You may have heard the term ‘antioxidant’ before. It refers to compounds with antioxidant properties that can help to protect the body from damage caused by oxidative stress.
However, you may not have heard of glutathione. Glutathione is a key antioxidant in the human body due to its crucial role in protecting the body’s cells.
In this guide, we explain what glutathione is, why it’s so important, and what recent science shows about how glutathione levels impact health. We’ll then explain the dietary choices that may help to naturally increase glutathione levels.
Table of contents
What is Glutathione?
Glutathione is an antioxidant that plays a crucial role in protecting the human body from damage caused by free radicals and oxidative stress.
It can exist in two forms within the body:
- Reduced glutathione: This is the natural form of glutathione in the body after it has been produced. However, this form of glutathione can donate one of its spare electrons to free radicals, which then neutralizes the harm they can cause.
- Oxidized glutathione: After donating an electron, the glutathione becomes ‘oxidized glutathione’ and can no longer neutralize free radicals in this form. However, it can be recycled back into reduced glutathione.
Higher relative amounts of oxidized to reduced glutathione can be a sign of high oxidative stress levels, and they are commonly observed in chronic illness and older age.
Glutathione is a Tripeptide
Glutathione is a tripeptide, which means a molecule containing three amino acids bound together. ‘Tri’ simply means three, and a ‘peptide’ is a chain of amino acids (proteins). In the case of glutathione, the three amino acids are cysteine, glutamic acid (or glutamate), and glycine.
While the human body can produce glutathione internally from cysteine, glutamate, and glycine, preformed glutathione is also found in specific foods and supplements.
However, external glutathione intake is thought to have low bioavailability, with one recent study reporting its bioavailability may be less than 1%. For this reason, endogenous (internal) production is generally thought to be the primary contributor to glutathione levels.
The Importance of Sufficient Glutathione Levels
Numerous recent studies have looked at how glutathione levels interact with health and various health outcomes.
- Depression: A 2026 systematic review of thirty studies found no significant differences in glutathione levels between people with depression and healthy controls. However, those with depression exhibited reduced activity of glutathione peroxidase – a key glutathione-based enzyme that protects cells.
- Skin health and aging: A 2026 systematic review noted that glutathione plays a key role in skin and tissue repair, thus helping to slow skin aging.
- Heart failure: A 2025 systematic review found that heart failure patients consistently have lower levels of glutathione. This represented a 25% average lower level.
- Lifespan glutathione levels: A 2023 systematic review demonstrated that glutathione levels in the blood typically fall with advancing age. The authors speculated that lower glutathione and higher oxidative stress levels may contribute to accelerated aging.
- Chronic obstructive pulmonary disease (COPD): A 2020 systematic review demonstrated that COPD patients had significantly lower reduced glutathione levels than healthy control subjects, potentially due to increased oxidation levels.
Nutritionist’s Note
You’ll notice that some of the above studies indicate that low glutathione levels have been observed in numerous chronic disease states.
It is important to note that this does not necessarily mean low glutathione caused the condition, and it may be an indicator of high oxidative stress levels, thus depleting glutathione.
However, it is probably fair to say that increasing glutathione levels may be beneficial in both these regards. For example, if oxidative stress levels are high, higher glutathione levels may better support the body’s antioxidant system.
Naturally Increasing Glutathione Levels
Scientific research has observed that various foods, diets, and lifestyle factors can either positively or negatively influence glutathione levels. In the table below, you can see some of the factors that can influence glutathione levels.
| Linked to Increased Glutathione | Linked to Lower Glutathione |
|---|---|
| Allium vegetables | Chronic alcohol intake |
| Cruciferous vegetables | Chronic paracetamol use |
| Dairy | Smoking |
| DASH diet | |
| Lean proteins | |
| Vitamin C | |
| Whey Protein |
Diet and Lifestyle Factors That May Increase Glutathione
Let’s now look at some of the foods and nutrients that can positively influence glutathione levels.
Allium Vegetables
Allium vegetables, such as garlic, leeks, onions, and shallots, are rich in sulfur compounds, which may help to increase glutathione production.
Sulfur has been shown to increase glutathione levels over two months in human participants.
Cruciferous Vegetables
Cruciferous vegetables, such as broccoli, cabbage, cauliflower, and kale, don’t directly increase glutathione levels. However, they may help your body use its existing reserves more effectively.
This is because they contain sulforaphane, a compound that can increase the activity of enzymes called Glutathione S-Transferases (GST). GST increases the activity and effectiveness of glutathione in the antioxidant system.
Dairy
In an observational study involving 60 healthy older adults, higher dairy consumption was associated with higher brain levels of glutathione. For the purposes of this study, dairy referred to cheese, milk, and yogurt consumption.
DASH Diet
A 2020 systematic review found that following the DASH diet significantly increased glutathione levels.
The DASH diet primarily focuses on the consumption of fruits, vegetables, lean proteins, seafood, nuts, seeds, and legumes.
Proteins
Protein-rich foods are abundant sources of amino acids, including the building blocks for glutathione – cysteine, glutamic acid, and glycine.
A 2024 study investigated the impact of various protein intakes on glutathione levels. The study found that consuming less than 1g protein per kilogram of bodyweight can adversely affect glutathione production. However, consuming more than 1g per kg did not lead to further increases in production.
Vitamin C
A study found that 500 mg of vitamin C per day could increase glutathione levels. However, higher doses (2,000 mg) did not further increase glutathione.
Whey Protein
A randomized controlled trial found that 45 grams of whey protein daily increased glutathione levels by 24% in just two weeks.
Whey protein is a rich source of amino acids, including notable amounts of cysteine, which can be harder to obtain from food.
Factors That May Decrease Glutathione Levels
Some lifestyle factors and medications have been linked to lower levels of glutathione:
- Chronic alcohol use: Research shows that chronic alcohol abuse significantly depletes glutathione levels.
- Paracetamol: A study shows that taking the recommended maximum daily dose of paracetamol for 14 days lowers antioxidant levels, possibly due to a decrease in glutathione levels.
- Smoking: Smoking introduces numerous chemicals and smoke into the body, which can increase oxidative stress. Studies show that total glutathione levels significantly increase in participants after quitting smoking.
Foods High in Glutathione Precursors
A diet high in the amino acid ‘building blocks’ of glutathione may potentially help to increase the body’s natural glutathione production.
For this purpose, the tables below list some of the richest food sources of the glutathione precursors: cysteine, glutamic acid, and glycine.
All data has been sourced from the USDA’s FoodData Central database; you can click the hyperlinked amount to see the raw data. Weights refer to cooked portions of food where applicable.
Cystine-rich Foods
Cystine is a more stable form of cysteine found in food, which breaks down into cysteine within the body.
| Food name | Cystine content per 100g |
|---|---|
| Soy protein isolate | 1.05g |
| Beef liver | 0.53g |
| Oats | 0.46g |
| Cuttlefish | 0.43g |
| Chia seeds | 0.41g |
| Chicken breast | 0.40g |
| Eggs | 0.29g |
| Soybeans | 0.27g |
Note: Whey protein is also very high in cysteine, but the USDA database doesn’t list the individual amino acids for whey.
Glutamate-rich Foods
| Food name | Glutamic acid content per 100g |
|---|---|
| Soy protein isolate | 17.5g |
| Parmesan cheese (hard) | 6.42g |
| Almonds | 6.21g |
| Peanuts | 5.39g |
| Chicken breast | 4.64g |
| Lean beef (95% lean) | 3.94g |
| Atlantic salmon | 3.3g |
| Soybeans | 3.22g |
Glycine-Rich Foods
| Food name | Glycine content per 100g |
|---|---|
| Gelatin powder | 19.0g |
| Pork skins (snack) | 11.9g |
| Soy protein isolate | 3.6g |
| Lean beef (95% lean) | 1.78g |
| Cuttlefish | 2.03g |
| Chicken drumstick (with skin) | 2.13g |
| Pumpkin seeds | 1.84g |
Can Glutathione Supplements Help?
Numerous forms of glutathione supplements are available. However, as previously mentioned, the bioavailability of preformed glutathione is thought to be low.
As a result, there are questions as to how effective glutathione supplementation is.
A 2025 systematic review analyzed the effect of glutathione supplementation on glutathione. Here are the key findings from the study:
- No increase: There were no significant differences in glutathione levels from glutathione supplementation as compared to placebo.
- Areas for future research: While the study did not support supplementation increasing glutathione levels, the authors couldn’t rule out higher dose supplementation over longer durations potentially increasing glutathione levels.
Key Takeaways
Here’s a quick recap of the most important learning points from this article:
- What glutathione does: Glutathione is a key antioxidant that can help to protect the body against oxidative stress.
- How it’s made: Glutathione is produced by the body through the combination of three amino acids: cysteine, glutamic acid, and glycine.
- Potential benefits: Lower levels of glutathione have been linked to several chronic disease states. This may be due to oxidative stress and the evidence can’t clearly tell us if the condition caused the low glutathione or vice-versa. However, maintaining higher levels of glutathione may better support long-term health.
- How to increase glutathione levels: Research supports whole-food-based diets like DASH increasing glutathione, which is high in foods like fish, lean proteins, fruits and vegetables, nuts, seeds, and whole grains. Studies have also supported milk, cheese, yogurt, whey protein, allium vegetables, cruciferous vegetables, vitamin C intake, and maintaining a protein intake of at least 1g per kg.
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