Is NAC Safe to Take Alone?


by Nils Osmar. June 27, 2022. Medical Disclaimer

NAC (N. Acetyl Chysteine) is a form of cysteine that is often taken as a nutritional supplement. Consuming adequate levels of cysteine important for several reasons. It’s been used medically for improving fertility, treating respiratory diseases. It has also been found to support brain health.

When taken along with glycine, NAC has been shown to extend lifespan in mice by 24%. But is NAC safe to take by itself?

Some early studies suggested that supplementing with NAC (alone) lengthens lifespan. When give to C. Eleganz, they lived significantly longer. See study: Lifespan extension and increased resistance to environmental stressors by N-Acetyl-L-Cysteine

Combining NAC with glycine

In a more recent study, when NAC was given to lab mice along with glycine (in equal amounts), it extended lifespan by as much as 24% by increasing glutathione. See study: GlyNAC (Glycine and N-Acetylcysteine) Supplementation in Mice Increases Length of Life by Correcting Glutathione Deficiency,

However, NAC (when taken alone in a large dose) is associated with a greatly shortened lifespan in some lab animals.

From the study:

Although NAC lengthens lifespan robustly at the lower concentrations, it severely shortens lifespan at the highest concentration. See study: Antioxidants reveal an inverted U‐shaped dose‐response relationship

So what to do?

  • There’s no one-size fits all answer. As with other data, the information around NAC supplementation is sometimes contradictory.
  • Animal studies have obvious limitations. But human studies can’t directly measure the effects of supplements on our lifespans. (It would take longer than a human lifespan to do so.)
  • At this point the evidence appears to suggest that NAC can have a potent life-extending effect in mammals as long as it’s accompanied by glycine.
  • I take glycine along with NAC because when they’re take in equal amounts, they have been shown to combine in the body to synthesize glutathione, a powerful life-extending molecule.
  • I used to take NAC alone at night because it clears up my breathing. But I may actually have been shortening my life.
  • I plan to keep taking them in combination, but I’ve stopped taking NAC alone.

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