N-Acetylcysteine (NAC): An Old Nutrient Attracts New Research

August 21, 2009

In a previous article, I discussed why AIDS researchers were excited about two nutrients, Vitamin C and N-acetylcysteine (NAC). While most Whole Foods readers know a great deal about the roles of vitamin C in nourishing the body, some readers may not be all that familiar with the roles of the sulfur-containing nutrients, such as NAC, in nourishing the body. Therefore, I promised to provide more background on NAC in this article. [1]Our understanding of the many nutritional and biochemical roles of sulfur-containing nutrients is expanding rapidly at this time. We are learning more about how glutathione and its sulfur-containing precursors are important in keeping our bodies nourished, our immune systems healthy, and in protecting us against cancer and heart disease.Glutathione, cysteine, methionine, selenocysteine and selenomethionine have been important in my research for over thirty years. Even before that, I believe that some of the health pioneers indirectly realized the importance of these compounds as a group, even though they didn't understand much about the roles of the individual compounds. When the "pioneers" spoke so favorably of getting adequate "sulfur" in the diet, I believe that they were really testifying to the importance of these sulfur-containing nutrients. Not much has been said about them in "mainstream" nutrition, but today, interest in learning how sulfur-containing nutrients nourish the body is increasing.Researchers are rushing to study the roles of these nutrients in halting the dreaded Human Immunodeficiency Virus (HIV), breaking up lipoprotein(a) [Lp(a)], detoxifying harmful chemicals, scavaging free radicals and possibly protecting against some cancer processes. Since these nutrients are normally produced in plants, man and other animals, they have always been a part of the human diet.BackgroundSulfur-containing nutrients play several critical roles in the body including detoxification and protecting cells and cellular components against oxidative stress. My interest in glutathione and cysteine began in the 1960's when they were found to be protective against nuclear radiation. I reasoned that the same mechanism of action would make them excellent free-radical scavengers as well. They did, and twenty-one years ago I reported that, "sulfhydryl compounds that are excellent radiation protectors are also free-radical scavengers, peroxide decomposers, catalysts of sulfhydryl-disulfide exchange, and possibly can implement repair of damaged sites. Sulfhydryl compounds and vitamin E also increase the body's tolerance to selenium." [2]Today, NAC is of greater interest than glutathione itself. NAC is produced in living organisms from the amino acid cysteine. Thus, NAC is a natural sulfur-containing amino acid derivative found naturally in foods and is a powerful antioxidant. [3,4] These dual properties help repair oxidative damage in the body.Both NAC and glutathione are well absorbed. [5-8] NAC is rapidly metabolized, and only about ten percent of the amount consumed stays in the blood for an appreciable time. [9] Much of the NAC is very rapidly consumed in producing intracellular glutathione. However, even the thiol metabolites of NAC are good antioxidants.NAC readily crosses cell membranes, even in HIV-infected cells, whereas glutathione does not enter into HIV-infected cells in adequate amounts. [10-12] Even so, NAC does not seem to raise tissue or blood levels of glutathione above the desired ranges. [9] Thus, the nutrient role of NAC is to help maintain healthy levels of intracellular glutathione , especially whenever a condition has limited glutathione production. This nutrient role of maintaining optimal levels of essential body compounds is different from "drug roles" in which body compounds are just elevated without homeostasis or normal body regulation.

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