Research On Why Two Drinks Help The Heart

Clues to Why Drinking Can Protect Heart
Alcohol 'Preconditions' Laboratory Guinea Pigs

By Charles Petit, Chronicle Science Writer

SF Chronicle Copywrite

San Francisco scientists are reporting today the first solid clues -- gleaned from feeding alcohol to guinea pigs -- to why moderate drinking reduces the risk of heart attacks.

For years, doctors have reported evidence that people who have one or two drinks a day reduce their chance of heart attacks by as much as a third, and significantly reduce the severity of heart attacks that do occur.

Heavier drinking leads to increased risk of heart disease as well as liver problems.

"It's a U-shaped risk distribution," said Dr. Vincent Figueredo, a cardiologist at San Francisco General Hospital and assistant professor of medicine at the University of California at San Francisco. "Alcoholics, and people who don't drink at all, are worse off than people who regularly drink a little."

Figueredo is the lead author of a study published today in the journal Proceedings of the National Academy of Sciences. It reports experiments that he, post-doctoral fellow Masami Mayamae, and three other colleagues performed on the hearts of laboratory guinea pigs to try to find out what alcohol does to allay heart attacks.

Alcohol, the scientists concluded, serves to "precondition" the animals' heart muscle to withstand a heart attack.

Its effect is identical to that of established laboratory methods used to toughen the hearts of lab animals against severe loss of oxygen. Such preconditioning is done by subjecting the animals' hearts to brief, but harmless episodes of low oxygen. Then, when the equivalent of a full heart attack is caused in such preconditioned animals, their survival goes up dramatically.

The new study of the hearts of guinea pigs revealed that alcohol increases levels of a natural substance called adenosine in the fluids surrounding the heart muscle cells. Adenosine is critically important to a cell's use of energy it gets from nutrients in the blood. Muscle cells also release large quantities of adenosine when they are cut off from oxygen, as in a heart attack.

Now, it looks as though alcohol causes heart muscles to prepare for an emergency in somewhat the same way as does a sudden drop in oxygen levels. So, if a heart attack occurs, with its prolonged lack of oxygen to parts of the heart, muscle cells there have already begun to get ready for hard times. "Maybe there is something about adenosine that causes the heart muscle to start hoarding energy," Figueredo said.

The next step toward helping hearts to protect themselves is to look for medications that might cause the same effect on adenosine levels and on the substances in the cells that react to adenosine -- but without the side effects of alcohol. In addition, further research is needed to learn exactly what changes occur inside a cell in response to higher levels of adenosine.

"The bottom line is that if you consume alcohol on a regular basis in moderation, you are more likely to survive a heart attack," Figueredo said. "What this paper is doing is to suggest a mechanism." Turning that mechanism into a useful medical procedure -- other than to recommend light drinking for people at risk of heart disease and with no history of alcoholism -- may take several years.

Tags: Alcohol and Health Effects