Antioxidants: Everything we need to know!

By Danae Evlogimenou

Dietitian Nutritionist (MSc)

What are antioxidants?

Antioxidants are substances that have the ability to control or eliminate active forms of oxygen (Reactive Oxygen Species (ROS)) and nitrogen (Reactive Nitrogen Species (RNS)) or free radicals known to the general public.

With the above property, antioxidants exert their protective actions on human health but also on maintaining the quality of food, protecting them from the alterations caused by oxidation.

What is the action of free radicals?

Free radicals are produced in the body under normal conditions, through the normal functions of the body and play an important role in maintaining health as they are involved in processes such as destroying pathogenic bacteria, cellular signaling, gene expression and ion transport.

When are free radicals harmful to our health?

Increasing the production of free radicals has a detrimental effect on our body. These active molecules have the ability to damage all components of the cell (oxidative damage) including proteins, polyunsaturated fatty acids, RNA and DNA and thus destroy cells.

Maintaining the balance between the production of free radicals and their neutralization through antioxidant mechanisms, is of utmost importance for maintaining human health.

Environmental factors such as stress, radiation, air pollution, drugs, smoking and unhealthy diet help increase the production of free radicals in the body. When the production of free radicals is very high and the production-neutralizing balance of ROS is lost, then oxidative stress is observed.

Oxidative stress, through studies seems to induce the development of various diseases such as:

• the cancer,
• diabetes mellitus,
• atherosclerosis,
• arthritis,
• neurodegenerative diseases,
• premature aging

Where do we find antioxidants in food?

• Most natural antioxidants are found in plant foods, mainly fruits and vegetables with a strong color.
• Fruits such as strawberries, different berries, black currants, pomegranate, peaches, cherries, orange, apples, cranberries, lemon
• Vegetables such as broccoli, spinach, red peppers, tomatoes, carrots, onions, cabbage
• But also other foods such as:
• Olive oil, avocado, nuts
• Whole grain products
• Herbs and spices e.g. oregano, thyme, dittany, marjoram, lavender, rosemary, ginger, turmeric, black pepper
• Beverages e.g. tea, coffee, cocoa, beer, wine

What are the benefits of antioxidants?

1. They play an important role in maintaining the health of the human body and prevent the occurrence of the aforementioned diseases caused by oxidative stress. Antioxidants exhibit a wide range of beneficial properties such as antibacterial, anti-inflammatory, anti-allergenic, anticoagulant, cardioprotective and vasodilator properties.

“Many antioxidant supplements are marketed in the industry for claiming that they improve health, but there is little that has actually been proven to actually promote it.”

2. They protect food from spoilage and thus maintain their quality and nutritional value. In particular, food antioxidants protect against the self-oxidation of fats, especially the unsaturated fatty acids in food, which results in the loss of nutrients, unwanted taste and the formation of harmful ingredients. Autooxidation occurs when fat comes in contact with oxygen. This is why antioxidants (natural or synthetic) are often added to food to maintain its quality.

In addition to auto-oxidation, degradation of fats is also observed in oxidation due to heat treatment for example during frying and in photooxidation due to exposure of food to light.

“This is why extra virgin olive oil, due to its high concentration of antioxidants – tocopherols – is more resistant to frying and retains its nutritional value, compared to other oils. »

What are the main antioxidants in food?

Vitamins C and E are the main nutrients that have antioxidant properties. Both vitamin C and vitamin E are powerful antioxidants, and the most important difference is that they dissolve differently in water. Vitamin C is water soluble and therefore is found especially in body fluids and not in tissues, and vitamin E is extremely lipophilic and is found mainly in cell membranes and lipoproteins.

The following are the main natural antioxidants found in food.

Vitamin C

Vitamin C or ascorbic acid is found in citrus fruits (eg lemon, orange, grapefruit), peppers, strawberries, gooseberries, broccoli, Brussels sprouts and potatoes. Humans are one of the few mammals that can not synthesize it, due to the lack of an enzyme called gluolactone oxidase, which is necessary for the synthesis of vitamin C. That is why it is necessary to take the vitamin from the diet.

Contributes to:

• Protection and maintenance of cell health
• Maintaining healthy skin, blood vessels, bones and cartilage
• Wound healing

Vitamin E

Vitamin E, or tocopherols, is found in a variety of foods and especially in vegetable oils – such as olive oil, sunflower oil and rapeseed oil, nuts and seeds, in wheat germ, ie whole grains. Vitamin E consists of 8 components that can be either tocopherols or tocotrienols.

For the absorption of vitamin E it is necessary to take fat as it is a fat-soluble vitamin. That is why people who reduce the intake of fat from their diet, at the same time show a reduced intake of vitamin E.

Contributes to:

• Maintaining skin and eye health
• Strengthening the body’s natural defenses against diseases and infections (the immune system)

Carotenoids

Carotenoids Another group of fat-soluble, antioxidants, consists of xanthophylls and carotenes. It has been documented that 90% of the carotenoids we get from our diet are β-carotene, α-carotene, lycopene, lutein and cryptoxanthin.

They are found in green leafy vegetables, carrots, tomatoes and cereal products. Tomatoes are very high in lycopene.

Carotenoids are associated with the red or orange color of the food it gives them.

Phenolic ingredients

Phenolic compounds, or polyphenols, are found in a variety of foods such as fruits (eg berries, apples, pineapples, grapes), vegetables (eg celery, broccoli, beans, artichokes, spinach), beverages (e.g. wine, tea, fruit juices), oils (eg olive oil), various spices and herbs. Phenolic constituents include flavonols, stilbenes, anthocyanins, phenolic acids, lignans and tannins.The anthocyanins found in fruits and vegetables are responsible for their red, blue and purple color.

Olive oil and antioxidants

Olive oil contains a high amount of natural antioxidants such as tocopherols, carotenoids and phenolic compounds. Hydroxytyrosol, one of the major phenolic constituents of olive oil, appears to reduce the risk of coronary heart disease and atherosclerosis.

According to the European Regulation 432/2012 (L 136 / 25.05.2012), an olive oil can have the “Health Claim”, if it has a high content of polyphenols, at least 250mg per 1 kg of olive oil. It has been documented that a daily intake of 20g, just over 1 tablespoon of Healthy Olive Oil, provides at least 5mg of hydrotyrosol and its derivatives, which help protect blood lipids from oxidative stress.

 

Caution!

Although antioxidants seem to be beneficial, great care must be taken to avoid over-consumption. Overdose of antioxidants through dietary supplements can lead to opposite results, ie toxicity due to prooxidative activity.

In conclusion, the intake of antioxidants through natural foods in our diet is considered necessary if we want to be and stay healthy! We are very lucky to be able to enjoy the foods that make up the Mediterranean Diet, a standard that seems to protect us from various diseases and is rich in foods with antioxidant activity, including olive oil which is the protagonist of fats that we should consume daily!

 

Bibliography

Cömert, E. D., & Gökmen, V. (2018). Evolution of food antioxidants as a core topic of food science for a century. Food research international (Ottawa, Ont.), 105, 76–93.

Cömert, E. D., Mogol, B. A., & Gökmen, V. (2019). Relationship between color and antioxidant capacity of fruits and vegetables. Current research in food science, 2, 1–10.

Fereidoon Shahidi, Priyatharini Ambigaipalan. (2015) Phenolics and polyphenolics in foods, beverages and spices: Antioxidant activity and health effects – A review. Journal of Functional Foods. Volume 18. Part B. Pages 820-897

Finley, J. W., Kong, A. N., Hintze, K. J., Jeffery, E. H., Ji, L. L., & Lei, X. G. (2011). Antioxidants in foods: state of the science important to the food industry. Journal of agricultural and food chemistry, 59(13), 6837–6846.

Yang, C. S., Ho, C. T., Zhang, J., Wan, X., Zhang, K., & Lim, J. (2018). Antioxidants: Differing Meanings in Food Science and Health Science. Journal of agricultural and food chemistry, 66(12), 3063–3068.

Βooks

Sareen S. Gropper, Jack L. Smith, James L. Groff, (2008). Διατροφή & Μεταβολισμός 2, Ιατρικές Εκδόσεις Π.Χ. Πασχαλίδης, σελ. 421-430, 298-309, 403-411.

Websites

FAO, Chapter 17. Dietary antioxidants: a consideration of factors influencing requirements, http://www.fao.org/3/Y2809E/y2809e0n.htm#bm23

NHS, Vitamin C-Vitamins and minerals, https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-c/

NHS, Vitamin E-Vitamins and minerals, https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-e/

Danae Evlogimenou

Dietitian Nutritionist (MSc)

He studied Dietetics-Nutrition at Harokopio University in Athens, where he graduated in 2018. As part of his internship, he worked at the 401 Military Hospital in Athens, at the private diet office NutriClinic, while gaining experience in food safety while working in the YOTIS industry. Her dissertation was entitled “Ten years of re-examination of the study ATTICA: Wine consumption and biochemical indicators of cardiovascular disease.” During her studies she attended numerous conferences and workshops on Nutrition while she continues to this day to be informed about new data and developments in this field.

She is currently working on her dissertation on “Diabetes mellitus and intestinal microbiome. The role of nutrition “, part of the postgraduate program” Diabetes and Obesity “which he attends in the Department of Medicine at the National Kapodistrian University of Athens. Finally, she maintains an active page on Instagram and Facebook, as a trustyourdietitian, informing the public about various nutritional issues in order to motivate, in a more interactive way, more people to adopt a healthier lifestyle. He also works as a dietitian in Greece and Cyprus.

He is a member of the Food Scientists Registration Council and a member of the Cyprus Dietitians Association since 2018. He has a license to practice in Greece.