph that talks about the recent retirement of Dr. Donald Henderson and start with the paragraph “All cells have a …”

Last week I attended a Noise Induced Hearing Loss Colloquium in honor of Dr. Don Henderson’s retirement. A lot of what we know about hearing loss prevention from loud noise (and loud music) comes from Dr. Henderson’s work, and that of his many students and colleagues over the past 40 years.  Personally I don’t think that Don will ever fully retire but who knows?  I have been wrong (once or twice before).  One of Don’s lasting contributions will be his work on anti-oxidants for the prevention of hearing loss from loud noise and music.

All cells have a metabolic process whereby they take in certain chemicals, and expel other chemicals.  Even though the metabolic process is very efficient, it is not perfect, and when the conditions are not optimal for the cell, the entire system degrades.  A side effect of non-optimal metabolism is the creation of oxygen molecules that are ions- also known as free radicals or Reactive Oxygen Species (ROS).  It is this proliferation of ROS that can damage the structure and chemistry of any bodily system, and this includes the hearing mechanism.

Anti- oxidants are “mops” that can remove many of the ROS molecules from the body.  And one whose name has been associated with Donald Henderson is N-acetyl-L-cysteine (L-NAC).  L-NAC can effectively undo many of the deleterious effects of an over active metabolism that may be caused by a range of phenomena such as loud noise and loud music.

A “mop” that is only used for kitchen floors will not be useful if it can’t be moved over the washroom floor.  An anti-oxidant that can’t get to where it is required will have no beneficial effect.  A “vector” or other mechanism must also be used to direct the anti-oxidant to where it is needed.  In the case of L-NAC it does seem that it can get to where it is required but more research is being performed to verify this.  Just because a food is high in anti-oxidants does not make it good for us.  Caution should be exercised when evaluating whether an anti-oxidant is potentially useful or whether it is merely marketing.

L-NAC is only one of several anti-oxidants that can absorb or mop up many of the free radicals that are the side effect of a cell’s normal metabolic requirement.  This is not the only anti-oxidant and there are others such as Src (pronounced ‘sarc”).   Different research teams are evaluating these different approaches.  L-NAC (and many of the other anti-oxidants being studied) have been known for years and had been used quite effectively in hospital emergency departments for people who have overdosed with Tylenol.  L-NAC acts to absorb the toxic elements that can accrue in the liver.

Other chemicals and vitamins have also shown to mitigate hearing loss from loud noise or music and this includes vitamins A, C, and E, as well the element magnesium.  Each of these vitamins has a slightly different mechanism.  Magnesium functions to improve blood supply which may be compromised with a stressed metabolic system.  Other chemical, or chemical combinations, have been shown to alter the transport of certain molecules across cell boundaries, thereby altering the susceptibility of the hearing mechanism to acoustic trauma from loud noise or loud music.  Although this is currently being studied, there may be a beneficial effect if an anti-oxidant such as L-NAC is combined with certain vitamins and other chemicals.

L-NAC  is currently going through the different phases of approval by the FDA and it is estimated that a commercially available pill that can be taken prior to going to a rock concert or any noisy activity will be available with 2 years.

It is to be noted that is not a cure for those with already existing hearing losses; just as one more preventative measure that can be used to minimize the potential of hearing loss.

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