Antioxidants are often touted as miracle substances for health and longevity. They are said to capture free radicals, prevent cell damage, and slow down the aging process. However, 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 amount, they protect our cells; in excessive doses, they can disrupt important cellular processes. We have examined these mechanisms in detail for you and would like to provide you with a good overview.
What is Oxidative Stress?
Free radicals are produced as byproducts of metabolism, but also through environmental factors such as UV radiation, environmental toxins, and stress.While they are necessary in moderation to activate the immune system, an excess can lead to (chronic) oxidative stress – a condition associated with aging processes and various diseases.
Oxidative stress occurs when the balance between free radicals and antioxidant protection mechanisms in the body is disturbed. Antioxidants are the natural opponents of these free radicals, but their effect is highly dose-dependent.
What antioxidants exist, how they work, and why a balanced intake is so important will be explained in this article.
How do antioxidants work on a molecular level?
Free radicals are unstable molecules that are missing an electron.You are looking for an electron to stabilize yourself – and in doing so, you tear it away from other molecules, such as in cell membranes or DNA. This 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), thereby reducing oxidative stress. They donate an electron and thus terminate the harmful chain reaction. An example is Vitamin C (ascorbic acid), which neutralizes free radicals in aqueous cell environments, or Vitamin E (tocopherol), which protects cell membranes as a fat-soluble antioxidant.
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. This regulates the expression of genes that activate antioxidant enzymes like glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase.
- Modulation of inflammation: Antioxidants influence signaling pathways like NF-κB, which play a role in the immune response and inflammation.
The significance of free radicals
Free radicals are highly reactive molecules with one or more unpaired electrons. Their name derives from their chemical nature: "free" means that they are unbound and therefore highly reactive, while "radicals" is a term for 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 signaling pathways, which are involved in cell growth, differentiation, and stress responses. For example, free radicals also contribute to muscle growth after intense 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, thereby promoting wound healing.
A certain level of oxidative stress is therefore necessary. The crucial factor is the balance between pro-oxidative and antioxidative mechanisms.
Classes of Antioxidants
Antioxidants can be divided into several categories:
Vitamins
Vitamin C (ascorbic acid): 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, a group of antioxidant enzymes that break down peroxides.
Zinc: Stabilizing element of antioxidant proteins, involved in redox reactions and protecting enzyme structures.
Secondary plant substances:
Polyphenols: z.B. Resveratrol or Curcumin. They are also found in berries, tea, and dark chocolate, acting molecularly in organisms as radical scavengers and activating 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 as well as the eyes.
Flavonoids: z.B. Fisetin. Modulate inflammatory processes, influence cell communication, and have antioxidant effects in various tissues.
Endogenous antioxidants:
Glutathione: 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: An enzyme that converts superoxide radicals into hydrogen peroxide, thereby reducing oxidative damage.
Catalase: Breaks down hydrogen peroxide into water and oxygen, thus protecting against toxic peroxides.
The Importance of Secondary Plant Compounds
Secondary plant compounds are a versatile group of bioactive compounds that plants synthesize as a protective mechanism against environmental stress, pathogens, and herbivores. Plants are constantly exposed to factors such as UV radiation, temperature changes, pest infestations, and oxidative processes. Antioxidants help them prevent cell damage and protect against these influences.Among the most important antioxidant substances produced by plants are polyphenols, carotenoids, flavonoids, and vitamins such as vitamin C and E.
These secondary plant substances act as a 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 human nutrition has diverse effects, similar to those in plants. The most significant secondary plant substances include:
- Flavonoids – A large group of polyphenols found in green tea, apples, and onions that possess antioxidant and anti-inflammatory properties.
- Carotenoids – Found in carrots, tomatoes, and pumpkins, they contribute to the maintenance of skin and eyes and act as precursors to vitamin A.
- Polyphenols – Abundant in berries, dark chocolate, and red wine, they are considered supporters of vascular health and act as free radical scavengers.
- Glucosinolates – Found in cruciferous vegetables like broccoli, cabbage, and mustard, they play a role in detoxification and cell protection.
Daily intake of resveratrol
Resveratrol is one of the secondary plant compounds from the group of polyphenols. Particularly high concentrations can be found in:
- Red wine: Contains about 1.9 to 2.7 mg of resveratrol per liter.
- Red grapes: Contain between 50 and 100 µg of resveratrol per gram.
- Peanuts: Contain between 0.03 and 0.14 µg of resveratrol per gram.
Perhaps you have heard that red wine is healthy despite the alcohol – this is due to the so-called French Paradox, which has later been proven to be incorrect. To reach the often recommended amount of 500 mg daily, you would have to consume extreme quantities:
- Red wine: Approximately 185 liters daily – definitely not a recommended strategy.
- Red grapes: About 5 kilograms daily – rather difficult to integrate into a normal diet.
- Peanuts: About 3.6 kilograms daily – a calorie-dense matter.
The role of sirtuins and their influence on oxidative stress
Sirtuins are a group of NAD-dependent enzymes and one of four longevity pathways, playing a central role in the regulation of cellular aging, metabolism, and antioxidant defense mechanisms. Particularly, SIRT1 is known for reducing 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 from oxidative stress.
The activation of sirtuins can be promoted by fasting, physical activity, and certain secondary plant compounds.
When can the intake of antioxidants be beneficial?
Nutrient deficiency: Individuals 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 pollution or tobacco smoke (e.g., due to their profession) could benefit from additional antioxidants. However, avoiding oxidative stress should be a priority.
Aging process: As we age, nutrient intake—and especially diversity—decreases, and the risk of chronic diseases increases. Studies suggest that a needs-based intake of antioxidants could counteract certain age-related changes, but the evidence is not conclusive.
Antioxidants and sports
The intake of antioxidants in relation to sports is a controversially discussed topic.On one hand, antioxidants can help reduce 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 athletic stress. Possible benefits: Moderate amounts of antioxidants such as vitamins C and E can, when taken with enough time before training, promote recovery and reduce muscle soreness. Possible disadvantages: High doses could block the cellular signaling pathways necessary for adaptation to physical stress. This may weaken the training effect.
Why oxidative stress is also useful: During exercise, free radicals are intentionally produced, which act as signaling molecules for adaptation mechanisms. They promote the production of the body's own antioxidants, increase mitochondrial biogenesis, and contribute to the improvement of physical performance.
Optimal intake time for antioxidants
Foods with antioxidants
The best absorption occurs throughout the day by consuming fresh, nutrient-rich foods to ensure a 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 the day – regularity is important.
Medications &and Interactions: Some antioxidants can affect the action 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 not only protect but can also be harmful in high doses.A varied diet is the best way to ensure adequate intake of antioxidants.
