Until recently, the gut hasn’t garnered a lot of attention, quite possibly because talking about poop (and what goes into making poop) is, well, gross. The human digestive tract is literally teeming with trillions of microbes and hundreds of types of bacteria. In fact, the human body contains 10 times more bacteria than it does human cells. (Score another point for the gross-out factor.)

More and more research is proving just how crucial your gut microbiota (all those microorganisms living inside of you) is in helping you digest food, stimulating your immune system, protecting you against infection and generally making you feel good and think more clearly.

Each person’s gut microbiota is unique and is influenced by the way they live and what they eat. Variation in gut micro-biota across the world can reveal a lot of information. “You can classify people by region with at least 99 percent accuracy based on their gut microbiota,” says Rob Knight, the scientific lead of the American Gut Project, based at the University of Colorado, Boulder.

The typical Western gut is less diverse than it is in most other places in the world. It is also widely believed that there are certain bacteria missing from the Westernized gut (that were present just a few decades ago) that can be found in other regions. This has caught researchers’ attention, because many adverse health conditions increased in frequency at the same time as these gut changes occurred.

“We don’t know if [the gut changes are] necessarily a bad thing, but they are consistent with the rise in asthma, allergies, diabetes, obesity, anxiety, depression and colon cancer,” says Knight. Researchers are trying to determine whether certain microbes need to be present for good health. Right now it’s clear that gut microbiota is important, but researchers are still determining how and why.

Building a healthy gut
When you were born, your gut looked very similar to your mother’s. The gut evolves quickly in the first few years and by age two and a half, a child’s gut flora resembles that of an adult. What happens in those first few years is crucial. “It becomes a fingerprint for your gastrointestinal future,” says Anita Kozyrskyj, a molecular epidemiologist at the University of Alberta.
 
Researchers are unsure of everything that can influence the development of early gut flora, but it is clear that these changes occur easily and rapidly. New research in the Canadian Medical Association Journal discovered that babies delivered through caesarean section were missing a specific group of bacteria found in vaginally delivered babies.

Infants who were formula-fed also had significant differences in their gut makeup compared to infants who were at least partially breast-fed. Researchers say these differences put babies born by caesarean section at an increased risk of developing allergies, asthma, obesity and type 1 diabetes, while breast-fed babies have some protection against them. But there may be other factors. “It’s not an all-or-nothing formula,” says Kozyrskyj, head researcher on the study.

The gut-health connection
The gut is so intricately tied to overall health and well-being that Dr. Michael Gershon, a Columbia University bowel specialist, named it the “second brain.” The gut has a sophisticated nervous system that interacts with your brain. “There’s a reason we get butterflies in our stomachs when we’re nervous,” says Gershon, author of The Second Brain (Harper Perennial, 1999).

In fact, many patients with anxiety and depression have altered gut function. “If you stimulate the vagus nerve, which connects the brain, gut and abdomen, and respiratory, circulatory and digestive systems, you can treat depression and epilepsy, and even stimulate memory,” says Gershon. He adds that the nerve may also simulate natural signals that the bowel sends to the brain.

In the same way that changes in your gut can make you feel bad (both emotionally and physically), the disruption of your gut microbiota can also result in a host of ailments, including inflammatory bowel disease, allergies, asthma, Parkinson’s disease, diabetes and cancer. It can even make you gain weight. “There are different gut profiles in children who are overweight,” says Kozyrskyj.

Researchers aren’t sure of the ideal gut makeup, but more diversity seems to be better than less, and taking antibiotics (which can wipe out the good bacteria with the bad) is detrimental.

A bright future for gut health
Fast-forward a few years, and it may become commonplace to receive healthy gut microbiota from a donor. A French study in Mucosal Immunology explores the possibility of treating diabetes and fatty liver disease through gut microbiota transplants. By implanting microbiota from healthy mice, researchers were able to prevent liver inflammation and insulin resistance in other mice.

“Microbiota transplantation is very effective for persistent Clostridium difficile infections that have resisted antibiotics,” says Knight. “Ninety-plus percent cure rates have been reported.” Knight adds that microbiota transplants have a lot of potential, but there are risks. One of them may be in matching gut types. In the same way that we have different blood types, we appear to each have one of three gut types. Scientists aren’t sure why, but it could be related to differences in how our cells release hydrogen waste or how our immune systems distinguish between good and bad bacteria. Once more research is done, genetic gut types may one day be used to help diagnose and predict diseases like colorectal cancer

How healthy is your gut?
“If you feel bad, chances are your gut may be at least partially to blame,” says Leonard Direnfeld, a Toronto-based doctor who specializes in functional medicine. Ask your doctor to order a comprehensive stool analysis for a detailed look at your gut’s bacteria and parasitology. Simple problems may require basic dietary changes, or your doctor might recommend following the 4-R program:
• Remove the bad bacteria
• Reinoculate with
good bacteria
• Replace missing
stomach acid
• Repair anything that might be irritating the gut

The American gut project
To learn about the makeup of your gut’s microbiota, sign up for the American Gut Project. For $99, you get a complete microbiome (the combined genetic material of the microorganisms in a particular environment)  analysis, and your data will become part of the project’s ongoing research. 

If you have tummy troubles, we have some simple fixes for common digestion problems.

This content is vetted by medical experts

This story was originally titled "Gut Feeling" in the November 2013 issue. Subscribe to Canadian Living today and never miss an issue!