Glutathione for Cats

References

Numbered references identify the sources used for specific claims. Read the study design, species and evidence boundaries alongside each finding.

1. [1]
   Reactome. GPXs reduce H2O2 to water. n.d.Species/context: Curated human reaction recordsEvidence boundary: This curated human reaction describes glutathione peroxidase using reduced glutathione to turn hydrogen peroxide into water. It explains a normal biochemical reaction, rather than a feeding or supplement result in cats.↩ 1 · ↩ 2 · ↩ 3 · ↩ 4
2. [2]
   Avika Ruparell et al. Glycine supplementation can partially restore oxidative stress-associated glutathione deficiency in ageing cats. 2024Species/context: Healthy colony cats; three separate study phasesEvidence boundary: An age comparison and complete-diet experiments examined feline glutathione. In the main feeding trial, 34 of 44 cats were analyzed after intake/weight-loss withdrawals; the glycine-group red-cell glutathione difference appeared at week 4 but not weeks 8 or 12. This was dietary glycine, not oral glutathione. Mars Petcare funded the work; most authors were employees, and the data contributed to a patent application.↩ 1 · ↩ 2 · ↩ 3 · ↩ 4 · ↩ 5 · ↩ 6 · ↩ 7 · ↩ 8
3. [3]
   Reactome. Glutathione synthesis and recycling. n.d.Species/context: Curated human biochemical pathway; conserved chemistry, not a feline trialEvidence boundary: The pathway describes joining glutamate, cysteine and glycine in two ATP-dependent synthesis steps, alongside glutathione recycling. These curated human biochemical pathways provide background, not a measured feline product response.↩ 1 · ↩ 2 · ↩ 3 · ↩ 4 · ↩ 5 · ↩ 6
4. [4]
   Cornell Feline Health Center. Feeding Your Cat. 2026Species/context: CatsEvidence boundary: Cornell describes complete feline nutrition, protein and amino-acid needs, life-stage feeding and the importance of balancing the whole diet.↩ 1 · ↩ 2 · ↩ 3 · ↩ 4 · ↩ 5
5. [5]
   La Petite Labs. Hollywood Elixir: Supplement Facts and Cat Directions. n.d.Species/context: Commercial product labeled for adult/senior dogs and catsEvidence boundary: The standard 2.5 g sachet lists 50 mg glutathione. Lite is half a sachet daily for under 7 lb or sensitive pets; Standard is one sachet for 7–30 lb. The directions specify mixing into usual food, serving immediately and daily use, with veterinary direction for kittens, pregnancy and nursing.↩ 1 · ↩ 2 · ↩ 3 · ↩ 4 · ↩ 5 · ↩ 6 · ↩ 7 · ↩ 8 · ↩ 9 · ↩ 10
6. [6]
   La Petite Labs. Hollywood Elixir Ingredients. n.d.Species/context: Product ingredient identityEvidence boundary: The ingredient guide identifies reduced L-glutathione, whey protein isolate and NR tartrate. The glutathione is not described as liposomal; the guide’s form declarations are separate from research on absorption or clinical outcomes.↩ 1 · ↩ 2 · ↩ 3 · ↩ 4
7. [7]
   Reactome. GSR reduces GSSG to GSH. n.d.Species/context: Human-curated reaction and human nutrition authority; basic biochemical bridgeEvidence boundary: This curated human reaction describes glutathione reductase using NADPH to restore reduced glutathione. It is the recycling step, distinct from the peroxide reaction and from making new glutathione.↩ 1 · ↩ 2 · ↩ 3
8. [8]
   M J Fettman et al. Effects of dietary cysteine on blood sulfur amino acid, glutathione, and malondialdehyde concentrations in cats. 1999Species/context: 12 healthy adult catsEvidence boundary: Twelve healthy cats ate diets with different cysteine concentrations. Blood glutathione increased with higher dietary cysteine, while the highest level also changed oxidized glutathione and other sulfur-related measures. The available abstract reports a food-composition experiment, not an oral glutathione dose trial.↩ 1 · ↩ 2
9. [9]
   Reactome. Glutathione conjugation. n.d.Species/context: Curated human reaction recordsEvidence boundary: Glutathione-S-transferases attach glutathione to particular compounds as part of their processing. Some conjugation reactions can activate compounds, so this pathway does not imply universal toxin neutralization.↩
10. [10]
    Sharon A Center et al. Liver glutathione concentrations in dogs and cats with naturally occurring liver disease. 2002Species/context: 20 cats and63 dogs with liver disease;15 healthy cats and12 healthy dogsEvidence boundary: The observational study found lower liver-tissue glutathione in cats with certain liver diseases, with results varying by disease and measurement basis. The indexed original abstract describes tissue measurements, not an oral treatment outcome.↩
11. [11]
    Sharon A. Center. Feline Hepatic Lipidosis. 2025Species/context: Cats with hepatic lipidosis; healthy-cat study context distinguishedEvidence boundary: Merck’s veterinary chapter explains the importance of nutritional support and discusses the different roles of NAC and SAMe. It distinguishes healthy-cat SAMe findings from an unstudied clinical response in hepatic lipidosis.↩ 1 · ↩ 2 · ↩ 3 · ↩ 4 · ↩ 5 · ↩ 6
12. [12]
    R F Keegan, C B Webb. Oxidative stress and neutrophil function in cats with chronic renal failure. 2010Species/context: 20 cats with chronic renal failure and10 age-matched controlsEvidence boundary: The original abstract reports lower overall antioxidant capacity but a higher reduced-to-oxidized glutathione ratio in this kidney-disease group. The authors considered a compensatory response; the study did not test an oral glutathione supplement.↩ 1 · ↩ 2
13. [13]
    K Piyarungsri, R Pusoonthornthum. Changes in reduced glutathione, oxidized glutathione, and glutathione peroxidase in cats with naturally occurring chronic kidney disease. 2016Species/context: 23 cats with naturally occurring CKD and13 age-matched healthy catsEvidence boundary: This separate feline CKD cohort had lower reduced glutathione and a lower reduced-to-oxidized ratio. The publisher abstract reports findings in a separate cohort; the available information does not establish why its results differ from the other kidney study.↩ 1 · ↩ 2
14. [14]
    Sharon A. Center et al. The effects of S-adenosylmethionine on clinical pathology and redox potential in the red blood cell, liver, and bile of clinically normal cats. 2005Species/context: 15 clinically normal catsEvidence boundary: A particular oral SAMe preparation increased liver glutathione and its reduced-to-oxidized ratio in healthy cats. It does not establish oral glutathione absorption or a treatment response in cats with liver disease.↩
15. [15]
    Allen and Bradley. Effects of oral glutathione supplementation on systemic oxidative stress biomarkers in human volunteers. 2011Species/context: 40 healthy adults enrolled,39 completedEvidence boundary: This four-week controlled human trial found no significant changes in the red-cell glutathione and oxidative-damage measures tested. Its result does not settle every preparation or duration, and human doses are not cat directions.↩ 1 · ↩ 2 · ↩ 3
16. [16]
    Richie et al. Randomized controlled trial of oral glutathione supplementation on body stores of glutathione. 2015Species/context: 54 healthy nonsmoking adultsEvidence boundary: A six-month trial in people reported increased glutathione in several blood and cell compartments. The original abstract supports a human oral response, not feline tissue delivery or a cat dose. Kyowa Hakko funded the work.↩ 1 · ↩ 2 · ↩ 3
17. [17]
    Sinha et al. Oral supplementation with liposomal glutathione elevates body stores of glutathione and markers of immune function. 2018Species/context: 12 healthy adults aged51–72;11 womenEvidence boundary: Twelve people received liposomal glutathione in a short pilot without a placebo or ordinary-glutathione comparison. It cannot establish liposomal superiority or a feline clinical benefit. Funding included Researched Nutritionals and NIH support.↩ 1 · ↩ 2 · ↩ 3
18. [18]
    ASPCA Animal Poison Control Center. Which Supplements and Vitamins Are Dangerous for Pets? 2021Species/context: Pets; species-specific toxicities varyEvidence boundary: ASPCA poison-control guidance explains why the whole supplement matters and recommends prompt veterinary or poison-service advice after suspected exposure. It does not provide a glutathione-specific cat toxicity threshold.↩ 1 · ↩ 2 · ↩ 3 · ↩ 4
19. [19]
    VCA Animal Hospitals Urgent Care. Diarrhea or Vomiting. n.d.Species/context: Pets, including cats; general clinical guidanceEvidence boundary: VCA describes several possible causes of gastrointestinal signs and recommends veterinary assessment for repeated vomiting or diarrhea and appetite loss. This is general pet guidance, not evidence that glutathione caused those signs.↩
20. [20]
    NIH Office of Dietary Supplements. Niacin — Health Professional Fact Sheet. n.d.Species/context: Human-curated reaction and human nutrition authority; basic biochemical bridgeEvidence boundary: NIH describes the relationship of niacin-family compounds to NAD and the related NADP coenzyme’s role in antioxidant function. This human nutrition background explains a biochemical connection; its intake and treatment amounts are not cat doses.↩
21. [21]
    Cornell Feline Health Center. Anorexia. n.d.Species/context: CatsEvidence boundary: Cornell explains that appetite loss can have many causes and warrants prompt veterinary attention. Forcing an unwanted food can worsen food aversion.↩