Antioxidants include a whole range of compounds who share the
ability to quench or eliminate potentially damaging free radicals.
As such they include naturally occurring vitamins, polyphenols,
phenolic acids or other complex molecules generated by heat (ie
cooking) such as elanoidins. It has been established that the
consumption of two 100ml glasses of red wine a day increases the
phenolic content of the average diet by 40%, but only a weak correlation
exists between polyphenolic content and antioxidant activity.
Research by Dr Alan Crozier from Glasgow University, reported in the August September 2002 edition of AIM, shows us which grape varieties are the highest in antioxidants (Pinot Noir generally and a young vatted Cabernet Sauvignon from Bulgaria). The research also established that antioxidant activity in unfermented grape juice is lower than in the finished wine - antioxidant activity increases during fermentation and maturation. So we have come to a stage where we can not only choose red wine, but a particular red wine to maximise our phenolic intake. Furthermore, new winemaking methods developed by Professor Geoff Skurray in Australia have uncovered an enzyme which can radically increase phenolic extraction during fermentation.
This is all very well, but what is just beginning to come to light
through recent research is that quantity may not be the answer,
more important may be the size and absorbability or the bioavailability
of the various antioxidants present in wine, beer and cider. Although
this has not been completely established, it would be expected
that the larger bulky antioxidants are likely to stay in the gut
rather than to get absorbed. The types and levels of antioxidants
in cider are fairly similar to wine whereas beer is very different
(being cereal rather than fruit). Beer tends to have the smaller
antioxidants in a higher proportion such as catechin, epicatechin,
and ferulic acid - but it also has bulky complex antioxidants
originating from the hops and roasted cereals. Taking resveratrol
as an example, recent research suggests that its biovailiability
could be low, ranging from 20-40%. This contrasts with reports
on the bioavailablity of ferulic acid from an alcoholic beverage
of nearer 100% (this time from beer).
Furthermore, research suggests that once absorbed, antioxidants
are often metabolised into other forms forms which may have
different biological activity. For example, much of the resveratrol
is modified in the liver by coupling to glucuronic acid. Therefore
establishing the absorption and further metabolism of antioxidants
is a key factor in establishing their biological effects. We have
also learnt that ethanol has a pro-oxidative effect on plasma
Hence the usefulness or bioavailability of the antioxidants available
in alcoholic beverages is not yet fully established. However the
importance of antioxidants themselves in vascodilation, fighting
cancer and dementia are established and further research as to
absorption by the human body is needed.