Both methods your body has to build its own.
The cells can’t take in glutathione whole. So both ways the body has to build it
A shot only has a few minute half life in the body and we don’t know if it down regulates our bodies natural production over time
The shots and precursors still have different effects.
- NAC and glycine are precursors, so they give your body the building blocks to make GSH later.
- Injected glutathione gives you GSH directly first, so it can enter the glutathione redox cycle immediately: GSH neutralizes oxidants, becomes GSSG, and then gets recycled back into GSH.
- GSH = reduced glutathione, the active antioxidant form.
- GSSG = oxidized glutathione, the “used” form after GSH has done antioxidant work.
That
immediate redox-cycle activity is the key difference, and that is what people, including myself, are likely feeling from shots. With NAC/glycine, your body still has to build GSH first, so the effect is more
gradual.
I agree that injectable glutathione has a short half-life and that cells may not simply absorb it whole, but short half-life does not mean no effect. It just means the direct redox window is brief. Downstream effects from the pulse can still matter, as with HGH.
Also, oral precursors like NAC/glycine are not absorbed whole or converted into intracellular glutathione immediately either.
As for down-regulating natural production over time, I have seen people raise that concern, similar to how they talk about suppression with other exogenous compounds, including HGH, but I have not seen concrete evidence proving this to be true with glutathione.
Also, glutathione is often cycled rather than run continuously, which would theoretically reduce any concern around long-term suppression.