How much glutathione can we eat without harmful?

Question: If I eat a lot of Glutathione, it would be harmful or not?

Answer: Glutathione is commercially available in various doses, generally one capsule may have 450 to 600 mg of glutathione.

Oral dose of glutathione is 1-2 capsules or equal to 450-1200 mg per day.

Searching for information found that no studies about the safety of eating glutathione clearly. But found that eating glutathione 500 to 1,000 mg daily for 6 months is not reported serious side effects.

Common side effects such as dizziness, back pain, hot flushes, liquid stool, eye twitching, ear infections, urinary tract infections, constipation, flatulence, and increasing body weight.

And there is no any study using oral glutathione more than 1,000 mg per day.

References:

1. Allen J, Bradley RD. Effects of oral glutathione supplementation on systemic oxidative stress biomarkers in human volunteers. J Altern Complement Med 2011; 17 (9): 827-33.

2. Arjinpathana N, Asawanonda P. Glutathione as an oral whitening agent: A randomized, double-blind, placebo-controlled study. J Dermatolog Treat 2012; 23 (2): 97-102.

3. John P, Richie JR, Nichenametla S, Neidig W, Calcagnotto A, Haley JS, et al. Randomized controlled trial of oral glutathione supplementation on body stores of glutathione. Eur J Nutr 2014; [Epub ahead of print].