Glutathione is often called the “master antioxidant” in health supplement circles. While that sounds like marketing fluff, there’s some truth to it. This small molecule, made from three amino acids (glutamic acid, cysteine, and glycine), sits at the centre of your body’s antioxidant defence system. Every cell in your body produces glutathione, and it does more than most other antioxidants simply because it can regenerate itself and recycle other antioxidants like vitamin C back into their active forms.

What is glutathione and why does it matter?

Your body uses glutathione for a surprisingly wide range of tasks. Beyond neutralising free radicals, it helps detoxify harmful substances, protects DNA from damage, regulates cell growth and death, influences immune function, and even plays a role in how scar tissue forms [1].

When glutathione levels drop, health problems tend to follow. Researchers have linked glutathione imbalances to cancer, cardiovascular disease, diabetes, inflammatory conditions, immune disorders, and neurodegenerative diseases like Parkinson’s and Alzheimer’s [1]. Whether low glutathione causes these conditions or results from them remains an active area of research, but the association is consistent across many studies.

Glutathione exists in two forms: reduced (GSH) and oxidised (GSSG). The reduced form is the active one that does the heavy lifting. When GSH neutralises a free radical, it becomes GSSG. Your body then recycles GSSG back to GSH using an enzyme that depends on selenium. This recycling ability makes glutathione unusual among antioxidants and explains why maintaining adequate levels matters so much.

What are the researched benefits of glutathione?

1. May support immune function

Your immune system requires proper oxidative balance to function well. When this balance tips toward oxidative stress, immune cells lose effectiveness at fighting infections and responding appropriately to threats.

A small study followed 12 healthy adults for 4 weeks while they took liposomal glutathione (a form designed for better absorption). Participants showed increased glutathione levels in both blood and cells, reduced markers of oxidative stress, and improved immune cell function, specifically in lymphocytes and natural killer cells [2].

Another controlled trial looked at 36 postmenopausal women over 4 months. Those taking N-acetylcysteine (NAC), a glutathione precursor, showed increased glutathione levels in white blood cells and improved immune markers [3].

These results are encouraging but preliminary. Both studies had small sample sizes, so we cannot draw firm conclusions yet. The biological rationale makes sense, but larger trials would help confirm whether glutathione supplementation meaningfully improves immunity in practice.

2. May help with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) affects roughly 20-30% of people in Western countries. It develops when fat accumulates in the liver without alcohol being the cause, typically linked to diet, sedentary habits, and metabolic dysfunction. Left unchecked, NAFLD significantly increases the risk of type 2 diabetes and cardiovascular disease.

The liver happens to be a major site of glutathione production and use, so researchers have been curious whether supplementation might help.

One study followed 34 patients with non-alcoholic fatty liver disease for 4 months. Those taking oral glutathione showed improvements in several markers: alanine aminotransferase (ALT, a liver enzyme that rises with liver damage), controlled attenuation parameter (CAP, measuring liver fat), free fatty acids, and ferritin levels [4].

This is a single small study, so treat the results as preliminary. But the mechanism makes sense given glutathione’s role in liver detoxification and the oxidative stress component of fatty liver progression. If you’re dealing with fatty liver, dietary changes and exercise remain the primary interventions, but glutathione supplementation might offer additional support.

3. May reduce atrial fibrillation after heart surgery

Atrial fibrillation, an irregular heart rhythm, commonly develops after cardiac surgery. Depending on the procedure (valve surgery and coronary artery bypass carry higher risks), between 10% and 65% of patients experience it. This complication extends hospital stays and increases stroke and death risk.

A meta-analysis pooled data from 10 randomised controlled trials including 1,026 participants. Patients who received preventive N-acetylcysteine (which boosts glutathione levels) before or during surgery had 44% fewer post-operative atrial fibrillation events and 60% lower all-cause mortality compared to controls [5].

The mortality reduction is particularly striking. Note that this used NAC rather than glutathione directly, but the effect is thought to work through increased cellular glutathione. Hospital length of stay showed no difference between groups, which suggests the benefits relate to acute complications rather than overall recovery speed.

4. May support patients with cystic fibrosis

Cystic fibrosis is a genetic condition causing abnormally thick secretions that block airways and pancreatic ducts. The resulting chronic inflammation and oxidative stress in the lungs makes this condition particularly relevant to glutathione research, since the antioxidant might help reduce ongoing tissue damage.

A Phase II clinical trial followed 70 cystic fibrosis patients for 24 weeks. Those taking oral NAC maintained or slightly improved lung function compared to placebo [6]. While “slightly improved” might sound underwhelming, in cystic fibrosis where lung function typically declines over time, stabilisation counts as meaningful progress.

A separate trial, also 24 weeks with 70 cystic fibrosis patients, found that oral reduced L-glutathione improved growth parameters (weight, height, BMI) and markers of intestinal inflammation [7].

Neither study showed dramatic results, but both suggest glutathione-boosting strategies might offer modest benefits for a difficult-to-treat condition.

5. May reduce exercise-induced muscle soreness

Delayed onset muscle soreness (DOMS) typically appears 6-12 hours after unfamiliar or intense exercise, especially exercises involving eccentric (lengthening) muscle contractions. The stiffness, swelling, and temporary strength loss usually resolve within 5-7 days, but the discomfort can interfere with training schedules and daily activities.

Oxidative stress contributes to muscle damage and inflammation after exercise, which provides the rationale for glutathione research in this area.

A controlled study of 29 men over 14 days found that supplementing with N-acetylcysteine helped reduce muscle soreness after eccentric exercise and partially suppressed pro-inflammatory markers [8].

I should note this is a modest effect, and the practical benefit for recreational exercisers might be minimal. For serious athletes or people doing intense training programmes, the reduction in inflammation might support faster recovery, but don’t expect supplements to eliminate soreness entirely.

Are there side effects of glutathione?

Glutathione appears relatively safe for most adults based on available research. Short-term use at moderate doses hasn’t shown significant adverse effects in clinical trials. However, long-term safety data remains limited.

Side effects that have been reported include:

Flatulence and bloating
Loose stools
Skin flushing

These tend to be mild and dose-dependent.

The NHS recommends caution with antioxidant supplements generally, as high doses may have unintended effects [9]. The Mayo Clinic notes that while glutathione shows promise in research, more studies are needed to establish optimal dosing and long-term safety [10].

Does oral glutathione supplementation actually work?

This is a legitimate question. Glutathione gets broken down in the digestive system, leading some researchers to argue that oral supplements simply become expensive amino acids.

However, a randomised, double-blind, placebo-controlled trial addressed this directly. Researchers followed 54 non-smoking adults for 6 months. Those taking oral glutathione showed increased levels in various tissues, with the increase correlating to both dose and duration of use [11].

So oral supplementation does appear to raise body stores, though whether this translates to meaningful health benefits requires condition-specific research.

Alternatives to oral glutathione include:

N-acetylcysteine (NAC): Provides cysteine, the rate-limiting precursor for glutathione synthesis. Generally better absorbed than glutathione itself.
Liposomal glutathione: Encapsulated in lipid bubbles to protect from digestive breakdown.
Intravenous glutathione: Bypasses digestion entirely, used in some clinical settings.

Safety precautions and contraindications

Pregnancy, breastfeeding, and children: Safety hasn’t been established in these groups. Until research demonstrates otherwise, avoidance is prudent.
Liver or kidney impairment: Since these organs process glutathione, people with compromised function should consult their doctor before supplementing.
Skin photosensitivity: Glutathione inhibits melanin production, which is why some people use it for skin lightening. This same mechanism may increase sensitivity to sunlight and UV damage. If you’re supplementing with glutathione, be more careful about sun exposure.
Asthma or allergic rhinitis: Some evidence suggests glutathione may worsen symptoms in these conditions. Inhaled glutathione in particular has triggered bronchospasm in some asthma patients.
Check product ingredients: Supplements may contain additives, fillers, or preservatives that cause allergic reactions in sensitive individuals. Read labels carefully.

References

Ballatori N, et al. Glutathione dysregulation and the etiology and progression of human diseases. Biol Chem. 2009;390(3):191-214. PubMed
Sinha R, et al. Oral supplementation with liposomal glutathione elevates body stores of glutathione and markers of immune function. Eur J Clin Nutr. 2018;72(1):105-111. PubMed
Arranz L, et al. Effect of oral N-acetylcysteine on glutathione levels in peripheral blood mononuclear cells. Biochem Pharmacol. 2008;76(9):1127-1134. PubMed
Honda Y, et al. Efficacy of glutathione for the treatment of nonalcoholic fatty liver disease: an open-label, single-arm, multicenter, pilot study. BMC Gastroenterol. 2017;17(1):96. PubMed
Gu WJ, et al. N-acetylcysteine reduces mortality and cardiac morbidity in cardiac surgery: A systematic review and meta-analysis. Heart Lung Vessel. 2014;6(1):38-47. PubMed
Tirouvanziam R, et al. High-dose oral N-acetylcysteine, a glutathione prodrug, modulates inflammation in cystic fibrosis. Proc Natl Acad Sci USA. 2006;103(12):4628-4633. PubMed
Calabrese C, et al. Effects of oral glutathione supplementation in cystic fibrosis patients. Pediatr Pulmonol. 2015;50(S41):325. PubMed
Silva LA, et al. N-acetylcysteine supplementation attenuates exercise-induced oxidative damage in skeletal muscle. Cell Biochem Funct. 2008;26(8):931-937. PubMed
NHS. Vitamins and minerals. NHS website
Mayo Clinic. L-glutathione. Mayo Clinic
Richie JP Jr, et al. Randomized controlled trial of oral glutathione supplementation on body stores of glutathione. Eur J Nutr. 2015;54(2):251-263. PubMed