Antioxidants are a group of substances formed by various chemical compounds. Among other things, they have the ability to prevent oxidation of biomolecules. In addition to vitamins, their precursors, and derivatives, the group of natural antioxidants also includes some amino acids, minerals, and phytochemicals.
Antioxidants act as free radical scavengers, which prevent oxidative stress at the cellular level and can stop harmful chain reactions. The best-known antioxidants include vitamins C and E, carotenoids, and secondary plant substances such as sulfides, phytoestrogens, and polyphenols. The antioxidant properties are also attributed to the minerals zinc and selenium.
Antioxidants also play a role as preservatives in food production. Due to the antioxidant effect, they can extend the shelf life of food because they prevent the reaction with oxygen (oxidation). The most common antioxidants are vitamin C (ascorbic acid) and vitamin E (tocopherols).
How do antioxidants work?
Metabolic processes take place in our body every day, in which free radicals can develop through oxidation. These processes can be increased particularly by stress, cigarette smoke, and sunbathing.
Only when free radicals are generated in excess they can harm us. This is where antioxidants come into play. They act against oxidation processes and can neutralize free radicals and make them harmless ( 1 ).
If there are too many free radicals in the body, there is the so-called oxidative stress, which in turn should promote the development of diseases and make the skin age faster.
A classic example of oxidation is a sliced apple, which turns brown after a short time due to contact with air. If you spray apple pieces with lemon juice, you will discover that the vitamin C contained in the lemon has the ability to prevent this oxidation and, therefore, of a brown color, that is why vitamin C is one of the antioxidants.
Vitamin C is also the most famous essential vitamin with antioxidant properties. Especially in winter, it is often used to fight colds, sometimes using vitamin C supplements or drinking orange juice, for example.
The literature is controversial, but a high dose of vitamin C does not seem to be effective when it comes to preventing colds in a healthy population. In people who practice a lot of exercises or are exposed to a cold environment, an extra dose of vitamin C may still be useful ( 2 ).
Antioxidants protect our cells from oxidative stress by neutralizing the free radicals that arise during different metabolic processes.
How healthy are antioxidants?
Numerous studies have observed a lower risk of high blood pressure, stroke, coronary artery disease, obesity, and certain types of cancer as the intake of vegetables and fruits increases.
Vitamin C and the combination with other antioxidants such as beta-carotene, vitamin E or zinc from food and supplements is associated with a lower risk of the opacity of the eyes and, consequently, a lower risk of poor vision in adulthood.
It seems that it is especially the variety of biologically active substances in fruits and vegetables that are so healthy for us. As a general rule, no clear connection was found between individual nutrients and a lower risk of disease in the studies.
So far, there are no clear recommendations on the exact amounts of phytochemicals that should be ingested daily to have the best possible protective effect. According to epidemiological data, about 400 grams of vegetables and 250 grams of fruits.
The variety of plant substances such as antioxidants, phytochemicals, and fiber make fruits and vegetables so healthy and contribute 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. When processing these plant-based foods (peeling or grinding), much of the secondary plant substances can be lost.
This partially reduces nutritional quality. Therefore, it should vary not only in the choice of food but also in the method of preparation. Peeled, unpeeled, cooked, scalded, and raw. Meat and fish also contain antioxidants, but to a lesser extent than vegetable products.
Foods are subject to natural fluctuations in their nutrient content due to different growing and storage conditions. This makes it difficult to establish precise numerical values for the antioxidant content.
Here is a brief list of examples of foods that are particularly rich in antioxidants.
Dark berries, such as blueberries, are an excellent source of phytochemicals. The anthocyanins they contain are suspected to have a positive effect on brain activity and improve memory in the elderly ( 3 ). Berries are also a delicious and healthy ingredient for a smoothie or juice rich in micronutrients with many antioxidants.
If you often use garlic when cooking, you are doing something good for your health because it is rich in antioxidants. Garlic has been shown to improve cardiovascular health by reducing blood pressure and increasing good cholesterol ( 4 ).
Garlic has great antioxidant benefits as it promotes the activity of the powerful antioxidant glutathione, which among other things strengthens our immune system. There is also evidence that eating garlic can help reduce fasting blood sugar.
Coffee and green tea
In the morning, you can take a small number of antioxidants with a cup of coffee or green or black tea. Coffee is one of the largest food sources for antioxidants worldwide, but it still cannot match fruits and vegetables ( 5 ).
Good news for all chocolate lovers: chocolate is also one of the foods with high antioxidant content. The content increases with increasing cocoa content.
This means that white chocolate barely provides significant amounts of antioxidants, while chocolate products with more than 50 percent cocoa contain good antioxidant content ( 6 ).
The antioxidant content in spices and herbs can be immense: the active ingredient in curcumin not only has an antioxidant effect but also has a strong anti-inflammatory effect.
Studies have mainly examined the effects of dietary supplements that contain high levels of curcumin, but turmeric may still contribute to the intake of valuable antioxidants ( 7 ).
Nuts and seeds
Valuable sources of nutrients and some antioxidants include nuts and seeds. Nuts, chestnuts, peanuts, hazelnuts, and almonds in particular provide higher amounts of antioxidants. Especially if they are eaten in the shell. It has been shown that many flavonoids in nuts are found in the shells ( 8 ).
Vegetable foods such as fruits, berries, vegetables, spices, nuts, and coffee in particular are rich in natural antioxidants and can be used to protect cells.
Should I supplement antioxidants?
Can dietary supplements and antioxidant capsules support healthy eating? Excessive intake of fats and energy often plays an important role in an unfavorable nutritional state.
There are no dietary supplements that can help here, but rather foods that you fill, such as fruits and vegetables with low-calorie density.
A meta-analysis by Bjelakovic et al. has examined the effects of supplemented antioxidants: no evidence has been found that they have a positive effect on cancer in the gastrointestinal tract, and could even increase the overall mortality rate.
Some isolated antioxidant substances may even have negative effects on our health. Only selenium could have a potential protective effect, but this must first be examined in appropriate studies ( 9 ).
Generally, there is insufficient scientific evidence for the effectiveness of food supplements based on fruits and vegetables.
Antioxidants are bioactive substances that neutralize free radicals and can protect our cells from oxidative stress. They have a protective and health-promoting effect if they are ingested as part of a diet rich in vegetables and fruits.
Free radicals arise in different metabolic processes and occur more frequently when smoking, absorbing environmental toxins or UV radiation from the sun.
Adequate intake of antioxidants is essential for a healthy diet. Vegetables and fruits offer a wide range of these valuable substances. In addition to fruits, berries, vegetables, and nuts, foods such as coffee, green tea, or dark chocolate are also particularly rich in antioxidants.
These various foods can be beautifully integrated into the menu. At least five servings of assorted fruits and vegetables are recommended per day. It is not necessary or useful to take high-dose supplements when it comes to antioxidants, as they can do more harm than good in certain conditions.