How much does your gut health impact your overall health? A lot, doctors say

You may be hearing a lot about the gut microbiome these days — it's been mentioned everywhere from wellness podcasts to the grocery aisle. Doctors are tapping into it to try and treat some diseases differently.

The gut microbiome is the community of all the bacteria and viruses in our intestines, including friendlier microbes that promote health as well as some foes that can cause illness.

One evolving procedure is the fecal transplant, where a small sample of stool from the colon of a healthy person is given to a recipient for therapeutic purposes. Despite the ick factor, they have been used to treat potentially fatal, recurring bacterial infections for which antibiotics have been less effective.

Now, doctors and researchers are looking to see whether fecal transplants can be used for other hard-to-treat illnesses.

Health Canada approved fecal transplants for recurrent C. difficile infections in 2015. Impacting the colon, these infections lead to diarrhea and, if recurring, dehydration that can wreak havoc on the body. The goal with the transplant is to have the healthy bacteria outcompete the C. difficile and wipe out the stubborn infection.

Overall, for recurrent C. difficile, fecal transplants were significantly more effective, greater than 85 per cent, compared with less than 50 per cent for antibiotics.

Dr. Nikhil Pai, a pediatric gastroenterologist and associate clinical professor at McMaster University in Hamilton, said antibiotics can create a terrible cycle.

"What ends up surviving after this scorched-earth antibiotic regimen are bacteria that cannot only make things worse, but can affect a lot of other things such as just general nutrition and metabolism," Pai said.

In adults, a 2023 review of clinical trials published by the respected Cochrane Library concluded fecal transplants may also help control Crohn's disease and ulcerative colitis, two forms of inflammatory bowel disease that harm the gut when the body's immune system mistakenly attacks itself.

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Bruce Vallance, a pediatrics professor at the University of British Columbia, said inflammatory bowel disease is essentially chronic inflammation of the gastrointestinal tract, possibly triggered by the bacteria living in our intestines. It can happen at any age, he said.

"We're trying to figure out whether certain microbes are driving the disease and whether we could target those microbes, deplete them and hopefully remove them from the intestine so there's no longer any trigger for disease."

Some researchers are also looking into using fecal transplants for teenage anorexia nervosa, known for its difficulty to treat and high death rate. Research suggests there is a gut-brain connection, and scientists are finding there is an association between anorexia and imbalances in the gut microbiome, which could influence a person's behaviour.

Vallance and his team are also studying whether certain microbes that may drive Crohn's and colitis can get through a key mucus layer in the intestines.

To that end, he's been working with doctors at BC Children's Hospital to take fecal samples and biopsies that offer a snapshot of what's going on in the human colon.

Vallance builds "mini guts" — a 3D model of the intestines in the shape of a ball — to study how the microbes function. He's focusing on growing bacteria in the epithelium, or gut lining, which contains proteins with sugars on them that form a slimy coating.

"It doesn't look nice and it doesn't sound nice, but that sticky coating is actually really important in terms of how we interact with our gut microbes," Vallance said. It's what creates the barrier against dangerous bacteria that can cause diseases like Crohn's and colitis.

Another trial focuses on short bowel syndrome in children who have had parts of their small intestine surgically removed. It can cause an excessive build-up of bacteria, leading to abdominal pain, bloating and diarrhea that's traditionally treated with antibiotics.

There have been other unintentional benefits of the fecal transplant. Pai recalled, while at his other position at Children's Hospital of Philadelphia, treating an autistic child who had recurrent C. difficile.

"After their treatment, there were comments from the family that this child was also just showing some real improvements and changes in their behaviour as well as noted by their teachers in school," Pai said. "I don't think it's any surprise that other aspects of him also got better."

Bringing back healthier bacteria also benefits the body as a whole, Pai said, which could be why the boy saw improvements in other areas.

"The comment or the idea that we are what we eat is very true," Vallance said.

What we eat and digest is also individualized, to that extent that everyone's poo is like a fingerprint — or poo print, he said. "Everybody has their own unique blueprint."

When people eat a high-fibre diet full of vegetables, for instance, more fibre reaches the colon, where microbes ferment it and release beneficial factors such as butyrate, a short chain fatty acid.

Vallance said butyrate can help signal our immune system what to do and when. But people with inflammatory bowel disease tend to have much less butyrate, a helpful regulator to prevent the immune system from overreacting, he said.

Carrie Daniel MacDougall, an associate professor at MD Anderson Cancer Center's epidemiology department in Houston, specializes in nutrition and the microbiome, including the role of dietary fibre.

Daniel MacDougall and her team showed that adding dietary fibre in the form of canned beans changed the gut microbiome of cancer patients within eight weeks and is thought to encourage beneficial gut bacteria to do their thing.

Cancer prevention guidelines already emphasize increasing fibre with whole foods like beans, as well as fruits and vegetables.

"A lot of what we're learning about the scientific mechanisms and the gut microbiome also has a huge impact on public health," Daniel MacDougall said. Gut health "has a lot of crossover with other diseases like heart disease, inflammatory bowel disease.

"We're all learning from each other's research."