In recent years, studies have shown that drinking alcoholic beverages—in moderation—can reduce your risk for heart disease. But there’s a flip side. Moderate alcohol consumption can also increase your risk for hemorrhagic stroke , a type of stroke caused by bleeding in the brain. Clotting is the common thread. A clot in an already narrowed artery can lead to a heart attack , while lack of clotting in an injured blood vessel in the brain can lead to hemorrhagic stroke.

Blood clots form when platelets in the blood aggregate , or cluster, to stem the flow of blood. When bleeding occurs, platelets are activated . They become stickier, thereby allowing them to adhere to the wall of the injured blood vessel. If blood cannot properly clot, it can lead to unchecked bleeding.

Blood thinners are a category of drugs that interfere with the blood’s ability to clot. Scientists have speculated that moderate alcohol consumption acts like a blood thinner.

Previous studies have suggested that moderate drinking interferes with the ability of platelets to aggregate. But to date, no one has studied whether alcohol consumption affects platelet activation.

In a study published in the October 2005 Alcoholism: Clinical & Experimental Research , researchers confirm previous findings that moderate alcohol consumption reduces the ability of platelets to aggregate. They also report that platelet activation is diminished in moderate drinkers.

About the Study

The researchers used data collected from individuals enrolled in the Framingham Offspring Study. The study participants were children of participants in the original Framingham Heart Study. For this study, researchers excluded individuals with any type of cardiovascular disease including heart attack, congestive heart failure , or stroke.

The study participants provided their medical history, including age, smoking status, physical activity level, body mass index, fasting total cholesterol, and presence or absence of diabetes and high blood pressure . They also responded to a questionnaire that asked about the average amount of beer, wine, and liquor they consumed per week.

The researchers collected blood samples from all of the study subjects. The ability of blood platelets to aggregate was measured in 879 men and 1,134 women, and the ability of blood platelets to activate was measured in 460 men and 577 women.

The Findings

The level of platelet activation was significantly lower in men consuming three to six alcoholic beverages per week than in men consuming fewer than three drinks per week. Drinking more than six alcoholic beverages per week did not further reduce platelet activation to a significant degree. The relationship between alcohol consumption and platelet activation was not significant in women.

Both men and women who drank three to six alcoholic beverages per week had significantly less platelet aggregation than men and women who had fewer than three drinks per week.

Although the researchers took relevant factors such as body mass index and smoking status into account, it is possible that the study results are due to other factors that were not considered.

How Does This Affect You?

This study showed that moderate alcohol consumption acts as a blood thinner. However, this was an observational study, and as such it did not address whether the blood-thinning effects of alcohol are responsible for its association with decreased heart attacks and increased hemorrhagic strokes.

This study is unlikely to affect the behavior of anyone who already drinks responsibly. But drinking can quickly get out of control, and the negative consequences of heavy drinking far outweigh any potential health benefits of drinking in moderation. So if you don’t drink, no study should convince you to start.