Introduction

• Antioxidants are molecules that neutralise reactive oxygen species (ROS) and other free radicals, preventing cellular damage.
• They exist in two forms: endogenous (made by the body) like glutathione, superoxide dismutase (SOD), and catalase; and exogenous (dietary) like vitamin C, vitamin E, carotenoids, polyphenols.
• Oxidative stress — when free radical production overwhelms antioxidant defences — contributes to ageing, DNA damage, inflammation, and chronic disease.
• Antioxidants support longevity and healthspan by protecting DNA, mitochondria, and lipids from oxidative injury.

At-a-Glance Facts

• Entity Type: Biochemical Class (Molecules & Compounds)
• Function: Neutralise ROS, prevent oxidative damage, maintain redox balance
• Sources: Endogenous (glutathione, SOD, catalase) & dietary (vitamins, minerals, plant compounds)
• Linked Processes: Ageing, DNA repair, mitochondrial health, inflammation control
• Declines With: Age, poor diet, environmental toxins, chronic stress
• Boosted By: Fruits, vegetables, polyphenols, supplements, lifestyle strategies (exercise, sleep)

What Are Antioxidants?

Antioxidants are protective molecules that stabilise or neutralise free radicals — unstable molecules with unpaired electrons. Without antioxidant defences, free radicals can damage DNA, proteins, and lipids, leading to cellular dysfunction and accelerated ageing.

Antioxidants act by:

1. Donating electrons to free radicals (neutralising them).
2. Regenerating other antioxidants (e.g., vitamin C recycles vitamin E).
3. Regulating signalling pathways related to inflammation and stress response.

Antioxidants and Ageing

• Ageing is partly driven by oxidative stress (the imbalance between ROS and antioxidants).
• Excess ROS contributes to the Hallmarks of Ageing, including DNA damage, mitochondrial dysfunction, and senescence.
• Antioxidants help:
• Protect mitochondria → preserve energy production.
• Support DNA repair → maintain genomic stability.
• Reduce chronic inflammation → slow inflammaging.
• Extend healthspan by preventing oxidative damage to tissues.

Types of Antioxidants

Endogenous (Produced by the Body)

• Glutathione (GSH): The master intracellular antioxidant.
• Superoxide Dismutase (SOD): Converts superoxide radicals into less harmful hydrogen peroxide.
• Catalase: Breaks down hydrogen peroxide into water and oxygen.
• Uric Acid, Melatonin, CoQ10: Additional internal antioxidants with broad effects.

Exogenous (From Diet or Supplements)

• Vitamins:
• Vitamin C (ascorbic acid)
• Vitamin E (tocopherols, tocotrienols)
• Vitamin A (retinol, carotenoids)
• Minerals: Selenium, zinc, copper, manganese (cofactors for antioxidant enzymes).
• Plant Polyphenols: Resveratrol, quercetin, catechins (green tea), curcumin.
• Carotenoids: Beta-carotene, lycopene, lutein, zeaxanthin, astaxanthin.
• Other Compounds: Alpha-lipoic acid, N-acetylcysteine (NAC), coenzyme Q10.

Interventions to Support Antioxidant Defences

• Dietary Strategies: Whole foods rich in polyphenols, fruits, vegetables, and herbs.
• Supplements: Vitamin C, E, glutathione, NAC, polyphenols.
• Lifestyle: Exercise (induces mild oxidative stress, boosting endogenous defences), sleep, stress reduction.
• Hormetic Stressors: Fasting, heat/cold therapy, and phytonutrients stimulate antioxidant pathways (NRF2 activation).

Discovery and Research History

• 19th century: Recognition of oxidative damage in cells.
• 1950s–60s: Free radical theory of ageing proposed by Denham Harman.
• 1980s–2000s: Antioxidant supplementation trials boom; mixed results in disease prevention.
• Modern view: Focus has shifted from high-dose supplementation to supporting endogenous antioxidant systemsand hormetic balance.

Safety and Considerations

• Supplementation Limits: Excessive antioxidant supplementation may blunt beneficial stress responses (mitohormesis).
• Context Matters: Dietary antioxidants are beneficial; mega-dosing certain supplements (e.g., beta-carotene in smokers) can be harmful.
• Balance: The goal is redox homeostasis, not eliminating all ROS (which also serve signalling functions).

FAQs

Are antioxidants anti-ageing?
Yes, by reducing oxidative damage, they slow cellular ageing, though effects vary by source and dose.

Is food or supplementation better?
Whole foods provide synergistic antioxidants; targeted supplementation can help in deficiency or high-stress states.

Can too many antioxidants be harmful?
Yes — excess supplementation can interfere with natural stress adaptation.

Do antioxidants prevent disease?
They reduce risk factors, but large trials show mixed results; benefits are strongest when coming from dietary patterns.

Glossary

• ROS (Reactive Oxygen Species): Harmful by-products of metabolism.
• Free Radicals: Molecules with unpaired electrons that can damage cells.
• Oxidative Stress: Imbalance between free radical production and antioxidant defences.
• Redox Balance: Cellular equilibrium between oxidation and reduction reactions.
• Hormesis: Beneficial adaptation to low-level stressors, including ROS.