What causes oxidative stress?
If you’re interested in health and wellbeing, you’ve probably heard of oxidative stress – but how much do you actually know about it? The science behind this term might seem complicated at first, but it’s really just a balance of good and bad influences in the body.
Understanding what these influences are and how they come about can help you to make informed lifestyle choices that better support your overall wellbeing.
Do free radicals cause oxidative stress?
Yes, free radicals are central to oxidative stress.
Free radicals are unstable molecules produced naturally in the body during everyday processes such as breathing and energy production.¹ In small amounts, they are normal and even necessary, as they help the body to fight infections and perform other vital functions.
The problem arises when free radicals accumulate faster than your body can neutralise them with antioxidants. This imbalance is what we call oxidative stress.
Over time, oxidative stress can damage cells, proteins and DNA. In real-world terms, this can contribute to faster ageing of the skin, increased inflammation, fatigue and even a higher risk of chronic conditions such as heart disease or diabetes.
Antioxidants don’t destroy free radicals, but they neutralise them. Nutrients such as vitamin C and vitamin E play an important role in neutralising these unstable molecules.²
When free radicals outnumber available antioxidants, oxidative stress develops. Over time, this can contribute to cellular damage and inflammation.³
How do you get oxidative stress?
Oxidative stress is always caused by this imbalance between free radicals and antioxidants in the body – but the imbalance itself can be influenced by a variety of factors. This means different people can experience oxidative stress for different reasons, and that’s part of why it’s so important to look after your overall wellbeing and not simply focus on one area.
Some contributing factors increase the production of free radicals in the body. Others reduce or limit your antioxidant levels. In many cases, several of these factors combine within everyday life without you even realising.
Why should you care? Well, by reducing your exposure to certain triggers for free radical production and maintaining a healthy intake of antioxidant nutrients, you can help to protect your body against the effects of oxidative stress.
Below are some of the most common contributors to oxidative stress in everyday life.
Smoking
Cigarette smoke contains a large number of oxidising chemicals, such as formaldehyde, benzene and free radicals themselves.⁴ These compounds significantly increase free radical production in the body.
Smoking can also affect your levels of certain antioxidants, including vitamin C.⁵ This happens because the free radicals and oxidising chemicals in cigarette smoke react with these antioxidants, using them up more quickly than your body can replace them.
As a result, your natural defence system is weakened, leaving cells more vulnerable to oxidative stress. This creates a double effect of more free radicals and fewer protective nutrients and, over time, this imbalance contributes to increased oxidative stress.
Secondhand smoke can have similar effects, meaning that even if you don’t smoke yourself, being around smokers can increase your oxidative stress. Similarly, while e-cigarettes or vapes are often marketed as safer alternatives, they still produce oxidising chemicals that may impact antioxidant levels – though research is ongoing.
Alcohol
Excessive alcohol consumption can increase oxidative stress because when your body breaks down alcohol, it produces reactive molecules called reactive oxygen species (ROS).⁶ These molecules are a type of free radical that can damage cells if they build up faster than your body can neutralise them. Over time, this extra oxidative stress can contribute to inflammation, liver strain and damage to other tissues in the body.
At the same time, alcohol can lower your body’s antioxidant defences, especially in the liver, by depleting key nutrients such as vitamin C and glutathione. These antioxidants normally help to neutralise free radicals, so when their levels drop, the liver becomes more vulnerable to oxidative damage from alcohol metabolism.
Having a drink now and then is usually fine and won’t cause major long-term issues for most people. However, drinking too much on a regular basis can add extra stress to your body and increase oxidative damage over time.
Poor diet
A diet low in fruit, vegetables and whole foods may, among other health impacts, reduce your overall antioxidant intake. Vitamins such as C and E, along with plant compounds like polyphenols, help to neutralise free radicals.²
Some examples of foods rich in these antioxidants include:
- Vitamin C: oranges, strawberries, bell peppers
- Vitamin E: almonds, sunflower seeds, spinach
- Polyphenols: berries, dark chocolate, green tea.
Including a variety of these foods in your diet can help to support your body’s natural defence against oxidative stress.
Highly processed foods, especially those high in refined sugars and unhealthy fats, can increase oxidative stress because they trigger the body to produce more free radicals.⁷ This happens in part because the metabolism of excess sugar and certain fats generates reactive molecules, which can overwhelm the body’s natural antioxidant defences if consumed in large amounts regularly.
Making sure you get enough nutrients with antioxidant properties is a great way to support oxidative balance, as well as your overall health and wellbeing. Most people can do this through a healthy, balanced diet – but some may need additional support.
This is where supplements can help. For example, a high-strength option such as Vitamin C 1000 mg tablets can complement a varied diet when needed. Broader nutritional support may also be helpful, so a multivitamin such as NX Multi Women could be a good choice for those looking to maintain overall micronutrient intake.
Excessive exercise
Regular physical activity is excellent for your health, but very intense or prolonged workouts can temporarily increase the amount of oxygen your body uses.⁸ More oxygen means your cells are working harder and producing more free radicals as a natural by-product of energy production.
Usually, your body’s antioxidant defenses can manage this, but during intense exercise the balance can tip slightly, leading to a temporary increase in oxidative stress. In most healthy individuals, the body adapts by strengthening its own antioxidant systems over time. Problems are more likely when recovery, nutrition and rest are inadequate.
To help combat this, you can prioritise proper post-workout recovery, eat a diet rich in antioxidant-containing foods like fruits and vegetables and ensure you get enough sleep and rest between intense exercise sessions.
Psychological stress
Chronic psychological stress has been associated with increased markers of oxidative stress.⁹ This means that ongoing stress can lead to higher levels of free radicals in the body, which can, over time, damage cells and tissues.
Studies have shown that people experiencing long-term stress – such as work pressure, caregiving responsibilities or emotional strain – tend to have higher oxidative stress markers in blood tests compared to those with lower stress levels. Stress hormones like cortisol may play a role by influencing metabolism and the body’s antioxidant defenses, making it harder for your body to neutralise free radicals effectively.
Stress hormones may also influence metabolic processes, potentially increasing free radical production. Studies are ongoing to understand the exact link between psychological health and oxidative stress, but early indications suggest that chronic stress may elevate free radical levels and reduce antioxidant efficiency, making it harder for the body to protect cells from damage.
At the same time, ongoing stress may impact healthy lifestyle habits such as balanced eating and adequate sleep, indirectly affecting antioxidant levels. This can create a vicious cycle, where reduced antioxidant protection contributes to more oxidative stress, which in turn can affect psychological health and increase feelings of emotional stress.
Underlying health conditions
Certain long-term health conditions are associated with elevated oxidative stress.¹⁰ Examples include:
- Diabetes
- Cardiovascular disease (e.g., heart disease, high blood pressure)
- Chronic kidney disease
- Neurodegenerative conditions (e.g., Alzheimer’s, Parkinson’s disease)
- Autoimmune disorders (e.g., rheumatoid arthritis).
These conditions can increase the production of free radicals or reduce the body’s antioxidant defences, making it especially important for affected individuals to maintain a healthy lifestyle and, where appropriate, discuss antioxidant support with their healthcare provider. In these cases, oxidative imbalance may be both a contributing factor and a result of the condition.
If this affects you, then managing your underlying condition with medical supervision is essential. While nutritional support can help to form part of a broader lifestyle strategy, medical advice is crucial to ensure you’re on the right track for what your body needs.
Certain medications
Some medications can influence oxidative pathways in the body.¹¹ Examples include:
- Chemotherapy drugs – can increase free radical production as part of their mechanism.
- Statins – while lowering cholesterol, they may influence antioxidant levels in some people.
- Certain antibiotics – can generate oxidative stress as a side effect.
- Nonsteroidal anti-inflammatory drugs (NSAIDs) – long-term use may affect oxidative balance.
These medications don’t necessarily pose a risk for everyone, but being aware of potential impacts can help you to discuss lifestyle adjustments or antioxidant support with your healthcare provider.
If this affects you, don’t panic. This doesn’t mean your medications are harmful towards you – if your doctor has prescribed them, it means the benefits to your health outweigh any risks. But it’s still important to understand possible side effects and what you can do to mitigate them.
Want to understand how your medication might be affecting oxidative stress? Speak to a pharmacist or doctor for advice tailored to your health and medications.
Pollutants and toxins
Exposure to certain pollutants and environmental toxins can increase free radical formation, contributing to oxidative stress.¹² Examples include:
- Air pollution – such as particulate matter from traffic or industrial emissions.
- Heavy metals – including lead, mercury and cadmium, which can accumulate in the body.
- Pesticides and herbicides – chemicals used in agriculture that can enter the food chain or water supply.
- Household chemicals – such as cleaning agents and solvents that release reactive compounds.
- Industrial by-products – including dioxins and polychlorinated biphenyls (PCBs) found in some workplaces or contaminated areas.
Exposure to pollutants is often unavoidable to some degree, particularly in urban environments. However, reducing personal exposure where possible – such as using air filters indoors, avoiding heavy traffic areas and choosing organic produce – can help. Maintaining a diet rich in antioxidants also supports the body’s natural defences.
On a wider scale, efforts to improve air quality at community and legislative levels, such as stricter emission controls and urban green initiatives, can make a meaningful long-term difference for everyone’s oxidative stress levels.
UV radiation
Ultraviolet (UV) radiation from the sun increases free radical production in the skin.¹³ When UV rays penetrate the skin, they can interact with oxygen molecules and other skin components, creating reactive oxygen species (ROS). These unstable molecules can damage skin cells, proteins and DNA, contributing to premature ageing, sunburn and other skin concerns.
This is one reason why excessive sun exposure is linked to premature skin ageing. However, moderate sun exposure is also important for vitamin D production and overall wellbeing, so finding a balanced approach – enjoying sunlight safely with protection when needed – is key.
Protective measures, including applying sunscreen and adopting sensible sun habits, can help to limit UV radiation’s impact on oxidative stress in your body.
A balanced perspective
At the end of the day, free radicals are a natural part of life – not all bad, but something to keep an eye on. Oxidative stress develops when the balance shifts too far in their favour, but there are things you can do to help prevent this.
Many everyday factors can contribute to oxidative stress, from smoking and pollution to diet and stress levels. While it’s not possible to completely eliminate all possible triggers of oxidative stress, making supportive lifestyle choices – including a varied diet rich in antioxidants – can help to maintain equilibrium.
As with many healthy choices, small, consistent changes often have the greatest long-term impact.
References
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https://www.hsph.harvard.edu/nutritionsource/antioxidants/ - Better Health Channel. (2021). Antioxidants.
https://www.betterhealth.vic.gov.au/health/healthyliving/antioxidants - National Cancer Institute. (2022). Cigarette smoke and oxidative damage.
https://www.cancer.gov/about-cancer/causes-prevention/risk/tobacco - NHS. (2022). Vitamin C.
https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-c/ - National Institute on Alcohol Abuse and Alcoholism. (2021). Alcohol metabolism.
https://www.niaaa.nih.gov/alcohols-effects-health - Harvard Health Publishing. (2020). Diet and inflammation.
https://www.health.harvard.edu/staying-healthy/foods-that-fight-inflammation - British Nutrition Foundation. (2021). Exercise and oxidative stress.
https://www.nutrition.org.uk/putting-it-into-practice/physical-activity/ - Harvard Health Publishing. (2018). Understanding the stress response.
https://www.health.harvard.edu/staying-healthy/understanding-the-stress-response - Cleveland Clinic. (2023). Oxidative stress.
https://my.clevelandclinic.org/health/articles/oxidative-stress - National Institutes of Health. (2022). Oxidative stress and medications overview.
https://www.ncbi.nlm.nih.gov/books/ - World Health Organization. (2021). Air pollution and health.
https://www.who.int/health-topics/air-pollution - Skin Cancer Foundation. (2022). UV radiation and skin damage. https://www.skincancer.org/risk-factors/uv-radiation/
