Understanding antioxidants

Antioxidants are agents our body uses to protect against cell damage caused by free radicals. These are molecules formed as a natural by-product of bodily functions such as breathing, burning glucose for energy and fighting infection. Free radicals can also be generated by external factors such as sunlight, radiation, smoking and pollution.

Free radicals and your health

Free radical damage (oxidative stress) is linked to the natural process of ageing and to a host of diseases, which become more common as we get older. These include cancer, cataracts, heart disease and stroke, diabetes, arthritis and Alzheimer's disease.

 "People who have a high level of antioxidants in their diet have better skin, a better quality of life and stay healthier for longer," says Catherine Collins, chief dietician at St George's hospital.

Eat a healthy diet for antioxidants

Fruit, vegetables and plant-based foods such as herbs and spices are the main sources of antioxidants. They include:

• Carotenoids These are plant compounds such as betacarotene and lycopene, which give orange, red, green and yellow fruits and vegetables their colour. Good sources include apricots, mangoes, passion fruit, carrots, red pepper, sweet potato and tomatoes.
• Vitamin C A key antioxidant found in leafy greens such as cabbage, spinach and kale as well as blackcurrants, kiwi fruit and peppers.
• Vitamin E A fat-soluble antioxidant needed for the formation of red blood cells. Sources include wheat germ, corn, nuts, seeds, olives, spinach, asparagus and other green leafy vegetables, vegetable oils
• Selenium A mineral present in soil, selenium is needed to make up an important enzyme which prevents free radical damage. Good sources include cereals, meat and Brazil nuts.
• Phenolic compounds These are a large group of plant chemicals with antioxidant properties. They include flavonoids, such as quercetin, found in onions, apples, tea, red wine and chocolate; lignans, found in flax seed and other grains; curcumin, found in turmeric and mustard; tannins found in red and green tea and isoflavones found in soya milk, tofu and miso.

Go the Mediterranean way

Putting a range of different coloured foods on your plate is one of the most effective ways to get the antioxidants you need, as is consuming a 'Mediterranean' diet.

Catherine Collins warns that taking isolated nutrients in supplement form may not have the same effect. And high doses may even do more harm than good.

Food is best for antioxidants 

US research carried out in 2004, for example, found that large doses of vitamin E (over 400 ius) actually increased the risk of dying. Other research has found that large amounts of betacarotene in supplement form increase the risk of lung cancer in smokers and people who have worked with asbestos.

The UK's Food Standards Agency advises smokers and people heavily exposed to asbestos against taking supplemental betacarotene and the rest of us not to exceed 7mg as a supplement a day.

Says Catherine Collins. “You can't just take the ingredients out and put them into supplements. It really is preferable to get your antioxidants in food.”