Sources: Core Biochemistry
“Glutathione functions primarily inside cells.”
Sources: Cysteine Delivery Methods Enhancing Endogenous Glutathione
1. N-Acetylcysteine (NAC)
NAC is the most widely studied cysteine precursor for glutathione synthesis.
Key Evidence
- Atkuri KR et al., NAC as a cysteine delivery system
- Rushworth GF & Megson IL, 2014—Existing and potential therapeutic uses for N-acetylcysteine
- Kasperczyk S et al., 2013
- Schmitt B et al., 2015
2. Ribose-Cysteine (D-Ribose-L-Cysteine) (RiboCeine)
Ribose-cysteine delivers cysteine intracellularly through metabolic cleavage.
Key Evidence
- Roberts JC et al., 1992
- Roberts JC et al., 1987
- Kader T et al., 2014
- Oz HS et al., 2007
3. Whey protein/cysteine-rich whey
These support whey as a cysteine/cystine donor that can support intracellular glutathione synthesis, though the literature is not as direct as NAC.
Key Evidence
- Bounous G, Gold P.
- Lands LC et al.
- Bounous G.
- Kent KD et al.
4. S-acetyl-L-cysteine/L-cysteine/cystine
No clean set of primary references in the same quality tier as NAC, RibCys, and whey.
Exogenous glutathione delivery methods and their drawbacks
1. Standard oral glutathione
- Witschi A et al.
- Richie JP Jr et al.,
- Schmitt B et al.
The evidence here is mixed but real. There is published evidence that liposomal glutathione can elevate body stores/markers, so it should not be presented as categorically ineffective. A fair drawback is that evidence is still limited, formulation-dependent, and does not equal direct proof of broad intracellular functional equivalence across tissues.
Liposomal glutathione may increase glutathione levels in some circulating cells and experimental models, but evidence is limited and inconsistent.
- Sinha R et al.
- Santacrose et al.
3. IV/injected glutathione
They bypass digestion and can raise circulating glutathione transiently, but they are invasive, require supervision, and are less practical/cost-efficient for routine us.
