Title:Probiotics and the Gut

The swap took place every month in Breezewood, a truck-stop town halfway between Washington, D.C., and Pittsburgh, Pennsylvania. Georgetown scientists would drive two hours with the goods, carefully stored in red picnic coolers. They’d pull into the parking lot and up to the waiting vehicle from Penn State, which held precious cargo: a fresh batch of strawberry yogurt infused with an added active bacteria known as Bifidobacterium lactis strain BB-12.

What Georgetown offered in return might surprise you.

A Hot Commodity

“We teamed up with Penn State because they’re a land-grant university, so they have cows and their own dairy,” says Dan Merenstein, MD, family medicine professor at Georgetown and lead investigator in the study. “They make us probiotic yogurt. And we give them poop.”

Not just another pile of fecal matter coming out of the nation’s capital. This set of samples came from children who were administered antibiotics. Because antibiotics strip the body of both bad and good bacteria, probiotics like those naturally occurring in yogurt and fermented foods may restore the healthy balance of flora in the body.

Up to 30 percent of people develop mild to severe diarrhea while taking antibiotics. While previous studies have found that probiotics can help prevent it, questions remain about which strains are most effective, how they work, and if a certain strain is more effective when taking a particular antibiotic.

Not all beneficial bacteria can survive the stomach’s acidity, but BB-12 is known to have that capability, explains Merenstein. The strain has also been found to help with chronic constipation by improving transit time, reducing bloating, and boosting immune function.

Today the collaboration includes University of Maryland, another site where scientists analyze Georgetown-provided fecal matter. They look at the genetic makeup of bacteria found in children’s stools during and after treatment to see which types are present and how they change over time.

Merenstein, who is also a professor of human science in the School of Nursing & Health Studies, tapped students for an important role
in the clinical research, helping recruit families for the study,” notes Merenstein. “Georgetown undergraduate students are working in doctors offices, and talking to parents and physicians about our study.”

Antibiotics and Immunity

Overuse of antibiotics in the U.S. continues to be a problem, said Merenstein, whose lab has been studying probiotics and the gut microbiome since 2005. Keeping a balanced bacterial community in the body can impact not just gut health but overall disease prevention, because the gastrointestinal tract is home to most of the human immune function.

“The main problem of overuse of antibiotics is that it makes you susceptible to so many other things,” he says.

Last year, Merenstein and his colleagues set out to better understand how probiotics work. The researchers tracked changes in the gut microbiome of 60 adults on antibiotics over a course of 30 days. One-third were given regular yogurt to take with their meds, and two-thirds were given a probiotic-infused yogurt to take.

Use of antibiotics appears to disrupt the production of short-chain fatty acids (SCFAs), which are the preferred food of gut bacteria. SCFAs are found in high-fiber foods and fermented foods, and play a big role in metabolism. A deficiency in SCFAs correlates to dysbiosis, an imbalance of gut flora that may be linked to colon cancer and obesity.

Fecal samples hold the key, because they offer a snapshot of how the microbiome is doing.

Early results from the study showed that participants who were on a regular course of antibiotics took a hit to the microbiome that lasted 30 days. Those taking the probiotic along with the antibiotics maintained their normal level of short-chain fatty acids throughout the month of observation.

“The probiotic we’re giving seems to protect the GI tract,” says Merenstein.

Watch This Space

Merenstein plans more studies to look at specifics—when is the best time to take the probiotics, should they be taken simultaneously with the antibiotics or spaced out. As is often the case, one question leads to a thousand more.

What does it mean to ingest live cultures? What can fermentation teach us about human health? A glance at the global human diet indicates some historic preference for consuming foods like yogurt, kimchi, and sourdough breads. Every country and culture has its favorite pickle, and some reports suggest a craving can even develop in vitro!

Pinaki Panigrahi, MD, pediatrician and director of international microbiome research at Georgetown, is studying the link between sepsis prevention and yogurt consumption in rural India. Look for more on his work in the near future as gut microbiome exploration and insights continue to multiply.

“Gut health is such a big part of our overall health,” says Merenstein. “It’s not just about having diarrhea or constipation, but it’s connected to our respiratory health, how we feel men- tally, and most importantly, our immune system.”

Georgetown researchers hope to shed light on the mysteries of gut health, by continuing to examine what exits the intestines. Thanks to fecal samples, the gastrointestinal tract offers no shortage of rich material to explore.

Merenstein serves in an unpaid executive position at the International Scientific Association for Probiotics and Prebiotics and occasionally as paid scientific consultant for Bayer and DuPont.