Antioxidants, what are they and what are they for?

ts intake is essential to maintain health in a state of fullness. But what, in detail, is the role they play in the body? Their role as a reducer of oxidative stress, a problem that worsens with age, is what makes them so essential. Eating vegetables or fruits to assimilate these compounds is a key factor in having a quality old age.

Everyone talks about antioxidants and their healthy effects, but there are few who know their chemical structure, their origin and, above all, what we should do to incorporate these natural agents so protective of our cells and tissues into our body. Basically, antioxidants are compounds synthesized by plants in their different parts (fruits, leaves, branches, roots, etc.) characterized by having hydroxyl groups (OH) linked together by benzene ringsIts presence in food is essential not only because they activate the natural organoleptic properties, preserving them, but because when ingested they protect the health of the consumer in a comprehensive and effective way, preventing the development of such serious diseases as cancer, myocardial infarction, stroke, neurodegenerative processes and the immune system.

What is oxidative stress?

We will hardly understand the effects of antioxidants without some basic notions about oxidative stress. In cellular metabolism – in which glucose reacts with oxygen to produce energy in the form of adenosine triphosphate (ATP) – there is a simultaneous release of a series of reactive oxygen compounds, which we usually call free radicals, whose effects on all cellular elements (nucleus, membrane, cytoplasm, mitochondria, etc.) are seriously deleterious.

It is a process comparable to the inevitable production of toxic gases that are released in internal combustion engines fueled with fossil fuels. In a young and healthy subject, oxygen free radicals are rapidly eliminated from the interior of the cell by natural antioxidants, but in chronic patients or the elderly this elimination is deficient, which leads to the appearance of chronic diseases, accelerating at the same time the aging.

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What are the most common antioxidants contained in food?

In general terms, we could divide them into three large groups: polyphenols, carotenoids and vitamins of groups C and E.


They are directly responsible for the maximum antioxidant activity of fruits and vegetables and also of certain herbal teas and natural drinks. Within them, we can divide them into two subtypes with different properties and characteristics: those that are flavonoids and those that are not.

All of them show in their chemical structure OH groups linked by aromatic rings. It is precisely the presence of OH groups that gives them their antioxidant properties since, depending on the circumstances, they can give up a hydrogen atom (H +) or donate an electron to an oxygen free radical to saturate and neutralize it.

Some of them also have chelating properties, that is, they adhere to toxic substances, such as lead, copper, iron, cadmium and other heavy metals, eliminating them via the kidneys or digestive system. These actions are important because we must not forget that these toxic agents are directly responsible for more than 80% of chronic diseases such as arteriosclerosis, diabetes or high blood pressure. But not only do polyphenols have antioxidant properties per se, but also many of them have shown anti-inflammatory, antibacterial, antiplatelet activity (to prevent thrombosis and embolisms), also enhancing the action of the immune system and facilitating the activity of certain enzymesessential for good digestion.

Flavonoids are subdivided, in turn, into flavones and isoflavones, anthocyanidins, flavanols and flavanones, all of them with antioxidant properties of more or less similar potency. The so-called non-flavonoid polyphenols are made up of alcohols, phenolic acids and stilbenes such as resveratrol. Like flavonoids, they exhibit the same properties that we have described above.

Its presence is abundant in fruits, vegetables, cereals and legumes, as well as in some drinks and infusions such as green tea, coffee , red wine and in other products such as chocolate with high concentrations of cocoa. There is abundant scientific literature that sufficiently supports the healthy properties of polyphenols due to their varied actions at the cellular and metabolic level.


They are pigments synthesized by plants in the photosynthesis process whose main activity is the neutralization of reactive oxygen species (ROS) whose role is decisive in the development and maintenance of cellular oxidative stress. Their presence in food is easily recognizable by the color they confer, since these pigments give peculiar shades that go from yellow to red through orange or violet. Thus, fruits and vegetables such as carrots, oranges, peaches, tangerines, tomatoes, watermelons, papaya, even Brussels sprouts, spinach or broccoli are rich in carotenoids even though the pigment in these vegetables remains masked by the high concentrations of chlorophyll they contain.

From a structural point of view, they are classified into carotenes (alpha and beta), lycopene, and xanthophylls of the beta-cryptoxanthin, lutein and zeaxanthin type. Both alpha and beta carotenes and beta-cryptoxanthin are precursors of vitamin A, which means that at the end of the transformation chain they are converted into vitamin A (retinol), whose role is essential to preserve the integrity of the retina and with it a correct vision and to keep the immune system at maximum activity .

For carotenoids to have good absorption at the intestinal level, it is necessary for certain fats and bile salts to release them from the matrix that binds them to food. Hence, the intake of a certain amount of fat (3-5 grams) is necessary to ensure good bioavailability.


Vitamin C

Ascorbic acid or vitamin C is considered the most genuine of antioxidants . As the human body, unlike other mammals, is unable to synthesize it, it is necessary to extract it in sufficient quantities from the food we consume daily. Therefore, vitamin C is listed as an essential nutrient, as are omega 3 acids.

Their primary actions are the structural protection of proteins, lipids and carbohydrates, and above all they preserve the nucleic acids that make up DNA and RNA from oxidative stress. Without its action we could not synthesize collagen and elastin, both components of extreme importance for the development and support of blood vessels, tendons, bones and ligaments. Similarly, its role is crucial in the synthesis of norepinephrine and carnitine and in the transformation of cholesterol into bile salts.

The natural sources of vitamin C are fruits and vegetables, but it should be noted that the concentration of ascorbic acid varies greatly from one to the other. Among the richest in vitamin C are orange, kiwi, lemon, papaya, melon, strawberries, tomatoes and vegetables such as peppers, Brussels sprouts, and in general green leafy vegetables such as broccoli and cauliflower. Five daily servings (3 of fruits and two of vegetables) ensure a minimum consumption of 200 mg .

Vitamin E

Two well-differentiated molecular compounds are included under the term vitamin E: tocopherols and tocotrienols. Like polyphenols, they include OH groups in their molecular structure linking aromatic rings. It is precisely these chemical characteristics that give them their antioxidant power by donating oxygen atoms or neutralizing free radicals and reactive species, stabilizing them. In foods rich in vitamin E, the concentration of tocopherols is much higher than that of tocotrienols.

From accumulated scientific experiences, only alpha-tocopherol would be the only molecule in the group with proven antioxidant properties. Its role is essential in the preservation of the function and architecture of the cell membrane as well as blocking the oxidation of LDL cholesterol (bad cholesterol). This, once oxidized, causes a rapid development of the atherosclerotic process leading to the intravascular formation of atheroma plaques that are the key structural units of occlusive arteriosclerosis, thereby favoring myocardial infarction, stroke and vascular insufficiency of the lower limbs. .

The daily doses of vitamin E recommended by scientific bodies range from 6 milligrams in childhood to 15 milligrams in adulthood . This is achieved with a frequent and varied consumption of olive, corn, soy, canola, safflower or sunflower oils or with the intake of small amounts of nuts such as almonds, peanuts, hazelnuts or walnuts (20 to 30 grams per day) and consuming vegetables like raw carrots and spinach in salad.