So, what are antioxidants? They are molecules that neutralise free radicals, unstable molecules that can damage cells, proteins and DNA. Your body makes its own antioxidants and gets others from food. The twist most labels skip: free radicals are not purely villains, and swallowing high-dose antioxidant pills has repeatedly failed to deliver the benefits that antioxidant-rich diets seem to.
Key takeaways
- Oxidative stress happens when free radical production outpaces your body's ability to neutralise them.
- Your body runs its own antioxidant defences, including glutathione and enzymes such as superoxide dismutase and catalase.
- Diets rich in fruit, vegetables, nuts and legumes are consistently linked to better health; isolated high-dose antioxidant supplements mostly are not.
- Some large trials found harm: beta-carotene increased lung cancer risk in smokers, and vitamin E increased prostate cancer risk in the SELECT trial.
- Topical antioxidants such as vitamin C serums, used alongside sunscreen, have reasonable evidence for skin.
What are free radicals, in plain English?
Most molecules have their electrons in pairs, which keeps them stable. A free radical has an unpaired electron, so it grabs one from whatever is nearby: a fat in a cell membrane, a protein, a strand of DNA. That molecule is now damaged, and sometimes becomes a radical itself, setting off a small chain reaction.
Think of it like rust on a car parked by the sea. Oxygen is essential, but it slowly corrodes metal. Your cells use oxygen to make energy in their mitochondria, and a small fraction of that process inevitably produces reactive oxygen species (ROS), the main family of free radicals in the body.
Outside sources add to the load. The big ones are:
- UV radiation, a major driver of skin ageing, which is why sun protection matters so much in the tropics.
- Cigarette smoke and vaping aerosols.
- Air pollution, including fine particles during haze season. We covered practical protection in our haze season survival guide.
- Heavy alcohol intake and some infections.
What is oxidative stress?
Oxidative stress is an imbalance: more free radical activity than your antioxidant systems can handle. Over time, it is thought to contribute to ageing and to conditions including heart disease, some cancers, diabetes complications and neurodegenerative disease. The honest word there is "contribute". Oxidative stress is one factor in these diseases, not a single master cause, which partly explains why simply "adding more antioxidants" has not worked as hoped.
Crucially, free radicals are not all bad. Your immune cells deliberately produce them to kill bacteria. They also act as signals. When you exercise, the burst of ROS in your muscles is part of what tells your body to adapt and get fitter. That is the concept of hormesis: a small, short stress that makes a system stronger.
How does your body fight oxidative stress?
You have layered defences.
| Antioxidant | Where it comes from | What it does |
|---|---|---|
| Glutathione | Made by your cells from three amino acids | The main antioxidant inside cells; also helps recycle vitamins C and E |
| Superoxide dismutase and catalase | Enzymes your body makes | Convert reactive molecules into oxygen and water in stages |
| Vitamin C | Guava, papaya, citrus, capsicum, broccoli | Water-soluble; works in blood and fluid around cells |
| Vitamin E | Nuts, seeds, vegetable oils including red palm oil | Fat-soluble; protects cell membranes |
| Carotenoids | Carrots, sweet potato, pumpkin, tomatoes, leafy greens | Include beta-carotene and lycopene |
| Polyphenols | Tea, coffee, berries, cocoa, many spices | A huge, varied family; many work partly by switching on the body's own defences |
Minerals such as zinc, selenium and manganese are also needed to build antioxidant enzymes, which is another reason overall diet quality matters.
Do antioxidant supplements work?
This is where the story gets humbling. In the 1990s, observational studies showed that people who ate more fruit and vegetables had less heart disease and cancer. The logical next step was to test high-dose antioxidant pills in large randomised trials. The results were mostly disappointing and, in places, worrying.
- In the ATBC and CARET trials, beta-carotene supplements increased lung cancer risk in smokers and asbestos-exposed workers.
- The SELECT trial found that 400 IU a day of vitamin E increased prostate cancer risk by about 17% in healthy men.
- A 2009 study in PNAS found that taking vitamin C and vitamin E during a training programme blunted some of exercise's benefits for insulin sensitivity, likely by dampening those helpful ROS signals.
The US National Center for Complementary and Integrative Health summarises it plainly: rigorous trials have generally not shown that antioxidant supplements prevent disease, and high doses may be harmful. Whole foods deliver thousands of compounds working together, alongside fibre and other nutrients, which a single isolated molecule cannot replicate.
That does not mean moderate, everyday-dose vitamins are dangerous. Vitamins C and E are essential nutrients, and meeting your needs matters. The lesson is about megadoses taken in the hope of extra protection.
One old idea is worth retiring: the ORAC score, once printed on "superfood" packaging to rank antioxidant power. The US Department of Agriculture withdrew its ORAC database in 2012, noting that test-tube antioxidant capacity says little about what happens in the human body.
What about antioxidants for skin?
Skin is where the antioxidant story is more encouraging, largely because you can apply them directly where UV damage happens. Topical vitamin C, particularly combined with vitamin E and ferulic acid, has laboratory and small clinical evidence for helping reduce UV-related damage and supporting collagen. It works best as a partner to sunscreen, never a replacement. We covered the oral side of this in vitamin C beyond colds.
Glutathione is often marketed for skin, and the evidence is genuinely mixed. Some small trials suggest oral glutathione can raise the body's stores over months, but results for visible skin outcomes are modest and inconsistent. We laid out the full picture, including why "whitening" claims deserve scepticism, in glutathione for skin: what the science says.
If you like the idea of a daily routine that includes these nutrients at sensible amounts, our GLOW effervescent tablet combines vitamins C and E with glutathione, collagen peptides and hyaluronic acid. Think of it as one easy addition to a colourful diet and daily sunscreen, not a substitute for them.
How to get antioxidants the way the evidence supports
- Eat colour daily. Aim for several different coloured fruits and vegetables: ulam, kangkung, papaya, guava, carrots, tomatoes, dragon fruit.
- Drink tea or coffee if you enjoy them. They are among the biggest sources of polyphenols in many diets. Go easy on the sugar.
- Add nuts and seeds for vitamin E.
- Wear sunscreen every day. Preventing UV damage beats trying to mop it up afterwards.
- Do not smoke, and limit alcohol.
- Keep exercising. It trains your body's own antioxidant defences.
This article is general information, not medical advice. Talk to a doctor or pharmacist before taking supplements, especially if you are pregnant, on medication (including blood thinners, which can interact with vitamin E) or managing a health condition.
Frequently asked questions
What are antioxidants in simple terms?
Antioxidants are substances that neutralise free radicals, unstable molecules that can damage cells. Your body makes some antioxidants, like glutathione, and gets others from foods such as fruit, vegetables, nuts, tea and coffee.
Are antioxidant supplements safe?
Everyday doses of vitamins like C and E are generally safe for healthy adults. High-dose antioxidant supplements have not been shown to prevent disease, and some trials found harm, such as beta-carotene raising lung cancer risk in smokers. Food is the better-supported source.
Can antioxidants slow ageing?
There is no good evidence that antioxidant pills slow ageing overall. For skin, daily sunscreen is the most effective anti-ageing step, and topical antioxidants like vitamin C may add some extra protection when used with it.
Which foods are highest in antioxidants?
Brightly coloured fruits and vegetables, berries, leafy greens, nuts, legumes, tea, coffee, cocoa and spices are all rich sources. Variety matters more than chasing any single "superfood" ranking.
Should I stop taking antioxidants when I exercise?
Normal food intake is fine. Some research suggests high-dose vitamin C and E supplements taken during training may blunt certain exercise benefits, so megadoses around workouts are not recommended.
