N-acetyl Cysteine – What’s It All About?

by Dr. Jason Barker July 22, 2014

N-acetyl Cysteine – What’s It All About?

N-Acetyl Cysteine (NAC) is a modified version of the amino acid cysteine, which is found readily throughout the body.  Its main job is to help restore levels of a very important antioxidant found within our cells, known as glutathione. Glutathione is used by our body to fight off the damage caused by reactive oxygen species, otherwise known as free radicals.

NAC has been used in medicine for several decades now, yet still remains relatively unknown. In conventional medicine, it’s been used as a mucolytic (mucus-thinner) in people with lung diseases like chronic bronchitis, emphysema, chronic obstructive pulmonary disorder, and cystic fibrosis.

It’s also the go-to remedy for acetaminophen poisoining – acetaminophen is a popular over the counter pain reliever and fever reducer. Given its popularity, overdose is extremely common, whereby it destroys liver cells and is one of the most common causes of liver damage and failure.

For athletes, NAC should be one of your go-to remedies, for a couple of reasons.

NAC is a potent antioxidant that is partial to lung tissue (thus its use in a variety of lung diseases). If you’re an athlete with asthma, NAC can work to limit the inflammation and damage that occurs in delicate lung tissue as a result of asthma.

Ever go on a run or ride on a cold winter day and get that hacking, “smoker’s cough” after? That’s because you’re lungs are sensitive to cold air and now inflamed. Taking NAC immediately before and after a cold weather bout of exercise will limit the inflammatory damage in your lungs.

Newer studies show a performance benefit from taking NAC.  A handful of smaller studies have shown improved antioxidant levels and decreased inflammation that lead to improved cycling performance (1) and limited fatigue (2,3).

Interestingly, the benefits of NAC in these studies were found in endurance exercise situations; other studies show that NAC may actually hamper muscle recovery in short term/explosive exercise (such as strength training).

This is due to blunting of antioxidant-induced muscle regeneration. In other words, some amounts of oxidation are critical to exercise recovery and muscle repair (4) (this is a relatively new finding that is being explored). So, taking NAC for it's protective effects in endurance exercise is probably a good idea, but if your main focus is on short, explosive-type activities (sprinting, strength training, etc), then NAC may not benefit your performance. Adding NAC to your regimen may be a good idea if you’re an athlete with asthma, cold-sensitive lungs, or if you exercise in an urban area with poor air quality.

Also, it won't hurt to take some NAC if you use acetominophen, as it still damages the liver even at suggested doses (here are some safer pain relievers, without liver damage as a side effect!).

1. Med Sci Sports Exerc. 2014 Jun;46(6):1114-23.

2. J Appl Physiol (1985). 2004 Oct;97(4):1477-85.

3. Int J Sport Nutr Exerc Metab. 2011 Dec;21(6):451-61.

4. Am J Clin Nutr. 2013 Jul;98(1):233-45.

Dr. Jason Barker
Dr. Jason Barker


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