Why do they say it is healthy to drink a glass of wine a day?

Question sent by Tomàs Ferrer (Castelló). LUIS TORRES answers:

We have evidence of wine consumption, especially red wine, preventing us from suffering coronary heart diseases or even preventing cancer, since 1992. This evidence sprang from what was called the French paradox. The French population is known for its low rates in coronary heart diseases although their diet is rich in fatty acids, allegedly balanced by the French tradition of drinking wine on a regular basis.

Since then, many studies have tried to explain the positive effects of moderate wine drinking (one or two glasses a day, 10-30 g of alcohol). These studies, basically carried out on in vitro (models (cell cultures), suggest that some substances found in grapes and wine, like polyphenols or more specifically resveratrol, are strong antioxidants and therefore might prevent some diseases like coronary heart diseases or cancer.

However, more recent studies have shown that these substances are destroyed by the digestive system pH levels and its flora, which reduces their availability in our organism.

Other studies suggest that the beneficial effects of moderate wine drinking is due to the alcohol found in this beverage. Tests have been run on animals that show that small alcohol doses induce HDL-cholesterol assimilation (also called «good cholesterol») and reduces LDL-cholesterol levels («bad cholesterol»), thus contributing to the prevention of coronary heart diseases. These studies encourage moderate alcohol consumption (10-30 g). This quantity is similar to the quantity found in liquor shots, one or two glasses of wine or a pint of beer. The synergic role of alcohol and polyphenols in cardiovascular protection has also been suggested.

On the other hand, public health studies carried out in the USA suggest that the relationship there is between wine intake, protection against coronary heart diseases and longevity only happens because the wine drinker usually belongs to higher classes and has healthier eating habits, and not so much because of the antioxidants found in this beverage.

Finally, studies carried out by the American Health Institute and some European institutions concluded that there is no clear evidence of alcoholic beverage intake, including wine, being beneficial for our health and say that what is clearly proven is alcohol’s toxicity. Therefore, their advice is not to drink at all.

For further reading:
Hollman, P. C. H. et al., 2011. «The Biological Relevance of Direct Antioxidant Effects of Polyphenols for Cardiovascular Health in Humans Is Not Established». The Journal of Nutrition, 141.

Luis Torres. Biochemistry and Molecular Biology Department. School of Pharmacy. University of Valencia.

© Mètode 2013