Antioxidants: effects, oxidative processes and good food sources

What are Antioxidants?

Antioxidants are substances that can inhibit oxidation reactions or intercept reactive molecules. These include the body's own systems such as glutathione and antioxidant enzymes as well as nutrients and plant substances from food.

Vitamin C and vitamin E can have a direct antioxidant effect. Selenium and zinc are components or cofactors of various enzymes that are involved in the regulation of oxidative balance. Plants also provide numerous phytochemicals, including carotenoids, polyphenols and anthocyanins. These substance groups differ in structure, absorption and biological effect.

Free radicals and oxidative stress

Normal metabolic processes produce reactive oxygen compounds (ROS) and other reactive molecules. Some of them have unpaired electrons and therefore react easily with other molecules. They can change proteins, lipids and DNA, among other things.

However, free radicals are not simply fundamentally harmful: reactive molecules also fulfill important tasks in immune defense and cellular signal transmission. Oxidative stress occurs when the formation of reactive molecules and the body's own protective and repair mechanisms become unbalanced, thereby promoting damage.

The body regulates this balance using a network of enzymes such as superoxide dismutase, catalase and glutathione peroxidases, as well as small molecules such as glutathione. Antioxidants do not all neutralize reactive molecules in the same way and do not always simply give off an “excess electron”. The chemical mechanisms are diverse.

Why oxidative stress is relevant

Sustained elevated oxidative stress is associated with various diseases and aging processes. It can be involved in disease mechanisms, but is not always the sole cause. Oxidative processes can also be the result of an illness or part of a normal adaptation reaction of the body.

Smoking, excessive alcohol consumption, certain environmental pollution and an overall unfavorable lifestyle can influence the oxidative balance. However, it does not follow that the highest possible amounts of isolated antioxidants are the best countermeasure. The body needs a finely regulated redox balance.

Are antioxidants useful as dietary supplements?

A sufficient supply of essential nutrients is important. However, it cannot be concluded from this that high doses of antioxidant preparations prevent diseases or slow down aging processes. Studies of isolated vitamin and antioxidant preparations do not show consistent preventive benefit. In certain groups, high doses can even be harmful: for example, beta-carotene preparations increase the risk of lung cancer in smokers.

Even during cancer therapy, high doses of antioxidants should not be taken without consulting the treatment team, as interactions and influences on the therapy are possible. It makes sense to specifically compensate for proven nutrient deficiencies and not to take supplements solely because of a general “antioxidant need”.

ORAC values: Is there a daily need?

No. There is no generally accepted daily requirement in ORAC units for antioxidants. ORAC (Oxygen Radical Absorbance Capacity) is a laboratory test that measures the ability of a sample to influence an oxidation reaction under certain test conditions.

The values cannot be reliably transferred to the effect in the human body. Digestion, absorption, metabolism and interactions change the effects of the substances. The previous recommendation of 5,000 to 7,000 ORAC units daily is therefore not a scientifically established nutritional recommendation. The previous USDA-ORAC database was also withdrawn because the laboratory values ​​do not allow reliable conclusions to be drawn about health effects in humans.

Which foods provide antioxidant substances?

Instead of evaluating individual foods based on supposed ORAC top values, a wide variety makes sense. Good sources include:

• **Berries and dark fruits:** such as blueberries, blackberries, raspberries, strawberries and aronia berries; They provide, among other things, anthocyanins and other polyphenols.

• **Leafy greens and other vegetables:** such as kale, spinach, broccoli, and peppers; They contain, among other things, vitamin C, carotenoids and other plant substances.

• **Whole grain products, legumes, nuts and seeds:** In addition to various plant substances, they also provide fiber and other important nutrients.

• **Tea and Spices:** Green tea, ginger and turmeric contain different bioactive compounds. However, their presence does not mean that they treat diseases.

• **Cocoa and dark chocolate:** Cocoa contains flavanols. However, chocolate can also provide a lot of sugar, fat and energy; it is therefore not a necessary health product.

• **Sea buckthorn and aronia juice:** can provide plant substances and vitamins. Whole fruits often have the advantage over juice in that they contain more fiber and are more filling.

Milk thistle and other plant extracts

Milk thistle contains silymarin, a mixture of various plant substances that, among other things, have antioxidant properties in laboratory studies. However, no reliable protective or detoxification effect for the human liver can be derived from this. Clinical studies on liver disease are inconsistent or do not provide sufficient evidence of reliable benefit. Milk thistle should therefore not be presented as proven liver protection or a replacement for medical treatment. Plant extracts can also have side effects and interactions.

Conclusion: diversity instead of antioxidant hunting

A varied, predominantly plant-based diet provides many different antioxidant substances and at the same time supports the supply of fiber, vitamins and minerals. A colorful selection of vegetables, fruits, legumes, whole grain products, nuts and seeds is particularly useful.

There is no set ORAC daily requirement and no reason to aim for the highest possible antioxidant levels through isolated preparations. What is crucial is a balanced nutritional pattern - not the hunt for individual superfoods or the highest possible laboratory values.