Intestinal Biome: We’re in This Gut Together

By Patrick Reed | 11/19/18 8:30 AM

Exploring the relationship between microorganisms in our intestinal tract, the food we eat, and our overall health is one of the most exciting and rapidly developing fields of study in medicine. Constantly, hundreds of species of bacteria work in our gut to break down food and send out nutrients to the body. How does this process occur, and what can we do to make our intestinal biome more healthy?

In this episode of Kentucky Health, Dr. Wayne Tuckson welcomes a professor of pharmacology and nutrition at the University of Kentucky to explain how the intestinal biome works and discuss the latest breakthroughs in research involving probiotics and dietary recommendations.

Loading video player...

Dr. Sara Police, PhD., is an assistant professor in the department of pharmacology and nutritional sciences at the University of Kentucky and is the associate director of graduate studies for the Nutritional Sciences MS-PhD. Program at the University of Kentucky College of Medicine.

Police says that one might ordinarily think about bacteria in the body as something that is bad and needs to be removed. But that’s not the case.

“The microbiome refers to all the trillions of bacteria that live in our bodies,” she says. “We have bacteria in our mouth – oral cavity – in our respiratory system, reproductive organs, and the bulk of it is in the GI tract.”

According to Police, the ratio of bacterial cells to human cells in the body ranges from 3 to 1 to 1 to 1, changing to the lower number after a bowel movement. There are roughly about four or five pounds of bacteria existing in the human body.

Building the Microbiome, and Exploring Its Benefits
Bacteria cells exist in the gastrointestinal tract before before childbirth, Police says, and introduced to the fetus by the mother’s microbiome. A lot of the seeding of bacteria occurs during the process of childbirth. A child born vaginally will have a different microbiome composition than one born through a Caesarean section, Police explains. “It’s like a first vaccination, you might say.”

Whether a child is breastfed or not is also a factor in building the microbiome. And the environment plays a role as well. A child living near the ocean will have a different microbiome compared with one living inland, for example. Our microbiomes are pretty unstable and in a very formative state for the first three years of life, Police says. “Once a child reaches three years of age, it has a microbiome that more closely resembles that of an adult.”

Regarding medicine, whether a child is given high doses of antibiotics is very important in determining the composition of their intestinal biome. If a child has an infection and is prescribed antibiotics, the resulting effect on the microbiome can last for years.

“I like to think of the microbiome like a garden,” Police says. “You’re seeding it in infancy, you’re seeding it in infant feeding practices, you’re seeding it with a diverse diet to make a nice, rich garden that yields lots of different kinds of fruit, lots of important functions. Antibiotics basically are tearing up a little bit of those vegetables by the roots. So they need to be re-seeded. And it can take a long time for the microbiome composition to recover after antibiotic use.”

A person’s microbiome is very important in building and maintaining the immune system, Police says, and every person’s microbiome is unique. She explains that the microbiome “trains” the immune system to recognize good and bad antigens in the body, and that bacteria in the gut compete against any harmful antigens a person ingests. “Usually, those pathogens don’t win out because of the health of the biome.”

The microbiome even affects neurological function, according to Police, who refers to the phrases “butterflies in the stomach” and “gut-wrenching” as examples of how this gut-brain relationship has entered the lexicon. The microbiome signals satiety and produces serotonin, Police says, which signals the hypothalamus to control food intake.

Although everyone’s microbiome is unique, Police says that research has found some similarities in gut bacteria for cohorts of obese patients.

“Studies that have looked at obese cohorts, found their microbial diversity is lower than in patients in lean cohorts,” Police says. The more diverse the microbiome, the more normative microbial function a person will have, she adds.

Police explains how the microbiome works differently when comparing obese and lean patients. “The microbiome in obese patients tends to be optimized for energy harvest,” she says. “So you see, even eating the same number of calories, this microbiome is tweaked to harvest more energy from food.

“This is why one diet really doesn’t work for everyone, because as we talked about, the microbiome is so distinct from person to person to person.”

Maintaining a Healthy Intestinal Biome
If a healthy intestinal biome works in symbiosis with the rest of the body, Police says that dysbiosis is the opposite, where the relationship is out of balance and too much of what she terms pathogenic bacteria is present in the gut.

“In a situation of dysbiosis you’re going to have increased populations of bacteria that you don’t really want in your body,” she says. “This has been associated with altered immune function and some auto-immune disorders. The microbiome for instance in ulcerative colitis patients and in Crohn’s patients with inflammatory bowel disease is markedly different from healthy patients.”

To maintain a good microbial balance, Police says that a healthy diet is most important. The food we eat make up what she calls the “pre-biotic” part of microbiome composition. “You have to feed the bacteria,” she says. “And they like fiber. Starch, dietary fiber. Their favorite food, I would say, are fruits and vegetables. Plenty of soluble and insoluble fiber to feed the healthy bacteria in the gut.”

One way to improve the diversity of good bacteria in the intestinal biome is to improve the diversity of your diet. Police says she attended a nutrition conference last June where researchers discussed a “magic number” of food types per month that would yield a higher diversity in the microbiome. That number: 30.

“Thirty types of vegetables and fruits per month,” Police says. “Not ten, not twenty, but thirty different types of fruits and vegetables was a stronger correlate with increased diversity than almost any other factor that they looked at. And so you have to be really intentional to get thirty different fruits and vegetables in your diet on a monthly basis.”

Once a healthy diet is established, persons with intestinal problems still may need to take probiotics to help introduce more good bacteria into the microbiome. Probiotics occur naturally in some foods such as yogurt and kefir (fermented cow’s milk) but are also available over-the-counter and through a prescription.

“The goal of probiotics is to offset dysbiosis, and hopefully provide some bowel regularity,” Police says. “Clinically, the most significant research I’ve seen to date with probiotics is in preventing diarrhea. You’re repopulating hopefully that microbiome.”

Police says that persons should talk to their clinician or physician before they start taking probiotics in order to determine the appropriate strain of bacteria they should take and the proper dosage. She says that taking a low dose of probiotics may not introduce enough bacteria into the intestinal biome – which has billions of bacteria cells – to make a difference in overall health.