Nutrition basicsAntioxidantsOxidative stressSupplements — honest
An antioxidant is any molecule that neutralises free radicals — unstable, reactive molecules that can damage cells. Your body makes its own antioxidant defences and tops them up from food. This page explains the concept honestly, lists the main dietary and supplemental antioxidants, and ends with the evidence on antioxidant supplements — which is not what the marketing suggests.
First, the big nuance. Free radicals (reactive oxygen species, ROS) are not simply "bad." Your body deliberately makes them for cell signalling, immune defence and adaptation to exercise. The goal is balance, not zero. This is exactly why flooding the body with high-dose antioxidant pills can backfire — covered at the end.
Read first. Doses here describe research and clinical use — they are information, not a prescription. Getting antioxidants from a varied, colourful diet is safe and recommended; high-dose isolated supplements are a different matter and can interact with medication or, in some cases, cause harm (see the supplement section). Always ask a doctor or pharmacist before therapeutic use, in pregnancy, or alongside medicines.
Free radicals & oxidative stress
What actually happens
Free radicals: molecules with an unpaired electron (mostly reactive oxygen species), produced normally when cells make energy, and raised by smoking, pollution, UV light, alcohol and inflammation. They "steal" electrons from DNA, proteins and fats, causing oxidative damage.
Oxidative stress: the state where free-radical production outpaces your antioxidant defences. Over time it is implicated in ageing and in heart disease, cancer and neurodegeneration — though it is usually one factor among many, not the sole cause.
The defence: a layered system — the body's own enzymes (superoxide dismutase, catalase, glutathione peroxidase) plus dietary antioxidants (vitamins C and E, carotenoids, polyphenols). They work as a team, recycling each other — which is why one isolated mega-dose rarely mimics the effect of whole food.
Antioxidant vitamins
Vitamin C (ascorbic acid)
What it does: the main antioxidant in the watery parts of the body and blood; it also regenerates vitamin E back to its active form. Where: citrus, berries, kiwi, peppers, broccoli. Full detail on the Vitamins page.
Vitamin E (tocopherols)
What it does: the main antioxidant protecting cell membranes and blood fats from oxidation. Where: vegetable oils, nuts, seeds, avocado. Full detail on the Vitamins page.
Carotenoids
The red, orange and yellow pigments in plants — fat-soluble antioxidants best absorbed with a little fat and often better from cooked food.
Beta-carotene
What it does: an orange pigment the body converts to vitamin A; antioxidant in plant foods. Where: carrots, sweet potato, pumpkin, dark leafy greens, apricots.
Does it make you tan? Only sort of — and not a real tan. Beta-carotene builds up in the skin and lends a faint golden-orange tint, but that is pigment deposited in the skin, not melanin, so it is not the protective tan you get from sun exposure. As sun protection it is weak: a meta-analysis found a small reduction in sunburn only after 10+ weeks of supplementing — no substitute for sunscreen.13 And the doses that would noticeably colour the skin are the same high doses tied to the smoker cancer risk. (Older "tanning pills" using canthaxanthin are worse — they can deposit crystals in the retina and are not approved for this use.)
Lycopene
What it does: the red carotenoid, a strong singlet-oxygen quencher; observational links to prostate and cardiovascular health. Where: cooked tomato (paste, sauce, ketchup — heat and oil boost absorption), watermelon, pink grapefruit, guava.
Lutein & zeaxanthin
What they do: concentrate in the macula of the eye, filtering blue light and protecting the retina. Where: kale, spinach, other dark greens, egg yolk, sweetcorn.
Astaxanthin
What it does: a red carotenoid from microalgae, a potent antioxidant; gives salmon and shrimp their pink colour. Where: wild salmon, trout, shrimp, and algae-based supplements.
Polyphenols & flavonoids
The largest family of dietary antioxidants — the pigments and bitter compounds in plants. More on the Phytochemicals page. A key modern insight: their benefit may come less from direct radical-scavenging and more from switching on the body's own antioxidant and anti-inflammatory defences (hormesis).
The key dietary polyphenols
Green-tea catechins (EGCG): green tea and matcha — studied for heart and metabolic health.
Anthocyanins: the blue-purple-red of blueberries, blackberries, black rice and red cabbage — among the most studied for vascular and brain health.
Quercetin: onions, apples, capers, tea — a flavonol sold as a supplement (~500–1000 mg) for allergy and exercise, evidence modest.
Resveratrol: red grapes, peanuts, berries — famous but with weak human evidence; supplement doses far exceed anything you get from food.
Curcumin (turmeric): studied for inflammation and joints; poorly absorbed alone (usually paired with piperine/black pepper).
Cocoa flavanols & olive polyphenols: dark chocolate/cocoa (blood-vessel function) and extra-virgin olive oil (hydroxytyrosol/oleocanthal — see ).
Pycnogenol & grape-seed OPCs
What it is: Pycnogenol is a branded extract of French maritime pine bark (Pinus pinaster), standardised to ~65–75% procyanidins (OPCs) — the same class of antioxidant found in grape-seed extract and to which it is closely related.
Where you find the parent compounds: OPCs occur naturally in grapes and grape seeds, cocoa, apples, berries and cinnamon; the extracts concentrate them.
Grape-seed extract (OPCs)
What it is: an extract of grape (Vitis vinifera) seeds, rich in the same proanthocyanidins (OPCs) as Pycnogenol — usually standardised to a high polyphenol content.
Where you find the parent compounds: grapes and grape seeds, and the wider OPC family (pine bark, cocoa, berries).
The body's own & thiol antioxidants
Glutathione (and NAC)
What it does: the body's main internal antioxidant, made from cysteine, glycine and glutamate; it recycles vitamins C and E. Boosting it: oral glutathione is poorly absorbed, so the building block N-acetylcysteine (NAC) is the usual route — see Amino acids. Also supported by protein, sulphur vegetables and selenium.
Alpha-lipoic acid (ALA)
What it does: an unusual antioxidant that works in both water and fat phases and helps regenerate other antioxidants; the body makes small amounts. Where: tiny amounts in red meat, organ meats and spinach; meaningful doses only from supplements.
Coenzyme Q10 (ubiquinol)
What it does: an antioxidant in every cell's mitochondria and part of energy production; levels fall with age and with statin use. Where: meat, oily fish, organ meats, some nuts and oils; the body also makes it.
Antioxidant minerals
Selenium, zinc, copper & manganese
These minerals don't neutralise radicals directly — they are built into the body's antioxidant enzymes. Selenium powers glutathione peroxidase; zinc, copper and manganese are needed for superoxide dismutase (SOD). Full detail on the Minerals page.
Where: selenium in Brazil nuts, fish, eggs; zinc in meat, shellfish, seeds; copper in nuts, cocoa, shellfish; manganese in whole grains, nuts, tea.
Also worth knowing
Melatonin
What it does: best known as the sleep hormone, melatonin is also a direct antioxidant that reaches the mitochondria and helps recycle glutathione. Made by the body; found in tiny amounts in some foods (pistachios, tart cherries). See the Sleep guide for dosing and safety.
Do antioxidant supplements actually work?
This is the part the supplement aisle won't tell you. The short answer: eat the rainbow, skip most of the pills.
The big trials that changed the science:
- ATBC (1994) & CARET (1996): high-dose beta-carotene (± vitamin A/E) increased lung cancer and death in smokers — the opposite of the intended effect.23
- SELECT (2011): vitamin E supplements slightly raised prostate-cancer risk in healthy men; selenium added no benefit.7
- Cochrane meta-analysis: across many trials, antioxidant supplements (beta-carotene, vitamin E, high-dose vitamin A) did not reduce mortality — and may slightly increase it.8
Why food wins. Whole foods deliver antioxidants in modest, balanced amounts alongside fibre and hundreds of co-factors that work as a team. Isolated high doses break that balance — and because your body uses some free radicals, blunting them all can be counter-productive. For example, high-dose vitamin C and E around training can blunt the muscle and endurance adaptations to exercise.9
And "ORAC" scores? The antioxidant-capacity ("ORAC") values once printed on superfood labels were withdrawn by the USDA in 2012 as misleading — a food's test-tube antioxidant score doesn't predict what happens in your body.10
The honest bottom line: a colourful diet — berries, leafy greens, tomatoes, tea, cocoa, extra-virgin olive oil, nuts, oily fish — gives you every antioxidant on this page in the form the evidence actually supports. Targeted supplements have a few specific, evidence-based uses (lutein/zeaxanthin as the safer substitute for beta-carotene in the AMD formulation, CoQ10 in heart failure, ALA in diabetic neuropathy, NAC as a medicine). Broad "antioxidant" pills for general health are not supported — and high-dose beta-carotene and vitamin E can do harm.
References
Doses are general values from research and official bodies; individual needs and cautions vary. Therapeutic doses describe clinical/research use, not prescriptions.
- US NIH Office of Dietary Supplements. Vitamin C, Vitamin E and Selenium — Health Professional Fact Sheets (functions, sources, upper limits, antioxidant evidence). ods.od.nih.gov/factsheets
- The Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study Group. The effect of vitamin E and beta carotene on the incidence of lung cancer in male smokers. N Engl J Med 1994;330:1029–35. nejm.org
- Omenn GS, et al. Effects of a combination of beta carotene and vitamin A on lung cancer (CARET). N Engl J Med 1996;334:1150–5. nejm.org
- The AREDS2 Research Group. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration (AREDS2). JAMA 2013;309(19):2005–15. jamanetwork.com
- Schoonees A, et al. Pycnogenol (extract of French maritime pine bark) for the treatment of chronic disorders. Cochrane Database of Systematic Reviews 2012, CD008294 (evidence insufficient). cochranelibrary.com
- Mortensen SA, et al. The effect of coenzyme Q10 on morbidity and mortality in chronic heart failure (Q-SYMBIO). JACC Heart Fail 2014;2(6):641–9. jacc.org
- Klein EA, et al. Vitamin E and the risk of prostate cancer (SELECT). JAMA 2011;306(14):1549–56. jamanetwork.com
- Bjelakovic G, et al. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database of Systematic Reviews 2012, CD007176. cochranelibrary.com
- Paulsen G, et al. Vitamin C and E supplementation blunts endurance training adaptations in humans. J Physiol 2014;592(8):1887–1901. physoc.onlinelibrary.wiley.com
- US Department of Agriculture, Agricultural Research Service. Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods — withdrawn (2012). ars.usda.gov
- Feringa HHH, et al. The effect of grape seed extract on cardiovascular risk markers: a meta-analysis of randomized controlled trials. J Am Diet Assoc 2011;111(8):1173–81. jandonline.org
- UK Expert Group on Vitamins and Minerals (EVM). Safe Upper Levels for Vitamins and Minerals (2003) — supplemental guidance level for beta-carotene ~7 mg/day; and EU Scientific Committee on Food opinion advising against ≥20 mg/day. cot.food.gov.uk (PDF)
- Köpcke W, Krutmann J. Protection from sunburn with beta-carotene — a meta-analysis. Photochemistry and Photobiology 2008;84(2):284–288. onlinelibrary.wiley.com
This article summarizes nutrition science from official health authorities and peer-reviewed sources for education. It is not a substitute for individual medical advice, and the doses given are not prescriptions — always consult a professional before therapeutic supplement use, in pregnancy, or alongside medication.