NAC and Flu:
Subject: N-acetylel-cysteine taken daily reduces flu symptoms to the degree people may never know they were sick. It may also slow Alzheimer's Disease.
Remeber NAC? It stands for n-acetyl-cysteine. I've written about it before in connection with liver transplantation.[NAC and liver transplantation] It is a precursor to glutathione and taking it raises glutathione levels in the body. It's been used for decades as a mucolytic agent especially with cystic fibrosis. Two recent studies suggest other promising uses for NAC. One looked at the effect of taking NAC on flu infections while the second looked at its effect on the progression of Alzheimer's disease.
In the first study, a double blinded placebo controlled trial, 262 participants, mostly older people, 65 years or older, took 1200 mg/day of NAC for six months. Let me quote the abstract:
Often when infected with the flu virus, the people taking the NAC didn't feel or act sick.
The second study looked at Alzheimer's. I don't have the dosing details yet but at both 3 month and 6 month evaluations, "Comparison of interval change favored NAC treatment on nearly every outcome measure....." 
Alzheimer's has been in the news recently because of current research suggesting that anti-inflammatory medicines taken for arthritis may prevent its development. These theories are not alltogether new and it has been suggested that herbal anti-inflamatories might have a similar preventive effect. This isn't a short story so I'll save it for another day.
N-acetylcysteine (NAC), an analogue and precursor of reduced glutathione, has been in clinical use for more than 30 yrs as a mucolytic drug. It has also been proposed for and/or used in the therapy and/or prevention of several respiratory diseases and of diseases involving an oxidative stress, in general. The objective of the present study was to evaluate the effect of long-term treatment with NAC on influenza and influenza-like episodes. A total of 262 subjects of both sexes (78% > or = 65 yrs, and 62% suffering from nonrespiratory chronic degenerative diseases) were enrolled in a randomized, double-blind trial involving 20 Italian Centres. They were randomized to receive either placebo or NAC tablets (600 mg) twice daily for 6 months. Patients suffering from chronic respiratory diseases were not eligible, to avoid possible confounding by an effect of NAC on respiratory symptoms. NAC treatment was well tolerated and resulted in a significant decrease in the frequency of influenza-like episodes, severity, and length of time confined to bed. Both local and systemic symptoms were sharply and significantly reduced in the NAC group. Frequency of seroconversion towards A/H1N1 Singapore 6/86 influenza virus was similar in the two groups, but only 25% of virus- infected subjects under NAC treatment developed a symptomatic form, versus 79% in the placebo group. Evaluation of cell-mediated immunity showed a progressive, significant shift from anergy to normoergy following NAC treatment. Administration of N-acetylcysteine during the winter, thus, appears to provide a significant attenuation of influenza and influenza-like episodes, especially in elderly high-risk individuals. N-acetylcysteine did not prevent A/H1N1 virus influenza infection but significantly reduced the incidence of clinically apparent disease
 Neurology 2001 Oct 23;57(8):1515-7 Controlled trial of N-acetylcysteine for patients with probable Alzheimer's disease. Adair JC, Knoefel JE, Morgan N. Neurology Service, Albuquerque Veterans Affairs Medical Center and Department of Neurology (Dr. Adair), University of New Mexico.
The antioxidant N-acetylcysteine (NAC) or placebo was administered in a double-blind fashion to patients who met National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for probable AD. Testing for efficacy occurred after 3 and 6 months of treatment. Comparison of interval change favored NAC treatment on nearly every outcome measure, although significant differences were obtained only for a subset of cognitive tasks.