How Antibiotics Can Change Your Body (for the Worse)


Antibiotic resistance is one thing — but new research says it’s not the only worry when it comes to popping pills. (Photo: Corbis/Garo)

Antibiotics were invented for a reason. Since the introduction of penicillin in the 1940s and the subsequent development of other antibiotics, illness and death from infectious diseases have dropped dramatically. But with widespread use as time has gone on, the bacteria the drugs were designed to destroy have adapted, becoming resistant to some strains. 

The worry surrounding antibiotic resistance is real. If bacteria become resistant to the drugs — because you’re consuming them unnecessarily (when you don’t have a bacterial infection; or from meat that came from cattle raised with antibiotics) — then they may not work when you need them most: while fighting a dangerous illness.

But according to an emerging field of research, resistance isn’t the only thing to fear about the medication — especially for children. In a new study, New York University Langone Medical Center researchers wanted to see what would happen when they gave mice a dose of a popular childhood antibiotic — amoxicillin or tylosin — in similar doses to those that kids receive. (Tylosin belongs to a class of drugs called macrolides, which are commonly used in children, though tylosin itself is usually used only in animals.) 

The results? Mice on antibiotics gained more weight, developed larger bones, and saw more disruptions to their gut microbiomes (bacteria in their gastrointestinal systems) than mice that were not fed any antibiotics. Tylosin seemed to have a stronger effect than amoxicillin on reorganizing the microbiome — suggesting this drug could have broader activity throughout the gut and intestines, researchers say.

While it’s not surprising that mice exposed to antibiotics experience changes to their microbiomes — since antibiotics work by killing or suppressing bacteria — what is interesting is “how long the changes lasted,” study lead author Martin Blaser, MD, director of the Human Microbiome Program at NYU School of Medicine, tells Yahoo Health. 

Even though antibiotic treatment ended on day 39 of the study, on day 160, researchers still saw differences in the guts of medicated mice. Here’s why that matters: Long-term changes to the bacteria in your gut can have metabolic consequences, like weight gain, Blaser says. Other research from the University of Minnesota has also linked early antibiotic use to allergies, autoimmune disorders, and other diseases later in life. 

Related: Can Antibiotics Early in Life Put Your Child at Risk for Obesity?

And while this most recent work was done on mice, Blaser says that the results are “consistent with the idea that early-life antibiotics affect how the microbiome is developing and may affect how a child might be developing.”

But what about adults? Are we at risk for all sorts of bodily changes, too? Blaser’s work has mainly focused on children and young animals — that’s when immunity and metabolism are developing and uber-fragile to changes, he says. “Earlier use seems to have more of an impact,” he says. But other research suggests adults aren’t immune to the effects either. One study in the European Journal of Endocrinology that looked at a million people found that people who suffered from diabetes had received more antibiotics than people without the condition. This suggests that antibiotics are changing the microbiome — even in adults — thereby affecting metabolism and predisposing some to diabetes, says Blaser. 

The answer to avoiding these potentially dangerous changes seems to go back to reconsidering how often we’re taking the drugs. Data suggests that the average American child receives 10 courses of antibiotics by age 10; four out of five Americans are prescribed the drugs each year; and nursing homes likely overuse antibiotics. Other research suggests 20 to 50 percent of all antibiotics prescribed in this country are unnecessary.

Related: When You Should Skip Antibiotics

That’s not to say the solution is cutting back on sick people using the drugs: “When someone is sick, they really need antibiotics,” reiterates Blaser. “It’s just that we’re overusing them for mild infections or when antibiotics aren’t needed at all because the infections are viral.”

Your best bet? If you have a sick kid — or if you’re sick yourself — head to your doctor’s office to make sure an infection is bacterial before dosing with the drugs. And try to stick to meat that’s raised without antibiotics. Some research suggests that 80 percent of antibiotics sold in this country wind up in livestock — not people. And even if the meds are carried in an animal, they can still reach your system.

Read This Next: Scientists Find Antibiotic That Kills Superbugs

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