Young adults who engage in just one bout of binge drinking may experience a relatively quick and significant drop in their immune system function, a new small study indicates.
It's well-known that drinking ups injury risk, and this new study suggests that immune system impairment might also hamper recovery from those injuries.
"There's been plenty of research, mainly in animals, that has looked at what happens after alcohol has actually left the system, like the day after drinking," said study lead author Dr. Majid Afshar, an assistant professor in the departments of medicine and public health at Loyola University Health Systems in Maywood, Ill. "And it's been shown that if there is infection or injury, the body will be less well able to defend against it."
Read: Immune response
The new research, which was conducted while Afshar was at the University of Maryland, found immune system disruption occurs while alcohol is still in the system.
This could mean that if you already have an infection, binge drinking might make it worse, he said. Or it might make you more susceptible to a new infection. "It's hard to say for sure, but our findings suggest both are certainly possible," Afshar added.
The findings appear in the current online issue of Alcohol.
The U.S. National Institute on Alcohol Abuse and Alcoholism defines binge drinking as drinking that brings blood alcohol concentration levels to 0.08 g/dL, which is the legal limit for getting behind the wheel. In general, men reach this level after downing five or more drinks within two hours; for women the number is four.
Tracked for five hours
About one in six American adults binge-drinks about four times a month, with higher rates seen among young adults between 18 and 34, figures from the U.S. Centres for Disease Control and Prevention indicate.
To assess the impact of just one bout of binge drinking, investigators focused on eight women and seven men who were between 25 and 30 years old.
Although all the volunteers said they had engaged in binge drinking prior to the study, none had a personal or family history of alcoholism, and all were in good health.
Depending on their weight, participants were asked to consume four or five 1.5-ounce shots of vodka. A shot was the equivalent of a 5-ounce glass of wine or a 12-ounce bottle of beer, the team noted.
Each drinker was tracked for five hours, with blood samples drawn 20 minutes following peak intoxication and at the two-hour and five-hour marks.
After 20 minutes, the researchers found immune systems had actually kicked into a higher gear. This meant higher levels of three types of white blood cells that are integral to good immune function: leukocytes, monocytes and so-called "natural killer" cells. Cytokine protein levels also went up.
A drop in immune activity
However, at the two- and five-hour marks, immune system activity had dissipated to levels below those typically seen with sobriety, with a notable drop in both monocytes and natural killer cells. Also, a bump was seen in another type of cytokine protein that signals a drop in immune activity.
The authors stressed that their study wasn't designed to show whether colds or flu are more likely after a drinking binge, only that the immune system seems to be dampened.
Read: Preventing colds and flu
"We can't answer directly whether the fast immune system disruption we see actually puts a binge drinker at risk for a new infection or a poorer recovery from an existing infection," Afshar said.
"The point is that not everyone realizes that just one binge-drinking episode can be harmful . . . This was a single episode among healthy people, and this is what we found, so it's certainly worth more exploration," he said.
Another expert seconded that point. "We shouldn't overstate the results," said Dr. Sean Patrick Nordt, an associate professor of clinical emergency medicine with the Keck School of Medicine at the University of Southern California, Los Angeles.
"It's really difficult to tease out what immune system risk is related to one episode of excessive drinking and what could be related to chronic drinking, which can lead to overall poor nutrition and chronic medical problems," Nordt said.
It's not possible to categorically say a binge-drinking episode will always make recovery from an accident worse, Nordt said. "But this study is great food for thought, and certainly this should be looked at further," he added.
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Moderate alcohol consumption may support immunity
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