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© Sphere 2006
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Professor Roger Corder, a research pharmacist from London University, proposes a ‘complete nutrition and lifestyle plan’ in his recently published book, The Wine Diet. His thesis, that certain components (flavonoids) present in red wine, chocolate, and certain berries and nuts, provide significant medical benefits, has proved both attractive and controversial. Welcomed by wine producers and wine merchants, it has received a more critical response from those with a less vested interest, such as Master of Wine Beverley Blanning. Blanning’s concern is that the science doesn’t add up. That is the subject of this brief review.
Corder’s own academic reseach involves the effects of compounds such as flavonoids (a sub-group of polyphenol phytochemicals) on blood vessels in a laboratory setting. His in vitro studies are of international quality, to include a paper published in the prestigious journal Nature in 2001. What he finds is that the addition of certain flavonoid compounds produces improved blood vessel function in laboratory cultures and from this he postulates a benefit to the living human body.
Corder’s second set of evidence to support his belief in the benefits of flavonoids to humans is from population studies. Anecdotal accounts of greater longevity in certain countries, as well as the documented ‘French parodox’ - where wine consumption conferred longer living to regular wine drinkers in France as compared to other, equivalent, non-drinking European populations – prompted Corder to explore wine drinking goups in isolated areas of Sardinia and Crete. Here he found significant numbers of men living to over 100 years of age and sought to correlate this with wine consumption, particularly of wine with high levels of flavonoids.
In France itself, tables of death rates and ages at death highlight significant regional differences. Corder expresses such differences in a longevity index. He seeks to correlate consuming wines with a higher flavonoid content with greater longevity, citing the Gers departement of the South-West with the other local areas such as Gironde. Unfortunately for Corder’s argument, he fails to note that Gers’s near neighbour Pyrenees-Atlantiques, an area with significantly worse mortality figures, ‘consumes’ similar red wines . Yet is there any evidence that the old folk of Gers actually drink the local Madiran (a wine high in flavonoids), and a relatively expensive wine? More likely they will have spent their lives consuming watered-down gros rouge. And some non-wine producing areas of France also have very good mortality figures! Corder makes no claim to expertise in the study of population medicine, so perhaps one must accept his potenial (and real) limitations in these matters.
More serious is Corder’s claim to find serious support for his argument form the mainstream medical literature. Here Corder becomes more contentious. The major review in the British Medical Journal in 1996 concluded that alcohol itself (of whatever type) was responsible for reduced mortality figures. In line with previous work on the French paradox, this effect was explained as alcohol’s effect on reducing the tendency of blood to clot, and hence reduce the number of coronary thromboses (heart attacks). Subsequent studies supported this general benefit of alcohol, but some researchers also began to look for an additive effect of red wine beyond that of alcohol alone. If there was a separate, additional, benefit from red wine (Corder’s flavonoids), then the story would be much more interesting.
In commenting on the medical papers Corder cites, the reviewer is faced with two major difficulties, selectivity and greater claims than the researchers themselves are prepared to make. Generally, the researchers are more cautious than Corder in the claims made for the benefits of red wine. Klatsky, for example, in his 2003 paper, claims that whilst wine drinking is associated with lower mortality, this is not specific to red wine, is more significant for wine rather than beer or liquor, but concludes that ‘it remains unclear whether this reduced risk is due to non-alcohlic wine ingredients, daily pattern or associated traits’. Equally, studies on the benefits of wine drinking after a heart attack are exactly that, and cannot be extrapolated to a healthy population (Renaud et al, 1999). Corder makes much of the work of the group led by KL Mukamal in New England. Mukamal has looked at stroke and heart attack prevention (Corder makes a basic mistake in confusing risk of stroke with stroke incidence), coming up with some initially promising evidence. However, in a study in 2006 (which Corder omits, perhaps as it came too late to make the book’s publication), Makamal is much less helpful to Corder.
Published in the Journal of the American Geriatric Society, Mukamal’s team looked at adults aged 65 and over in the local Boston population. This was their conclusion – ‘in this population, consumption of 14 or more drinks per week was associated with the lowest risk of coronary heart disease’ but this was irrespective of whether they drank beer, wine of liquor. Such findings highlight the complexity of drawing specific conclusions once one gets beyond the proven benefits of alcohol (of any type) in moderation. To be fair to Corder, he emphases the need for moderate alcohol intake repeatedly.
How then to conclude? Corder’s argument in The Wine Diet for the benefits of certain red wines (with high flavonoids content) is attractive, entertaining and engaging. However, a more careful analysis of the evidence leaves the reviewer with the judgement of ‘ case not proven’. Perhaps, in the fullness of time, the research of the likes of Klatsky, Mukamal, and Renaud, will give a definite answer to the question of whether flavonoids do indeed benefit human beings leading normal lives. Laboratory and population studies offer pointers, but, as is said concerning the consequences of the French Revolution, ‘it’s still too soon to tell’!
Jamie Harrison writes on medicine and on wine. He holds a degree in physiological sciences from Oxford University, medical degrees from the University of London, and is a Fellow of the Royal College of General Practitioners.