We hear a lot about the little health helpers in our food – antioxidants. But how do these valuable radical scavengers work and in which foods do they occur? We’ll tell you what these protective helpers are all about.
What are antioxidants?
Antioxidants are a group of substances made up of various chemical compounds. Among other things, they have the ability to prevent the oxidation of biomolecules. The group of natural antioxidants includes vitamins, their precursors and derivatives, as well as some amino acids, minerals and secondary plant substances.
Antioxidants act as “radical scavengers”, which can prevent oxidative stress at the cellular level and stop harmful chain reactions. The best-known antioxidants include vitamins C and E, carotenoids, and secondary plant compounds such as sulfides, phytoestrogens and polyphenols. The minerals zinc and selenium are also thought to have antioxidant properties.
Secondary plant compounds can be classified into different chemical groups based on their molecular structure. A presentation by Dr. Watzl of the German Association of Nutritional Medicine (BDEM e.V.) shows that the structure and number of all existing secondary plant compounds in plant foods are still insufficiently known.
Antioxidants also play a role in food production as preservatives. Due to their antioxidant effect, they can prolong the shelf life of foods by preventing the reaction with oxygen (oxidation). Especially in vegetable oil or fat, this can protect against rapid “rancidity”. The most common antioxidants are vitamin C (ascorbic acid) and vitamin E (tocopherols). They are declared on the ingredient list of packaged foods with the numbers E 300 and E 306. Ref.
In addition to vitamins and secondary plant substances, antioxidants also include some amino acids and minerals. They have the property of preventing oxidation processes.
How do antioxidants work?
Every day in our body metabolic processes take place in which free radicals can be produced by oxidation. In particular, these processes can be increased by stress, cigarette smoke and sunbathing. Only when free radicals are produced in excess can they harm us – this is where antioxidants come into play. They counteract oxidation processes and can neutralize and render harmless free radicals.
If there are too many free radicals in the body, this leads to so-called oxidative stress, which in turn is said to promote the development of diseases and causes the skin to age more quickly. A classic example of oxidation is a cut apple, which turns brown after a short time due to contact with the air. If you sprinkle pieces of apple with lemon juice, you will find that the vitamin C in the lemon has the ability to prevent this oxidation and thus brown discoloration – which is why vitamin C is one of the antioxidants.
Vitamin C is also probably the best-known essential vitamin with antioxidant properties. It is often used to ward off colds, especially during the winter season, and vitamin C supplements are sometimes resorted to. The literature on this shows controversy, but routine high doses of vitamin C do not appear to be effective in preventing colds in the healthy population. Nevertheless, in people who exercise a lot or are exposed to cold environments intermittently, an extra dose of vitamin C could be helpful. Ref.
Antioxidants protect our cells from oxidative stress by neutralizing free radicals that are produced during various metabolic processes.
How healthy are antioxidants?
Numerous studies have observed a reduced risk of hypertension, stroke, coronary heart disease, obesity and certain cancers with increasing intakes of vegetables and fruits. Vitamin C and the combination with other antioxidants such as beta-carotene, vitamin E, or zinc from foods and supplements is associated with a reduced risk of lens opacities and consequently vision loss in adulthood.
It seems that it is primarily the variety of biologically active substances in fruits and vegetables that are so healthy for us. Studies have generally failed to find a clear link between individual nutrients and a reduced risk of disease.
To date, there are no clear recommendations on the exact amounts of phytochemicals that should be consumed daily to have the best possible protective effect. Based on epidemiological data, nutritional institutions such as the DGE advocate the “5 a day” campaign, which corresponds to approximately 400 grams of vegetables and 250 grams of fruit. Since fruits and vegetables provide a wide range of valuable ingredients, one should take advantage of this variety of food offerings and pay attention to regionality and seasonality. Ref.
The diversity of plant substances, such as antioxidants, phytochemicals, and dietary fiber, is what makes fruits and vegetables so healthy and contributes to disease prevention.
What foods are rich in antioxidants?
In addition to vegetables and fruits, whole grains, nuts and legumes also contribute to the supply of phytochemicals. Many of these substances from vegetables, fruits or grains are found in the outer shell components. When these plant foods are processed by peeling or grinding, large parts of the secondary plant compounds can be lost.
In part, this reduces the nutritional quality. Therefore, one should not only vary in the choice of food, but also in the method of preparation. Peeled, unpeeled, cooked, blanched and raw – it’s all in the mix. Meat and fish also contain antioxidants, but to a lesser extent than plant products. Ref.
Foods are subject to natural variations in their nutrient content due to different growing and storage conditions. This makes it difficult to establish precise numerical values for antioxidant content. For guidance, here is a short list of food examples that are particularly rich in antioxidants:
Blueberries and other dark berries are particularly good sources of phytochemicals. The anthocyanins they contain are strongly suspected to have a positive effect on brain activity and improve memory in the elderly. Berries are also a delicious and healthy ingredient for a micronutrient-rich smoothie or juice with plenty of antioxidants.
If you make frequent use of garlic in your cooking, you’re doing your health a favor because it’s rich in antioxidants. Garlic has been shown to improve cardiovascular health by lowering blood pressure and improving cholesterol levels.
Garlic also provides antioxidant benefits by promoting the activity of the powerful antioxidant glutathione, which strengthens our immune system, among other benefits. In addition, there is evidence that eating garlic can help lower fasting blood sugar levels.
Coffee and green tea
First thing in the morning, you can get a small amount of antioxidants by drinking a cup of coffee or green and black tea. Coffee is one of the world’s greatest dietary sources of antioxidants – but it still can’t rival fruits and vegetables.
Good news for all chocolate lovers: Chocolate is also one of the foods with a high antioxidant content. The content increases with increasing cocoa content. This means white chocolate provides hardly any significant amounts of antioxidants, whereas chocolate products with more than 50 percent cocoa content provide good antioxidant content.
The antioxidant content of spices and herbs can be immense: The active ingredient curcumin from turmeric not only has an antioxidant effect, but also a strong anti-inflammatory effect. While studies have mostly examined the effects of supplements containing strong curcumin, turmeric can still contribute to the intake of valuable antioxidants.
Nuts and seeds
Nuts and seeds are excellent sources of minerals and some antioxidants. Walnuts, chestnuts, peanuts, hazelnuts, and almonds in particular provide higher amounts of antioxidants. Especially if they are stored with the shell and the membrane is eaten along with them. Many flavonoids of nuts have been shown to be found in the thin nut skins.
In particular, plant foods such as fruits, berries, vegetables, spices, nuts, as well as coffee are rich in natural antioxidants and can help protect cells.
Should we supplement with antioxidants?
Can supplements and antioxidant capsules support a healthy diet? The German Nutrition Society (DGE) views them critically and as no alternative to the daily consumption of five servings of vegetables and fruit in raw and heated form.
Dietary fiber in particular is hardly found in processed products. In addition, an excessively high fat and energy intake often plays the essential role in an unfavorable nutritional state. This cannot be remedied by dietary supplements, but much more by satiating foods such as fruits and vegetables with a low caloric density.
The German Nutrition Society questions the nutritional efficacy of such vegetable and fruit products offered as dietary supplements, since proof of bioavailability is often lacking. Products fortified with vitamins and minerals cannot be compared with fruits and vegetables in their effect.
A meta-analysis by Bjelakovic et al. also looked at the effect of supplemented antioxidants: No evidence was found that they had a beneficial effect on cancers in the gastrointestinal tract, but could even increase the overall mortality rate. Some antioxidant substances may even have negative effects on our health in isolated form. Only selenium could have a potential protective effect, but this needs to be investigated in adequate studies for now. Ref.
Adequate scientific evidence is generally lacking for the efficacy of fruit- and vegetable-based dietary supplements.
Knowledge to go
Antioxidants are bioactive substances that can neutralize free radicals and protect our cells from oxidative stress. They have a protective and health-promoting effect when consumed as part of a diet rich in vegetables and fruits. Free radicals are produced during various metabolic processes and are more prevalent when smoking, ingesting environmental toxins or UV radiation from the sun.
An adequate intake of antioxidants is essential for a healthy diet. The colorful palette of vegetables and fruits offers a wide range of these valuable substances. However, in addition to fruits, berries, vegetables and nuts, stimulants such as coffee, green tea or dark chocolate are particularly rich in antioxidants.
These diverse foods can be wonderfully integrated into the diet. At least five servings of varied fruits and vegetables per day are recommended. It is neither necessary nor useful to take high-dose supplements when it comes to antioxidants, as they can do more harm than good under certain conditions.