Antioxidants are often touted as a miracle cure for health and longevity. They are said to scavenge free radicals, prevent cell damage and slow down the ageing 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 more detail for you here and would like to give you a good overview.
What is oxidative stress?
Free radicals are produced as by-products 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 that is associated with ageing 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 antagonists of these free radicals, but their effect is highly dose-dependent.
In this article, you can find out what antioxidants there are, how they work and why a balanced intake is so important.
How do antioxidants work on a molecular level?
Free radicals are unstable molecules that lack an electron. They are in search of an electron to stabilize themselves -and in the process snatch it from other molecules, for example in cell membranes or DNA . This process is known as oxidation and can trigger a chain reaction that damages cell structures.
Antioxidantscounteract this by binding free radicals without becoming unstable themselves. They are molecules that neutralize reactive oxygen species (ROS) and reactive nitrogen species (RNS) and can thus reduce oxidative stress. They release an electron and thus end the harmful chain reaction. One 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 at 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 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 immune response and inflammation .
The importance of free radicals
Free radicals are highly reactive molecules with one or more unpaired electrons. Their name is derived 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 fulfill 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 ensure 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 level of oxidative stress is therefore necessary.The balance between pro-oxidative and antioxidative mechanisms is crucial.
Classes of antioxidants
Antioxidants can be divided into several categories:
Vitamine
Vitamin C (ascorbic acid):Water-soluble antioxidant that can release 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.
Mineralien
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.
Sekundäre Pflanzenstoffe:
Polyphenole:z.B . Resveratrol or curcumin . They are also found in berries, tea and dark chocolate, act as molecular 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 therefore have an effect on the skin and eyes.
Flavonoide:z.B . Fisetin . Modulate inflammatory processes, influence cell communication and have an antioxidant effect in various tissues.
Endogene Antioxidantien:
Glutathione:An intracellular protective factor that reacts directly with ROS and is regenerated by glutathione peroxidase. Precursor molecules are glycine and N-acetylcysteine - GlyNAC for short.
Superoxide dismutase:Enzyme that converts superoxide radicals into hydrogen peroxide and thus reduces oxidative damage.
Catalase:Degrades hydrogen peroxide to water and oxygen and thus protects against toxic peroxides.
The importance of phytochemicals
Secondary phytochemicalsare a diverse group of bioactive compounds that plants synthesize as a protective mechanism against environmental stress, pathogens and predators. Plants are constantly exposed to factors such as UV radiation, temperature changes, pest infestation and oxidative processes. Antioxidants help them to prevent cell damage and protect themselves against these influences. The most important antioxidant substances that plants produce include polyphenols, carotenoids, flavonoids and vitamins such as vitamin C and E .
These phytochemicals act as a protective shield in the plant by neutralizing reactive oxygen species and minimizing oxidative damage to cell structures.
The consumption of phytochemicals as part of the human diet has a variety of effects similar to those of plants. The most important phytochemicals 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 help to maintain the 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 free radical scavengers.
- Glucosinolates- 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 about 1.9 to 2.7 mg 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.
You may have heard that red wine is healthy despite alcohol - this is due to the French paradox described above, which later turned out to be false. To reach the often recommended amount of 500 mg per day, you would have to consume extreme amounts:
- Red wine : Approximately 185 liters a day - definitely not a recommended strategy.
- Red grapes : About 5 kilograms a day - 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
Sirtuinsare a group of NAD-dependent enzymes and one of four longevity pathways that play a central role in the regulation of cell 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.
Sirtuin activation can be promoted byfasting , physical activity and certain phytochemicals.
When can it be useful to take antioxidants?
Nutrient deficiencies: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 there is a deficiency.
High oxidative stress:People who are frequently exposed to environmental pollution or tobacco smoke by necessity ( z.B. occupationally) could benefit from additional antioxidants. Nevertheless, avoiding oxidative stress should be a priority.
Ageing:As we age, nutrient intake and especially nutrient diversity decreases and the risk of chronic diseases increases. Studies suggest that an adequate intake of antioxidants may counteract certain age-related changes, but the evidence is not clear.
Antioxidants and exercise
The intake of antioxidants in connection with sport is a controversial topic. On the one hand, antioxidants can help to 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 exercise can impair the body's adaptation processes to exercise.
- Possible benefits: Moderate amounts of antioxidants such as vitamins C and E, when taken in sufficient time after exercise, can promote recovery and reduce muscle soreness.
- Possible disadvantages: High doses could block the cellular signaling pathways that are necessary for adaptation to physical stress. This can weaken the training effect.
Why oxidative stress is also beneficial:Exercise specifically generates free radicals that act as signaling molecules for adaptation mechanisms. They promote the production of the body's own antioxidants, increase mitochondrial biogenesis and contribute to improving physical performance.
Optimal intake time for antioxidants
Lebensmittel mit Antioxidantien
The best intake is spread throughout the day by eating fresh, nutrient-rich foods to ensure a consistent antioxidant defense.
Nahrungsergänzungsmittel
Fat-soluble antioxidants (A, D, E, K): Best taken with a high-fat meal to improve absorption.
Water-soluble antioxidants (vitamin C, polyphenols, flavonoids): Can be taken at any time of day - the important thing is regularity.
Medications & Interactions: Some antioxidants can influence the effect of certain medications. It is advisable to consult a specialist 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 get enough antioxidants.
