Everything You Need to Know About Antioxidants: Oxidative Stress and Sources

ANTIOXIDANTS: 60 capsules

A formula combining

9 synergistic active ingredients : glutathione, N-acetylcysteine, alpha-lipoic acid, coenzyme Q10, vitamins C and E, zinc, manganese, selenium. 5 nutrients have an official EFSA health claim for cell protection against oxidative stress. An approach scientifically consistent with current recommendations: moderate doses, complete composition, no beta-carotene. See our ANTIOXIDANTS formula →

IN BRIEF

What is an antioxidant?

A precise biochemical definition

From a chemical perspective, an antioxidant is a substance that, at low concentrations compared to those of an oxidizable substrate, can delay or prevent oxidation of that substrate. This is the classical definition proposed by Halliwell and Gutteridge, world authorities in oxidative biochemistry.

In practice, antioxidants work through several complementary mechanisms:

• Direct electron donors : they provide an electron to the free radical to neutralize its unstable charge (vitamin C, vitamin E, glutathione)
• Enzymatic cofactors : they allow antioxidant enzymes to function (zinc, manganese, selenium for superoxide dismutase, glutathione peroxidase, catalase)
• Metal chelators : they trap metal ions (iron, copper) that catalyze free radical formation
• Intracellular reducers : they maintain the redox status of cells (glutathione, alpha-lipoic acid)

Endogenous and exogenous antioxidants

Two major categories of antioxidants are distinguished based on their origin:

• <<<27>>> Endogenous antioxidants antioxydants endogènes are produced by the body. The most important are glutathione, superoxide dismutase (SOD), catalase, glutathione peroxidase and coenzyme Q10. They constitute our first line of defense, but their production decreases with age.
• <<<40>>> Exogenous antioxidants antioxydants exogènes come from food. They include vitamins C and E, carotenoids, plant polyphenols , and trace elements that activate antioxidant enzymes (selenium, zinc, manganese).

Oxidative stress and free radicals: mechanisms

What is a free radical?

A free radical is a chemical species possessing at least one unpaired electron on its outer shell. This configuration makes it extremely reactive: it seeks to "steal" an electron from a neighboring molecule to regain stability. This reaction often triggers a chain cascade, where the attacked molecule becomes in turn a radical and continues the process.

The free radicals most studied in biology are reactive oxygen species (ROS) : superoxide anion (O₂•⁻), hydrogen peroxide (H₂O₂), hydroxyl radical (OH•), as well as reactive nitrogen species (NO•, ONOO⁻).

Where are free radicals formed?

ROS production is physiological and continuous. According to the review by Pizzino et al. 2017 published in Oxidative Medicine and Cellular Longevity, they are primarily generated in:

• <<<34>>> mitochondria mitochondries (inevitable byproducts of cellular respiration and ATP production)
• <<<37>>> immune cells cellules immunitaires (which use ROS as a weapon against pathogens)
• <<<40>>> enzymes enzymes such as NADPH oxidases and cytochrome P450
• Theauto-oxidation of certain molecules (catecholamines, hemoglobin)

This normal production is amplified by external factors : UV exposure, air pollution, active and passive smoking, excessive alcohol consumption, chronic stress, heavy metals, certain medications, and certain physiological situations such as intense exercise or aging.

The important nuance: hormesis

Here is an essential point rarely addressed by marketing content. Oxidative stress is not inherently harmful. At moderate doses, ROS play essential physiological roles:

• Cell signaling : ROS are chemical messengers involved in regulating cell proliferation, apoptosis, and differentiation
• Immune defense : neutrophils and macrophages produce ROS to kill bacteria and viruses
• Exercise adaptation : moderate oxidative stress induced by sport stimulates endogenous antioxidant defenses and improves mitochondrial efficiency (hormesis)

It is only when ROS production durably exceeds the body's antioxidant capacity that we speak of deleterious chronic oxidative stress. This nuance, highlighted by the Pizzino 2017 review, is crucial to understanding why massive antioxidant supplementation is not always beneficial, and can even be counterproductive in certain contexts.

Proven benefits: the 5 EFSA health claims

Why EFSA claims matter

The European system is one of the strictest in the world. For a claim to be authorized under Regulation (EC) No 1924/2006, it must be based on generally accepted scientific evidence evaluated by EFSA experts. Many popular claims (anti-aging, detox, anti-cancer) are prohibited on dietary supplements because they do not meet these standards.

When a serious brand presents an antioxidant supplement, it must necessarily rely on these 5 validated claims for cellular protection:

Related antioxidant EFSA claims

Beyond the claim "protection of cells against oxidative stress," some of these nutrients have additional claims relevant to our topic:

• Vitamin C : "contributes to normal collagen formation to ensure normal skin function," "contributes to normal energy metabolism," "contributes to normal functioning of the immune system"
• Vitamin E : non-specific beyond oxidative stress
• Zinc : "contributes to the maintenance of normal skin," "contributes to the maintenance of normal bone structure," "contributes to normal DNA synthesis"
• Selenium : "contributes to normal thyroid function," "contributes to the maintenance of normal hair and nails"

These claims allow for the legal promotion of the benefits of a combined formula on skin, energy, immunity and overall wellness, in strict compliance with European regulations.

Major families of antioxidants

Family 1: Antioxidant Vitamins

<<<14>>> Vitamin C vitamine C (ascorbic acid) is the water-soluble antioxidant par excellence, present in blood plasma and intracellular fluids. It acts as a first-line defense in aqueous compartments and also regenerates oxidized vitamin E.

<<<17>>> Vitamin E vitamine E (tocopherols) is the major fat-soluble antioxidant, integrated into cell membranes where it protects polyunsaturated fatty acids against lipid peroxidation. Tocopherols (alpha, beta, gamma, delta) have complementary activities.

Family 2: Trace Mineral Cofactors

These minerals do not have direct antioxidant action, but they are essential cofactors of antioxidant enzymes :

• Selenium : cofactor of glutathione peroxidase and thioredoxin reductases
• Zinc : cofactor of cytoplasmic superoxide dismutase (Cu/Zn-SOD)
• Manganese : cofactor of mitochondrial superoxide dismutase (Mn-SOD)
• Copper : cofactor of Cu/Zn-SOD and ceruloplasmin

This is why a deficiency in these trace minerals can compromise endogenous antioxidant defenses, even in someone consuming plenty of fruits and vegetables.

Family 3: Plant Polyphenols

<<<33>>> Polyphenols polyphénols constitute the largest family of natural antioxidants with more than 8,000 molecules identified in the plant kingdom. They include:

• Flavonoids : quercetin (onion, apple, berries), catechins (green tea, cocoa), anthocyanins (red and blue berries, grapes), isoflavones (soy)
• Phenolic acids : chlorogenic acid (coffee), caffeic acid, ferulic acid
• Stilbenes : resveratrol (grapes, red wine, berries)
• Lignans : flax seeds, sesame
• Tannins : teas, pomegranate, red wine

Family 4: Carotenoids

Fat-soluble plant pigments that give their color to orange, yellow, and red fruits and vegetables:

• Beta-carotene (precursor of vitamin A): carrot, sweet potato, pumpkin
• Lycopene : cooked tomato, watermelon, pink grapefruit
• Lutein and zeaxanthin : spinach, kale, corn (important for eye health)
• Astaxanthin : salmon, shrimp, microalgae (Haematococcus pluvialis)

Important precaution : this is the family where beta-carotene is found, which was particularly flagged by the Bjelakovic 2012 meta-analysis in high-dose mono-supplementation in smokers. Dietary intake of beta-carotene (carrots, sweet potatoes) remains without any concern.

Family 5: Endogenous antioxidants and their precursors

This is the most interesting family from a therapeutic standpoint as it includes the major intracellular antioxidants :

• Glutathione (GSH) : the most abundant intracellular antioxidant, a tripeptide composed of glutamate, cysteine, and glycine
• N-acetylcysteine (NAC) : precursor of glutathione, supplies the limiting cysteine residue for synthesis
• Alpha-lipoic acid (ALA) : "universal" antioxidant, both water-soluble and fat-soluble, regenerates glutathione, vitamin C, and vitamin E
• Coenzyme Q10 (ubiquinone/ubiquinol) : mitochondrial antioxidant essential to the functioning of the respiratory chain and ATP production

Essential distinction: these antioxidants were NOT included in the Bjelakovic 2012 meta-analysis (which covered beta-carotene, vitamins A, C, E, and selenium). Their safety profile is therefore evaluated on different bases.

Food sources: top foods and ORAC method

The ORAC Index: Interest and Limitations

TheORAC index was developed by the American National Institute on Aging to quantify the antioxidant capacity of a food. It is expressed in µmol Trolox equivalent per 100 g (Trolox = water-soluble analogue of vitamin E used as a standard).

Important limitations to know honestly : ORAC measures an activity in vitro, which does not necessarily reflect biological activity in vivo after digestion, absorption and metabolism. The USDA (United States Department of Agriculture) actually removed its official ORAC database in 2012, considering that this method had become too misleading for consumers. Nevertheless, ORAC remains a roughly informative indicator for comparing foods richest in antioxidant compounds.

Top foods richest in antioxidants

For a detailed and hierarchical ranking of the most powerful natural antioxidants, you can consult our complementary article The 9 most powerful natural antioxidants.

Supplementation: when is it useful?

Who can benefit from antioxidant supplementation?

According to available scientific reviews, several profiles may justify considering supplementation (always as a complement, never as a replacement for a good diet):

• Adults 45 years and older : progressive decline of endogenous antioxidants (glutathione, CoQ10) documented with age
• People exposed to amplified oxidizing factors : chronic urban pollution, intense UV exposure, exposed professionals (laboratory, chemical industry)
• Smokers and recent former smokers : with major caution, avoid high-dose beta-carotene supplements (see CARET and ATBC studies)
• Regular alcohol consumers : documented glutathione depletion
• Intensive athletes : moderate approach, do not overdose around training sessions (possible counterproductive effect on adaptation)
• People wishing to support a global anti-aging approach : cosmetic and wellness approach, in synergy with skincare routine and sun protection
• Restricted dietary patterns : unbalanced diet, severe caloric restrictions, aging with diminished appetite

Who should avoid or seek medical advice?

• Pregnant and breastfeeding women : not recommended without medical advice
• Diabetics : certain active ingredients such as alpha-lipoic acid may modulate blood sugar levels; medical advice required
• People undergoing chemotherapy or radiotherapy : these treatments use oxidation to destroy cancer cells; antioxidants may theoretically interfere; oncological advice is essential
• People taking anticoagulants : possible interactions with certain polyphenols and vitamin E at high doses
• People on chronic medication : always report supplement use to your doctor and pharmacist

The honest scientific nuance: what Bjelakovic 2012 says

Why this study is crucial

Bjelakovic 2012 is not an isolated study: it is a Cochrane meta-analysis, the highest level of evidence in evidence-based medicine. It aggregates results from 78 double-blind randomized trials versus placebo, totaling nearly 300,000 participants followed for an average of 3 years. The methodology is extremely rigorous: only trials with low risk of bias were retained for the main conclusions.

What this study really says, and what it doesn't

Let us clarify this important result point by point:

• The mortality signal primarily concerns high-dose monotherapy, not normal nutritional intakes. The included trials often used doses far exceeding the RDA (for example 400–800 IU/day of vitamin E, or 268–536 mg, versus an RDA of 12 mg).
• Beta-carotene and vitamin E are the most affected, particularly in smokers (CARET and ATBC studies stopped prematurely due to increased lung cancer risk with high-dose beta-carotene in smokers).
• Vitamin C, selenium, and vitamin A at normal doses did NOT show a mortality signal.
• Intracellular antioxidants (glutathione, NAC, coenzyme Q10, alpha-lipoic acid, specific polyphenols) were not included in this meta-analysis. Their safety profile must therefore be evaluated separately.
• Dietary antioxidant intakes (fruits, vegetables, tea, cocoa, spices) are absolutely not affected by this signal: the meta-analysis covers only isolated supplements.

The scientific lesson for 2026

This study does not invalidate antioxidant supplementation as a whole. It invites us to rethink intelligently the strategy:

1. Foodremains the primary source : always prioritize fruits, vegetables, herbs, tea, cocoa before any supplement
2. If supplementing, avoid megadoses of single actives, especially high-dose isolated beta-carotene and vitamin E
3. Prioritize complete formulas at moderate doses, compliant with RDAs, where each active supports the others in a network
4. Include endogenous antioxidants (glutathione, NAC, ALA, CoQ10) which do not present the unfavorable signal
5. Adapt the duration: 1 to 3-month courses rather than unjustified permanent daily intake

This is exactly the logic we adopted in designing our ANTIOXIDANTS formula, as explained in detail below with full transparency.

What criteria for choosing an antioxidant supplement?

7 criteria to check before purchase

Our ANTIOXIDANTS formula: complete transparency

Detailed composition per 2 capsules (daily dose)

Why this formulation is consistent with 2026 scientific data

You will note several key points that align with our scientific transparency approach:

• No beta-carotene in the formula. It was one of the most problematic ingredients in Bjelakovic 2012.
• Vitamin E at moderate dose (10 mg, or 100% NRV), very far removed from the problematic doses used in the trials included in Bjelakovic (which ranged from 268 to 536 mg).
• 5 official EFSA claims respected in the formula (vitamins C/E, zinc, manganese, selenium for cell protection against oxidative stress).
• 4 major intracellular actives (glutathione, NAC, ALA, CoQ10) that are not affected by Bjelakovic's unfavorable signals.
• Combined formula at moderate doses, consistent with the "antioxidant network" logic rather than isolated megadosing.

What we honestly acknowledge (limitations)

• No clinical trial has tested this exact formula, as is the case for virtually all multi-active supplements on the market. Evidence of efficacy is based on individual studies of the active ingredients and on the logic of network synergy.
• The Individual doses of certain active ingredients are lower than those used in certain clinical studies (for example Mortensen 2014 used 300 mg of CoQ10 vs 20 mg here, and Richie 2014 used up to 1 g of glutathione vs 150 mg here).
• Antioxidant supplementation has not demonstrated clear benefit in primary prevention (Bjelakovic 2012). We therefore position this supplement as a supporting aid, not as a medical prevention device.
• No therapeutic claims are made: no cancer prevention, no treatment of disease. Only EFSA-validated claims are asserted.

Diet and lifestyle habits combined

The Mediterranean diet as a nutritional cornerstone

The Mediterranean diet remains the best-documented dietary model for its favorable antioxidant profile. According to numerous observational studies (PREDIMED study, EPIC cohorts), this diet naturally provides:

• Varied polyphenols (olive oil, moderate red wine, aromatic herbs)
• Carotenoids (tomato, bell pepper, carrot)
• Lutein and zeaxanthin (spinach, leafy greens)
• Omega-3 fatty acids (fatty fish, walnuts)
• Prebiotic fiber (legumes, whole grains)
• Selenium (fish, shellfish, Brazil nuts)

The 10 most impactful habits

1. Consume 5 to 10 servings of fruits and vegetables per day, varying the colors (red, orange, yellow, green, purple) to cover a broad spectrum of polyphenols
2. Include berries several times a week (blueberries, raspberries, blackberries, strawberries) for their richness in anthocyanins
3. Cook with herbs and spices (turmeric, ginger, rosemary, thyme, garlic) rather than over-salting
4. Drink green tea or coffee in moderation (without excess, ideally in the morning)
5. Consume 70%+ dark chocolate in moderation (10-20 g/day) for cocoa flavanols
6. Prioritize healthy fats : extra virgin olive oil, avocado, nuts, fatty fish
7. Limit ultra-processed foods high in added sugars, oxidized fats and pro-oxidant additives
8. Practice regular moderate physical activity (30 min/day, walking, cycling, swimming) : science shows that moderate exercise stimulates endogenous antioxidant defenses through hormesis
9. Sleep 7-9 hours per night : sleep is a crucial period for cellular repair and antioxidant regeneration
10. Manage chronic stress : meditation, breathing, nature walks, social connection

Supplement + nutrition synergy

An antioxidant supplement achieves its full potential when part of a good lifestyle regimen. It helps bridge nutritional gaps or support specific periods (seasonal transitions, stress periods, intense UV exposure, intensive exercise), but it never replaces the complex nutritional intake and overall synergy of a balanced life.

Decision table: your profile

FAQ: Your questions about antioxidants