Which Is Better, NAC or L-Cysteine?

Q In a recent article about N-acetylcysteine (NAC) being good as a defense against some of the harmful effects of air pollution, your product Root Food II was recommended because it is a good source of L-cysteine. But the list of ingredients does not include NAC. My question is: is NAC formed automatically in the lungs as long as there is enough L-cysteine, or do we have to take a product with the NAC already in it, like the one given to the laboratory rats?

Julio, Kennedy Shores, TX

A The article you referred to is “Risk of Heart Attack and Exposure to Traffic” in Durk Pearson & Sandy Shaw’s Life Extension News, January 2005, which was reprinted in Life Enhancement, March 2005, p. 27. Durk & Sandy prefer L-cysteine to NAC for several reasons, but principally because NAC can indiscriminately acetylate many things in the body, which is not desirable. Also, NAC has not been tested for long-term use, and Durk & Sandy do not feel that enough is known about it to assume that it’s safe for such use. By contrast, L-cysteine has been examined far more extensively. Provided that it is taken with at least twice as much vitamin C, it represents no problems in long-term use. (See “Why We Take Cysteine Rather Than N-Acetylcysteine” in Durk & Sandy’s Life Extension News, October 2002, reprinted in Life Enhancement,January 2003, p. 29.)