Healthier Tummy, Happier You?

6 min read  |  June 07, 2018  | 

A strong stomach — one that digests food without rebelling — is a blessing not everyone can claim. But good gut health is more than easy digestion, more than moving food through the highly complex gastrointestinal tract. Research increasingly points to a connection between the health of our twisty, gurgling insides and other parts of our body.

In short, the microbes in your GI are important for your heart, brain, metabolism, immune system — and even your feelings.

The GI ecosystem

“The microbiome,” explains Dr. Amar Desphande, a gastroenterologist with the University of Miami Health System, “plays a very important role in our health. Some people think our skin is the biggest exposure we have to the outside world, to the environment. But it’s really our GI system.”

That’s because our digestive system is huge. The microbiome, which is the GI ecosystem, contains an estimated 100 billion bacteria, as well as fungi, parasites and viruses.  Scientists figure that these organisms weigh between one and three pounds, on average, and how they interact with each other and their combined metabolic products play an important role in how the rest of our body functions. Deshpande calls our gut microbiome a “key regulator.”

Yet trying to figure out the details of this regulating mechanism has been challenging. “We agree that it’s important, but we don’t even have a universal agreement about how to measure that microbiome — at the beginning of the GI tract or at the end or somewhere else,” Deshpande says.  “Even at the end, in the fecal measure, one-quarter of the bacteria doesn’t come out in feces because it sticks to the lining.”

While much research is still needed on the connection between our gut and our bodily functions, this much we do know:

Our gut is smart

It communicates with its neighbors through several pathways, including hormones, the nervous and immune systems, and the very important vagus nerve, that multiple-branched nerve that begins in the cerebellum and brainstem and extends to the lowest part of your abdomen, touching most major organs in between.

The vagus nerve, according to a 2014 study published in the Journal of Neuroscience, carries sensory information from your body’s organs to your brain — and vice versa.

What’s more, the gut’s biodiversity — or the combination of gut microbes —plays an important role in our health. (Yes, it’s that age-old mythical battle between good and evil, or in this case good bacteria and bad bacteria.) Researchers have speculated that the loss of certain bacteria in our interior ecosystem, even “predatory bacteria,” leads to an unstable environment that can result in dysbiosis, which we experience as bloating, diarrhea, abdominal pain, constipation, indigestion, and acid reflux.

How does the health of our gut affect us?

Let us count the ways:

  • A microbiome with plenty of good bacteria appears to magnify the good results of cancer immunotherapy treatment, according to studies. Conversely, these immunotherapies were not as effective when patients were also taking antibiotics, which are known to kill important flora in the gut. Researchers noted that those patients who did well had greater bacterial diversity in their gut, whereas patients whose tumors didn’t shrink measurably had fewer varieties of microbes present. Those that responded well to the immunotherapy also had more T cells, which attack cancer. Patients with higher T cell density count had a notable presence of Faecalibacterium and Clostridiales bacteria.
  • Bacteria can influence depression and anxiety. A study published in Neuroscience found that when mice were given an antidepressant, either bifidobacterium or Lexapro when subjected to stressful situations, they had reduced levels of stress hormones. Another study, conducted in Canada, found that when gut bacteria from anxious humans was transferred into germ-free mice, the mice behaved more anxiously. A similar transfer study of this bacteria from mice to mice also resulted in tranquil mice exhibiting more anxious behavior.
  • The gut-mood connection is not new. Scientists know that bacteria produce serotonin, dopamine and GABA, neurotransmitters that are essential to our moods. It’s believed that bacteria also affect the way we metabolize these compounds. A gastroenterology journal study involving 25 healthy women, for example, showed that those who ate yogurt twice a day reacted more calmly when shown certain facial expressions. Researchers speculate that bacteria in the yogurt — in this case, bifidobacterium, streptococcus, lactococcus, and lactobacillus — promoted the production of compounds that modify brain chemistry.
  • Certain gut bacteria can block arteries and pave the way to heart disease, according to various research reports. That’s because they convert nutrients found in red meat and other animal-based sources into a chemical that appears to promote heart attacks and stroke, called trimethylamine N-oxide or TMAO. Interestingly enough, a small 2015 study published in Circulation Research, found that a healthy gut microbiome can promote good cholesterol, known as HDL cholesterol. Also, certain gut bacteria, principally Lactobacilli, appears to reduce bad cholesterol when taken as a probiotic.
  • There’s a convincing link between the gut microbiome and certain neurodevelopmental disorders, though scientists still don’t know the microbes’ exact function in relation to the illnesses. Recently, several studies explored why three-quarters of autistic people suffer from digestive issues, including food allergies, frequent indigestion, and gluten insensitivity. Researchers discovered that the study group with autism had a significantly different microbiome than the control group. One example: Autistic children have smaller quantities of Bacteroides fragilis.
    When scientists fed human B. fragilis to mice with the autistic-like symptom, their microbiome changed, as did their behavior. They connected more with other mice and did not exhibit as much repetitive behavior.

Takeaway: eat healthy

While the potential of using this research to reverse or cure ailments is promising, Deshpande warns that this information is still preliminary. “There’s potential but it’s a long way off.”

So, in the meantime: Deshpande says eating a balanced and varied diet, with an emphasis on vegetables and fruits as well as grains, legumes and healthy sources of protein, is essential. Fiber intake is also important to keep you gut working effectively.

And as for probiotic supplements, which are not regulated by the government?
“Don’t get caught up in the hype. The research is inconclusive,” he says. “They work for some people, but not for others.”

Ana Veciana-Suarez, Guest Contributor

Ana is a regular contributor to the University of Miami Health System. She is a renowned journalist and author, who has worked at The Miami HeraldThe Miami News and The Palm Beach Post. Visit her website at or follow @AnaVeciana on Twitter.

Tags: Dr. Amar Desphande, GI system, gut health, healthy diet, Miami gastroenterologist, microbiome, probiotics

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