Popular Antioxidant Supplement May Feed Cancer Cells and Promote Tumors

Researchers from the Wilmot Cancer Institute at the University of Rochester have discovered that cancer cells can utilize the antioxidant glutathione as a fuel source, potentially promoting the growth and survival of tumors.

The study, published in the journal Nature on March 18, 2026, indicates that cancer cells possess a specific strategy to break down this antioxidant to acquire nutrients, which are often scarce in the tissues and cells surrounding a tumor.

This finding challenges the traditional understanding of glutathione. While most scientists have previously focused on the antioxidant’s ability to prevent or repair cellular damage, this research highlights its role as a pro-tumor nutrient.

The Role of Glutathione in Tumor Growth

Glutathione is a substance produced naturally by the body, though it is also commonly available as a dietary supplement. The University of Rochester study, conducted by Isaac Harris, PhD, and his team—including Fabio Hecht, PhD, and Marco Zocchi, PhD—found that cancer cells devour glutathione as fuel.

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Specifically, the research suggests that cancer cells utilize the cysteine contained within glutathione to support tumor growth. The study utilized both mice and human tissue to demonstrate these effects.

According to Isaac Harris, PhD, cancer cells and normal cells may rely on different food sources, and the discovery of how cancer cells specifically break down this antioxidant opens new avenues for understanding how tumors acquire nutrients.

The Antioxidant Paradox in Cancer Treatment

The use of antioxidant supplements during cancer treatment has long been a subject of therapeutic controversy. While some patients use them to reduce treatment toxicities, prevent oxidative stress, and improve outcomes, other evidence suggests a risk.

Some research indicates that antioxidants can protect both healthy cells and tumor cells from oxidative damage. This protection can potentially reduce the efficacy of cancer treatments.

The effects of antioxidants on cancer progression can vary depending on the type of cancer and the levels of reactive oxygen species (ROS). For example, antioxidants may accelerate the growth of primary lung tumors by reducing ROS-induced DNA damage and the tumor suppressor p53.

Conversely, doses of antioxidants that lower ROS can have the opposite effect in other cases, such as blocking the growth of certain B-cell lymphomas.

Potential Therapeutic Strategies

The discovery that glutathione acts as a nutrient for cancer cells suggests a new pathway for medical intervention. Researchers believe that restricting the way tumors use this nutrient or depriving them of extracellular glutathione could be a viable treatment strategy.

The University of Rochester team is investigating drugs that can restrict the ability of tumors to use glutathione as fuel.

Study Limitations and Future Research

Despite the findings, experts have noted several areas where further research is required. Lluís Espinosa, Coordinator of the Research Group on Molecular Mechanisms of Cancer and Stem Cells at IMIM-Hospital del Mar, noted that while the study provided a solid demonstration of the importance of extracellular glutathione in murine models of breast tumors, some limitations remain.

• The relative contribution of other amino acid sources, including cysteine, in the tumor interstitial fluid has not yet been defined.
• The exact origin of the glutathione that accumulates in the tumor compartment remains unclear.
• It is not yet known if external factors, such as glutathione-rich diets or the intake of antioxidant supplements, influence the levels of glutathione in the tumor microenvironment.

Future validation of these results in patient samples and correlation with clinical information and dietary habits will be essential to fully understand the impact of glutathione on human cancer progression.