We shit you not: Volunteers chugged a glass of E. coli so scientists could see whether a person’s blood type influences the severity of traveler’s diarrhea.
We know what you’re thinking. This must be the sorriest bunch of volunteers inhabiting planet Earth—or they got some really great incentives (maybe a Cheese of the Month Club) to say ‘Thanks for letting us turn your gastrointestinal system into a Thunderdome.’
In the Washington University School of Medicine study, published in The Journal of Clinical Investigation, researchers conducted controlled human infection clinical trials at Johns Hopkins University. Healthy men and women, 106 in total, drank E. coli-laced water—a strain from an individual in Bangladesh who had intense, cholera-like diarrhea—then hung out at the (hopefully-well-ventilated) clinic for five days.
Researchers obtained blood samples and observed all participants, administering antibiotics to those who developed moderate to severe diarrhea. Don’t worry: The lucky few who were healthy at the end of the study were also given antibiotics to wipe out any lingering bacteria.
Thankfully there was a takeaway.
People with blood type A experience symptoms sooner and with greater ferocity than those with blood types B or O. Particularly, 81% of blood type A volunteers developed diarrhea that required treatment, compared to just half of the people with blood group B or O. Researchers believe it’s because E. coli bacteria produce a kind of protein that binds to sugars specific to blood type A.
The E. coli bacteria then cling to the intestinal wall, transmitting diarrhea-causing toxins. Delightful.
Don’t freak if you’re blood type A, though.
“I don’t want anyone to cancel their travel plans to Mexico because they have type A blood,” study author Matthew Kuhlmann, M.D., said in a press release. “Or the converse: I don’t want anyone to think they’re safe because their blood group is not A. There are a lot of different species of bacteria and viruses that can cause diarrhea, so even though this blood-group association is strong, it doesn’t change your overall risk. You should continue taking the same precautions whatever your blood type.”
Your best odds at avoiding E. coli and staying healthy while you travel? Wash your hands often and make sure you’re drinking purified water.
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