Dr. Martin Blaser links the obesity epidemic to antibiotic resistance and the destruction of a centuries-long human-bug relationship. [Image credit: Flickr user Sheep Purple ]
It’s a game of telephone. A scientist can whisper, or a scientist can shout. But by the time his or her message hits the ears of the public, there’s a big chance it’ll be a whole lot different from when it started.
That’s why microbiologist Martin Blaser decided to try dialing direct, with a book called Missing Microbes: How the Overuse of Antibiotics is Fueling Our Modern Plagues that he hopes will connect with a broad audience and convey his message that antibiotic overuse is a global crisis.
Blaser argues that the indiscriminate use of antibiotic drugs is destroying millions of years of happy co-existence between humans and the microbes in our gut. This destruction, he asserts, is the most important cause of what he calls modern plagues — obesity, juvenile diabetes, allergies and autism. And much of that damage occurs during the first three years of life.
“If kids are starting with an abnormal relationship [with gut microbes], they’re heading for trouble,” warns Blaser, who spoke Nov. 5 at a Sci Café talk at the American Museum of Natural History.
Considering how crucial antibiotics are to modern medicine, some experts still regard Blaser’s sweeping assertions about their overuse skeptically. But he’s no wild-eyed outsider. A physician and director of the Human Microbiome Program at New York University’s Langone Medical Center, Blaser is a past president of the Infectious Diseases Society of America and a member of the American Academy of Arts and Sciences.
Blaser has received worldwide attention for his work showing that the stomach bacterium Helicobacter pylori — previously regarded only as a menace to health and a target of antibiotics — actually plays a crucial role in protecting people from a wide array of illnesses, including acid reflux and perhaps childhood diarrhea and asthma.
He argues early childhood is the most crucial period when humans need a diverse array of gut microbes. During natural childbirth, a baby inherits the gut microbes of its mother, but the increased use of cesarean sections has disrupted this process. And so has the widespread use of antibiotic medications, which indiscriminately wipe out microbial life regardless of whether it’s beneficial or harmful. As a result, a mother with fewer microbes passes down her diminished microbiome to her children, who lose some of the advantages that some of those microbes can confer, such as the development of a robust disease-fighting immune system.
This gradual microbial impoverishment gets progressively worse over generations, which is why Blaser thinks the future of medicine will be a lot different. He acknowledges there’s still so much we don’t know about that process. “It’s going to take a lot of science to get there.”
Already his evidence is alarming. A map of obesity trends in the U.S. almost exactly matches one depicting the number of doctor-prescribed antibiotics, according to Blaser. “Something extremely powerful must be going on to produce a trend of this scale,” he said.
His ideas are not only based on statistical correlations, but also animal and human studies. Studying the microbiomes of farm animals is particularly important, he reasons, because farmers have been feeding animals antibiotics for 70 years to make them bigger and fatter. If it happened with them, could it happen in humans?
He first confirmed his speculation in mice. Antibiotics such as penicillin made them fatter, whether the mice were young or old. In fact, giving mice antibiotics early in life made them prone to obesity for the rest of their lives. Blaser then took it further with a fecal transplant — transferring microbes from antibiotic-fed mice to germ-free mice. The recipients got fatter without consuming antibiotics. This meant that the microbial environment of the host that had taken antibiotics was enough to transfer its obesity risk.
And now there’s data from human studies, too. The Avon Longitudinal study, which has been ongoing since the early ‘90s, linked infant exposure to antibiotics and cesarean births to future obesity rates in 10,000 children. In the 2013 study, Blaser and his colleagues found that antibiotic exposure within the first six months of life, but not later, were associated with increases in body mass before the age of 3. The effect was small for individuals in the study, but Blaser claims the trend is important to the health of whole populations.
Blaser thinks solutions to the microbial deficit are straightforward but not easy: do more science, educate doctors, create better diagnostic tools, limit antibiotic use only to extreme cases, make targeted antibiotics to spare beneficial microbes and replace lost microbes with scientifically-developed probiotics, perhaps including bugs from the Amazon.
But Blaser doesn’t advocate quitting antibiotics. There are certain times when they’re necessary, he says. Lyme disease patients should follow a full course and we should all use antibacterial soap and hand-sanitizer — not necessarily with dirty children on a playground, but during flu season and in hospitals.
Although he acknowledges that implementing his advice will be quite difficult, Blaser doesn’t address how much it will cost, how long it will take, or what happens in the meantime. What if people give up on doctors? What if physicians don’t comply? What if people seek out illegal antibiotics, or they decide not to take them when they should and die?
Evolutionary biologist Mark Siddall, a curator at the American Museum of Natural History, wonders how Blaser’s message feeds into the strong anti-interventionist mentality that exists in the United States, seen in individuals who choose not to vaccinate their children because they think vaccines cause autism. He agrees with Blaser that antibiotics should be limited, but worries the public may take Blaser’s message too far.
At Blaser’s museum talk, Siddall asked Blaser twice how antibiotics and vaccines are different, but Blaser brushed him off each time. “I am a scientist, and my job is to find the truth,” said Blaser. “Vaccination is a separate issue and I don’t want to [merge] the two.”
Afterwards, Siddall said he thought avoiding the question was “a total copout.” He suggested that Blaser’s argument could feed into the noble savage mode for nonintervention in which some believe going back to the way things were before modern medicine would be better. This is a fallacy, Siddall argued, noting that life spans were much shorter then and bacterial infections were rampant.
And though Blaser said he supports vaccination, praising it as one of the great miracles in public health, he would not speak directly about anxious parents who might wrongly assume that his hesitation about antibiotics applies to all medical interventions, including vaccination. The role of scientists, he said, is to give the public the best information they can. How the public interprets that information, he added, is up to them. “That’s the joy of living in a free country.”