''So it suggests that there may be a physiological underpinning to this relationship in populations where one drink a day seems to be more beneficial than two drinks a day. And it may be that over time, revving up the nervous system, increasing the heart rate, increasing the pumping action of the heart may be part of the reason heavy drinking has been shown to have adverse effects.''
Dr. George Fodor, head of research for the University of Ottawa Heart Institute's Minto Prevention and Rehabilitation Centre, said the findings provide a solid challenge to ''the nonsensical statement that the French have low levels of heart disease because they drink red wine.''
''The bottom line is if there is any benefit in alcohol, the range is very narrow,'' Fodor said Tuesday from Ottawa, commenting on the research. ''So this study, I think, is a warning against trying to justify the drinking of alcohol for alleged health benefits.''
Toronto cardiologist Beth Abramson, a spokeswoman for the Heart and Stroke Foundation, said that although the study looked at only a small number of subjects, it is important because it gives insights into how the heart, blood vessels and body react when exposed to alcohol.
''This is another piece of evidence — and it's done very elegantly — that suggests that just because a small amount of alcohol may be beneficial, more of it can actually be harmful,'' said Abramson, who was not involved in the study.
''Although it is enticing to think that alcohol would be a quick fix ... it actually isn't.''
To conduct the study, published in the February issue of the American Journal of Physiology: Heart and Circulatory Physiology, researchers enrolled 13 healthy, non-smoking adults who were not heavy drinkers or total abstainers.
Participants attended three separate morning sessions, two weeks apart, during which ''standard'' drinks of red wine, ethanol or water were randomly administered. A 120-millilitre glass of wine and a 44-millilitre shot of spirits is considered a standard drink. The study used a moderately priced pinot noir with a high polyphenol content.
While agreeing the study is small, Floras said it is unique because it compares three different drinks — water, ethanol and red wine — in the same individuals on separate occasions, looking at different doses.
And because his lab contains a variety of testing methods, the researchers were able to simultaneously measure heart rate, blood pressure, blood vessel diameter and electrical impulses sent from the brain to the heart and the rest of the circulatory system.
''It would appear that following two or more drinks, the alcohol seems to turn on systems that do stress the circulation,'' he said.
''And our concern is if these stressful actions are repeated on a daily basis in individuals who have high alcohol consumption, they ultimately may be at higher risk of a heart attack or stroke or high blood pressure because of this potential mechanism.''