On the Gut-Brain Axis

An illustration of bacterium shapes in bright green on a black backdrop. Sarah Becker ’18 has had an interest in the microbiome—the bacteria, fungi, viruses and other microscopic organisms that live in our guts—since she was in eighth grade. That’s when she came back from a family trip to Cambodia with a bad case of intestinal parasites. The doctor put her on round after round of antibiotics, after which, she says, “My gut was just wrecked.” And yet she wasn’t getting better with standard treatment protocols. “I started doing research about probiotics, supplements and the mind-body connection,” she says. “I became convinced that changes in the microbiome affect the so-called ‘gut-brain axis’ and contribute to our overall health and well-being.”

Becker began to see improvement in her health during high school. She also became an accomplished cross-country skier, which planted a question in her mind: Could there be a connection between athletic performance and the microbiome? During Becker’s time at Williams, interest in the microbiome and in the potential of fecal transplants to treat illnesses have become more widespread. So Becker decided to complete her own thesis on the microbiome.

“My project looks at how the gut mediates our tolerance for artificial sweeteners,” says the art history and biology major, explaining that we have long known about a connection between diabetes and the consumption of artificial sweeteners, but we didn’t know where the causality lay.

“A 2014 study shows a direct correlation from the consumption of artificial sweeteners like saccharin and aspartame to the inducement of glucose intolerance,” she says, adding that the correlation was proven through the study of the microbiome. “When researchers transplanted fecal matter from mice that had been fed artificial sweeteners into mice with a sterile microbiome, glucose intolerance developed.”

Becker’s thesis extends the 2014 study by examining a different sweetener, Stevia. Because Stevia is derived from a plant, it’s considered a more natural sugar substitute. Some researchers have hypothesized that, unlike other artificial sweeteners, Stevia could lower glucose levels. Becker hopes her research this year will help determine whether or not that’s the case.

“Understanding the effect of Stevia on the microbiome will provide insight into its use as a safer alternative to other commercially available non-caloric sweeteners to help populations that struggle with weight gain and blood sugar control,” she says.

Becker is also planning to look more closely at the connection between endurance sports and the microbiome. An endurance athlete for much of her life, she’s captain of Williams’ Nordic ski team, and she’s curious about the possible connections between these sports and a person’s overall well-being.

Next year, she hopes to study cross-country skiers in Sweden. “My research plans include the collection and study of fecal and blood samples taken before, during and after endurance sporting events, such as long ski races,” she says. “One of my questions is: does endurance training encourage growth of certain bacteria, and, if so, how do these populations affect performance and overall health?”

Becker hopes that answering that question, and all the others she’s been asking since eighth grade, will inform her future career as a physician. “I hope one day to specialize in gastroenterology and endocrinology with a focus on the gut-brain axis, nutrition and hormonal health,” she says.
—Julia Munemo