What is oxidative stress and how to limit it?

Different factors influence the formation of oxidative stress, including:

• Internal factors : mitochondrial alteration, endothelial dysfunction (abnormality of blood vessel dilation of endothelial tissue), chronic inflammation (activation of white blood cells), iron overload, hyperglycemia, hypercholesterolemia.

• External factors : air pollution, exposure to asbestos and nanoparticles, irradiation, surgical operations, etc.

• The lifestyle : smoking, exposure to the sun, sedentary lifestyle, overweight and obesity, intense physical exercise, diet poor in fruits and vegetables, excessive cooking (fried food, grill, barbecue), taking medications (such as birth control pills), consumption of meals high in lipids (postprandial oxidative stress).

The body needs a balance between oxidizing and antioxidant molecules. Indeed, the latter has some advantages to being in a state of oxidative stress. ROS play a key role in the inflammatory response, in cell signaling and in the signaling pathways involved during exercise such as insulin sensitivity and the formation of mitochondria (component of cells allowing energy production) . As for the famous free radicals, they are part of ROS and play a beneficial role in force production. This is one of the reasons why oxidative stress is greatly increased during physical exertion, in addition to the increase in oxygen consumption.

However, modern lifestyle exposes the population to favor oxidative stress much higher than it should be. This excess free radicals therefore brings negative actions on the body, and in particular on the oxidation of cellular constituents. Indeed, ROS are unstable molecules composed of one free electron, and seeking at all costs to stabilize. They therefore attack the cellular constituents of lipids (alteration of membranes), proteins (inactivation of carbonyl derivatives), and also causes DNA mutations (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid). Indeed, oxidation generally affects proteins, but the latter remains reversible. However, in the event of an imbalance in oxidative stress, oxidation becomes irreversible and also affects lipids and DNA.

Oxygen therefore has paradoxical effects because it is both essential for maintaining life, but it is also responsible for the production of ROS which causes serious oxidative damage to the body. The consumption of antioxidants is therefore essential since they help fight against the harmful effects of an excess of free radicals.

Oxidative damage induces cellular mutations and impacts cell nuclei. Overexposure to oxidative stress is therefore the cause of numerous consequences on the body:

• Different types of illness :

• Disease by protein oxidation : Alzheimer (modification of beta-amyloid peptides by protein oxidation); Parkinson's (damage to brain cells by protein oxidation).

• Disease by lipid oxidation : myocardial ischemia, atherosclerosis, hypertension, cardiomyopathy, cardiac hypertrophy, congestive heart failure (due to peroxynitrite, a free radical).

• Disease by DNA oxidation : Cancers.

• Chronic inflammations : asthma, rheumatoid arthritis, tendonitis, osteoarthritis, acute glomerulonephritis, renal failure and allergy.

• Acceleration of aging cellular : degradation of the immune system (viral and bacterial infections), premature aging of tissues (skin, hair, etc.) and organs.

• Reduced performance for athletes : intense physical exercise leads to an overproduction of free radicals, which causes venous insufficiency causing muscle pain, cramps and injuries.

Halliwell and Gutteridge gave the following definition to antioxidants: “Substance which inhibits or significantly delays the oxidation of a substrate, although it presents a very low concentration in the environment in which it occurs”. Chemically, an antioxidant is therefore a reducing compound that reacts with an ROS to neutralize it, by stabilizing the negative charge of the free radical with a positive charge. Antioxidants therefore protect molecules from oxidation and the damage that can result from it. It is therefore recommended to increase antioxidant intake through diet. In general, these antioxidants have a trapping role, and particularly in trapping superoxide ion O_2-. This oxygen molecule carries an extra electron and constitutes a highly reactive free radical and toxic. The modern diet is too low in antioxidants, which leads to an excess of free radicals. THE dietary antioxidants the best known are vitamin C, vitamin E, beta-carotene, zinc, selenium or certain polyphenols such as curcumin, quercetin, etc.

Overweight and obesity have been shown to optimize oxidation. A unbalanced diet is also a major factor in oxidative stress. It has been noted that hyperglycemia (high blood carbohydrate levels) and hypercholesterolemia (high cholesterol levels) chronicles favored the formation of free radicals. Finally, for high-level athletes carrying out intense activities, oxygen consumption increases tenfold, causing at the same time an increase in ROS. It is therefore recommended to optimize dietary intake of antioxidants because it is not possible to reduce the increase in oxygen consumption induced by exercise.

Polyphenols have also been the subject of numerous studies recently, and it has been accepted that they have a very specific role in oxidative stress. In fact, they act in hormesia, that is to say they adapt according to oxidative stress. Therefore, if oxidation is significant, the polyphenols will act as antioxidants. Conversely, they can play the role of oxidizing molecules when supplied in small quantities. They thus make it possible to maintain the body's antioxidant systems and their ability to "react" in the event of greater oxidative stress. Thus, recent studies advocate an increase in their consumption in everyday foods, with more fresh and colorful products, aromatic plants and spices. Polyphenols are very common in plants, and they are known for their abundance in the red wine and the green tea. Be careful when drinking red wine. Indeed, the induction of oxidative stress is part of the mechanisms of alcohol toxicity. In addition, given the impacts of overconsumption of alcohol on health, it is recommended not to consume more than 2 glasses of red wine per day.

Antioxidants are generally present in most spices and aromatics, as well as in fruits and vegetables. It is recommended to vary food sources in order to diversify the intake of antioxidant molecules.

• Vitamin E (tocopherol and tocotrienol): Vitamin E requirements are estimated at 10 mg per day by ANSES (National Agency for Food Safety). Food sources of vitamin E are: wheat germ oil, sunflower oil, avocado vegetable oil, sweet Almond vegetable oil, cod liver oil, nuts (sun-flower seeds, almonds, hazelnut) and cereal sprouts.

• Vitamin C (ascorbic acid): Vitamin C requirements are estimated at 110 mg per day by ANSES. Food sources of vitamin C are: acerola powder, guava, blackcurrant, parsley, thyme, avocado, lamb's lettuce, spinach, watercress, garlic, cabbage, asparagus, Brussels sprouts, broccoli, beetroot and peppers (especially red).

• Beta carotene (precursor of vitamin A): Vitamin A requirements are estimated by ANSES at 750 mcg per day for men, and 650 mcg per day for women. Food sources of beta-carotene are mainly the following plant foods: sweet potato, carrot, pumpkin, dandelion, parsley, lettuce, spinach, mango and melon.

• Zinc : Zinc requirements are estimated around 11 mg per day on average by ANSES. Food sources of zinc are: meat (especially beef), fish, eggs, dairy products, oysters, crab, wheat germ and sesame.

• Selenium : Selenium requirements are estimated at 70 mcg per day by ANSES. Food sources of selenium are: royal kombu, brazil nut, fish (cod, red monkfish, pomegranate, tuna), egg, meat (pork kidney, raw mullet, duck liver).

• Polyphenols : Generally speaking, these polyphenols are found in spices and herbs, but also in all colored fruits and vegetables:

  • Fruits and vegetables red (anthocyanins, lycopenes): beetroot, cherry, red cabbage, strawberry, tomato, red onion, red pepper, red apple and red radish.

  • Fruits and vegetables blue-purple (polyphenols, flavonoids): eggplant, blackcurrant, raspberry, blackberry, plum, prune, grape.

  • Fruits and vegetables greens (polyphenols): avocado, broccoli, spinach, kiwi, Brussels sprouts, green beans, green pear and green pepper.

  • Fruits and vegetables yellow orange (beta-carotene, lutein, zeaxanthin, quercetin): apricot, pineapple, carrot, lemon, mango, orange, papaya, peach and yellow pepper.

• Sulfur compounds : garlic in particular.

There are different ways to limit the formation of ROS. First of all, it is recommended to:

• favor natural products and limit the consumption of food pollutants present in the food and cosmetic industries (contaminants, preservatives, colorings, sweeteners, etc.).

• limit the excessive cooking such as barbecues, grilling, planchas, frying and cooking in oil at high temperatures. In fact, they quickly induce a Maillard reaction (reactions between a reducing sugar and proteins) which give particularly pleasant aromas and colors to certain foods. Unfortunately, this set of reactions is a big cause of oxidative stress.

• reduce alcohol and tobacco consumption.

• do not abuse sun exposure (especially without full screen).

• move away from stressful environments and reduce daily stress. To reduce the latter, it is possible to turn to meditation and breathing techniques (cardiac coherence). Moreover, essential oils are very effective against stress. Infusions also help limit daily stress, such as Fragrant Verbena, Rose and Lavender. Sleep also plays an important role in the formation of the latter, also inducing oxidative stress.

• find time during the day to rest well, and especially at night. Indeed, even naps of 15 to 30 minutes can have a truly beneficial impact on the body, and particularly on stress.

• avoid meals that are too large, too fatty and too sweet. Indeed, it has been proven that overweight and obesity optimize oxidation. A unbalanced diet is also a major factor in oxidative stress. It has been noted that hyperglycemia (high blood carbohydrate levels) and hypercholesterolemia (high cholesterol levels) chronicles favored the formation of free radicals.