What is oxidative stress? Causes, symptoms and how to fight it
What is oxidative stress? Causes, symptoms, and how to fight it
In the modern Western world, stress can become a daily companion. Among its various forms is oxidative stress. What is it? What causes oxidative stress? And how can it be fought?
Oxidative stress results from the loss of balance between oxidizing and antioxidant factors inside the cell. If prolonged, it can damage numerous cellular structures, increasing the risk of serious health problems. The damage caused by oxidative stress also generates more oxidizing factors. This can create a vicious circle where oxidative stress sustains itself. Fortunately, fighting this health enemy can be done with a tool available to everyone: maintaining as healthy and balanced a lifestyle as possible.
Oxidative stress and free radicals
The two main classes of oxidizing molecules (or free radicals) are reactive oxygen species (ROS) and reactive nitrogen species (RNS). Under physiological stress (eustress), ROS and RNS are present in small amounts and regulate gene expression, receptor activation, pathogen recognition, cell survival, and its ability to proliferate, migrate, and differentiate. However, if their production is elevated, toxic stress (distress) can occur.
In this condition, free radicals can oxidize molecules other than their natural targets, damaging them and impairing their function. Distress worsens when excessive production of oxidizing molecules is paired with weakened protective mechanisms against oxidation. The cell is equipped with defenses against free radical damage, including bilirubin, melatonin, uric acid, and antioxidant enzymes.
What causes oxidative stress?
The production of oxidizing factors is natural and necessary; they are generated during cellular energy production using oxygen and during enzymatic activity. However, there are also external causes of oxidative stress that can promote distress.
Common causes include:
- tobacco smoke;
- pollution;
- infrared rays;
- ultraviolet rays;
- exercise.
Oxidative stress and exercise
The main reason exercise and physical activity are associated with increased oxidative stress is simple: exercise increases oxygen flow in the body. Additionally, exercise-induced muscle microtrauma attracts white blood cells, whose activity increases free radicals. These phenomena are physiological but their consequences should be limited to avoid unwanted effects.
Oxidative stress is linked to inflammation. A certain degree of inflammation after physical activity is beneficial for muscle regeneration and new muscle mass formation. However, prolonged inflammation can impair recovery, causing weakness, muscle pain, and reduced performance in subsequent days. Conversely, reducing oxidative stress improves post-exercise and post-competition performance.
How does oxidative stress manifest?
Before evident symptoms like decreased athletic performance appear, high oxidative stress damages key biomolecules: lipids, proteins, and nucleic acids (DNA and RNA). Lipids can undergo peroxidation, including Omega-3 fats, which lose their properties through this process. Peroxidized lipids and Omega-3s are highly reactive and can modify proteins and DNA undesirably. DNA and RNA building blocks can be oxidized; oxidative stress can even break DNA strands, causing mutations and dangerous genetic rearrangements. Protein oxidation changes their shape and function.
Long-term irreversible alterations of lipids, proteins, and nucleic acids and their structural and functional damage may lead to health issues. Sustained high oxidative stress can manifest as:
- Neurodegeneration: oxidative stress plays a role in Alzheimer’s disease and is hypothesized to be involved in Parkinson’s disease.
- Cardiovascular disorders: increased ROS are linked to functional and structural changes impairing circulation. Free radicals associate with atherosclerosis, stroke, heart attack, and peripheral artery disease.
- Diabetes: oxidative stress can impair insulin synthesis and function, affecting blood sugar control. It also contributes to diabetic vascular complications.
- Cancers: even moderate oxidative stress can cause mutations favoring cancer development. Protein and lipid oxidation associate with tumor onset and progression.
- Autoimmune diseases: oxidation can create molecules seen as foreign by the immune system, triggering autoimmune responses.
- Rheumatoid arthritis: oxidative stress both causes and results from inflammation characteristic of this disease. ROS can kill cartilage cells and promote joint degeneration.
- Kidney diseases: oxidative stress is a major cause of kidney damage and links to risk factors like hypertension, diabetes, and atherosclerosis.
- Eye diseases: macular degeneration, cataracts, uveitis, retinopathy of prematurity, keratitis, and ocular inflammation are linked to oxidative stress.
Oxidative stress analysis
There are three approaches to oxidative stress analysis. One involves tests evaluating oxidative stress by analyzing levels of oxidation products. Another measures free radical levels directly; such tests are used for assessing oxidative stress in sperm of men with fertility issues, employing chemiluminescence and flow cytometry. Indirect measurements include lipid peroxidation, redox potential, and total antioxidant capacity.
Finally, oxidative stress can be analyzed via genetic testing, which assesses predisposition to accumulate free radicals as encoded in genes rather than current stress levels.
How to fight oxidative stress?
As mentioned, cellular defenses are not always sufficient to effectively combat free radicals, especially in high quantities. What can be done to reduce oxidative stress? Prevention by limiting exposure to agents that promote free radical formation, like tobacco smoke, is one way. Another is enriching defenses with exogenous antioxidants from foods and supplements.
How do antioxidants from food and supplements work?
There are different types of antioxidants:
- Primary antioxidants prevent free radical formation;
- Secondary antioxidants eliminate free radicals;
- Tertiary antioxidants repair molecules damaged by oxidative stress.
What are the best natural antioxidants?
Among the best natural exogenous antioxidants are vitamin C, vitamin E, carotenoids, selenium, zinc, phenolic compounds, lecithins, and coenzyme Q10. They are found mainly in plant foods; a diet rich in fruits and vegetables effectively counters oxidative stress consequences.
| NATURAL EXOGENOUS ANTIOXIDANTS | SOURCES |
| Vitamin C | Fruits and vegetables (citrus, kiwi, strawberries, spinach, broccoli, Brussels sprouts, red peppers), supplements |
| Vitamin E | Vegetable oils, broccoli, almonds, walnuts, seeds, supplements |
| Carotenoids | Leafy green vegetables (cabbage, spinach), fruits and other vegetables (kiwi, apricots, tomatoes, carrots) – better consumed with a significant amount of fat like eggs – supplements |
| Phenolic compounds | Fruits (berries, grapes, citrus, apricots, apples, plums, cherries, peaches, tropical fruits), vegetables (onions, spinach, broccoli, cauliflower, artichoke, tomatoes, carrots), legumes, olives, spices and herbs (cloves, turmeric, parsley, celery, mint, rosemary, thyme, sage, ginger), infusions (tea, cocoa), oils, supplements |
| Lecithins | Vegetable oils (soy, corn, sunflower), supplements |
| Selenium | Shrimp, oysters, tuna, meat, nuts, pasta, supplements |
| Zinc | Meat, shellfish, peas, mushrooms, spinach, legumes, asparagus, broccoli, nuts, cocoa, supplements |
| Coenzyme Q10 | Fatty fish (salmon, tuna), offal (liver), whole grains |
| Curcumin | Turmeric, supplements |
Omega-3 fatty acids are also attributed antioxidant properties. This is one reason why they are considered allies of athletes’ health: they can help manage post-workout and post-competition oxidative stress and the associated inflammatory phenomena.
What are the best antioxidant supplements?
Many antioxidants found in food can also be taken as supplements against oxidative stress today. Unfortunately, their effectiveness is not always comparable to that of consuming fruits and vegetables. In some cases, unexpected side effects have been documented. For example, beta-carotene supplements are not recommended for smokers: despite their antioxidant potential, they may increase lung cancer risk in smokers. In other cases, such as vitamin E, negative effects are linked to very high doses of antioxidants.
It is therefore essential that supplements against oxidative stress are taken only after ensuring no contraindications (such as smoking in the case of beta-carotene). At the same time, it is important to make sure that antioxidant doses are not excessive. These precautions, along with preferring products guaranteeing high standards of purity and freshness of ingredients, allow getting the maximum benefits from antioxidant supplements without health risks.
Finally, a curiosity. In some supplements, antioxidants serve a specific collateral function: protecting other ingredients from oxidation. For example, vitamin E, used in safe concentrations, can be used to prevent oxidation of Omega-3s in fish oil supplements and thus ensure product quality. In Omega-3 supplements from krill oil, this action is performed by another natural antioxidant, astaxanthin, a carotenoid naturally present in this oil.
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