There are a few good posts here describing the mechanism, but I want to add some additional info. I'll be brief in summarizing what has already been said:
NAC is used for a lot of different toxicity conditions as well as mucus management for COPD. We find it here because of Glutathione which is a major antioxidant that has particular relevance to our ears. One of the presumed benefits of adequate Glutathione levels is the protective effect after loud exposures because it prevents the subsequent free radical damage to the inner ear from in the days following. Some military studies use it before and after noise exposure and have seen benefits. Additionally, as we age Glutathione status drops and this may be part of the cause of age related hearing decline.
It appears that studies confirm protective effect but can it help existing tinnitus or hyperacusis? The anecdotal report of the woman taking NAC for other reasons states that her tinnitus improved so that gets our interest but is not a placebo controlled study so... Also, correlation is not always causation. Maybe it was the NAC but it corrected a different condition that then helped with tinnitus and any one of us may not have that issue. It may also be a coincidence.
Getting Glutathione safely into the healthy range can have many health benefits because it's a general antioxidant. It is synthesized by three amino acids: Cysteine, Glutamate and Glycine, plus other co-factors (necessary for the complete multi step conversion process) such as B2, Selenium, Magnesium...
In a study comparing a young group to an elderly cohort, Glutathione status was much lower in the elderly population but so was glycine. Glutamate was not an issue. We also know that any given individual can be deficient in Selenium and B12. This is part of why we are all bio-individual. If you are chronically deficient in Magnesium, as many are, then you may see dramatic results from supplementation. I did. A person with adequate tissue levels of Magnesium, not so much, just loose stools. In other studies there is such a thing as Glutamate being too high and causing problems. Fixing Glutathione synthesis might help that because we are using up the Glutamate in the process.
So, how do we get Glutathione at healthy and protective levels? Direct oral supplementation is not very effective because absorption is poor. That is where NAC comes in. It turns out direct supplementation with cysteine can be dangerous but NAC is a precursor to cysteine which is easily absorbed and is safer. So we get our cysteine from NAC and are we done? I don't know, we are all different, we are all bio-individual. I am 66, so statistically I may also be deficient in amino acid number 2, Glycine. I may also be deficient in some of the co-factors to make sure that the complete process takes place. Candidates are Selenium, Magnesium, B2, vitamin C, Lipoid Acid, and vitamin E. It's hard to confirm without testing, but a safe and mainstream daily supplement helps take care of many of these.
I read on ingredients will help you find one that has say elevated Selenium for instance if you're working on this. Everything together is always better because there is so much interdependency. Also, mega dose anything with great care as some things are dangerous in high quantities like Zinc for instance. The mechanism for harm through excess dosing can be direct toxicity or say the depletion of the antagonist. That study of the elderly versus young population dosed NAC plus Glycine and the elderly population got their Glutathione status slightly higher than the young group.
As mentioned here, NAC may be off the market in the US shortly, Amazon has already pulled everything, so now what? I will refrain from a rant about big pharma, lobbyists and so forth. In another study they compared oral Glutathione to NAC and a new patented (read expensive) sublingual reduced Glutathione and the results confirm that oral Glutathione is ineffective but the other two had similar results in raising Glutathione status. I believe that the latest incarnation of the effective sublingual reduced Glutathione is called Terry Naturally Clinical Glutathione. I'm not affiliated and have not tried it.
Now for the big question, can this help tinnitus and hyperacusis after years of suffering? I don't know. Can it make it worse, I don't know? The data that I have reference certainly suggests a protective effect and damage control with the first week after the exposure but beyond that? Logic dictates that it might protect from further damage but I don't know.
I'm only a month in myself with tinnitus and hyperacusis, and I'm in the research phase so I don't even know what might work for me. I'm starting with getting all of the safe and effective stuff up to par and considering this as well as a number of other things mentioned often here, as well as reading research papers. This process has helped me solve decades old problems without drugs so I'm giving it a go again. Will I have similar success, I don't know. One thing I do know is that science based knowledge is power and ignorance brings chaos (Lucy, although I can't watch movies right now). In my experience you can either do extensive expensive testing or select trials based on science and your symptoms. Keep what works and get rid of what doesn't. Listen to your body. I am getting my B12 baseline next week and if low as I suspect, I will be fixing that because correcting a B12 deficiency has lowered tinnitus loudness scores but no help for people with adequate B12.
I have zero qualifications in nutritional counseling, tinnitus and hyperacusis treatment or the medical field. I'm just a technical guy doing research and trying to solve problems. Please seek the advice of qualified practitioners and always check for unsafe levels and interactions. Best to you all, at extreme levels this is quite a challenge, but I have faced many before. Now I will give this one a go.
George
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