“We aren’t single individuals, but colonies of trillions. Our bodies, and our guts in particular, are home to vast swarms of bacteria and other microbes. This “microbiota” helps us to harvest energy from our food by breaking down the complex molecules that our own cells cannot cope with. They build vitamins that we cannot manufacture. They ‘talk to’ our immune system to ensure that it develops correctly, and they prevent invasions from other more harmful microbes. They’re our partners in life.
What happens when we kill them?
Farmers have been doing that experiment in animals for more than 50 years. By feeding low doses of antibiotics to healthy farm animals, they’ve found that they could fatten up their livestock by as much as 15 percent. You can put the antibiotics in their feed or in their water. You can give the drugs to cows, sheep, pigs or chickens. You can try penicillins, or tetracyclines, or many other classes of antibiotics. The effect is the same: more weight.
Consistent though this effect is, no one really understands why it works. The safe bet is that the drugs are exerting their influence by killing off some of the microbiota. Now, Ilseung Cho from the New York University School of Medicine has confirmed that hypothesis. By feeding antibiotics to young mice, he has shown that the drugs drastically change the microscopic communities within their guts, and increase the amount of calories they harvest from food. The result: they became fatter.
Cho exposed young mice to a range of different antibiotics including penicillin, vancomycin, the two together, or chlortetracycline, all at levels that the US Food and Drug Administration approves for use in agriculture. After 7 weeks, the treated mice were no heavier than those that didn’t drink any drugs, but they had more body fat – around 23 percent, compared to a typical 20 percent…..”