Do Antioxidant Supplements Promote Cancer? | Isaac Harris | Episode 296

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New research finds that excess antioxidants can support tumor growth in preexisting cancers.

TOPICS DISCUSSED:

• Oxidative Stress: Reactive oxygen species (ROS) generated by mitochondrial metabolism cause damage; context determines whether they promote or suppress cancer.
• Glutathione Biology: Primary cellular antioxidant made from cysteine, glycine, and glutamate; works with peroxidase enzymes to protect against ROS.
• Antioxidant Paradox: Clinical trials (SELECT vitamin E, beta-carotene) showed supplements increased cancer rather than preventing it.
• Cancer Antioxidant Hijacking: Tumors ramp up antioxidant systems to handle high metabolic rates and survive stress including metastasis.
• Extracellular Glutathione Catabolism: Cancer cells break down external glutathione into amino acids, particularly cysteine, to fuel growth (new findings).
• Therapeutic Window: Blocking glutathione breakdown slows tumors in models while sparing normal cells.
• Diet vs Supplements: Balanced diets support glutathione needs; excess isolated antioxidants may enrich the tumor microenvironment.

ABOUT THE GUEST: Isaac Harris, PhD is a biologist working on the role of antioxidants in health, disease, and cancer metabolism.

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