How it fits together · lesson 4 of 11
Redox & detox — handling damage and toxins
Free radicals, the glutathione system, and the liver's two-phase detox — plus why 'eat antioxidants' is half a myth.
7 min read · reviewed October 2026
Making energy with oxygen has a side effect: a steady trickle of free radicals — unstable molecules missing an electron that 'steal' one from whatever's nearby, damaging proteins, fats, and DNA. This is oxidative stress, and it's a normal byproduct of being alive, not a disease.
Your body isn't passive about it. It runs a built-in repair and neutralization system — and that system, not the antioxidants in your smoothie, does most of the heavy lifting.
Your best antioxidants are the ones you MAKE
The big players — glutathione, plus enzymes like superoxide dismutase and catalase — are produced inside your cells, and they're regenerable. Dietary antioxidants (vitamin C, E) help mainly by recycling these and quenching radicals at the edges. The popular 'load up on antioxidants' framing overstates the dietary side and ignores the powerful endogenous one.
The redox & detox machinery
Your master cellular antioxidant — a small molecule that donates electrons to neutralize radicals, then gets recharged. Cofactors to make/recycle it: cysteine (from NAC or dietary sulfur), glycine, glutamate, plus riboflavin and selenium for the recycling enzymes.
Glutathione peroxidase uses selenium to scrub hydrogen peroxide using glutathione's electrons. This is why selenium is essential to the whole antioxidant defense — too little starves these enzymes.
Vitamin E guards cell membranes from fat oxidation; vitamin C regenerates 'used' vitamin E back to active form; glutathione in turn recharges vitamin C. They work as a relay team, not solo.
The liver's first detox pass (cytochrome P450 enzymes) chemically modifies a toxin or drug to expose a handle — but this step often makes a more reactive intermediate that must be cleared fast.
Conjugation: the liver tags that reactive intermediate with a water-soluble group (often using glutathione, sulfur, glycine, or a methyl group from the methylation cycle) so it can be safely excreted in bile or urine. Phase II depends heavily on the same nutrients as the antioxidant system.
Why high-dose antioxidant supplements can backfire
A little oxidative stress is actually a signal your body uses to adapt — for example, it's part of how exercise makes you fitter. Flooding your system with antioxidant pills can blunt that signal. Getting antioxidants from whole foods is reliably good; chasing benefit through megadoses of isolated ones is not.
How it works →
Reactive oxygen species act as redox signaling molecules (hormesis): a transient post-exercise oxidative spike activates pathways like Nrf2 that upregulate your own antioxidant enzymes and mitochondrial biogenesis. High-dose exogenous antioxidants can quench that signal, blunting the adaptive response. The endogenous system is also tightly regulated, so dumping in more substrate doesn't linearly raise protection.
What the studies show →
Large trials of high-dose isolated antioxidants have been disappointing or worse: beta-carotene supplements increased lung-cancer risk in smokers (CARET, ATBC trials), and high-dose vitamin E has shown no cardiovascular benefit and signals of harm in some analyses. Some studies suggest vitamin C/E supplementation can blunt endurance-training adaptations. Meanwhile, antioxidant-rich whole diets are consistently linked to better outcomes — the food matrix and dose, not the isolated molecule, seem to be what matter.
Which best reflects current evidence on antioxidants?
- Megadosing isolated antioxidants reliably extends lifespan
- Oxidative stress is purely harmful and should be eliminated
- Your endogenous system (e.g. glutathione) does most of the work; whole-food antioxidants help, but high-dose isolated supplements can disappoint or harm
- Vitamin C in huge doses is proven to prevent most diseases
Show the answer →
C.Your endogenous system (e.g. glutathione) does most of the work; whole-food antioxidants help, but high-dose isolated supplements can disappoint or harm
The body's own glutathione-and-enzyme system is the main line of defense, and a little oxidative stress is a useful adaptive signal. Whole-food antioxidants support the system; isolated high-dose supplements have repeatedly underperformed and occasionally caused harm (e.g. beta-carotene in smokers). Feed the system; don't try to flood it.
Selenium, sulfur amino acids, riboflavin, and the methylation B-vitamins all feed glutathione and Phase II. See where you stand.