Antioxidants are molecules that are extremely important for your health. They reduce the effects of harmful molecules called free radicals which are responsible for tissue ageing, DNA damage and diseases, such as cancer. Antioxidants come from your diet and are produced by your genes. When not enough antioxidants are present in your body, your cells become damaged. This is known as oxidative stress.

What is oxidative stress?

During the everyday functioning of the body, free radicals are produced as a by-product. Antioxidants are responsible for keeping free radicals at a safe level.

Oxidative stress occurs when free radicals are produced at such a high rate that antioxidants are unable to control them to a safe level. This leads to high levels of free radicals, which are responsible for tissue ageing, DNA and cell damage. In the long run, oxidative stress is linked to the development of several chronic illnesses such as cancer and cardiovascular disease.

How do antioxidants protect the body?

Antioxidants protect the body against oxidative stress by preventing the formation of free radicals, removing free radicals already formed and repairing damaged caused by free radicals. Lower levels of free radicals reduce oxidative stress and cause less damage to cells.

What is the difference between exogenous and endogenous antioxidants?

Endogenous antioxidants are produced by specific genes that code for antioxidant enzymes. Some individuals have risk alleles that produce enzymes that are less efficient. This results in some individuals having a higher risk of having high levels of free radicals and oxidative stress.

Exogenous antioxidants are obtained from the diet. Any foods rich in vitamin C, vitamin E and carotenoids, such as fresh fruit and vegetables, are also rich in antioxidants.

A diet high in antioxidants modifies the relationship between endogenous antioxidants and oxidative stress. This means even if an individual has lower levels of endogenous antioxidants, they can obtain sufficient antioxidants from their diet instead.

If free radicals are so bad, why haven’t humans evolved to eliminate them completely?

There is an optimal level of free radicals in the body. High levels of them lead to oxidative stress and disease. However, having low levels of free radicals is also bad. If the levels of free radicals are too low, the body is unable to protect itself from disease. This is why antioxidants are essential for maintaining the optimal level of free radicals.

Do free radicals cause aging?


High levels of free radicals result in impaired physiological function of cells, which results in random cell damage and the stimulation of specific pathways. This ultimately results in ageing, disease and cell death.

Ageing is a complex process and there a are a lot of mechanisms that are hypothesised to contribute to the process. It is a popular area of research and our understanding is continuing to improve in this area. Despite this, scientists are still not certain about the key mechanism involved in ageing.

Backed by Science

Our in-house scientists have sorted through thousands of studies and we only use genes that are backed by a significant body of peer-reviewed research. Check out Nell’s Science Standard for more information.