Does oxidative stress increase antioxidant demand and potentially deplete supporting nutrients?

Oxidative stress is best understood as a redox burden that increases use of endogenous defenses, particularly the glutathione system. The biochemical basis is strong; whether it causes measurable depletion of nutrient stores in humans is less certain.

Antioxidant-defense demand

• Glutathione peroxidase detoxifies peroxides by converting reduced glutathione (GSH) to oxidized glutathione (GSSG), shifting the redox pool toward GSSG and lowering the GSH/GSSG ratio.
• Regeneration of GSH requires glutathione reductase, NADPH, and riboflavin-derived FAD. Cysteine availability constrains new GSH synthesis. Consequently, persistent peroxide exposure can outstrip recycling and synthesis, reducing the functional reduced-GSH pool.
• Cells may compensate through Nrf2-regulated induction of glutathione synthesis and antioxidant enzymes. Human observations are compatible with this: in diabetes/diabetic-foot-ulcer groups, higher oxidative-damage markers accompanied lower SOD but higher glutathione-peroxidase activity; acute exercise modestly increased erythrocyte glutathione-peroxidase activity. Responses differ by tissue, duration, and disease state.

Nutrient-related implications

• Oxidative stress can plausibly increase utilization and functional demand for substrates supporting antioxidant defenses, but this differs from proving depletion of whole-body nutrient status.
• Selenium is relevant because glutathione peroxidase activity depends on selenium status. In 343 healthy Brazilian adults, erythrocyte selenium was positively associated with glutathione-peroxidase activity. Cross-sectional Spanish data also linked higher selenium with lower GSSG/GSH ratio and malondialdehyde, though selenium above approximately 110 μg/L was associated with higher urinary 8-oxo-dG.
• These associations do not establish that oxidative stress depletes selenium, cysteine, riboflavin/FAD, or niacin/NADPH stores; diet, illness, inflammation, and distribution may contribute.

Bottom line

• Oxidative stress reliably increases demand on antioxidant systems and can lower functional GSH availability. Actual depletion of antioxidant-related nutrient stores in humans remains biologically plausible but not consistently demonstrated.