A new study on the effects of moderate drinking on cardiovascular health has found that alcohol acts as a blood thinner, which can be both a benefit and a drawback.
Alcohol consumption interferes with the activation of platelets in the blood, preventing them from clumping together to cause clots in the arteries, according to the authors of the report, published in the October issue of Alcoholism: Clinical & Experimental Research. Yet, this interference also slows the rate at which blood coagulates for beneficial reasons, such as in response to injuries, leading to a greater risk of hemorrhaging, especially during surgery.
"Our findings add to a large body of evidence showing that moderate drinking has effects on blood coagulation, which may have both good and bad effects," said lead author Dr. Kenneth Mukamal of Beth Israel Deaconess Medical Center in Boston. "But [we] now identify a new avenue by which this effect may occur."
Moderate drinkers are known to have lower rates of heart disease, but the reasons behind this are not completely understood, the authors of the study wrote. It is also known that moderate drinking prolongs bleeding time, above and beyond the use of aspirin, a known blood thinner, said Mukamal, a noted researcher in the field of alcohol and heart health. (His most recent study determined that there was no link between moderate drinking and heart arrythmia.)
Mukamal's team had speculated that alcohol consumption may affect platelets, a type of blood cell responsible for clotting. When a person is cut, "activated" platelets rush to the scene, group together, swell and adhere to the injury in order to plug the hole. Platelets may also clot together where there is no injury, in blood vessels or in the heart, leading to blockage of the blood flow. "No one before had looked at whether alcohol affects how easily platelets are activated," Mukamal said. "This is important because activated platelets are much stickier than normal ones."
For the current research, the team examined data and blood samples taken from 2,013 participants in the larger, ongoing Framingham Offspring Study, a study of risk factors for heart disease. Started in 1971, the study looks at the health of thousands of residents of Framingham, Mass., through biennial questionnaires and physical checkups. Mukamal's analysis excluded aspirin users, as well as current or past sufferers of heart conditions.
The participants reported their levels of alcohol consumption, along with other lifestyle factors. The volunteers were categorized by the average number of drinks they consumed in a typical week: zero, one to two, three to six, seven to 20 or more than 21. One drink was defined as approximately 12 ounces of beer, 5 ounces of wine or 1.5 ounces of liquor.
The researchers examined blood platelet activity using five different markers, including levels of triglycerides and HDL cholesterol, and then compared the results to drinking habits. For each type of measurement, they found that the more people drank, the less "activated" the platelets were. The difference began to be significant at the level of three to six drinks a week, according to Mukamal, and continued to increase as the amount of drinks increased.
However, few people drank more than 21 drinks per week, so the results could not be extrapolated to heavier drinkers.
The scientists found that men and women did not show different responses. Nor did the type of beverage consumed—wine, beer or spirits—appear to make a consistent difference in platelet activation. However, the study did not distinguish between red and white wine, which Mukamal said would be interesting to look at more closely.
The study results, while important for understanding risk factors for vascular disease, should not be used as a reason to modify one's drinking habits, either to reduce the risk of heart attack or of hemorrhaging, Mukamal said. He said that, in the United States, heart attacks greatly outnumber "bleeding-type strokes," in which copious amounts of blood cause a vessel to burst. "I don't think these findings have an immediate clinical application," he explained, "although they emphasize that doctors need to take even moderate drinking into account when thinking about timing for surgery or prescribing certain medications."
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