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Supplement · amino_acid

N-Acetylcysteine (NAC)

Quick read: N-Acetylcysteine (NAC) is a sulfhydryl-containing derivative of the amino acid L-cysteine, serving as a pharmaceutical agent and dietary supplement.

Quick facts · N-Acetylcysteine (NAC)

Dose
600 mg
Per day
1200 mg
Timing
Twice a day
Course
90 days + break 30 days
Scientific background
N-Acetylcysteine (NAC) is a sulfhydryl-containing derivative of the amino acid L-cysteine, serving as a pharmaceutical agent and dietary supplement. Biochemically, it is a precursor to glutathione (GSH), a critical endogenous antioxidant found in nearly all cells. NAC's primary physiological role stems from its ability to replete intracellular GSH levels, which are often depleted during oxidative stress. Its mechanism of action involves providing cysteine for GSH synthesis via the gamma-glutamyl cycle, directly scavenging reactive oxygen species, and modulating the redox environment. NAC also exhibits mucolytic properties by cleaving disulfide bonds in mucoproteins, reducing mucus viscosity. Clinically, NAC is well-established as an antidote for acetaminophen overdose due, in part, to its role in restoring hepatic GSH and detoxifying reactive metabolites. It is also utilized in respiratory conditions like chronic bronchitis and cystic fibrosis for its mucolytic effects. Emerging research explores NAC's potential in neurological and psychiatric disorders, addiction, and conditions associated with inflammation and oxidative stress, highlighting its broad therapeutic versatility and ongoing investigation into its diverse cellular pathways.

Form & dosage

Single dose
600 mg
Daily
1200 mg
Course
90 days
Break
30 days
Timing
Twice a day
How we rate evidence

Probability — how likely the effect is to show up

  • Very high
  • High
  • Medium
  • Low

Evidence — where the data comes from

  • Scientific Meta-analyses and randomized trials
  • Clinical Clinical trials and practice
  • Animal research Animal studies
  • People reports User reports and anecdotes
  • Theoretical Mechanistic reasoning, not yet tested

Side effects

Medium probability(1)

  • Nauseahealthclinical

    Feeling queasy or upset in your stomach, sometimes due to NAC's strong sulfur taste or its potential to irritate the digestive lining, especially when taken without food or in larger amounts.

Low probability(4)

  • Diarrheahealthclinical

    Loose or frequent stools might occur as your digestive system adjusts to the supplement, or if you take higher doses that can accelerate gut motility.

  • Vomitinghealthclinical

    Though less common than nausea, some individuals may experience vomiting, particularly if they are sensitive to the supplement, take it on an empty stomach, or at very high doses.

  • Digestive Discomforthealthclinical

    You might experience a general feeling of unease in your stomach or intestines, such as mild cramps or indigestion, as your body processes the supplement.

  • Garlic Breath/Body Odorbodypeople_reports

    A distinctive, often unpleasant, sulfur or 'rotten egg' smell from your breath or skin can develop as your body metabolizes the sulfur-containing compounds in NAC.

Low probability(4)

  • Headachehealthpeople_reports

    Some users report mild headaches, which might be a non-specific reaction to the supplement or related to changes in blood flow or neurotransmitter activity as your body adapts.

  • Histamine Releasehealthclinical

    NAC can sometimes trigger the release of histamine in the body, leading to symptoms like flushing, itching, or nasal congestion, especially in sensitive individuals or at higher doses.

  • Anaphylactoid Reactionhealthclinical

    In rare instances, NAC can cause a severe, non-allergic systemic reaction resembling anaphylaxis, characterized by symptoms like difficulty breathing, low blood pressure, or widespread rash, often linked to rapid administration or high doses.

  • Allergic Reactionhealthclinical

    Though rare, some individuals may experience mild allergic responses such as skin rashes, itching, or hives, indicating an individual sensitivity to the compound.

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