eggsCysteine is a sulfur containing amino acid.  Cysteine has six major function in the body:
    – Building block for proteins. 
    – The rate-limiting precursor for glutathione (the body’s major detox and antioxidant molecule).
    – Precursor for taurine (important for nerve function and bile production).
    – Provides sulfate for connective tissue. 
    – Source of pyruvate for energy or glucose production.
    – Acts as a neurotransmitter. 



Chronic diseases like aging, atherosclerosis and heart disease, arthritis and auto-immune disorders, neurodegenerative diseases, autism, infections, and pulmonary diseases are made worse by oxidative stress and free radicals due to the lack of antioxidant function.  Increased infections or the accumulation of toxins may result.  Disorders that have been known to improve with cysteine supplementation include: skin disorders, hair loss, asthma, allergies, bronchitis, lung disease including cystic fibrosis, diabetes and it’s complications, seizures, HIV, and alcoholism. 

The fact that benefits have also been seen with addiction disorders to cocaine, cannabis, and tobacco, Alzheimer’s, Parkinson’s, autism, schizophrenia and bipolar, speaks to the importance of this amino acid and likely the importance of proper glutathione function.



Cysteine is found in all proteins but is highest in eggs, meats, dairy and wheat germ.  Cooking can oxidize the cysteine.  



Supplementation should be given as NAC (N-acetyl-cysteine).  It has been found to be safe up to doses of 2000 mg in adults.  Many do not recommend its use as it can promote yeast over growth in the intestines if you have a yeast issue.  Anti fungal treatments may be needed before or after use of cysteine and a diet low in sugars may be helpful in minimizing the yeast overgrowth issue. 

NAC is life-saving in cases of Tylenol/ acetaminophen / paracetamol poisonings.  

Here are some links that you may find useful:

Criteria for acetylcysteine treatment and clinical outcomes after paracetamol poisoning… 

The promise of N-acetylcysteine in neuropsychiatry…

N-acetylcysteine for antioxidant therapy: pharmacology and clinical utility…

Systematic review of N-acetylcysteine in the treatment of addictions…

Potential Role of N-Acetylcysteine in the Management of Substance Use Disorders…


Dr. Paul



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