Antioxidants in fruit. They are often talked about because of their potential positive effects on health. An adequate intake of these compounds is commonly considered a key factor in a correct diet and an excellent strategy for staying fit and healthy over time. In fact, antioxidants are considered in the collective imagination, as also underlined by the guidelines for healthy eating, as something positive, particularly useful for getting sick less and for aging better and more slowly. But is it really like that? And what is special about fruit antioxidants compared to those found in other vegetables? To clarify, we talked about it with the nutritionist Roberto Melecoordinator of the Nutrition Biology area ofIRCCS San Raffaele Hospital from Milan.
What are antioxidants?
«Antioxidants are chemical substances, mainly molecules, which oppose the oxidation of other substances, interrupting a chain of oxidation reactions, potentially harmful to cellular structures and, ultimately, to our organism» explains nutritionist Roberto Mele. «An oxidation reaction is a chemical phenomenon that alters the structure of a molecule, making it unstable, to the point of producing very reactive chemical species, also known as free radicals. The formation of free radicals commonly occurs in our cells, as a result of their physiological metabolic activity, but can also be caused by external chemical or physical agents, such as cigarette smoke or ultraviolet radiation. Free radicals “vampirize” other molecules, transforming them in turn into aggressive molecules to the point of affecting, for example, the DNA contained in our cells. A chain of reactions of this type can also lead to the onset of a chronic-degenerative, inflammatory pathology or a tumor.”
What are antioxidants used for?
«The antioxidant potential of foods and, in particular, of the antioxidant molecules contained in them, has been studied for many years and for a certain period of time it was believed that the beneficial action of a diet rich in vegetables was determined by the mechanisms of antioxidant action of these molecules” explains nutritionist Roberto Mele. «In reality this statement has been questioned, because there is no in vivo evidence to this effect. Certainly foods rich in antioxidants are beneficial for health, but we cannot say with certainty that this is due to their antioxidant action. Antioxidant molecules, in fact, often carry out essential tasks for our body that go beyond the ability to fight free radicals. Let’s think for example of vitamin C, present in varying degrees in many varieties of fruit such as kiwis, citrus fruits, cherries and berries, whose main role is to contribute to the construction of collagen, a fundamental protein for cartilage and bones. In any case, oxidation phenomena, within certain limits, are physiological, and also concern aging. The body has an antioxidant system, made up of cellular compartments and enzymes, which neutralizes the free radicals that continually form, even just as a result of the normal functioning of our metabolism. To this system, foods can add antioxidant molecules, which sacrifice themselves in the presence of a free radical or regenerate the system itself, helping the organism to defend itself.”
What are the best antioxidants?
«First of all, there are antioxidant enzymes normally produced by our cells, each of which intervenes at a different level in the process of formation of free radicals, neutralizing them» explains nutritionist Roberto Mele. «Through nutrition, however, we can introduce other antioxidant molecules, for example some vitamins (A, C, E), which in addition to having a real regulatory function of some physiological processes, also exert an antioxidant action. In addition to vitamins, in foods of plant origin such as fruit there are polyphenols and carotenoids, which also generally have an antioxidant action. Depending on its chemical characteristics, the antioxidant action takes place in different parts of the cell. The large family of polyphenols includes molecules with various functions within plants: they color them, promoting their propagation by making them more attractive, or helping them protect themselves from fungi or other parasites. The best known are flavonoids, including anthocyanins, which give the typical blue color of blueberries or black grapes and also tannins and resveratrol.”
What’s special about fruit antioxidants
Among the foods richest in antioxidants there are therefore the different varieties of fruit. What is special about the compounds present in these foods compared to those rich in other vegetables, i.e. vegetables and legumes? «Fruit is often coloured: this implies that it is rich in pigments, that is, molecules that give the characteristic color to the fruit, but the antioxidants we are talking about are often pigments themselves. In reality, vegetables are also rich in antioxidants, often giving a bitter taste to the leaves, to defend themselves from potential predators. On the contrary, the fruits are often sweet because they contain seeds, therefore they attract potential consumers to encourage their diffusion” explains nutritionist Roberto Mele. «The cooking to which vegetables such as vegetables and legumes are often subjected almost always cancels the antioxidant potential of these molecules, oxidizing them, or degrading them completely. Vitamin A and vitamin C, for example, are thermolabile and are therefore more available if fresh fruit is consumed rather than cooked vegetables. Other antioxidant molecules such as lycopene present for example in tomatoes, but also in many fruits such as watermelon and pink grapefruit, on the contrary, are activated only following cooking.”
Which fruits contain the most antioxidants of all: the 10 richest fruits
Is there a ranking of the fruits richest in antioxidants? «The so-called ORAC index, which measured the antioxidant capacity of biological samples exclusively in vitro, which is still often referred to, should not be taken at face value or as an index of antioxidant activity in vivo: it is therefore a mere theoretical reference , from which no specific dietary guideline has ever been derived. It was discontinued in 2012 due to its lack of applicability to everyday life” explains nutritionist Roberto Mele. «In any case, laboratory tests showed that correctly preserved Goji berries had the highest ORAC index (over 30,000), followed by the pomegranate (over 10,000), the blueberry (3,750), the blackberry (2,650), the strawberry (2475), avocado (782), orange (750), black grapes (739), kiwi (610) and peach (170)».
