Page last updated: Monday, April 07, 2008
One drink is relaxing to circulation, but two drinks are stressful
One drink benefits the heart and blood vessels, but the positive effects on specific biological markers disappear with two drinks, according to researchers at the Peter Munk Cardiac Centre of the Toronto General Hospital.

Researchers conducted a real-time study of thirteen volunteers to determine whether a red wine with a verified high polyphenol content differs from alcohol in its effects on specific markers associated with a greater risk of high blood pressure, coronary artery disease and heart failure. Healthy, non-smoking adults who were not heavy drinkers or total alcohol abstainers were studied. Participants attended three separate morning sessions during which “standard” drinks of red wine, ethanol or water were administered at random, single-blind, two weeks apart. A 4-oz glass of wine (120 ml), and a 1.5-oz (44 ml) shot of spirits is considered to be one standard drink. All blood alcohol levels alcoholic were below .08, the legal limit for drivers. The study measured simultaneously a broad spectrum of factors such as blood pressure, heart rate, sympathetic nerve firing and arterial diameter.

The findings of this study showed virtually identical effects of red wine and alcohol on the specific markers tested. After one drink of either red wine or alcohol, there no effect on heart rate, blood pressure or sympathetic nerve activity, which activates the “fight or flight” reaction and generally modulates heart rate and sets the diameter of blood vessels in order to redistribute blood. The brachial artery dilates - blood vessels were more “relaxed” or dilated, which reduced the amount of work the heart had to do.

After two drinks of either alcohol or red wine, the heart rate, amount of blood pumped out of the heart, and action of the sympathetic nervous system all increased. At the same time, the ability of the blood vessels to expand in response to an increase in blood flow diminished. This counteracted the beneficial effect of one drink of red wine or alcohol.

Dr. John Floras, Director of Cardiology Research at the Peter Munk Cardiac Centre cautioned this study measured the effects of these drinks on one occasion only. The effects of daily wine or alcohol intake may be quite different, as would drinking with food or drinking slowly during the evening.

“Our findings point to a slight beneficial effect of one drink be it alcohol or red wine on the heart and blood vessels, whereas two or more drinks would seem to turn on systems that begin to stress the circulation. If these actions are repeated frequently because of high alcohol consumption these effects may expose individuals to a higher risk of heart attacks, stroke or chronic high blood pressure,” noted Dr. Floras.

Source: “Dose-related effects of red wine and alcohol on hemodynamics, sympathetic nerve activity, and arterial diameter”, published in the February edition of the American Journal of Physiology, Heart and Circulatory Physiology

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