Antioxidant Substances and Their Influence on Human Health

Antioxidant substances, also known as antioxidants, are a large group of compounds present in food. They can be vitamins, minerals, and bioactive substances. Their main source is plant products such as fruits and vegetables. Almost every plant contains these substances. Their primary function is to neutralize free radicals in the human body. Free radicals, also known as oxidants, are naturally produced in small amounts in the body, for example, through cellular respiration. Certain amounts do not pose a risk, but excess can have negative effects on human health. This condition is known as oxidative stress and occurs when the ratio of the amount of oxidants to the amount of antioxidants is not correct. This can increase the risk of developing many types of cancer, metabolic, neurodegenerative diseases, and disorders of the cardiovascular system. To combat oxidative stress, it is recommended to maintain a healthy and balanced diet that allows the intake of the required amounts of antioxidant substances. Antioxidant substances include vitamins C, A, and E. On the other hand, minerals that have an antioxidant effect are selenium, zinc, copper, cobalt, and manganese. Other antioxidant substances are, for example, carotenoids and flavonoids.

Fruits and vegetables are distinguished by the highest content of antioxidants. Small amounts are also present in legumes, nuts, seeds, and kernels. The main source of Vitamin C in food is the already mentioned fruits and vegetables. There is an understanding that citrus fruits (especially lemons) are the main source of Vitamin C, however, their sour taste does not mean that they contain the greatest amount. The most important characteristics of cereal fruits, plants, grains, and nuts are the aforementioned fruits and vegetables. Vitamin A can also be found mainly in eggs, meat, cheese, and butter. One of the strongest antioxidants is beta-carotene, which is referred to as provitamin A because it is made exactly from it. The amount of Vitamin A in 100 g of selected products (H.. Kunachowicz and colleagues 2016). Vitamin E is contained in plant products. Its particularly good source are vegetable oils, such as rapeseed oil, olive oil, or sunflower oil. It can also be found in margarine, nuts, seeds, kernels, and grain products. The amount of Vitamin E in 100 g of selected foods (H.. Kunachowicz and colleagues 2016). The most well-known minerals that have an antioxidant effect are zinc and selenium. The former can be found in meat, offal, grain products, nuts, and seeds. The main source of selenium are Brazil nuts, fish, meat, and eggs. The amount of zinc and selenium in 100 g of selected products (M.. Jarosz, H. Stolińska, D.. Wolańska 2014). The next antioxidants are carotenoids. This is a group of compounds that occur mainly in vegetables such as spinach, chard, carrot, broccoli, pepper, and tomato. They are pigments that give plants a yellow, orange, and red color. Carotenoids also include the previously mentioned beta-carotene, which has the highest antioxidant activity. However, this group also includes lutein, zeaxanthin, and lycopene. Zeaxanthin can be found mainly in green vegetables, lutein in orange and yellow vegetables and fruits, and lycopene in red vegetables (J.. Igielska-Kalwat, J. Gościańska, I.. Nowak 2015). Flavonoids are another group of compounds that have a strong antioxidant effect. They can be divided into flavones, isoflavones, flavanones, flavonols, and anthocyanins. This classification results from the structural differences of the compounds. They can not only give food color but also aroma and taste. Products that are particularly rich in these compounds are fruits and vegetables, but also cocoa, coffee, tea, and some grain products (K.. Kałwa 2019).

As previously noted, the main function of antioxidants in the human body is to counteract free radicals. An excess of oxidizing substances leads to oxidative stress, which can contribute to disorders in the functioning of numerous bodily systems and the development of severe diseases. Hypertension, atherosclerosis, diabetes, and cancer are among the most common ailments. Furthermore, the accumulation of free radicals may lead to impairment of the immune and nervous systems, as well as premature skin aging.

Free radicals contribute to the development of many types of cancers, such as skin cancer caused by UV radiation. In human skin, there are lipid-containing structures that can be quickly and easily oxidized by free radicals. Providing antioxidants can counteract this process at an early stage, i.e., the first mutation. Numerous studies have particularly highlighted the anti-cancer activity of carotenoids and flavonoids (H. Puzanowska-Tarasiewicz, H. L. Kuźmicka, M. Tarasiewicz 2010). Flavonoids not only lower the risk of cancer due to their antioxidant properties, but they can also reduce the mutagenic activity of certain promutagens that require activation. Furthermore, they induce the apoptosis process, i.e., cell death, which also lowers the risk of cancer. Research has shown that genistein, an isoflavonoid, can reduce the risk of breast, colon, and prostate cancer (R. M. Tamimi et al. 2002).

Free radicals can also influence the development of cardiovascular diseases. They have been shown to particularly increase the risk of atherosclerosis and coronary artery disease. The oxidation of LDL lipoproteins accelerates the formation of atherosclerotic plaques, which can lead to significant damage to endothelial cells. This plays an important role in the pathogenesis of respiratory diseases. An appropriate intake of antioxidant substances can significantly reduce this risk before free radicals can cause serious damage. The preventive role of vitamins E and C, as well as carotenoids and flavonoids, is particularly noteworthy (K.. Malekmohammad, R. D. E. Sewell, M. Rafieian-Kopaei 2019). Furthermore, it has been shown that flavonoids reduce the risk of LDL cholesterol and strengthen the walls of blood vessels (K.. Kałwa 2019).

Each of the antioxidants has a positive impact on the functioning of the body of both women and men. Vitamin A protects against genital tract infections and promotes the proper course of pregnancy. Vitamin C affects the quality of semen in men and is extremely important in the ovulation phase in women. Vitamin E supports vascular blood vessels and strengthens cell membranes, which is also very important for maintaining high fertility. However, mineral ingredients that have antioxidant properties may primarily affect the growth of semen and the development of male genital cysts. Adequate zinc intake supports the proper course of the menstrual cycle in women. The authors of a scientific article analyzed 50 different studies to investigate the effects of antioxidants on the fertility of women. However, based on the obtained results, no conclusions can be drawn. The evidence is of poor quality, and no positive impact of oral supplementation on the fertility of women can be confirmed (M.. G. Showell 2017). In another study, it was noted that supplementation with antioxidants does not have any special effects in the treatment of infertility in women. However, a positive impact was observed in the partners of the women studied. However, it is not known which compounds and in which doses are responsible for this, but their positive impact on the fertility of men is emphasized (A.. J. Gaskins, J. E. Chavarro 2018). Inadequate nutrition and insufficient intake of antioxidants from the diet can worsen the quality of semen and reduce the mobility of sperm. Furthermore, oxidative stress associated with an excess of free radicals significantly reduces the fertility of men (K.. Wiktorowicz, K. M. Okręglicka, A.. Nitsch-Osuch 2019).

Numerous cosmetic products encompass antioxidant compounds, frequently in the form of vitamin E and C supplements, e.g. in ointments or balms. These compounds exert a beneficial impact on the condition of skin coverings. Oxidative stress can instigate the oxidation of skin proteins, which leads to the weakening of the skin conditions and the acceleration of the aging process.

Based on extensive research, it can be concluded that antioxidants have a positive impact on the functioning of many body systems. A deficiency in these substances is primarily a result of a disrupted ratio between their quantity and the quantity of free radicals. This in turn leads to oxidative stress, which can contribute to the development of many dangerous diseases, including cancers. It is recommended to adhere to a diet rich in vegetables and fruits, as these are the primary sources of antioxidants.