Antioxidants

Antioxidants are molecules that neutralize reactive oxygen species (ROS) and free radicals before they can damage DNA, proteins, lipids, and mitochondrial membranes. Some are synthesized by the body, others must come from food and supplements, and many work in linked networks — one antioxidant regenerating another in a continuous redox cycle. Oxidative stress underlies aging, cardiovascular disease, neurodegeneration, diabetes, cancer initiation, and most chronic illness, which is why antioxidant biochemistry sits at the center of integrative and functional medicine.

Endogenous & Mitochondrial Antioxidants
Vitamin Antioxidants
Mineral Cofactors
Plant Polyphenols & Flavonoids
Herbal Antioxidants
Amino Acid Antioxidants
Mushrooms, Algae & Marine Sources
Antioxidant-Rich Foods
How Antioxidants Work
Connections
Featured Videos

Endogenous & Mitochondrial Antioxidants

These are the molecules the body either synthesizes itself or relies on to keep the mitochondrial electron transport chain leak-free. They form the inner ring of the antioxidant network — the molecules that protect ATP production at its source.

Alpha Lipoic Acid (ALA / R-LA) — the only antioxidant that is both fat- and water-soluble; functions as a cofactor in pyruvate dehydrogenase and α-ketoglutarate dehydrogenase; regenerates vitamin C, vitamin E, glutathione, and CoQ10; the most clinically validated treatment for diabetic peripheral neuropathy
N-Acetylcysteine (NAC) — the rate-limiting precursor for glutathione synthesis; replenishes intracellular cysteine when oxidative demand exceeds supply
NAD+ & NMN — not antioxidants themselves but essential cofactors for sirtuins and DNA-repair enzymes that defend against oxidative aging
Methylene Blue — an alternative electron acceptor that bypasses damaged Complex I/IV in mitochondria, reducing electron leak and ROS production
Glutathione (GSH) — the master endogenous antioxidant; tripeptide of cysteine, glycine, and glutamic acid; rate-limited by cysteine availability (which is why NAC works); declines ~50% with age
Coenzyme Q10 (CoQ10 / Ubiquinol) — mitochondrial electron shuttle between Complexes I/II and Complex III; lipid-phase antioxidant; statins deplete it; 43% mortality reduction in the Q-SYMBIO heart failure trial
PQQ (Pyrroloquinoline Quinone) — the only nutritional antioxidant that drives mitochondrial biogenesis (creates new mitochondria via PGC-1α / TFAM); cycles through ~20,000 redox cycles without breakdown vs vitamin C's ~4; improves cognition, sleep, and inflammation at 20 mg/day

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Vitamin Antioxidants

Several vitamins double as antioxidants. They occupy different physical compartments — water-soluble vitamins work in plasma and cytosol; fat-soluble vitamins protect cell membranes and lipoproteins.

Vitamin C (Ascorbic Acid) — the primary water-phase antioxidant in plasma; donates electrons to neutralize ROS and regenerates oxidized vitamin E at the membrane interface
Vitamin E (Tocopherols & Tocotrienols) — the principal lipid-soluble antioxidant; protects polyunsaturated fatty acids in cell membranes and LDL particles from peroxidation
Vitamin A & Beta-Carotene — carotenoids quench singlet oxygen in the retina, skin, and lung tissue
Vitamin K2 (MK-7) — protects mitochondrial membranes via gamma-carboxylated proteins and quinone redox cycling
Vitamin B2 (Riboflavin) — FAD/FMN cofactor for glutathione reductase, the enzyme that regenerates reduced glutathione
Vitamin B3 (Niacin) — precursor to NAD+ and NADP+, the redox currencies that drive every antioxidant enzyme

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Mineral Cofactors

The body's three major antioxidant enzymes — glutathione peroxidase, superoxide dismutase, and catalase — cannot function without specific mineral cofactors. Deficiency in any of these collapses the enzymatic antioxidant defense even when dietary antioxidants are plentiful.

Selenium — essential for glutathione peroxidase (GPx), the enzyme that detoxifies hydrogen peroxide and lipid peroxides; selenoprotein synthesis
Zinc — cofactor for cytosolic copper-zinc superoxide dismutase (Cu/Zn-SOD); also stabilizes cell membranes against oxidative attack
Copper — second cofactor for Cu/Zn-SOD and for ceruloplasmin (a plasma ferroxidase that prevents iron-driven oxidation)
Manganese — cofactor for mitochondrial Mn-SOD (SOD2), the front-line defense against superoxide leaking from the electron transport chain
Iron — needed for catalase, but excess free iron drives Fenton-reaction ROS production — iron homeostasis is itself an antioxidant strategy
Sulfur — the redox-active atom in glutathione, lipoic acid, taurine, NAC, and the methionine cycle

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Plant Polyphenols & Flavonoids

Polyphenols are the most diverse antioxidant class — over 8,000 identified compounds. They work by direct radical scavenging, by chelating pro-oxidant metals (iron, copper), and increasingly through epigenetic and signaling pathways (Nrf2 activation, NF-κB inhibition).

Quercetin — flavonoid with anti-histamine, mast-cell-stabilizing, and zinc-ionophore properties; abundant in onions, capers, apples
Curcumin (from Turmeric) — potent Nrf2 activator and NF-κB inhibitor; most studied polyphenol for inflammation
Berberine — isoquinoline alkaloid; AMPK activator that improves mitochondrial function and reduces oxidative stress in metabolic disease
Resveratrol (Japanese Knotweed source) — stilbene; sirtuin activator; mimics caloric restriction
Fisetin — flavonol; senolytic compound that clears senescent cells
Spermidine — polyamine that induces autophagy and protects against oxidative protein damage
EGCG (Green Tea Catechins) — among the most potent direct radical scavengers in the plant kingdom
Cocoa Flavanols — epicatechin improves endothelial nitric oxide bioavailability

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Herbal Antioxidants

Many traditional medicinal herbs owe their effects to a combined polyphenol-triterpenoid-saponin profile that delivers antioxidant action plus modulation of stress, immune, and detoxification pathways.

Astragalus — isoflavones (formononetin, calycosin) plus astragalosides; cardioprotective and renal-protective antioxidant
Milk Thistle (Silymarin) — flavonolignan complex that protects hepatocyte membranes and increases intracellular glutathione
Rosemary — carnosic acid and rosmarinic acid; Nrf2 activation and neuroprotection
Ashwagandha — withanolides; adaptogenic antioxidant for stress-related oxidative load
Bacopa Monnieri — bacosides; brain-targeted antioxidant for cognition and memory
Ginkgo Biloba — ginkgolides and flavone glycosides; microcirculation and neuronal antioxidant defense
Schisandra — lignans (schizandrin); liver-targeted antioxidant and adaptogen
Holy Basil (Tulsi) — eugenol and ursolic acid; reduces cortisol-driven oxidative stress

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Amino Acid Antioxidants

Sulfur-containing amino acids and the precursors to glutathione synthesis form the foundation of intracellular redox defense.

Cysteine — the rate-limiting amino acid for glutathione synthesis; supplied therapeutically as NAC
Glycine — second amino acid in the glutathione tripeptide; often deficient in older adults and limits GSH synthesis
Glutamine — supplies the glutamate backbone of glutathione and supports gut-barrier antioxidant defense
Methionine — sulfur donor that feeds the transsulfuration pathway to cysteine and ultimately glutathione
Taurine — the most abundant free amino acid in tissue; scavenges hypochlorite (HOCl) and protects mitochondrial tRNA
Histidine — precursor to carnosine, a dipeptide that quenches reactive carbonyls and singlet oxygen in muscle and brain
Arginine — substrate for nitric oxide; required for balanced redox signaling at the endothelium

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Mushrooms, Algae & Marine Sources

Fungi and aquatic organisms produce unique antioxidant chemistries — ergothioneine, fucoxanthin, astaxanthin, and beta-glucans — that terrestrial plants do not.

Chaga Mushroom — one of the highest ORAC scores ever measured; melanin and betulinic acid content
Reishi Mushroom — triterpenes and beta-glucans; liver and immune antioxidant
Turkey Tail — PSK and PSP polysaccharopeptides; integrative-oncology mainstay
Lion's Mane — hericenones and erinacines; neurotrophic antioxidant for cognition
Spirulina — phycocyanin; potent COX-2 inhibitor and direct radical scavenger
Chlorella — chlorophyll and CGF (chlorella growth factor); heavy-metal binding
Sea Moss — carrageenans and trace minerals; iodine and selenium delivery
Omega-3 Fatty Acids (EPA/DHA) — not antioxidants themselves but reduce inflammatory oxidative damage and pair with vitamin E
Astaxanthin — xanthophyll carotenoid from Haematococcus pluvialis microalgae (also krill and salmon); the only carotenoid that crosses both the blood-brain and blood-retinal barriers, the only one with membrane-spanning geometry, 6,000× more potent than vitamin C at singlet-oxygen quenching, and structurally incapable of becoming a pro-oxidant under physiological conditions

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Antioxidant-Rich Foods

Whole foods deliver antioxidants in their natural matrix — fiber, cofactors, and accompanying phytochemicals that supplements cannot fully replicate.

Blueberries — anthocyanins; among the highest ORAC of any common fruit
Pomegranate — punicalagins and ellagic acid; cardiovascular and prostate protection
Tomatoes — lycopene; lipid-soluble carotenoid concentrated in prostate and skin
Broccoli & cruciferous vegetables — sulforaphane; the most potent natural Nrf2 inducer
Spinach & Kale — lutein and zeaxanthin; macular pigment antioxidants
Beets — betalains; unique antioxidant-anti-inflammatory phytonutrients
Green Tea & Coffee — polyphenols and chlorogenic acids; among the largest dietary sources for most adults
Extra-Virgin Olive Oil — hydroxytyrosol and oleocanthal; Mediterranean-diet antioxidant signature
Dark Chocolate (≥85%) — flavanols and theobromine
Walnuts — ellagitannins, alpha-linolenic acid, and melatonin

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How Antioxidants Work

Reactive oxygen species (ROS) are a normal byproduct of mitochondrial respiration — roughly 0.1–2% of all oxygen consumed leaks from the electron transport chain as superoxide (O&sub2;−). Additional ROS arise from immune-cell respiratory burst, peroxisomal beta-oxidation, ionizing radiation, environmental toxins, and inflammation. At physiological levels ROS serve as signaling molecules; in excess they damage lipids (lipid peroxidation), proteins (carbonyl formation), DNA (8-OHdG adducts), and mitochondrial membranes.

The body's defense operates in three coordinated layers:

Enzymatic defense — superoxide dismutase converts O&sub2;− to H&sub2;O&sub2;; catalase and glutathione peroxidase convert H&sub2;O&sub2; to water. These enzymes require selenium, zinc, copper, manganese, and iron as cofactors.
Small-molecule antioxidants — vitamin C, vitamin E, glutathione, alpha lipoic acid, CoQ10, uric acid, bilirubin, and carotenoids donate electrons to neutralize free radicals directly. They operate in a redox-cycling network — each regenerates the others.
Signaling and induction — the Nrf2/Keap1 pathway senses oxidative stress and upregulates more than 200 cytoprotective genes (glutathione synthesis, NQO1, HO-1, glutathione-S-transferases). Phytochemicals like sulforaphane, curcumin, and rosmarinic acid are powerful Nrf2 activators.

The redox-cycling network means that no single antioxidant works in isolation. Vitamin E quenches a lipid radical and becomes the tocopheryl radical — vitamin C donates an electron to regenerate vitamin E and becomes the ascorbyl radical — glutathione donates an electron to regenerate vitamin C — NADPH regenerates glutathione via glutathione reductase. Alpha lipoic acid uniquely participates in every step of this cycle and is the only antioxidant that can regenerate all of the others, which is why deficiencies anywhere in the network produce systemic oxidative load.

See the Oxidative Stress hub page for the full clinical picture and mechanistic detail.

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Connections

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