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Glutathione

Glutathione is an antioxidant used by every cell and tissue in the body. Although critical for a number of processes, it has limited use as dietary supplement due to rapid breakdown during oral ingestion. Its metabolite, L-cysteine, can increase glutathione in the body but consuming L-cysteine via glutathione is inefficient and costly.

Our evidence-based analysis on glutathione features 121 unique references to scientific papers.

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Summary of Glutathione

Primary information, health benefits, side effects, usage, and other important details

Glutathione (γ-L-Glutamyl-L-cysteinylglycine) is a small amino acid containing molecule (peptide) comprised of one molecule of L-glutamic acid, L-cysteine, and Glycine each. The molecule is found in the food supply and in the human body where it acts as an antioxidant. The 'glutathione system' comprises the enzymes that synthesize glutathione within a cell as well as dedicated enzymes that use glutathione as the means to exert antioxidant effects. Supplementation of glutathione is thought to support this pool of glutathione in a cell and thus maintain the efficacy of the entire glutathione system. Despite the pervasive role of glutathione in cell biology, it currently has a limited role in nutritional supplementation due to the following pharmacokinetic properties:

  • There may be some absorption of glutathione intact from the intestines, but it cannot enter cells intact. It must be metabolized to form L-cystine (two molecules of L-cysteine bound together) before being taken up.

  • Provision of L-cysteine within the cell is all that is needed to increase glutathione synthesis, and N-Acetylcysteine does this efficiently at a lower financial cost than glutathione.

In effect, glutathione is an indirect and expensive way to provide dietary L-cysteine. Dietary protein itself, including L-cysteine rich sources such as Whey Protein, are effective but inefficient ways to increase L-cysteine intake in the diet and N-Acetylcysteine is both more efficient and cheaper than glutathione.

Although oral glutathione supplementation does not efficiently increase intracellular glutathione levels for the above reasons, it can be absorbed intact into the blood stream. Since increased glutathione levels in the blood have been shown to slow the breakdown of nitric oxide, glutathione supplementation may be useful to augment nitric oxide boosters such as L-Citrulline or L-Arginine.

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Human Effect Matrix

Unlocked for Examine members

The Human Effect Matrix summarizes human studies to tell you what effects Glutathione has on your body, how much evidence there is, and how strong these effects are.

Full details are available to Examine members.
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
Notes
grade-c - - See study
grade-c - - See study
grade-c - - See study
grade-c - - See study
grade-c - - See study

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Frequently Asked Questions and Articles on Glutathione

Combining citrulline with glutathione could increase your pump

Things to Note

Is a Form Of

Other Functions:

Do Not Confuse With

N-acetylcysteine (prodrug for L-cysteine to produce glutathione)

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Click here to see all 121 references.