Unintended Consequences

Most of us are aware by now that antibiotics are overprescribed for human use and overused in animal feed to increase livestock weight. The consequences are tragic; disease-causing bacteria develop resistance when repeatedly exposed, and many antibiotics have become ineffective.

Physicians are left with fewer and fewer tools to combat serious bacterial infections. Thousands of patients die annually in Canada alone due to infections from antibiotic-resistant bacteria, a medical travesty that could be avoided if we reduced antibiotic usage.

But I read an article in the New York Times on Sunday that slapped me in the face with an obvious realization that I had completely missed (by Pagan Kennedy, 8 March 2014, “The Fat Drug”). If antibiotics fed to livestock result in their gaining weight, what happens to our human weight when we ingest antibiotics?

Turns out there were studies performed in the 1950’s asking just that question. Antibiotics were fed to Guatemalan school children in one study, severely mentally disabled kids in Florida in another, and Navy recruits in a third, all with the same result of increased weight gain following weeks to a full year of antibiotic exposure. And it wasn’t just a minor weight increase; children showed up to three times the weight gain when fed antibiotics compared to those not fed drugs.

Leaving aside the reprehensible ethics of using third-world and mentally disabled children, and soldiers, for these studies, it’s tempting to attribute the current obesity epidemic in the developed world to antibiotics, at least in part. It turns out that there are known mechanisms by which antibiotics might lead to human weight gain, in addition to the obvious observation that it does so in other animals.

For one thing, antibiotics flip a switch in animal digestive systems that turn extra calories into fat, which is one mechanism leading to weight gain. Antibiotics also disrupt the diverse microbial flora in the gut that play a critical role in digesting food, again causing weight gain and possibly contributing to obesity.

Antibiotics have been on my mind lately because of the book about bees I’m working on (Bee Time: Lessons From the Hive, http://winstonhive.com/?page_id=164, due out in October). Beekeepers are like many farmers, overusing antibiotics to stimulate their animals’ weight gain. In the case of beekeepers it’s been colonies gaining due to the increased honey production that results by preventing the bacterial disease American Foul Brood (AFB).

But resistance finally developed, and AFB is now epidemic. The only “cure” is to kill the bees and either burn the entire hive or subject the comb and boxes to intense radiation.

It’s not surprising that antibiotic resistance arose, given how much drug beekeepers have been feeding to bees in sugar syrup or dusting into colonies a few times a year. But giving antibiotics to bees has had another unexpected impact, synergizing the effects of pesticides and making these agricultural chemicals toxic to bees at low doses thought to be benign.

Antibiotics fed to bees increase their susceptibility to many pesticides, including neonicitinoid insecticides, which many blame for colony collapse disorder. Essentially, antibiotics reduce the effectiveness of a component in bees’ immune systems that detoxify pesticides, lowering the dose at which a pesticide will harm bees.

Similar antibiotic interactions are well known in human medicine. For example, women have been surprised to get pregnant after taking certain antibiotics that neutralize birth control pills. Antibiotics also interfere with commonly used blood thinning medications and insulin; a simple web search reveals dozens of other harmful interactions.

There’s a bigger issue here, for bees and for us. We’re exposed to hundreds, perhaps thousands, of chemicals every day, from medicines to nutritional supplements, pesticides to industrial plastics, fertilizers to smog. We have some idea about the effects of each alone, but are mostly clueless as to the impacts of minute chemical exposures from multiple sources.

It’s the law of unintended consequences, a perverse effect contrary to what was originally intended. Whether it’s human weight gain from antibiotics or the demise of bees, we’re becoming increasingly aware of how little we understand the side effects of scientific progress.

We’re paying some serious penalties for own health and that of the environment around us. Perhaps it’s time for interactions to be more carefully studied before we release new dangers into the world around us.