NAC was shown in an Italian study to help prevent symptoms of H1N1 flu in almost 2/3 of the people taking it, when compared to a placebo.
In the Italian study, people received either a placebo or NAC 600 milligrams twice a day for 6 months. During this time, a little over a quarter of all these people developed antibodies to the H1N1 flu strain in circulation, indicating that they had become infected with the virus.
Among the people receiving the placebo, 79% developed symptoms of flu. Among the people taking NAC, only 25% developed symptoms.
In addition, the symptoms that developed were significantly milder in the group taking NAC. And there was a significant improvement in measures of immune function in the NAC group compared to the placebo group over the 6 months of the study.
NAC is one of my favorite supplements, not only for flu prevention and improving respiratory health, but also for supporting the actions of medications.
When I started working on a web application that highlights drug-supplement interactions, I found that NAC has been shown to enhance effectiveness of several types of medication, including drugs used in treating high blood pressure, depression and inflammatory bowel disease.