NAC Bodybuilding Supplement May be Hazardous
NAC stands for N-acetylcysteine, a supplement widely advertised on bodybuilding web sites as a muscle building supplement and antioxidant. Cysteine is an amino acid and this NAC form of cysteine is supposed to enhance protein metabolism as well as improve the immune system. So says the promotional material.
I could find no scientific support for the value of NAC in bodybuilding, nor has it been tested adequately for safety over the long term when used in this way.
And now a new study suggests it may actually be harmful. Although the experimental study was with mice, three weeks of supplementation with NAC caused dangerously high blood pressure in the arteries that carry blood to the lungs. This condition is called pulmonary arterial hypertension, which can cause swelling to the right side of the heart.
Although the amounts fed to mice were high and further comparisons need to be made with quantities recommended for human supplement taking, this study highlights a caution that applies to supplements in general. Taking nutritional supplements that are untested and unproven for effect and safety is not only a waste of money but can be dangerous.
Source: Palmer LA, Doctor A, Chhabra P, Sheram ML, Laubach VE, Karlinsey MZ, Forbes MS, Macdonald T, Gaston B. S-Nitrosothiols signal hypoxia-mimetic vascular pathology. J Clin Invest. 2007 Sep;117(9):2592-601.
Comments
When “reasearch or studies suggest” I would like to know who did the research, when, for how long.
Thanx! carolyne
Hello Carolyne,
I quoted the reference at the bottom of the article.
Cheers, Paul
i didnt know that thank you for the artical i will have to think twice now about if i should use it again
However well intentioned the information was meant to be… it is incomplete and disingenuous. When a comment is made such as
“Although the amounts fed to mice were high and further comparisons need to be made with quantities recommended for human supplement taking, this study highlights a caution that applies to supplements in general.”
… what amounts were fed? What were the controls? I understand the references and if they are to explain my two questions… then what is the use of this article? It sounds like a scare article. If people taking supplements are not aware of what they are ingesting, then they should not take supplements. I would have expected more substance from a person with your background.
Curt, I don’t understand your problem or follow your logic. I posted a short summary of a study about a relatively common supplement used in weight training and bodybuilding — or at least recommended as such. Presumably, this would be of interest to readers. Most would be unlikely to come across this article themselves unless they read the scientific literature regularly, which I do.
I added some comments and gave the reference from the peer-reviewed journal for anyone to follow up on the detail.
As I’ve described elsewhere — and this applies in this short article — there are 4 things that prospective users need to know about dietary supplements:
1. Does it work? Does it do what it says it does.
2. Is it safe? Can you take it without suffering acute, chronic or delayed adverse effects.
3. Are the constituents of the quality and of the quantity listed on the label (if it has a label)? Eg, no impurities or adulterants, hazardous or otherwise, accidental or otherwise.
4. If it has been shown to be safe and effective, is the dose supplied (according to the label) sufficient to produce the effect? That is, no cheating.
NAC has been used for various medical applications and conditions, particularly treatment of acute poisoning by acetaminophen (Paracetamol) and heavy metals; and in lung diseases like cystic fibrosis. Its acute toxicity is low (human LDlo likely in the >1000 mg/kg/bw based on rodent LD50 studies).
However, I could find no relevant studies of mutagenicity (in vitro or in vivo), carcinogenicity, teratogenicity or neurotoxicity in chronic studies in animals or humans. Please post a summary here if you are aware of any.
I found no examples of randomised studies, preferably double blinded, for efficacy as a weight training or bodybuilding supplement. Please let me know if you are aware of any.
Under the circumstances, and considering that supplementation of this kind is often taken for lengthy periods of time, possibly inducing chronic and delayed effects, I thought my article was entirely appropriate. And yes, I do know better
.
Paul Rogers