Rock Doc

It’s astonishing to think about, but when my grandfather was born, tuberculosis was the number one cause of death in our country. Worse still, one in five children didn’t live to see their fifth birthday, in large part due to endemic and epidemic diseases. Today that’s all changed.

But although doctors can now often do a great deal to help the ill, it’s also true that chronic diseases plague us. And a number of these maladies seem to be on the rise. Diabetes, asthma, celiac disease and food allergies are all increasing in frequency. Most obvious of all, obesity is becoming more and more common.

Dr. Martin Blaser of New York University thinks he understands at least part of what’s going on. And according to him, medical treatments themselves are contributing to the rise of some chronic health problems. His new book, “Missing Microbes: How the overuse of antibiotics is fueling our modern plagues,” explores the link between changes in our internal microbes and the list of chronic diseases so many of us now face.

Antibiotics are a blessing. But if Blaser is right, they are also a curse. Both things can be true. To take just one malady, let’s focus on obesity.

There’s no doubt obesity is on the rise. Back in 1990, about 12 percent of people in the U.S. were obese. Recently, the figure has grown to about 30 percent. And people in other countries are following our lead, packing on the pounds. Those are just facts. What other facts can we bring to bear on the issue?

Your body is host to many trillions of microorganisms. The microorganisms on and in your body change over time. One simple example is that the proportions of bacteria in your mouth are altered depending on whether you are breathing through your nose or your mouth. That’s because some microorganisms can’t live in the presence of oxygen. At night, you breathe mostly through your nose and the proportion of bacteria in your mouth that don’t cope with oxygen can increase. They are stinky little buggers, and that’s what gives you “morning mouth” when you wake up.

Important changes in populations of microorganisms within us occur when we take antibiotics. When a doctor gives you penicillin or one of the host of newer antibiotics, the goal is to eradicate what’s making you ill. Blaser’s book outlines the ways in which a number of microorganisms, including ones that are useful to you, are also affected by antibiotics.

I was surprised to learn from the book that most antibiotic doesn’t end up in pills we get from pharmacies. Instead, most of the drugs go into the cattle, swine and poultry that we eat. The reason so much antibiotic is given to livestock is that the animals gain more weight when they are given antibiotics in their feed. It pays for farmers to buy antibiotics and give them to whole herds.

Blaser’s book asks whether antibiotics given to people could have a similar effect as in livestock. Antibiotics, especially those given to kids, may be leading both to more growth and to putting on more fat, including in later life. The book reviews experiments with mice in Blaser’s lab that address this connection, as well as studies in human populations. Blaser concludes we may be inadvertently fatting up our young in our rush to use antibiotics to treat every sore throat or cough.

As Blaser sees it, antibiotics contribute to obesity and a host of other chronic diseases that have been on the rise in recent decades. He argues that our attitudes need to change. Doctors should be trained to think twice before prescribing antibiotics. The drugs should be reserved for truly serious conditions that aren’t going away on their own.

“Doctors and patients alike have never fully taken into account all the costs of using antibiotics. Once they do, I predict their use, especially in early childhood, will greatly diminish,” Blaser wrote in an email to me.

The progress we’ve made combatting many diseases is stupendous. No one wants to go back to the problems that were common when my grandfather was born. But it’s time we looked at what the overuse of antibiotics may be costing us.

Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. This column is a service of the College of Agricultural, Human, and Natural Resource Sciences at Washington State University.