Anti-oxidants operate to neutralise the activity of so-called "free radicals"; compounds produced in the body as by-products of normal biochemical reactions, but which may nevertheless be highly damaging as they produce oxidative reactions damaging to cell structures. Ultimately this damage may contribute to the development of degenerative diseases characteristic of ageing, including cardiovascular disease, Parkinson's Alzheimer's and even some cancers.

The best known anti-oxidant nutrients are vitamins C and E, although these can only function properly when supported by adequate supplies of a wide variety of micro-nutrients, which include many of the flavonoids found in common fruits and vegetables. These compounds may therefore be regarded as important elements in the body's anti-oxidant defences, but many of the more than 4,000 flavonoids identified have also been hailed for their beneficial effects on the immune system and anti-inflammatory properties.

From the point of view of incorporating flavonoids into a daily health regime, the good thing is the ease with which this can be achieved. Flavonoids are very widely found in fruits, vegetables, and even drinks normally regarded, for other reasons, as unhealthy. So even a diet ordinarily well provided with common fruits and vegetables may provide anything up to 800mg of various flavonoids.

Authoritative research has indicated that this level of flavonoid consumption may help protect against coronary heart disease and hardening of the arteries (atherosclerosis), an important precursor of both heart disease and stroke. These remain two of the major causes of premature mortality and disability in the Western world, and to this extent the UK government and health advisors' frequent advice to consume five servings of fruit and vegetables each day is well founded.

The most potent of all the anti-oxidant flavonoids is believed to be a compound called quercetin, which is widely found in common or garden vegetables. The consumption of fruits with their skins on, such as apples, pears, grapes, bilberries, tomatoes etc will also provide a good supply. But perhaps the richest source is onions, a foodstuff also known since ancient times as a powerful anti-bacterial, anti-viral and anti-inflammatory agent.

There's no doubt that a diet including plentiful supplies of fresh fruit and vegetables can only be beneficial to health. But the anti-oxidant properties of the flavonoids found in many common, even supposedly unhealthy, beverages should not be neglected.

For example, the anti-oxidant properties of the catechin polyphenols found in black and green tea and red wine are now well known and attested. But, as remarkable as it may sound, there is now evidence that even beer may contain unique anti-oxidants equal in potency to vitamin E. The flavonoid compounds, xanthohumol and isoxanthumol appear to be found only in beer and the hops that flavour it and although they have not been studied directly, there is speculation that they may be responsible for the remarkable and counter-intuitive finding that lager type beers may be more effective as anti-oxidants than red wine, grape juice or even green tea. Obviously there are other reasons, not least its high calorific value, why you wouldn't want to depend on a high consumption of lager for your anti-oxidants, but in moderation it may indeed be beneficial.

In fact studies suggest that these particular flavonoid anti-oxidants may have a particular role in combatting the oxidation of low density lipids (LDLs), the so-called "bad cholesterol", which is a known risk factor for the development of atherosclerosis and cardiovascular disease. The other main fat-soluble anti-oxidant which fights this process is vitamin E, and although there is evidence that the anti-oxidant potential of xanthohumol and isoxanthumol may be comparable with that of the vitamin, it is also clear that each of the three compounds functions best in the presence of each of the others.

Whilst orthodox medicine concedes, in fact insists, that further research is necessary, the implications of these findings are exciting; suggesting that there may be many more as yet undiscovered benefits of flavonoids. As always, however, the holistic functioning of the body means that maximum benefits will only be obtained by the consumption of the widest possible variety of all these compounds. As flavonoids are not yet widely available as supplements, this consumption is best achieved through the foodstuffs and beverages which combine them as nature intended. Such a flavonoid rich diet can only be of benefit to the action of the better known anti-oxidants, such as vitamins E and C, which are more readily obtainable in supplement form.