Antioxidant supplements – do you need them, or is food enough?

What are antioxidants?

Antioxidants is a broad term for substances that can neutralise free radicals – unstable molecules that can damage cells, proteins and DNA. Free radicals are formed naturally in the body during normal metabolism, but also through things like physical exertion, infections, smoking, air pollution and exposure to UV radiation.

Antioxidants can be grouped into several categories, including:

• Vitamins, such as vitamin C and vitamin E
• Minerals, for example selenium and zinc, which are part of the body’s antioxidant enzymes
• Plant compounds, such as polyphenols and carotenoids (for example beta-carotene and lycopene)

Together, these substances help maintain a balance between free radicals and the body’s defence systems.

Oxidative stress and free radicals – what does it mean?

Free radicals are constantly being formed in the body and they also have important roles, including supporting the immune system and acting as signalling molecules in various biological processes. Problems arise when the amount of free radicals becomes greater than the body’s ability to neutralise them. This is known as oxidative stress.

Oxidative stress is a biochemical imbalance where the body’s antioxidant defences are not sufficient. When this happens, free radicals are more likely to react with the building blocks of cells, which can affect cell membranes, proteins and DNA. Long-term oxidative stress can contribute to inflammation and increase the risk of certain diseases, such as cancer, heart disease, diabetes, neurodegenerative conditions like Alzheimer’s and Parkinson’s, and kidney disease.

How do antioxidants neutralise free radicals?

Free radicals are unstable because they are missing an electron in their outer shell. Electrons normally exist in pairs, and when a molecule has an unpaired electron it becomes chemically reactive. To become more stable, a free radical easily reacts with other molecules and can “steal” an electron from them. When that other molecule loses an electron, it can in turn become reactive, setting off a chain reaction.

Antioxidants can stop this process. They are able to donate an electron without becoming highly reactive themselves. When an antioxidant gives up an electron, the free radical becomes stabilised and the risk of further reactions is reduced. In this way, antioxidants help slow down oxidative reactions and protect the structure and function of cells.

Antioxidant supplements – what does the research show?

Antioxidants have long been linked to health, partly because they can reduce oxidative reactions in the body. This led to the idea that antioxidants in tablet form might provide extra protection. However, when this has been tested in research, the results have often shown the opposite.

In a well-known study involving 29,133 male smokers, participants were given either vitamin E, beta-carotene, a combination of both, or a placebo. The aim was to see whether antioxidant supplements could reduce the risk of lung cancer. The results showed no protective effect. In the groups receiving beta-carotene, there were actually more cases of lung cancer, which led researchers to stop that part of the study early.

Similar findings have been seen in other large studies. Supplements of vitamin E and selenium, for example, have not shown any clear cancer-preventive effect. Instead, vitamin E supplements have been linked to an increased risk of prostate cancer, while selenium did not provide any protection.

One explanation is that free radicals can act as a natural brake on cancer cells. Cancer cells often produce large amounts of free radicals, which can make it harder for them to grow and spread. When large amounts of antioxidants are added through supplements, this braking effect may be reduced, making it easier for cancer cells to grow. Research has also shown that antioxidants can increase blood flow to tumours by stimulating the formation of new blood vessels. This supplies the tumour with more oxygen and nutrients, which can speed up both growth and spread. There is therefore no evidence that antioxidant supplements protect against cancer. In some cases, they may actually worsen and accelerate disease progression.

Nutritious food, fruit and vegetables – the body’s best protection

Studies that follow people over time often show that those who eat plenty of fruit, vegetables, wholegrains and pulses tend to be healthier and have a lower risk of many diseases. This protection does not seem to come from a single antioxidant, but from the whole food package.

When antioxidants come from food, they are consumed in relatively low doses and alongside many other substances that work together and affect the body in several ways at once. Antioxidants in food also tend to act more indirectly, by stimulating the body’s own defence systems and enzymes that deal with oxidative stress.

Supplements work differently. They usually contain one or a few antioxidants in concentrated form and in much higher doses than you would normally get from food. This can disturb the balance between free radicals and antioxidants and interfere with the natural signalling roles of free radicals. This helps explain why supplements do not provide the same benefits as food and can sometimes be unsuitable.

How are antioxidant supplements different from standard vitamin and mineral supplements?

Supplements that contain antioxidants differ from standard vitamin and mineral supplements in both purpose and dosage. Antioxidant supplements are often marketed as providing extra protection against disease or ageing, and may therefore contain very high levels of individual substances, such as vitamin E, vitamin C or beta-carotene. These amounts are often far higher than what the body normally gets from food.

Standard vitamin and mineral supplements are mainly used to prevent or treat deficiencies, for example with a limited diet, certain health conditions or increased needs. The doses are usually close to the recommended daily intake and designed to support normal bodily processes. When a deficiency is confirmed or suspected, these supplements may be appropriate. Antioxidant supplements generally do not serve the same purpose. Taking them “just in case” has not shown clear health benefits and can, in some cases, be unsuitable.

Summary

Antioxidants, such as vitamin C, vitamin E and selenium, are sometimes described as the body’s defence against free radicals and can help prevent or slow down cell damage. They help neutralise free radicals, allowing the body to regulate their levels and keep them within a healthy range.

Research has not shown any benefits from antioxidants taken as supplements. The body needs antioxidants in balanced amounts, but it is not adapted to high doses from supplements. In some cases, these can have negative effects and increase the risk of conditions such as cancer. More is not always better.

The best way to get the right amount is by eating plenty of fruit, vegetables and other nutrient-dense foods that also provide important vitamins, minerals and fibre – in a form the body can absorb and use naturally.

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