WORK IN PROGRESS - Aiming to be essentially complete in the next month


Glutathione is a tri-peptide, made from the three amino acids cysteine, glutamine and glycine. In the stomach glutathione is rapidly broken down into the three separate amino acids. The key amino, cysteine, is reactive due to its sulfhydryl group, and rapidly reacts with other molecules or form bonds together to create cystine (note the subtle spelling difference).

Food Sources

To support glutathione levels from your diet the two key factors are protein, where you will get the amino acid cystine, and foods which contain Nrf2 activators which increase the synthesis of glutathione. Animal proteins tend to be higher in cysteine.

Two of the most well known foods for Nrf2 activators are cruciferous vegetables (broccoli, brussels sprouts etc) and the spice tumeric, which gets its yellow colouring from the active component curcumin. Concentrated extracts of these two can often been found in glutathione enhancing and detox supplements.

There are many fruits, vegetables, herbs and spices which contain Nrf2 activators in varying levels. In fact the whole anti-oxidant craze with juices, berries etc actually works in the opposite way. These activators can have a pro-oxidant effect which by activating the Nrf2 stress response pathway causes the body to create much more of it’s own antioxidants.

However no matter how good your diet is, your glutathione levels still decline as you age. A number of studies measuring the redox status in blood cells/plasma have shown a rapid decline from the age of 40 in healthy people. Hence the growing interest in glutathione supplementation given it’s critical role in your health.

Oral Reduced GSH

The reduced (active) form of glutathione is cheaply available as a supplement. On hearing how glutathione is the body’s master antioxidant and detoxifier (and the primary determinate of the intra-cellular redox status) a bottle of reduced L-Glutathione seems like a bargain, but however has its limits in increasing cellular glutathione levels.

The benefit of oral glutathione orally has shown mixed results. Witschi et al. showed that patients given 3000 mg of oral GSH led to no significant change in blood GSH or cysteine. However this was a single large dose.

Other studies over longer periods in humans and mice have shown oral reduced glutathione to increase

After 6 mo in the high dose group [1000mg/day], GSH levels were increased 30–35% in RBC [Red blood cells], plasma, and lymphocytes and 260% in buccal [inside of cheek] cells (P<0.05). In most cases, the increases were dose and time dependent and levels returned to baseline after a 1-month washout.
So oral reduced glutathione can’t rapidly increase GSH levels as quickly as other pro-drugs (e.g. one study with showed a 1.8x increase in heart and 2.5x increase in muscle GSH from a single dose of the cysteine pro-drug RiboCeine). However it is a dietary source of cysteine, and appears to supplement any dietary deficits, plus more given the decrease to baseline after ceasing supplementation in the study quoted above.

As discussed in detail in part 2 of this blog post series there are many factors which affect the glutathione levels, and dietary cysteine supply is just on factor.

So what other options are there?

Effective glutathione supplementation can be broken down in the 3 main area’s/methods.

The first two are the pro-drug approach. A pro-drug is a compound which is metabolised into the active drug in the body. This is done by attaching additional molecules to the compound, which are then removed inside the body, releasing the active compound. For glutathione supplementation this is done in two ways,

  1. Glutathione pro-drugs, such as S-Acetyl-Glutathione, and
  2. Cysteine pro-drugs, such as N-Acetyl-Cysteine and Ribose-Cysteine.
The third method is delivery mechanisms for reduced glutathione, such as in a liposomal form or intravenous.

The 2010 article tk published in Molecules, looks at the research of a number of cysteine and GSH pro-drugs in the laboratory. However I will only look closely at the different practical (i.e. commercially available) options to choose from.



ALA and extracellular GSH

Lipoic acid increases de novo synthesis of cellular glutathione by improving cystine utilization. Biofactors. 1997

The effect depends on metabolic reduction of lipoic acid to dihydrolipoic acid. Dihydrolipoic acid is released into the culture medium where it reduces cystine. Cysteine thus formed is readily taken up by the neutral amino acid transport system and utilized for glutathione synthesis. By this mechanism lipoic acid enables cystine to bypass the xc- transport system, which is weakly expressed in lymphocytes and inhibited by glutamate. Thereby lipoic acid enables the key enzyme of glutathione synthesis, gamma-glutamylcysteine synthetase, which is regulated by uptake-limited cysteine supply, to work at optimum conditions.

Intravenous (IV)

To bypass the breakdown of GSH in the digestive tract another method of delivery which has been used for a while is intravenous injection. More common uses are for treatment of conditions such as Parkinson’s, which has a tell tale loss of glutathione in the substantia nigra, and toxicity from heavy metals etc.

IV GSH has also quietly been used in anti-aging regimes where the high cost doesn’t deter those who can afford it, including a number of well-known celebrities (ref).

IV delivers GSH straight into the blood stream, however we still run into another roadblock into raising intra-cellular levels. Most cells are unable to transport extra-cellular GSH inside the cell. (some epithelial cells are a main exception ref ). Glutathione first has to be broken down into the constituent amino acids, which then can be transported into the cell.

Cysteine (Cys) is rapidly converted to Cystine (CySS), with Cys/CySS being the major extra-cellular redox couple. Cystine is the major source of cysteine for the cells, and is transported in by the X-c transporter. However this transporter is weakly expressed in lymphocytes and inhibited by glutamate.

Also Cysteine is readily transported into cells for GSH synthesis by the efficient ASC transport system for neutral amino acids (ref). Cysteine is in much lower concentrations, but another mechanism by which extracellular GSH may increase intracellular GSH levels in cultured cells is by reducing cystine to cysteine, which is then rapidly transported and used as a substrate for intracellular GSH synthesis. (ref)

The other downsides to intravenous glutathione therapy include the costs and inconvenience of regular injections. To maintain increased glutathione levels required injections about every 3 to 4 days.


Lipsomal Glutathione

Another form of glutathione which has become more popular which has the advantages of intravenous delivery is the liposomal form. Liposomes are small bubbles made out of the same material as a cell membrane, phospholipids. Liposomes can be filled with drugs/compounds to enhance their delivery.

Can liposomal glutathione deliver it into the cell?

“Blocking ?-glutamylcysteine synthetase with buthionine sulfoxamine prevented replenishment with liposomal-GSH demonstrating the requirement for catabolism and resynthesis.”

Liposomal-glutathione provides maintenance of intracellular glutathione and neuroprotection in mesencephalic neuronal cells. Neurochem Res. 2010 Oct

“Because they are made of the same type of material as our cell membranes, liposomes penetrate mucosal tissues allowing for rapid release into the blood stream. Nutrients that are not in liposomes have to pass through the stomach to reach the liver where they are metabolized and released into the bloodstream. Some nutrients are destroyed or compromised by stomach acids. Liposomes avoid the digestive system by penetrating the mucosal tissue.” -

Never the less the published studies on liposomal glutathione have shown potential benefits for pulmonary heart neuronal maintenance atherosclerosis

Many liposomal glutathione products can be found on Amazon.

Dave Asprey’s Bulletproof liposomal glutathione which claims to be stronger than other liposomal glutathione due to the innovative and pharmaceutical grade delivery system.



Undenatured Whey

Before moving onto the next section, I’ll quickly cover high quality undenatured whey protein is also used/sold as a glutathione booster. One product in this space is Immunocal. The human clinical showed a 36% increase in lymphocyte glutathione (compared to 276% for a NAC formulation). While not as effective as dedicated glutathione options, quality whey has additional health benefits from the other valuable aminos and compounds it contains.


N-Acetyl-Cysteine (NAC)

The most commonly used form of glutathione supplementation in a clinical setting and by consumers would be the cysteine pro-drug N-Acetyl-Cysteine.

Many published studies have shown benefits of NAC over a wide range of disease conditions.

There are some downsides to NAC which preclude it from being a highly effective means to raise intra-cellular GSH levels. Its use has been limited by several drawbacks, including low membrane penetration and low systemic bioavailability (ref). Studies have shown while NAC is good at preventing liver damage from acetaminophen (e.g. Tylenol, Panadol) it is not so effective in protecting the kidneys (ref).

NAC is rapidly de-acetylated in the blood tk


“Administration of NAC [over 5 days] significantly increased cysteine levels in human plasma and rat bronchoalveolar lavage, but the levels in human neutrophils and rat alveolar macrophages after NAC did not differ from control levels. GSH levels were not altered significantly by NAC.” (ref)

The other downside is that it has its own activity separate to being a GSH precursor and can have pro-oxidant effects.

“Because of a potential prooxidative action indicated by lower reduced glutathione and higher oxidised glutathione plasma levels in healthy subjects at a dose of only 1.2 g NAC (Kleinveld et al., 1992), Kelly (1998) concluded, that the chronic daily supplementation with NAC by healthy individuals, who are not subject to excessive oxidative stress, may be ill advised” (ref)

One study of a 3-week protocol in which mice received high-dose NAC in vivo found the NAC-treated mice developed pulmonary arterial hypertension (PAH) that mimicked the effects of chronic hypoxia due to in vivo conversion of NAC to S-nitroso-N-acetylcysteine (ref). Uowever it’s not unlikely to be a concern with modern moderate dose NAC formulations, as many studies have shown NAC has positive pulmonary effects.

NAC is also used intravenously for ac

There is a large number of studies on PubMed showing many benefits to NAC supplementation. It is widely accepted now that NAC should be taken in a cocktail with other anti-oxidants such as Vitamin C and Alpha-Lipoic Acid to enhance its absorption, utilization and recycling.

Which was refined over a decade of use in a clinical practice by the late Dr Robert Keller, an accomplished doctor and researcher

A daily serve contains 750mg NAC, 500mg Vitamin C and 150mg Alpha-Lipoic acid.

Dr Robert Keller’s NAC formulation was originally launched as MaxGXL in 2007 and can also be found slightly cheaper as the Original Glutathione Formula at the Rob Keller MD website




S-Acetyl-Glutathione (SAG)

SAG is a more recently commercially available glutathione pro-drug which in unique in being able to deliver GSH into the cell. tk?? However the published studies have only been in vitro, so it is not clear if SAG would be deacetylated to normal GSH in the digestive tract and blood stream before it can be absorbed into the cells. If it is de-aceteylated in the digestive tract and blood stream, as NAC is, then it would be similar to taking a liposomal form for GSH.

My last look showed 4 published articles looking at glutathione levels in regards to herpes, fibroblasts, cancer and HIV (If you know of any more please leave a comment)

As noted in one article for people with a reduced ability to synthesise glutathione (e.g. deficiency in glutathione synthetase) then SAG is likely the best option as it can deliver GSH directly into the cell.

There are a handful of S-Acetyl Glutathione products on Amazon

Another interesting option is SynergiaGSH which contains SAG along with 23 other ingredients for a convenient all-in-one anti-aging supplement.

Nrf2 activators

A number of products exist on the market which aim the increase glutathione levels solely via compounds which activate the Nrf2 pathway (eg ProVantage, Nuley).

They are capable of increasing glutathione levels in the short term by increasing the activity of the enzymes which synthesize glutathione. However the supply of cysteine will eventually be the limiting substrate in glutathione synthesis. Glutathione, and the crucial cysteine amino, is lost from the body when it conjugated to toxins and removed by the kidneys.

Furthermore some of the compounds which activate Nrf2 such as tk are metabolised by conjugation with glutathione.


Nrf2 activators have shown promise in conditions such as tk. Pharmaceutical companies spending big to develop their own patentable version, such as tk.

The Nrf2 pathway creates more than just the various glutathione enzymes, and its benefits tk.


Ribose-Cysteine (RibCys, RiboCeine)

One of the oldest studied cysteine pro-drugs is also one of the newest commercially available glutathione enhancers, D-Ribose-L-Cysteine. The first published study on it was in 1982, many years before glutathione had any mainstream recognition. Since then there is a total of 22 published studies on RibCys. RibCys was originally developed by a research team led by Dr Herbert Nagasawa at the Veterans Administration medical research center. The aim was to protect the livers of alcoholic war veterans by effectively and safely delivering cysteine inside the cell for glutathione production.

RiboCeine studies

RibCys is able to be absorbed through the digestive tract and intra-cellularly. Blocking the enzyme for glutathione synthesis inhibits the action of RibCys indicating it works solely by supply cysteine for glutathione synthesis (ref).

Inside the cell RibCys is cleaved by a non-enzymatic hydrolisis reaction, which releases ribose and cysteine.

Ribose is sugar which is used as substrate for synthesis of nucleotides (eg ATP, NAD+), and it is part of the building blocks that form DNA and RNA molecules. Under hypoxic conditions ribose synthesis can be a limiting factor in ATP synthesis.

Like many, if not most, elements and compounds in the body there is a delicate balancing act. Like other sugars ribose can react in a process called ribosylation (as a glucose reaction is glycation). However many studies have shown significantly higher doses of ribose to have beneficial effects (ref)

One acetaminophen (APAP) toxicity study showed “RibCys is nontoxic to CD-1 mice at the doses employed (up to 3g or 11.86 mmol/kg over 3 hours) and thus may be a candidate for use as an alternative antidote for treatment of APAP poisoning. The apparently large dose of RibCys used in these studies is not very different from the large amount of NAC that is routinely employed for treatment of APAP overdose in humans.” (ref)


A property of RibCys (referred to as ‘Release On Demand’) is being able to be absorbed into the cell and utilized as required. On the low stress end of the scale a mouse study showed an increase in glutathione levels 16 hours after a single dose. Other toxicology studies shows it is able to rapidly provide cysteine for glutathione synthesis under stressful conditions such as acetaminophen poisoning.

  • Ability for slow release under low stress conditions as to not adversely affect redox state.

  • Indescriminate anti-oxidant use has shown to be detrimental by interfering with ROS signalling. Transient oxidative stress allows Nrf2 activation which produces the other enzymes which are required for glutathione to perform its detoxification and anti-oxidant functions , autophagy,

Why RibCys?

So what are my reasons for continuing to take RiboCeine over other front runners (liposomal and SAG)

  • More studies (including in vivo) over longer period detailing bio-distribution, efficacy and safety.
  • Doesn’t have a direct effect interfering with ROS signalling/redox, works with normal synthesis pathways and allows maximum Nrf2 activation and transient oxidative stress to induce autophagy and other beneficial stress responses.
  • Provides Ribose as a bonus.
  • Herb Nagasawa credentials are unmatached in the glutathione space, researching glutathione technology for over 25 years, and a world renowned medicinal chemist. If he’s gone to this effort to make RibCys available then that’s a sign.
Cellgevity is available to order online here on the Max International website.


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