Can I take vitamin C and glutathione tablets together, and what doses are safe for a healthy adult?

Can You Take Vitamin C and Glutathione Together?

Yes, you can safely take vitamin C and glutathione tablets together, and this combination may provide additive antioxidant benefits, as these compounds work synergistically in cellular antioxidant defense systems. 1, 2

Biochemical Rationale for Combined Use

Vitamin C and glutathione have deeply interconnected antioxidant functions and are mutually essential to each other. 3

• Vitamin C enhances glutathione recovery after oxidative stress, providing cells with enhanced survival potential even when glutathione is present in 10-fold molar excess 2
• Glutathione influences vitamin C recycling and increases its protective effect against oxidative stress 4
• Endothelial cells accumulate ascorbic acid with participation of glutathione-dependent dehydroascorbic acid reductases, demonstrating their metabolic interdependence 2

Evidence for Combined Supplementation

A 2020 study demonstrated that dietary supplementation combining glutathione precursors with resveratrol precursors significantly increased endogenous levels of vitamins C, E, and A while improving overall redox status. 1

• Both reduced glutathione (GSH) content and other reduced thiol species increased significantly 1
• Oxidized species decreased significantly 1
• The inflammatory marker neopterin was reduced 1

Safe Dosing Recommendations for Healthy Adults

Vitamin C Dosing

For healthy adults, target approximately 200 mg/day of vitamin C, as this achieves near-complete tissue saturation and maximizes potential health benefits. 5, 6

• The recommended dietary allowance (RDA) is 75 mg/day for women and 90 mg/day for men 6
• The tolerable upper intake level (UL) is 2000 mg/day 6
• Doses of 1000 mg/day are safe but unlikely to provide additional benefit beyond 200 mg/day for mortality, morbidity, or quality-of-life outcomes in healthy individuals 6
• Intestinal absorption saturates at higher oral doses, with plasma concentrations plateauing at intakes of 200-400 mg/day 6

China's proposed intake (PI) of 200 mg/day aims to raise plasma vitamin C concentrations to 70 mmol/L, which represents saturation. 5

Glutathione Dosing

While specific dosing guidelines for oral glutathione supplementation in healthy adults are not established in the provided guidelines, research suggests:

• Glutathione precursor supplementation (rather than direct glutathione) was effective in improving redox status over 8 weeks 1
• The study used precursors that support endogenous glutathione synthesis rather than direct supplementation 1

Important Safety Considerations

Vitamin C Precautions

Do not exceed 2000 mg/day to avoid gastrointestinal disturbances, primarily diarrhea due to osmotic effects of unabsorbed vitamin C. 6

• Avoid high-dose vitamin C supplementation in patients with hemochromatosis, G6PD deficiency, active oxalate kidney stones, or severe renal dysfunction 7
• In chronic kidney disease patients on hemodialysis, vitamin C at 0.25 g (250 mg) alone showed a pro-oxidant effect, decreasing reduced glutathione levels 4

General Antioxidant Guidance

Antioxidants as high-dose monotherapy should not be administered without proven deficiency. 5

• Doses exceeding 10 times the dietary reference intake should not be used in clinical settings without proven severe deficiency 5
• For healthy individuals without documented deficiency, there is no clear evidence that dietary supplementation with vitamins or minerals improves outcomes 5

Practical Implementation

Prefer dietary sources over high-dose supplements when possible, as whole foods provide additional beneficial phytochemicals. 6

• An intake of 200 mg/day vitamin C can be obtained from a diet of five or more servings of fresh fruits and vegetables, provided at least one serving is a high vitamin C food 5
• Dietary supplements have comparable bioavailability to food sources 5

If using supplements, consider starting with:

• Vitamin C: 200 mg/day (optimal for tissue saturation) 5, 6
• Glutathione: Use precursor forms (such as N-acetylcysteine or whey protein containing cysteine) rather than direct glutathione supplementation for better absorption 1, 4

Common Pitfalls to Avoid

• Do not assume "more is better" – vitamin C absorption efficiency decreases dramatically above 200 mg/day, and doses above this threshold provide diminishing returns for healthy adults 6
• Avoid isolated high-dose vitamin C in kidney disease – this may paradoxically decrease glutathione levels and worsen oxidative stress 4
• Do not use antioxidant supplementation as monotherapy in high doses without documented deficiency, as this approach lacks evidence for benefit and may cause harm 5
• Recognize that plasma vitamin C levels are difficult to interpret during inflammation (when CRP >10 mg/L), so testing is only recommended for suspected scurvy or chronic low intake 6