Mechanism of Action
N-acetylcysteine is a stabilised form of cysteine, a sulphur-containing amino acid. The acetyl group attached to the molecule shields it from oxidation in the digestive tract, allowing it to reach the bloodstream intact. Once absorbed, NAC releases cysteine, which enters cells to serve as a building block for glutathione. Glutathione is a tripeptide (a small protein made of three amino acids: glutamate, cysteine and glycine) that neutralises free radicals and regenerates other cellular antioxidants. Cysteine is the rate-limiting component in this production chain. NAC also participates in hepatic conjugation reactions, a set of biochemical transformations through which the liver neutralises and eliminates unwanted compounds. It further contributes to the production of taurine, a sulphur amino acid with multiple functions whose tissue reserves diminish with age.
Key Benefits
- Strong
A meta-analysis of controlled trials confirms that NAC supplementation significantly reduces oxidative stress and systemic inflammation biomarkers in adults.
- Strong
A meta-analysis indicates that oral NAC supports respiratory function by reducing the frequency of bronchial discomfort episodes in adults exposed to environmental factors.
- Strong
Selenium contributes to the protection of cells from oxidative stress. NAC, by providing the primary substrate of glutathione, supports this same antioxidant defence network.
- Moderate
A randomised controlled trial in older adults supplemented with GlyNAC (NAC plus glycine) for 16 weeks shows significant improvement in muscle strength, walking speed and exercise capacity.
- Moderate
Multiple clinical trials report a reduction in systemic inflammation markers (C-reactive protein, interleukin-6) following NAC supplementation at doses of 600 to 1,200 mg per day.
- Emerging
Preliminary clinical data in humans suggest that NAC supports age-related cognitive functions, possibly through reduced cerebral oxidative stress.
Dosage & Forms
Cysteine can be delivered in several oral forms. Free L-cysteine oxidises rapidly in the digestive tract and has limited bioavailability. NAC circumvents this issue through its protective acetyl group. Clinical studies use doses ranging from 600 to 1,800 mg per day, depending on the objective and population. The most frequently studied dose for antioxidant support is 600 mg per day in a single intake. Trials investigating the NAC and glycine combination (often called GlyNAC) employ higher doses. The form selected by Singular is a NAC produced by fermentation, a biological process distinct from conventional chemical synthesis. This form offers high purity and rapid water solubility.
In the Singular Formula
Inclusion rationale
Acetylated form of cysteine offering superior oral bioavailability compared to free cysteine, which oxidizes spontaneously in the digestive tract. N-acetylcysteine is the most effective precursor of glutathione, the body's main intracellular antioxidant. Glutathione is a sulfur-containing tripeptide composed of three amino acids: glutamate, cysteine and glycine. Its synthesis is limited by cysteine availability, the most fragile link. NAC resolves this limitation by providing cysteine in stable form. Glycine (also present in the formula) supplies the second component, while glutamate is abundant in the body. The formula thus brings together both rate-limiting substrates of glutathione synthesis. NAC also participates in phase II hepatic detoxification and in the regeneration of oxidized vitamins C and E. Furthermore, the cysteine provided by NAC is also a precursor of taurine (present in the formula), a sulfur amino acid whose tissue concentrations decline with age. NAC has been used in Europe for several decades, with a safety profile well documented across tens of thousands of patients.
Selected form
N-Acetyl-L-Cysteine produced via fermentation. The acetyl group shields cysteine from oxidation during digestion, allowing significantly higher intestinal absorption than free L-cysteine. Once absorbed, NAC releases cysteine, the rate-limiting sulfur amino acid in glutathione biosynthesis, the body's primary cellular defence system. Unlike conventional chemically synthesised forms, this NAC is produced through fermentation. Freely soluble in water. Quality: vegan, non-GMO, allergen-free, Halal and Kosher certified.
Formula dosage
0 to 600 mg.
Synergies in the formula
Safety & Precautions
NAC has been used in Europe for several decades. Clinical trials report a favourable tolerability profile at standard doses (600 to 1,200 mg per day). Mild digestive effects (nausea, gastric discomfort) are the most commonly reported and generally remain transient. Supplementation is not recommended for individuals taking anticoagulants without medical advice, due to a potential interaction with platelet function. It is also not recommended during pregnancy and breastfeeding in the absence of sufficient data. Individuals with asthma should consult a healthcare professional before use. If taking nitroglycerin concurrently, medical advice is recommended.
Scientific Studies
| Authors | Year | Type | Journal | |
|---|---|---|---|---|
| Faghfouri AH et al. | 2020 | Meta-analysis | European Journal of Pharmacology | View on PubMed |
The effects of N-acetylcysteine on inflammatory and oxidative stress biomarkers: A systematic review and meta-analysis of controlled clinical trials Meta-analysis of controlled trials showing that NAC significantly reduces oxidative stress and systemic inflammation biomarkers in humans. | ||||
| Kumar P et al. | 2023 | Randomised Controlled Trial | The Journals of Gerontology: Series A | View on PubMed |
Supplementing Glycine and N-Acetylcysteine (GlyNAC) in Older Adults Improves Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Physical Function, and Aging Hallmarks: A Randomized Clinical Trial Randomised controlled trial showing that 16-week GlyNAC supplementation restores glutathione and improves muscle strength, oxidative stress and multiple ageing hallmarks in older adults. | ||||
| Cazzola M et al. | 2015 | Meta-analysis | European Respiratory Review | View on PubMed |
Influence of N-acetylcysteine on chronic bronchitis or COPD exacerbations: a meta-analysis Meta-analysis confirming that oral NAC reduces the frequency of respiratory episodes in at-risk populations. | ||||
| Kumar P et al. | 2021 | Randomised Controlled Trial | Clinical and Translational Medicine | View on PubMed |
Glycine and N-acetylcysteine (GlyNAC) supplementation in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, insulin resistance, endothelial dysfunction, genotoxicity, muscle strength, and cognition: Results of a pilot clinical trial Randomised pilot trial showing that GlyNAC supplementation improves glutathione levels, oxidative stress and cognitive function in older adults. | ||||
| Sadowski M et al. | 2024 | Meta-analysis | Journal of Cellular and Molecular Medicine | View on PubMed |
The impact of N-acetylcysteine on lactate, biomarkers of oxidative stress, immune response, and muscle damage: A systematic review and meta-analysis Recent meta-analysis confirming the impact of NAC on oxidative stress biomarkers, immune response and muscle damage markers. | ||||