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What is oxidative stress?

Oxidation, how does it work?

Oxidation is a chemical reaction that takes place in the presence of oxygen. You can see it when you cut an apple: once cut, the apple tends to turn brown because one of its enzymes reacts with oxygen and transforms a molecule (called phenol) into another molecule (called quinone) which will decompose into a brown pigment. The addition of lemon juice will slow down this browning because it contains vitamin C, a strong antioxidant, which will reduce the quantity of quinones and thus prevent the brown pigment from appearing.

It is the same balance between oxidation and anti-oxidation that takes place in each of our cells. Of course, we need oxygen to live and each of our cells uses it in many processes. During some of these reactions, for example when ATP cell energy is produced, free radicals (ROS – reactive oxygen species) are formed. Their presence – in small quantities – is normal, and they have certain functions such as communication between cells, the synthesis of cellular components or as a weapon of the immune system against pathogens. At the same time, ROS are constantly detoxified by certain antioxidant enzymes or by other mechanisms, to become harmless products, such as water H2O.1,2 An oxidative balance is reached, and normally works very well! Except that this is not always the case…

It’s all a question of balance… Otherwise, it’s oxidative stress!

Oxidative stress is a phenomenon caused by an imbalance between the production and accumulation of free radicals (ROS) in cells and tissues, and our body’s ability to detoxify these reactive products.1

While the presence of ROS created by our cellular metabolism is normal, certain environmental factors, such as UV rays, ionizing radiation, pollutants, heavy metals, tobacco, alcohol, certain drugs and chemicals, contribute to a significant increase in the production of ROS. This large amount of ROS cannot be fully detoxified by our antioxidant defences, and this imbalance leads to cell and tissue damage. This is called oxidative stress.

To counteract this, there are also exogenous antioxidants which can react with ROS to render it harmless, prevent its production or activate antioxidant enzymes.1,2  Vitamins B2, C, E, selenium, copper, manganese, zinc and polyphenols in olive oil help protect cells from oxidative stress.

Why is oxidative stress negative?

When there is too much ROS in relation to our antioxidant defences, the membranes of our cells and our proteins, lipids, DNA etc. will be “attacked” and damaged.1 Changes in the DNA of a cell lead to a deregulation of its functions and “behaviour”, which will impact the tissue in which it is located. 

Aging can be defined as “the progressive loss of function of our tissues”, and the repetition of damage due to excess ROS can therefore accelerate it. Thus, over time, if oxidative stress is not reabsorbed, damage accumulates, tissues are no longer able to maintain their homeostasis and become dysregulated.1 Moreover, with age, antioxidant defences are reduced, making us more sensitive to excess ROS.4

Fortunately, it is never too late to get involved in reducing oxidative stress in our bodies. The generation of exogenous ROS can be minimised by avoiding exposure to radiation, pollutants, heavy metals, tobacco and alcohol, certain drugs and chemicals.

Beneficial physical activity

Moderate and regular aerobic physical activity (long, low-intensity aerobic exercise using oxygen in the muscles) is also important to limit the accumulation of oxidative stress because it stimulates antioxidant defences, especially in the muscles. It is also essential for maintaining good health in general. However, high-intensity physical activity will increase oxidative stress in our bodies.4


Disclaimer of liability:
The information published on does not claim to be complete and is not a substitute for individual medical advice or treatment. It cannot be used as an independent diagnosis or to select, apply, modify or discontinue treatment of a disease. In case of health problems, it is recommended to consult a doctor. Access to and its contents is at the user’s own risk.


  1. Pizzino, G. et al. Oxidative Stress: Harms and Benefits for Human Health. Oxidative Medicine and Cellular Longevity vol. 2017 (2017).
  2. Burton, G. J. & Jauniaux, E. Oxidative stress. Best Practice and Research: Clinical Obstetrics and Gynaecology vol. 25 287–299 (2011).
  3. Birben, E., Sahiner, U. M., Sackesen, C., Erzurum, S. & Kalayci, O. Oxidative stress and antioxidant defense. World Allergy Organization Journal vol. 5 9–19 (2012).
  4. Liguori, I. et al. Oxidative stress, aging, and diseases. Clinical Interventions in Aging vol. 13 757–772 (2018).
  5. Salim, S. Oxidative stress and the central nervous system. Journal of Pharmacology and Experimental Therapeutics vol. 360 201–205 (2017).
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