Free radicals also have their benefits – the body needs them in reasonable amounts for immunity, cellular communication and adaptation to exercise. Problems only arise when too many are produced over a long period, leading to oxidative stress.
The goal is to maintain a balance between free radicals and antioxidants – you can support your body’s own antioxidant system mainly through regular exercise, a varied diet, good‑quality sleep, proper recovery, not smoking and reducing long‑term stress.
Free radicals are often described as something we never want in the body. In reality, it is a bit more complicated. Free radicals and related reactive molecules are constantly being produced in the body during energy production, immune defence, inflammatory responses and normal cellular communication. The problem is not their mere existence, but imbalance. When too many are produced, or when the body’s antioxidant protection cannot keep them under control, this is known as excessive oxidative stress.
What are free radicals?
You can think of free radicals as very active tiny particles that are constantly being formed in the body. They are a bit “restless” because they are missing one electron. Because of this, they try to quickly react with surrounding molecules, such as fats, protein or DNA.
But that does not mean they are bad. Your body routinely works with them and even needs them in reasonable amounts. For example, they help the immune system fight harmful microorganisms and are involved in important signalling between cells.
In scientific literature, alongside the term free radicals, you will often come across reactive oxygen species, or ROS, and reactive nitrogen species.
The risk lies in their excess
Problems only arise when too many free radicals are produced and the body cannot balance them with its own antioxidant protection. At that point, they can start to damage cells. The good news is that lifestyle can significantly support the body’s natural defences.
Where are they formed in the body?
Free radicals are not only formed when you do something “unhealthy”. On the contrary, they are produced completely naturally every day, even in a healthy body. They are a normal part of how the body functions.
One of the main places they are formed is in the mitochondria. You can think of mitochondria as small cellular power plants that produce energy for your muscles, brain, heart and other organs. During this energy production, a small amount of reactive substances can be formed, including free radicals. This is a normal by‑product of metabolism.
Free radicals are not only formed as waste products, though. Sometimes the body produces them deliberately because it needs them. For example, immune cells use them as one of their weapons against bacteria and other harmful microorganisms.
What function do free radicals have in the body?
Free radicals and reactive oxygen species act as cellular signals, a bit like cellular messengers. They help cells respond to stress, infection, changes in nutrient availability and physical activity. In low to moderate amounts, they are not considered simply harmful waste products, but part of normal physiology.
One of their best‑known functions is immune defense. Some white blood cells, such as neutrophils and macrophages, can create a sharp increase in reactive oxygen species, which helps destroy bacteria and other pathogens. This process is essential for the body’s defence.
Free radicals are also produced during exercise
Free radicals are also involved in adaptation to physical stress. During exercise, the production of ROS temporarily increases, which can activate defence and adaptation mechanisms. Regular, moderate exercise “trains” the body not only in terms of muscles and cardiovascular health, but also in terms of antioxidant protection.
This is a great example of the “just right” principle. A small, reasonable dose of stress can strengthen the body. Just as muscles adapt through training, cells can also adapt better thanks to mild stress. Problems only arise when there are too many free radicals over a long period and the body cannot keep them under control.
When do they start to cause harm?
Free radicals start to cause harm when they are produced over a long period in greater amounts than the body can handleand oxidative stress develops.
This does not mean every free radical is a problem. As mentioned above, the body needs them in reasonable amounts. The issue begins when the balance is disrupted.
With long‑term excess, free radicals can start to damage different parts of cells. They can affect, for example:
Cell membranes, which are the protective envelopes of cells and contain fatty substances that can be sensitive to damage
Proteins, which perform many important functions in the body, such as building tissues, transporting substances and helping regulate chemical reactions
DNA, which is the genetic information stored in cells
Long‑term oxidative stress is therefore associated with connections to ageing, chronic inflammation and a higher risk of certain lifestyle‑related diseases. However, oxidative stress is usually not the only culprit. It is more often part of a bigger picture, which also includes diet, exercise, sleep, stress, smoking, alcohol, body weight and overall metabolic health.
And that is the good news. It is not something you have no influence over. Every step towards a better lifestyle — more exercise, better food, better sleep, less smoking or alcohol, and more recovery — helps the body maintain a healthier balance.
Antioxidant protection in our body
Many people think of vitamin C, vitamin E or a supplement when they hear the word antioxidant. In reality, the most important antioxidant protection is the one the body controls itself. The body’s antioxidant system is a precisely regulated network of enzymes, molecules and signalling pathways.
The main enzymatic antioxidants include:
Superoxide dismutase (SOD) – converts the superoxide radical into less reactive molecules
Catalase (CAT) – helps break down hydrogen peroxide into water and oxygen
Glutathione peroxidase (GPx) – uses glutathione to neutralise peroxides
A healthy lifestyle can support the function of these enzymes
These enzymes form the first line of defence against excessive oxidative load. For them to function properly, the body needs enough of certain minerals, including selenium, zinc, copper and manganese, because these elements are components or cofactors of antioxidant enzymes.
In addition to enzymes, there are also non‑enzymatic antioxidants. These include glutathione, uric acid, coenzyme Q10, vitamin C, vitamin E, carotenoids and various polyphenols from plant foods.
Importantly, these substances do not work in isolation. In the body, they form an interconnected network where one molecule can help regenerate another.
Are more antioxidants always better?
In simple terms, free radicals are often considered bad and antioxidants good. But the situation is more complicated.
If we suppressed free radicals too strongly, we could also disrupt their useful functions, such as cellular signalling, immune response and adaptation to training. Some studies show that high doses of antioxidant supplements, especially vitamin C and vitamin E, may under certain circumstances suppress some cellular adaptations to endurance training.
With food supplements, it is also not true that they are automatically safe just because they contain antioxidants. For example, beta‑carotene supplementation was associated in clinical studies with an increased risk of lung cancer in smokers and people exposed to asbestos. This does not mean that carrots or vegetables containing carotenoids are a problem. The issue was high doses of isolated beta‑carotene in supplement form in at‑risk groups.
How can you support the body’s antioxidant function?
The foundation is not to take lots of antioxidant supplements. Ideally, you want to support the body’s own regulatory systems. The body can adapt to reasonable stress.
Regular physical activity. A very strong stimulus is regular exercise. Moderate exercise temporarily increases the production of reactive molecules, but this activates mechanisms that improve cells’ resistance to oxidative stress over time. On the other hand, extreme physical stress without sufficient recovery can increase oxidative stress.
A varied diet. Fruit, vegetables, legumes, whole grains, nuts, seeds, herbs, spices, cocoa, coffee and green tea contain a wide range of polyphenols, carotenoids, vitamins and minerals.
Sleep. Lack of sleep is associated with disruption of the balance between oxidative load and antioxidant defence. Good‑quality sleep is therefore not just important for energy and mental health, but also for restoring cellular balance.
What leads to excessive production of free radicals?
Excessive production of free radicals and oxidative stress is mainly promoted by factors that put long‑term strain on metabolism, the immune system or mitochondria.
Smoking. Cigarette smoke contains free radicals and other substances that promote oxidative damage and inflammation. Smoking is therefore one of the best‑documented external sources of oxidative load.
Chronically elevated blood sugar. This is typical in insulin resistance or diabetes. Hyperglycaemia promotes the formation of reactive oxygen species and links oxidative stress with inflammation and metabolic damage.
Obesity.This is especially relevant when obesity is associated with chronic low‑grade inflammation. Fat tissue is not just a passive energy store, and excess fat can contribute to hormonal and inflammatory changes that increase oxidative load.
Chronic stress can put further strain on the body, including through long‑term activation of stress systems such as the hypothalamic‑pituitary‑adrenal axis. It may also be associated with higher markers of oxidative damage. However, this does not mean you have to live without stress. The main thing is to regularly give your body time to recover. Good‑quality sleep, exercise, rest and nourishing food can all help keep oxidative stress better controlled.
Other factors include excessive UV radiation, ionising radiation, air pollution, certain toxins, excessive alcohol intake, infections, lack of sleep and long‑term overexertion without recovery. These factors do not always cause harm through the same mechanism, but they often converge in disrupting redox balance.
Three supplements that can support the body’s own antioxidant protection
With food supplements, do not just look at whether they contain antioxidants. It can also be useful to consider substances that help the body better activate its own protective mechanisms, such as glutathione production, antioxidant enzyme activity or cellular pathways that help manage oxidative load.
Sulforaphane from broccoli sprouts
Sulforaphane is a compound formed from cruciferous vegetables. It is interesting because it can activate the Nrf2 pathway, which helps switch on genes involved in the body’s own antioxidant and detoxification protection. So it is not just about supplying the body with an external antioxidant, but rather about giving the body a gentle signal to strengthen its own defence systems. Clinical and mechanistic studies with sulforaphane describe its effect on Nrf2, redox balance and protective cellular processes.
N‑acetylcysteine (NAC)
NAC is a source of cysteine, an amino acid needed for the production of glutathione, one of the most important substances in internal antioxidant protection. A meta‑analysis of clinical studies showed that NAC supplementation can increase total antioxidant capacity, glutathione levels and catalase activity, although the effect on some other enzymes was less clear‑cut.
Curcumin
Curcumin, the main active ingredient in turmeric, can support some indicators of antioxidant protection as well as influencing inflammatory processes. A meta‑analysis of randomised studies showed that curcuminoids increased the activity of superoxide dismutase and catalase, increased glutathione levels and reduced lipid peroxidation.
Bottom line
Free radicals are not simply bad. The body needs them for immune defence, cellular communication and adaptation to physical stress. They become harmful mainly when too many are produced over a long period or when the body’s antioxidant system cannot maintain balance.
The aim of a healthy lifestyle is therefore not to completely eliminate free radicals. The aim is to create an environment where they are produced in reasonable amounts and the body has enough capacity to regulate them. The best way to achieve this is through regular exercise, a varied diet rich in natural plant foods, good‑quality sleep, not smoking, good metabolic health and sufficient recovery.
