Antioxidants are chemicals that are believed to help protect the body from the harmful effects of other chemicals called free radicals. Free radicals exist in the body's cells, but have been found to cause damage to the cells.
Antioxidants, including beta-carotene, vitamin A, vitamin C, vitamin E, and selenium are found mainly in fruit, nuts, grains and vegetables. Some people chose to take supplements as an additional source of antioxidants.
Antioxidants have been studied as helping to give some additional immunity against colds, as anti- ageing supplements and even as a protective effect against some cancers.
However, evidence about the protective health benefits of antioxidant supplements is mixed.
There is also some evidence that antioxidant supplements may be harmful in some cases.
A major review of high quality research about the health benefits of antioxidant supplements was carried out for the Cochrane Library in 2012. It found that overall, people who took supplements were slightly more likely to die than people who weren't taking supplements. This applied to healthy people and those taking antioxidants who had health conditions.
The researchers concluded that there is not enough evidence to support people taking antioxidant supplements.
However, that doesn't mean eating food sources of antioxidants are bad for health or unlikely to be beneficial for health.
Whether it is antioxidants in fruit, veg and nuts, or other substances, a healthy balanced diet with 5-a-day portions of fruit and vegetables is recommended by the NHS.
Although certain foods have gained unofficial tags as 'superfoods', often because of their antioxidant content, most experts advise against eating too much of one kind of food in the hope of gaining health benefits from it. Instead, a healthy balance is usually preferred.
Antioxidants in food
Some foods are higher in antioxidants than others. The three major antioxidant vitamins are beta-carotene, vitamin C and vitamin E. You will find them in colourful fruits and vegetables - especially those that are purple, blue, red, orange or yellow. To get the greatest benefits from their antioxidants, it is usually best to eat these foods raw or lightly steamed. Do not overcook or boil.
Beta-carotene and other carotenoids: Apricots, asparagus, broccoli, cantaloupe, carrots, corn, green peppers, kale, mangoes, turnips, nectarines, peaches, pink grapefruit, pumpkin, squash, spinach, sweet potato, tangerines, tomatoes and watermelon.
Vitamin C: Berries, broccoli, Brussels sprouts, cantaloupe, cauliflower, grapefruit, honeydew melon, kale, kiwi fruit, mangoes, nectarines, oranges, papaya, red, green or yellow peppers, snow peas, sweet potato, strawberries, and tomatoes.
Vitamin E: Broccoli, carrots, chard, mustard and turnip greens, mangoes, nuts, papaya, pumpkin, red peppers, spinach and sunflower seeds.
Other foods that are rich in antioxidants include:
- All berries
- Red grapes
- Alfalfa sprouts
Vitamins are not the only antioxidants in food. Other antioxidants that may help support the immune system include:
- Zinc: Found in oysters, red meat, poultry, beans, nuts, seafood, whole grains, fortified cereals and dairy products;
- Selenium: Found in Brazil nuts, tuna, beef, poultry, and fortified breads and other grain products.
If you cannot get enough antioxidants in your diet by eating fruit and vegetables, seek medical advice about vitamin supplements.
However, be cautious about taking individual immune system supplements to boost immunity. With antioxidants, as with most things, moderation is essential. Vitamins A and E, for example, are stored in the body and eliminated slowly. Taking too much could be harmful.
If you give your children vitamins, they should take ones specifically made for children and are age-appropriate.