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Antioxidants

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The processes of life lead to the presence free radicals in our cells usually as byproducts of the metabolism. These free radicals are powerful oxidising agents which act on the contents of the cell leading to many of the health problems we encounter. They are linked to some of the most common diseases such as cancer, immune disorders and heart disease. Recent research has shown that they are responsible, in part at least, for the ageing process.
Our bodies produce enzyme antioxidants to neutralize the free radicals within the cell and prevent the oxidation which causes the damage. Unfortunately current lifestyles, poorly balanced diets and pollution can result in an excess of free radicals being present in the body increasing the risk of damage to the cells.
Birds and bats are thought to produce more protective antioxidants because of their high metabolic rate needed to sustain flight and as a result they have relatively long lives when compared to mammals of similar size. A synthetic antioxidant has been developed and experiments with nematodes have greatly slowed the ageing process leading to a doubling of the lifespan of some, the same tests are now in progress in mice with promising results so far.
Plants also produce these antioxidants so eating fruit and vegetables is a good way to obtain them. There are a number of so-called Superfoods which contain a higher proportion of antioxidants than others, eg. the bright colours of fruit are caused by Flavenoids which have antioxidant properties. However, analysis of the levels of antioxidants in the blood has shown that the body maintains them at similar amounts regardless of any extra that is consumed. So eating a balanced diet with enough fruit and vegetables should be enough to provide all of the antioxidants that the body needs, similar to vitamins where any additional intake is broken down or excreted.

The cooking process tends to destroy phytochemicals so it is best to consume them in the raw state, with the notable exception of Lycopene which is found in tomatoes and improves in potency when processed or cooked. As they are locked up within the cells they may not be released or may be broken down in the gut by the normal digestion process. Breaking up the cells before ingestion releases the contents so the antioxidants are available for immediate absorption. This is the thinking behind juicing and the recommendation to swill the juice around the mouth before swallowing. So including some of the fruit and vegetables listed below in juices is one method of obtaining the benefits they may provide.
Researchers have developed some genetically modified plants which produce greater amounts of antioxidants. By taking genes from blackcurrants and incorporating them into tomatoes we get a dark fruit with extra Flavenoids. This is still experimental and much testing would be required before such a plant could be released for consumption. Also the general unacceptability of such plants may mean their development will remain as a scientific curiosity. Since blackcurrants have a greater amount of antioxidants than most fruit it would be best to just eat them instead.

Cooking methods and the length of time the food is exposed to high temperatures can have a marked effect on the amount of beneficial compounds which survive the process. Broccoli and other Brassica have a high content of antioxidants, particularly Glucosinolate which gives them their bitter taste. The more they are boiled the greater the loss, so that cooking for about 5 minutes causes a 5% decrease in potency and after 30 minutes about 70 to 80% will be lost. However the 'goodness' leaches from the vegetable to the cooking water - so mother was right to make you drink the cabbage water saying it was good for you. Steaming or microwaving retains most of the beneficial compounds.
Vegetables are at their best when harvested then eaten as soon as possible; to prolong the freshness of leafy vegetables, store at about 5°C - normal 'fridge temperature. The antioxidants and vitamins in fruit are more stable so do not need such cool storage - anyway storing tomatoes at low temperatures ruins their flavour.

The molecules which give the pigment to many fruit and vegetables are powerful Flavenoid antioxidants. Lycopene gives the red colour to tomatoes, Anthocyanins are part of the pigments of berries such as blackcurrants and bluberries - the former having about ten times that of the latter. They reduce the deterioration of blood vessels in both body and brain so keeping atherosclerosis and dementia at bay.
The colouring of red wine occurs when the skins and pips are kept with the pulp and the Polyphenol antioxidants which give them their colour leach into the juice. The Polyphenols help blood vessels relax and reduce the build-up of fatty deposits, so reducing the risk of cardiovascular disease. This is the reason given for the French Paradox, in that although they consume many foods which are considered unhealthy, they have a reduced incidence of heart disease compared to other nations which eat similarly unhealthy diets. Alcohol produces increased amounts of antioxidants but, if it is consumed slowly and with food, the liver can process it without a damaging effect. Cabernet Sauvignon grapes have a high proportion of Polyphenols and it is important that the wine is produced in a traditional method where the pulp and skins are fermented together for about two weeks to ensure the antioxidants are transferred to the resulting wine. However this health-giving property only applies to light consumption, anything over the recommended daily or weekly amount is detrimental to health.

Lutein found in spinach and kale, is a protective yellow pigment of the retina that absorbs the blue UV part of sunlight which is harmful. The Macula is the area at the centre of the retina with a high concentration of light-sensing receptors. Age-Related Macular Degeneration (AMD) occurs in later life and is associated with a reduction of the protective pigment. Eating foods rich in Lutein may halt or even slightly improve vision where damage to the Macula has been observed.
Consuming about 50g of tomato puree daily can give some protection to the skin from the damaging rays in sunlight, which leads to premature wrinkling. Lycopene is thought to be the antioxidant which is giving this protection.

The bioflavonoid Quercetin found in some purple or red fruit and vegetables such as apples, garlic and red cherries, inhibits the production of histamine and boosts the immune system by increasing the production of white blood cells. Unfortunately for people who suffer from hayfever some of these foods can exacerbate their problems. Tomatoes and oranges contain histamine as does red wine. Eating some Pineapple may counteract this as the enzyme Bromelain contained in the stem reduces the production of mucus.

The Flavonoid Apigenin found in some herbs has been found to help with the development of neurons from stem cells in rats, so could be useful in the treatment of brain injuries and neurological diseases. Research has also found that it can improve memory and brain function.

Many foods and supplements are described as containing antioxidants and are given a value of the amount they contain. The term ORAC is used which stands for Oxygen Radical Absorption Capacity and is usually quoted for a 100g portion. (Extracts contain a higher concentration as much of the water and fibre have been removed). The value is obtained by analysis, but this is done in vitro, ie. in a test tube, so bears no relation to how it is utilized in the body (in vivo). For example an ORAC value of 5,000 for one antioxidant may be worth less than 1,000 for another if the latter is better absorbed by the body and targets harmful free radicals in a particular part of the body more effectively. Also, as with vitamins, the body can only utilize so much at a time, so taking excessive amounts is no more beneficial - the excess is excreted. The maximum is estimated at around 3,000 to 5,000 ORAC units per day for any given antioxidant. Eating foods containing the beneficial compounds is probably the best method of obtaining them as the availability from supplements may not be reliable.