Joseph F. McCaffrey MD, FACS


N-Acetyl Cysteine


I have another supplement (n acetyl cysteine) that I want to tell you about, but first I want to give my usual disclaimer. I believe that one of the foundation principles of good health is a healthy diet. The most concise summary of what constitutes a healthy diet that I’ve seen is ”Eat real food, mostly vegetables, not too much.”


Diet, exercise and a proper mental attitude (including stress management) are the keys to good health. However, once you have those in place, you can get additional benefit from appropriate supplements.


In fact, n acetyl cysteine (NAC for short)  has such  remarkable proven benefits that I’m amazed it isn’t more widely known and recommended. For example, one randomized, placebo controlled trial showed a reduction in the people who developed symptoms after being exposed to avian flu from 79% to 25%!


You’d think everybody would be talking about this supplement on the basis of that study alone, not to mention all the other beneficial effects I’m about to tell you about. I’m not one for conspiracy theories, but I have to think that part of the reason this supplement isn’t better know is because there’s no money in it. It’s cheap and available over the counter. If you haven’t heard of NAC, I’m not surprised.


N-Acetyl cysteine is a chemical variant of the amino acid cysteine. In the body it acts as a precursor to glutathione. Glutathione is an important anti-oxidant and detoxifier, so maintaining adequate levels is crucial.


Acetaminophen (Tylenol) overdose commonly caused liver failure. Acetaminophen causes liver problems because one of its metabolites is toxic. Normally, glutathione detoxifies this metabolite and eliminates it from the body. However, if a person takes too much acetaminophen, the metabolite overwhelms the cells glutathione reserves and cell damage results. NAC prevents this by restoring intercellular levels of glutathione.


In addition, NAC modulates the expression of several genes involved in an overactive inflammatory response and improves cellular response to insulin, both of which contribute to several chronic diseases.


I’ve been particularly impressed with studies on the effect of NAC on viruses. In both cultures and laboratory animals, NAC inhibits viral replication. Not only that, but it reduces the release of inflammatory molecules that a viral infection usually triggers. It’s this massive release of damaging molecules that causes much of the lung damage during a severe flu infection.  It is probably these abilities of NAC that led to the dramatic results in that study I mentioned earlier.


Another area that the anti-oxidant abilities of NAC come in handy is helping the body deal with the free radicals caused by exercise. Exercise is one of the best things you can do for yourself, but vigorous exercise causes the release of several inflammatory factors, including tissue necrosis factor.


Studies have shown that supplementing with NAC prevents most of the deleterious effects of exercise in healthy individuals. Perhaps even better, one study in patients with COPD showed that NAC actually improved their exercise tolerance by 25% compared to a placebo.


Another study I was interested in showed that NAC given prior to angiograms (X-rays that require the injection of a dye into arteries) greatly reduced the risk of kidney damage caused by the dye.


On the safety side of the equation, NAC seems to be exceptionally safe, even in doses much greater than those used for treatment. The most common side effects are GI upset. The only report of a serious side effect that I’ve seen is an allergic reaction when it was given IV to treat acetaminophen poisoning.


Who should take NAC? Well, I think a lot of people. I don’t recommend taking Tylenol routinely, but if you are, even at normal doses, supplementing with NAC is prudent. Also, I think anyone with chronic lung problems should supplement regularly. Ditto vigorous exercisers.


I think the evidence on flu prevention is good enough that I’m going to start taking it every winter as part of my flu prevention plan (vitamin D is another big part or that plan).


The usual dose is 600 mg – 1800mg per day in divided doses. That is, 600mg 1 to 3 times a day.



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