By now you probably haven’t escaped hearing about antioxidants and likely also know they are good to have in your diet even if you are not sure what they are.
To understand what an antioxidant is you have to know what a free radical is so we need to remember some high school chemistry and revisit the atom.
- atoms have various numbers of electrons
- these electrons orbit the atom
- an atom strives to have a paired number of electrons in their outer shell (like dance partners)
- this makes them stable and less reactive
However oxygen can come along and interact with some molecules creating an unpaired electron in the outer shell (the wallflower at the dance). This changes the structure of the molecule and it is now called a free radical. These structures desperately want to find a dance partner for their lonely electron so it makes them very reactive and they can damage body cells.
Fortunately we have a defence system of antioxidants. Antioxidants are able to donate an electron and make the free radical safe again. Think of antioxidants as playing hot potato. The circle of antioxidants must be large, unbroken and no single antioxidant must touch the hot potato for too long or too often.
The most important antioxidants are beta-carotene (precursor to vitamin A), vitamin C, vitamin E and selenium.
Beta-carotene is a precursor to vitamin A and is found in yellow and orange fruits and vegetables and leafy green vegetables. In the body it is converted to vitamin A. There are no recommended levels set for beta-carotene, just eat lots of fruits and vegetables. Vitamin A itself has no antioxidant properties and can be toxic if taken in excess.
Beta-carotene is a member of a group called carotenoids. We have identified around 600 different carotenoids so far and all have antioxidant functions.
Vitamin C is one of the water soluble vitamins and is also known as ascorbic acid. We get our vitamin C from citrus fruits, red and green peppers, dark leafy greens, most vegetables and also from sprouted seeds. It is probably one of the best known vitamins and has numerous functions in the body. The recommended daily intake is 75mg but this may be insufficient for many people although you should not exceed 2000mg per day.
Vitamin E is one of the fat soluble vitamins and is found in nuts, seeds, vegetable and fish oils and whole grains. The recommended intake is 15mg per day and you should not exceed 1000mg per day.
Selenium and vitamin E work together in partnership. It is a mineral found in brewer’s yeast, wheatgerm, liver, fish like salmon and halibut, many vegetables, whole grains, nuts (especially Brazil nuts), oats, brown rice and shellfish. The recommended intake is 55mcg (micrograms) per day and you should not exceed 400mcg per day.
You may also have heard of bioflavinoids. So far we have found around 4,000 bioflavinoids and most of them have antioxidant properties. However, some have been found to promote oxidation and trigger free radical formation. This does not appear to be a problem if we get our flavinoids from food but can be a concern with over-supplementation.
Some people see antioxidants as the panacea for bad lifestyle choices. Many people also believe they protect against cancer but no well designed study has proven this yet. In fact, in one study, it showed an increased risk of lung cancer in male smokers who took antioxidants. It wasn’t proven to be due to the antioxidants but we just don’t understand them properly yet. We do know that at higher concentrations they can become pro-oxidant, in other words they can trigger free radical generation.
Antioxidants are necessary to good health but they should come from a varied diet. Over-supplementation with antioxidants could be harmful because we don’t know enough yet about long term consequences of megadoses.