Praised for many years, antioxidants are considered to be essential allies in the fight against certain diseases, to limit the effects of ageing and to support the immune system. Naturally present in the diet, antioxidants are essential to our health and well-being. But why is it so important to consume them? And what role do antioxidants play in our health? Here's how it works.
Also called oxidative stress, oxidative stress corresponds to an aggression of our cells by free radicals. Our body has natural weapons to fight against these molecules, notably by producing antioxidant enzymes, such as glutathione, catalase or superoxide dismutase. However, if free radicals are in excess, the body is overloaded: this is known as oxidative stress.
All living things need oxygen to live, but they must also protect themselves from it because it can be toxic. The source of this is free radicals, highly reactive oxygen molecules.
Our cells contain mitochondria, which provide the cells with energy. The more energy a cell needs to function, the more mitochondria it contains. In these mitochondria a series of very complicated chemical reactions take place, such as the burning of sugars and fats, which releases energy. Unfortunately, the reaction chain in our mitochondria is imperfect and leads to the formation of reactive oxygen species, including free radicals.
Free radicals are therefore formed during various biological processes. But their production is increased by external factors (pollution, UV rays, etc.), which can lead to a situation of oxidative stress, and therefore to the ageing of our cells (see our article on the power of antioxidants).
To protect itself from the toxic effects of these free radicals, the body has developed antioxidant defence systems consisting of enzymes, vitamins, trace elements and proteins. But when oxidative stress is too great, it is essential to provide our bodies with new sources ofantioxidants through the diet. Antioxidants in food (mainly vitamins A, C and E, polyphenols and minerals) are agents that can prevent, delay or slow down the oxidation process.
Once the oxidation reaction in our body is initiated, it must be stopped. Without the intervention of antioxidants, the production of free radicals would lead to the ageing of our cells, and consequently to the onset of many diseases.
Let's take the example of a fruit, such as a banana, an apple or an avocado, which, once cut, starts to turn brown. How can we explain this phenomenon? For this enzymatic browning process to take place, it needs 3 elements:
The enzymes and polyphenols are located inside the fruit cells, in small compartments. So they never touch each other. But when you cut the fruit or bite it, you damage the cells. The cells are then exposed to the air, which contains oxygen. This causes the oxidation reaction that leads to enzymatic browning.
Antioxidants therefore have the task of blocking the production of these free radicals. By pouring lemon juice on the fruit, for example, the vitamin C it contains (a powerful antioxidant), will modify the chemical composition of the molecules and slow down the ageing process. This phenomenon is exactly the same in our body: by neutralising the excess free radicals in the body, the antioxidants will block their production to prevent the premature ageing of our cells and favour the natural regeneration process.
In small quantities, free radicals help fight viruses, bacteria and microbes. In the opposite case, they can damage cells and accelerate their ageing.
Oxidative stress can promote the development of diseases such as atherosclerosis, arthritis, cardiovascular disorders and premature skin ageing.
Antioxidants are a source of vitamins that help the body fight various diseases. A regular and sufficient supply of vitamins allows good blood circulation, accelerates cell renewal, increases vascularity, stimulates the immune system and improves resistance to infection.
Oxidative stress is the main cause of skin ageing. It creates an inflammatory state and affects the upper layers of the epidermis. It is recommended to favour foods rich in vitamin C, as it helps collagen and elastin fibres to fight against excess free radicals, thus preventing the premature appearance of wrinkles and age spots.
This antioxidant of the carotenoid family is an excellent tanning activator. It increases the skin's tolerance to sunburn. By promoting the synthesis of melanin, which is responsible for tanning, beta-carotene prepares the skin for the sun and the aggression of ultraviolet rays. One of the best sources of beta-carotene is the Klamath algae, which contains 10 times more than in carrots.
Although all antioxidants are essential for vision, carotenoids are proving to be very effective. Specifically, lutein and zeaxanthin have been shown to have a preventive effect on degenerative eye diseases such as age-related macular degeneration and cataracts. These two pigments, which are naturally present in the retina, filter blue light from the sun and neutralise free radicals. They thus help to preserve ocular acuity and slow down the effects of ageing. As doesastaxanthin, which also combats eye fatigue and intraocular pressure that can lead to glaucoma.
The membranes of neurons are composed of unsaturated fatty acids that are easily oxidised. This oxidation is therefore likely to accelerate brain ageing. Several scientific studies have shown that a reduction in the level of vitamin E in the brain favours the progression of neurodegenerative diseases, such as Alzheimer's disease.
Zinc stimulates the white blood cells that fight infection and neutralises the free radicals generated by inflammation. Zinc deficiency may be involved in various chronic diseases in which inflammation plays an important role, such as cardiovascular disease and diabetes.
Studies show that the consumption of polyphenols has a significant effect on reducing inflammatory stress, which is the cause of many diseases such as diabetes, Alzheimer's and cardiovascular disease. They would thus help to reduce the release of pro-inflammatory mediators in people at risk of chronic inflammation.
The Roles of Vitamin C in Skin Health, Juliet M. Pullar, Anitra C. Carr and Margreet C. M. Vissert, Nutrients, 2017.
B-Carotene and other carotenoids in protection from sunlight, Wilhelm Stahl, Helmut Sies, The Amercian Journal of Clinical Nutrition, Volume 96, Issue 5, November 2012.
Dietary Sources of Lutein and Zeaxanthin Carotenoids and Their Role in Eye Health, El-Sayed M. Abdel-Aal, Humayoun Akhtar, Khalid Zaheer, Rashida Ali, Nutrients, 2013.
Effects of Vitamin E on Cognitive Performance during Ageing and in Alzheimer's Disease, Giorgio La Fata, Peter Weber, Nutrients, 2014.
Zinc metabolism with special reference to its role in immunity, M.T. Kidd, P.R. Ferket and M.A. Qureshi, World's Poultry Science Journal, 2019.
Oxidative Stress and Inflammation: What Polyphenols Can Do for Us? Tarique Hussain, Bie Tan, Yulong Yin, François Blachier, and al, Oxid Med Cell Longev, 2016.