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Biology for $1000, Alex: An integral part of the cell walls of Gram-negative bacteria, these toxic compounds can trigger inflammation and other immunological responses after a single episode of heavy drinking.

Answer: What are endotoxins?

The outer membranes of gram-negative bacteria contain toxic elements known as endotoxins, or lipopolysaccharides. An endotoxin is released when a bacterial cell wall is breached, allowing virulent proteins to enter the bloodstream. When endotoxins engage with the immune system, the result is inflammation—a necessary part of healing, yet potentially damaging to surrounding cells and tissue. When you come down with a cold, those aches and pains come are caused by your immune system inducing inflammation to fight the virus. Chronic inflammation is not a good thing. Higher levels of circulating endotoxins have been linked to numerous health issues.

Binge drinking: Almost everybody does it now and then, and some drinkers do it every day. So what is binge drinking, anyway? The NIAAA defines it as a drinking pattern that results in a blood alcohol level of 0.08 or above. This means about four drinks for women and five for men over a period of about two hours. "In chronic alcohol use activation of the inflammatory cascade is a major component of organ damage in the brain and liver," according to researchers at the University of Massachusetts Medical School. "Alcohol binge can cause altered immune functions that can also contribute to immunosuppression and reduced immune-mediated host defense to pathogens."

Nobody ever claimed binge drinking was good for you. But the work done by researchers at the University of Massachusetts Medical School on a small group of drinkers shows that a single episode of five drinks or more "can cause damaging effects such as bacterial leakage from the gut into the blood stream," said Dr. George Koob, director of the National Institute on Alcohol Abuse and Alcoholism (NIAAA). The work was funded by the National Institutes of Health (NIH). The study "tested the effects of acute binge drinking on serum endotoxin and bacterial 16S rDNA in normal human adults." Led by Gyongyi Szabo, a professor at the University of Massachusetts Medical School, the study in PLOS ONE documented increases in endotoxin levels in the blood and evidence of bacterial DNA from the gut.

The investigators found that the concentration of endotoxin observed in the serum after an acute binge had significant biological activity, in particular a "significant induction of inflammatory cytokines." In a prepared statement, Szabo said: "We found that a single alcohol binge can elicit an immune response, potentially impacting the health of an otherwise health individual. Our observations suggest than an alcohol binge is more dangerous than previously thought." Fever, hypotension, and septic shock may develop due to endotoxins.

Compounding the harm to internal organs caused by alcohol is "gut permeability," meaning that toxins have a better chance of escaping through the intestinal wall, wandering to other parts of the body, where they do harm. When you combine greater gut permeability with increased levels of circulating endotoxins, you get alcohol-related liver damage and other problems. Binge drinking, the researchers believe they have shown, is a good way to speed up that process.

In short, binge drinking helps gram-negative bacteria break the gastric barrier, escape the stomach, and colonize the small intestine, which puts them into systemic circulation. Bad news. The only bacteria that should be colonizing the small intestine is your neighborhood-friendly graham-positive Lactobaccilus, which aids digestion.

Unfortunately, the study also added to the growing mountain of evidence showing the ways in which alcohol effects women differently than men (See my report on gender-specific alcohol treatment in Scientific American.) Binge drinking showed a greater effect on women with respect to both endotoxemia and bacterial DNA levels.

According to the report: "Compared to men, women showed a slower decreased in blood alcohol levels (BAL), and even 24 hours after the alcohol binge BALs were higher in women than that in men…. Serum endotoxin levels were also higher in women after alcohol intake and a significant difference in endotoxin level was observed at 4 hours between men and women."

Bala S., Marcos M., Gattu A., Catalano D. & Szabo G. (2014). Acute binge drinking increases serum endotoxin and bacterial DNA levels in healthy individuals., PloS one, PMID: 24828436

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