Antioxidants are often touted as miracle cures for health and longevity. They are said to scavenge free radicals, prevent cell damage, and slow the aging process. But as with many biological processes, the truth is more complex: Not only a deficiency, but also an excess of antioxidants can have negative effects.

In the right amounts, they protect our cells; in excessive doses, they can disrupt important cellular processes. We've examined these mechanisms in more detail here and would like to provide you with a comprehensive overview.

What is oxidative stress?

Free radicals are formed as byproducts of metabolism, but also by environmental factors such as UV radiation, environmental toxins, and stress. While they are necessary in moderation, for example, to activate the immune system, an excess can lead to (chronic) oxidative stress—a condition associated with aging and various diseases.

Oxidative stress occurs when the balance between free radicals and antioxidant defense mechanisms in the body is disturbed. Antioxidants are the natural antagonists of these free radicals, but their effect is highly dose-dependent.

In this article you will learn which antioxidants there are, how they work and why a balanced intake is so important.

How do antioxidants work at the molecular level?

Free radicals are unstable molecules that lack an electron. They are looking for an electron to stabilize themselves – and thereby snatch it from other molecules, such as those in cell membranes or DNAThis process is called oxidation and can trigger a chain reaction that damages cell structures.

Antioxidants counteract this by binding free radicals without becoming unstable themselves. They are molecules that can neutralize reactive oxygen species (ROS) and reactive nitrogen species (RNS) and thereby reduce oxidative stress. They donate an electron, thus ending the damaging chain reaction. One example is Vitamin C (ascorbic acid), which neutralizes free radicals in aqueous cell environments, or Vitamin E (Tocopherol), which acts as a fat-soluble antioxidant to protect cell membranes.

Function and signaling pathways of antioxidants

Antioxidants have effects on three different levels:

• Direct neutralization: They react with free radicals and render them harmless.
• Indirect effect: They activate cellular defense mechanisms, such as the Nrf2 signaling pathway, which regulates the expression of genes that activate antioxidant enzymes such as glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase.
• Modulation of inflammation: Antioxidants influence signaling pathways such as NF-κB, which play a role in the immune response and Inflammations play.

The importance of free radicals

Free radicals are highly reactive molecules with one or more unpaired electrons.Their name derives from their chemical nature: "free" means they are unbound and therefore highly reactive, while "radicals" refers to atoms or molecules with unpaired electrons. This property makes them important players in biological processes, as they can accept or donate electrons from other molecules.

Although free radicals are often portrayed as harmful, they perform important physiological functions:

• Signal transduction: Free radicals such as reactive oxygen species (ROS) play a central role in cell communication. They regulate various signaling pathways, including the MAPK and NF-κB pathways, which are involved in cell growth, differentiation, and stress responses. For example, free radicals also cause Muscle growth after strenuous strength training.
• immune defense: Macrophages and other immune cells use free radicals as a weapon against pathogens. During the so-called "oxidative burst reaction," large amounts of ROS such as superoxide (O₂⁻) and hydrogen peroxide (H₂O₂) are released to eliminate bacteria and viruses.
• Wound healing: ROS are essential for the regulation of tissue regeneration. They influence angiogenesis (the formation of new blood vessels), the proliferation of fibroblasts and the production of Collagen, which promotes wound healing.

A certain degree of oxidative stress is therefore necessary. The balance between pro-oxidative and antioxidant mechanisms is crucial.

Classes of antioxidants

Antioxidants can be divided into several categories:

Vitamins

Vitamin C (ascorbic acid): A water-soluble antioxidant that can donate electrons to neutralize free radicals. It regenerates oxidized vitamin E and supports enzymatic processes.

Vitamin E (tocopherols and tocotrienols): Fat-soluble antioxidant that protects cell membranes by preventing lipid peroxidation.

Minerals

selenium: Essential component of glutathione peroxidase, an antioxidant enzyme group that breaks down peroxides.

zinc: Stabilizing element of antioxidant proteins that is involved in redox reactions and protects enzyme structures.

Secondary plant substances:

Polyphenols: e.g. Resveratrol or CurcuminThey are also found in berries, tea, and dark chocolate, act as radical scavengers in organisms, and activate the Nrf2 signaling pathway.

Carotenoids: These include beta-carotene, lutein, Astaxanthin and zeaxanthin, which inhibit membrane-associated oxidation reactions and thus have an effect on the skin and eyes.

Flavonoids: e.g. FisetinModulate inflammatory processes, influence cell communication and have an antioxidant effect in various tissues.

Endogenous antioxidants:

Glutathion: An intracellular protective factor that reacts directly with ROS and is regenerated by glutathione peroxidase. Precursor molecules are Glycine and N-acetylcysteine - short GlyNAC.

Superoxide dismutase: Enzyme that converts superoxide radicals into hydrogen peroxide, thus reducing oxidative damage.

Catalase: Breaks down hydrogen peroxide into water and oxygen, thus protecting against toxic peroxides.

The importance of secondary plant substances

Secondary plant substances are a diverse group of bioactive compounds that plants synthesize as a defense mechanism against environmental stress, pathogens, and herbivores. Plants are constantly exposed to factors such as UV radiation, temperature changes, pest infestation, and oxidative processes. Antioxidants help them prevent cell damage and protect themselves against these influences. The most important antioxidant substances produced by plants include polyphenols, carotenoids, flavonoids and vitamins such as vitamin C and E.

These secondary plant substances act as a protective shield in the plant by neutralizing reactive oxygen species and minimizing oxidative damage to cell structures.

The consumption of secondary plant substances as part of the human diet has diverse effects similar to those of plants. The most important secondary plant substances include:

• Flavonoids – A large group of polyphenols found in green tea, apples, and onions that have antioxidant and anti-inflammatory properties.
• Carotenoids – Found in carrots, tomatoes and pumpkin, they contribute to the maintenance of skin and eyes and act as precursors of vitamin A.
• Polyphenols – Abundant in berries, dark chocolate and red wine, they are considered to support vascular health and act as radical scavengers.
• Glucosinolate – Found in cruciferous vegetables such as broccoli, cabbage and mustard, they play a role in detoxification and cell protection.

Resveratrol intake in everyday life

Resveratrol is one of the secondary plant substances from the group of polyphenols. Particularly high concentrations are found in:

• red wine: Contains approximately 1.9 to 2.7 mg of resveratrol per liter.
• Red grapes: Contains between 50 and 100 µg of resveratrol per gram.
• Peanuts: Contains between 0.03 and 0.14 µg resveratrol per gram.

You may have heard that red wine is healthy despite its alcohol content—this is due to the French Paradox, which later turned out to be false. To reach the often recommended 500 mg daily, you would have to consume extreme amounts:

• red wine: About 185 liters per day – definitely not a recommended strategy.
• Red grapes: About 5 kilograms daily – rather difficult to integrate into a normal diet.
• Peanuts: Around 3.6 kilograms a day – a high-calorie affair.

The role of sirtuins and their influence on oxidative stress

Sirtuins are a group of NAD-dependent enzymes and one of four Longevity paths, which play a central role in the regulation of cellular aging, metabolism, and antioxidant defense mechanisms. SIRT1, in particular, is known to reduce oxidative stress by activating the Nrf2 signaling pathway and promoting the expression of antioxidant enzymes such as superoxide dismutase (SOD) and catalase. Studies show that increased sirtuin activity can contribute to improved mitochondrial function and a reduction in DNA damage caused by oxidative stress.

The activation of sirtuins can be Fast, physical activity and certain secondary plant substances are promoted.

When can taking antioxidants be useful?

Nutrient deficiency: People with limited access to antioxidant-rich foods due to dietary habits, allergies, or other factors may benefit from supplements. A doctor can determine if a deficiency exists.

High oxidative stress: People who are frequently exposed to environmental pollution or tobacco smoke (e.g., occupationally) may benefit from supplemental antioxidants. Nevertheless, avoiding oxidative stress should be a priority.

Aging process: With increasing age, nutrient intake and especially nutrient diversity decreases, and the risk of chronic diseases increases. Studies suggest that a needs-based Antioxidant supplements may counteract certain age-related changes, but the evidence is inconclusive.

Antioxidants and exercise

The use of antioxidants in conjunction with exercise is a controversial topic. On the one hand, antioxidants can help reduce the oxidative stress caused by intense physical activity. On the other hand, recent studies show that an excessive intake of antioxidants shortly before or after training can impair the body's adaptation processes to physical exertion.

• Possible benefits: Moderate amounts of antioxidants such as vitamins C and E can, if taken sufficiently long after training, promote recovery and reduce muscle soreness.
• Possible disadvantages: High doses could block the cellular signaling pathways necessary for adaptation to physical exertion, potentially weakening the training effect.

Why oxidative stress is also useful: During exercise, free radicals are specifically produced, which act as signaling agents for adaptive mechanisms. They promote the production of the body's own antioxidants, increase mitochondrial biogenesis, and contribute to improved physical performance.

Optimal intake time for antioxidants

Foods with antioxidants

The best absorption is achieved throughout the day by eating fresh, nutrient-rich foods to ensure consistent antioxidant defense.

Dietary supplements

Fat-soluble antioxidants (A, D, E, K): Best taken with a fatty meal to improve absorption.

Water-soluble antioxidants (Vitamin C, polyphenols, flavonoids): Can be taken at any time of day – regularity is important.

Medications & Interactions: Some antioxidants may interfere with the effectiveness of certain medications. It is advisable to seek professional advice in this case.

The dose makes the poison

Antioxidants are essential for health, but the right balance is crucial. Current research shows that they are not only protective, but can also be harmful in high doses. A varied diet is the best way to get enough antioxidants.