Page last updated: Tuesday, November 18, 2008
The Antioxidant debate
by Helena Conibear
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 lipids.

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.

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