According to recent research, bacteria in the gut may influence brain development and human behavior.
It sounds like science fiction, but it seems that the gut bacteria deep within us – which greatly outnumber our own cells – may very well be affecting both our human cravings and moods to get us to eat what they want, and even driving us toward obesity!
Scientists have been working to find the answer to a really obvious question — how do the gut bacteria microbes talk to the brain?
A big nerve known as the vagus nerve, which runs all the way from the brain to the abdomen, is the prime suspect. And when researchers in Ireland cut the vagus nerve in mice, they no longer saw the brain respond to changes in the gut or gut bacteria.
“The vagus nerve is the highway of communication between what’s going on in the gut and what’s going on in the brain,” says John Cryan of the University College Cork in Ireland, who has collaborated with Collins.
Additionally, in an article published in the journal BioEssays, researchers from UC San Francisco, Arizona State University and University of New Mexico concluded from a review of the recent scientific literature that gut microbes influence human eating behavior and dietary choices to favor consumption of the particular nutrients they grow best on, rather than simply passively living off whatever nutrients humans choose to send their way through their food choices.
The Connection Between The Gut, Digestive Tract, and Brain
Research suggests that gut bacteria may be affecting our eating decisions in part by acting through the vagus nerve, which connects 100 million nerve cells from the digestive tract to the base of the brain.
“Microbes have the capacity to manipulate behavior and mood through altering the neural signals in the vagus nerve, changing taste receptors, producing toxins to make us feel bad, and releasing chemical rewards to make us feel good,” said Aktipis, who is currently in the Arizona State University Department of Psychology.
In mice, certain strains of bacteria increase anxious behavior. In humans, one clinical trial found that drinking a probiotic containing Lactobacillus casei improved mood in those who were feeling the lowest.
A Power Struggle Inside The Gut
Athena Aktipis, who is an evolutionary biologist and a psychologist, was drawn to the opportunity to investigate the complex interaction of the different fitness interests of gut microbes and their hosts and how those play out in our daily lives. Maley, a computer scientist and evolutionary biologist, had established a career studying how tumor cells arise from normal cells and evolve over time through natural selection within the body as cancer progresses.
In fact, the evolution of tumors and of bacterial communities are linked, points out Aktipis, who said some of the bacteria that normally live within us cause stomach cancer and perhaps other cancers.
“Targeting the microbiome could open up possibilities for preventing a variety of disease from obesity and diabetes to cancers of the gastro-intestinal tract. We are only beginning to scratch the surface of the importance of the microbiome for human health,” she said.
“Because microbiota are easily manipulatable by prebiotics, probiotics, antibiotics, fecal transplants, and dietary changes, altering our microbiota offers a tractable approach to otherwise intractable problems of obesity and unhealthy eating,” the authors wrote.