Does glutathione (GSH) supplementation cause cancer?

Does Glutathione Supplementation Cause Cancer?

No, current clinical evidence does not indicate that glutathione supplementation causes cancer, but there is insufficient evidence to recommend its routine use for cancer prevention or treatment. 1

Understanding Glutathione

Glutathione (GSH) is a naturally occurring tripeptide found in most cells of the body and serves several vital functions:

• Acts as an antioxidant
• Maintains cellular redox homeostasis
• Modulates immune response
• Detoxifies carcinogens and xenobiotics

Glutathione's Dual Role in Cancer

Glutathione plays a complex role in relation to cancer:

Protective Functions

• Crucial for detoxification of carcinogens 2
• Helps maintain cellular redox balance
• Present in many healthy foods, particularly fruits and vegetables 3, 4

Potential Concerns

• Elevated glutathione levels in existing tumor cells may confer resistance to chemotherapeutic drugs in various cancers (bone marrow, breast, colon, larynx, and lung) 2
• Excess glutathione may promote tumor progression and increased metastasis in established cancers 5

Clinical Evidence and Guidelines

The most recent clinical nutrition guidelines (2025) explicitly state that:

• There are insufficient consistent clinical data to recommend glutathione supplementation during conventional cytotoxic or targeted cancer therapy 1
• Long-term safety data for glutathione supplementation is lacking 1
• Intravenous glutathione administration has inadequate safety data, particularly for chronic use 1

A 2024 study investigating glutathione levels in bladder cancer patients found that:

• Healthy controls had higher reduced glutathione levels compared to cancer patients
• However, glutathione levels did not appear to affect cancer prognosis once the disease was established 6

Recommendations for Glutathione Intake

Based on current guidelines:

1. Dietary Sources: Obtaining glutathione and its precursors through food is the recommended approach rather than supplementation 1

   • Foods rich in GSH precursors include those high in sulfur-containing amino acids
   • Fruits and vegetables, particularly those consumed raw, are good dietary sources 3, 4

2. Supplementation:

   • Not recommended for the general population due to insufficient evidence 1
   • May be considered in specific cases of documented deficiency, but should be discussed with healthcare providers

3. During Cancer Treatment:

   • The American Cancer Society advises caution with high-dose supplements during cancer treatment 7
   • Open dialogue between patients and healthcare providers is essential regarding dietary supplementation to ensure no contraindication with prescribed cancer therapy 7

Important Considerations

• Glutathione metabolism plays both beneficial and pathogenic roles in various malignancies 5
• The effect of glutathione appears to differ between cancer prevention and cancer treatment scenarios
• Experimental therapies like IV glutathione should be reserved for clinical trials or when conventional approaches have failed 1

For individuals concerned about cancer prevention, focusing on a diet rich in fruits and vegetables that naturally contain glutathione and its precursors is a more evidence-based approach than supplementation.