WHY ARE ANTIOXIDANTS GOOD?

To begin we must understand what oxidative stress is, what compounds cause it and why it happens.

During cellular metabolism, which is the process used by cells to obtain energy and form macromolecules, multiple products and intermediates are produced. These include the famous free radicals, highly reactive (unstable) atoms or molecules that attack the bonds of tissue proteins, phospholipids in cell membranes, carbohydrates and DNA. There are different types of free radicals depending on the atoms they are made of, the most common being reactive oxygen species and reactive nitrogen species . These are generated physiologically, i.e. naturally in the body, and this does not pose any problem, since the basal levels of these free radicals are necessary to perform some physiological functions and are subsequently neutralised by our antioxidant system .

However, sometimes there is an excess of free radicals or a deficiency in the defense system, which causes an imbalance known as oxidative stress. This phenomenon plays an important role in aging and various diseases such as obesity, cardiovascular diseases, neurodegenerative diseases, kidney diseases, diabetes, cancer and chronic inflammation, among others.

So, we know that cells produce free radicals but our defense mechanism acts to maintain the balance . This antioxidant defense system includes antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase, among others) which are the most effective system, and other small molecules such as vitamins A, C and E, glutathione , coenzyme Q10 , polyphenols (mostly flavonoids), carotenoids , melatonin , curcumin and lipoic acid . Some of these are endogenous , that is, they are produced by our body and others are exogenous , we provide them through the diet.

What external situations increase the production of free radicals?

Some examples are excessive exposure to ultraviolet radiation , prolonged stress situations, an inappropriate diet , very intense physical exercise, tobacco and alcohol consumption, and the consumption of certain stimulant substances or drugs.

In terms of diet, excessive consumption of carbohydrates such as glucose and fructose, red meat and saturated fats leads to the formation of free radicals that cause oxidative stress and subsequently an inflammatory environment. This decreases insulin sensitivity, increases the proliferation of cancer cells and is also related to the formation of adipose tissue (fat).

Therefore, a sedentary lifestyle and a diet based on these foods are associated with obesity, as well as other related diseases, such as diabetes, cardiovascular disease and cancer. On the contrary, the consumption of foods such as whole grains containing fiber, nuts, fruits and vegetables (rich in antioxidants such as vitamins E and C, beta-carotene and flavonoids), fish and legumes contribute to the reduction of oxidative stress and the inflammatory environment.

Illustration 1. Adapted from Sharifi-Rad M, Anil Kumar NV, Zucca P, et al. Lifestyle, Oxidative Stress, and Antioxidants: Back and Forth in the Pathophysiology of Chronic Diseases. Front. Physiol. 11:694. (2020) doi: 10.3389/fphys.2020.00694

What about antioxidant-based supplementation?

Although a priori, the extra supply of synthetic antioxidants can improve the body's ability to combat oxidative stress, their use is controversial. In some cases the recommended daily intake is not sufficient to counteract oxidative stress and excessive antioxidant supplementation with vitamin A, vitamin E and beta-carotene can be unsafe or result in pro-oxidants. This may be due to the differences in the functionality and composition of antioxidants that come from natural sources and those that are synthetic. However, there are multiple compounds and studies on the subject that show certain benefits, so it is ideal to analyze them individually.

In short, the best strategy is to prevent the formation of free radicals by complementing our endogenous antioxidant defense with a diet rich in antioxidants and adopting healthy lifestyle habits. Let us not forget that a high intake of antioxidants does not compensate for an unhealthy lifestyle.

Written by Maria Caballero

Pharmaceutical

Literature:

Guo, Q., Li, F., Duan, Y. et al. Oxidative stress, nutritional antioxidants and beyond. Sci. China Life Sci. 63, 866–874 (2020). https://doi.org/10.1007/s11427-019-9591-5

 Jomova, K., Raptova, R., Alomar, SY et al. Reactive oxygen species, toxicity, oxidative stress, and antioxidants: chronic diseases and aging. Arch Toxicol 97, 2499–2574 (2023).

Pisoschi AM, Pop A. The role of antioxidants in the chemistry of oxidative stress: A review. Eur J Med Chem. 2015 Jun 5;97:55-74. doi: 10.1016/j.ejmech.2015.04.040. Epub 2015 Apr 22. PMID: 25942353.

Sharifi-Rad M, Anil Kumar NV, Zucca P, et al. Lifestyle, Oxidative Stress, and Antioxidants: Back and Forth in the Pathophysiology of Chronic Diseases. Front. Physiol. 11:694. (2020) doi: 10.3389/fphys.2020.00694

Tan BL, Norhaizan ME, Liew WP. Nutrients and Oxidative Stress: Friend or Foe? Oxid Med Cell Longev. 2018 Jan 31;2018:9719584. doi: 10.1155/2018/9719584. PMID: 29643982; PMCID: PMC5831951.