Body Handbook Catalogue Profile Ranking
Supplements BODY HANDBOOK
Supplements Β· Β§531
N-Acetyl Cysteine (NAC)
NAC is the antidote paramedics push into the vein to stop a paracetamol overdose from killing the liver. That same molecule sits on the supplement shelf sold as a hangover cure, an antioxidant, a longevity pill. Here's what you didn't know you didn't know: it works, but only for three narrow profiles, and none of them is you unless you have a specific problem. Fit one and it's a cheap, slow, real fix. Fit none and you're buying an expensive sulfur burp.
Do Β· Daily Evidence Moderate Chapter Supplements

What it does: NAC is the amino acid cysteine with a cap that lets it survive the gut. Your cells strip the cap and use the cysteine to build glutathione, the antioxidant they make for themselves. Cysteine is the bottleneck, so NAC keeps the line stocked 1. The catch the marketing skips: it only helps when glutathione is already depleted. Eat eggs, dairy and chicken and your cells are stocked; topping up a full tank does nothing 2.

Three uses hold up. Chronic bronchitis and moderate COPD: at 1,200 mg a day, exacerbations dropped about a fifth, more if you're not already on a daily inhaled steroid 3. The older 600 mg dose showed no effect, so the dose matters 4. Compulsive hair-pulling and skin-picking: in adults, more than half improved on NAC against 16% on placebo, the first drug to clearly beat placebo where SSRIs do nothing 5. Bipolar depression, as an add-on to a mood stabiliser: a modest lift in the depressive floor, but only after months 6. PCOS is a weaker maybe, mostly as a metformin adjunct 7.

The dose is set by the reason, not the bottle. The 600 mg capsule on the shelf is the lung dose; the psychiatric dose is three to four times that.

Slow on every axis. Nobody texts a friend two days in.

  • Weeks: if you have a wet cough, the mucus loosens; clearing your throat takes one effort, not five. Otherwise you feel nothing.
  • Months two to three: the pulling or picking urge starts to soften; the loop gets shorter and easier to break 5. A winter cold that would have floored you passes as a normal cold.
  • Month six: the bipolar floor lifts a little, a Sunday that feels like a Sunday 6.
  • Year one: one or two fewer chest flare-ups than your old baseline is the win worth staying on for.
The fine print β€” when to skip it, and what people get wrong

Marketing myths. "Master antioxidant": no, it feeds one, only when yours is low 2. "Cures hangovers": doesn't 8. "Longevity pill": no data; one trial saw more heart events 9. "For kids": didn't replicate 10.

Check first if: on warfarin, a DOAC or daily aspirin (it mildly thins blood); on nitrates (it deepens the pressure drop, avoid); pregnant (no data); brittle asthma (start half-dose) 11.

Why "nothing happened": you quit at a month (psychiatric effects need 24 weeks); you took the 600 mg lung dose for a psychiatric problem; or your diet already had you stocked 2.

References
  1. 1Aldini G, Altomare A, Baron G, et al. (2018). N-acetylcysteine as an antioxidant and disulphide breaking agent: the reasons why. Free Radical Research. link
  2. 2Rushworth GF, Megson IL (2014). Existing and potential therapeutic uses for N-acetylcysteine: the need for conversion to intracellular glutathione for antioxidant benefits. Pharmacology and Therapeutics. link
  3. 3Zheng JP, Wen FQ, Bai CX, et al. (2014). Twice daily N-acetylcysteine 600 mg for exacerbations of chronic obstructive pulmonary disease (PANTHEON): a randomised, double-blind placebo-controlled trial. The Lancet Respiratory Medicine. link
  4. 4Decramer M, Rutten-van MΓΆlken M, Dekhuijzen PNR, et al. (2005). Effects of N-acetylcysteine on outcomes in chronic obstructive pulmonary disease (Bronchitis Randomized on NAC Cost-Utility Study, BRONCUS): a randomised placebo-controlled trial. The Lancet. link
  5. 5Grant JE, Odlaug BL, Kim SW (2009). N-acetylcysteine, a glutamate modulator, in the treatment of trichotillomania: a double-blind, placebo-controlled study. Archives of General Psychiatry. link
  6. 6Berk M, Copolov DL, Dean O, et al. (2008). N-acetyl cysteine for depressive symptoms in bipolar disorder β€” a double-blind randomized placebo-controlled trial. Biological Psychiatry. link
  7. 7Thakker A, Mantri S, Pal A, et al. (2025). Efficacy of N-acetylcysteine in polycystic ovary syndrome: systematic review and meta-analysis. Nutrients. link
  8. 8FDA (2022). Policy regarding N-acetyl-L-cysteine (NAC): guidance for industry β€” enforcement discretion. link
  9. 9Martinez FJ, de Andrade JA, Anstrom KJ, King TE Jr, Raghu G (2014). Randomized trial of acetylcysteine in idiopathic pulmonary fibrosis. New England Journal of Medicine. link
  10. 10Bloch MH, Panza KE, Grant JE, Pittenger C, Leckman JF (2013). N-acetylcysteine in the treatment of pediatric trichotillomania: a randomized, double-blind, placebo-controlled add-on trial. Journal of the American Academy of Child and Adolescent Psychiatry. link
  11. 11Calverley P, Rogliani P, Papi A (2021). Safety of N-acetylcysteine at high doses in chronic respiratory diseases: a review. Drug Safety. link
Related in the handbook (4)
Helps
  • β€” Chronic bronchitis is one of NAC's three real indications β€” daily capsules cut the winter flare-ups for some COPD patients.
  • β€” NAC raises ovulation and progesterone in PCOS β€” useful for the clomiphene-resistant patient or as a metformin add-on.
Related
  • β€” Both are studied for PCOS ovulation. Inositol is the better-evidenced first pick; NAC is a reasonable add-on.
  • β€” NAC is cheap, but potency and purity vary. Buy a tested brand so you get the dose the trials actually used.
Β·
531