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Toddler holding toilet lid

The straight poop: How bugs in your bowel affect your health

“Poop,” my 2-year-old granddaughter says enthusiastically. “Me. Look … Woooow!”

She’s acquired the curiosity bug and wants to view the poop before it’s flushed away. She’s clearly on to something, because that poop is a significant indicator of her health.

Wait, what?

I am talking about the intestinal microbiome (the entire colony of bacteria that resides in our bowel) and the intestinal microbiota (the specific bacteria that live in the colony).

We used to consider bacteria in the bowel as purely discarded waste and the source of contamination and serious infections. But over the past two decades we have come to view them in an entirely fresh light.

Here are some fun facts about the bacteria that live in our intestine, mouth and skin:

  • 100 billion bacteria live in stool the size of one’s pinkie
  • The entire colony of bacteria weighs about 3 pounds, nearly the size of your brain
  • We have 10 times more bacterial cells than we do human (eukaryotic) cells

The colony of bacteria affects our health in two main ways:

  • Our immunity by influencing the development of inflammatory bowel disease, food allergies, and even celiac disease
  • Our metabolism by influencing the development of obesity and diabetes

Linking obesity to bacteria

How is excess weight gain linked to bacteria? We’ve known that they help keep us well hydrated by fermenting sugars to short-chain fatty acids that help absorb water from the colon. When your child takes antibiotics like Augmentin, you reduce this fermentation and water absorption, and may develop diarrhea. In obese individuals, the microbiota profile is altered to work at high efficiency to absorb extra calories from carbs.

In one clever study, the colonic bacteria from human twins — one obese and one not — was injected into sterile mice. Those receiving the obese bacteria gained weight faster than those given the slim microbiota. This excess weight gain could be reversed by using the “slim bacteria” or by a vegetarian-type diet. So, mouse obesity may be transferred (and reversed) through those little bugs in the bowel!

The role of bacterial diversity

How do we acquire our own intestinal microbiota? It begins when we become fully colonized by bacteria within 24 hours of being born. Birthing profoundly affects the microbiota, as those born by cesarean section have different and less diverse microbiota than those born vaginally. This appears to increase the subsequent risk of developing food allergies and inflammatory bowel disease (IBD), Crohn’s disease or ulcerative colitis later on.

Although the microbiota largely become set by the time we’re toddlers, other factors influence its composition. Diet is a major one, especially poorly digestible sugars and fibers. Repeated courses of antibiotics in toddlers reduce the bacterial diversity and raise the risk of developing IBD. Finally, probiotics (beneficial bacteria) can alter the microbiota as long as they are taken, but in most disorders we don’t know exactly which bacteria, the exact dose, how long to treat, or whether they should be used in combination.

I could wax probiotically on and on but I’ll save that topic for another blog post.

The power of poop transplants

Dangerous infections like Clostridia difficile (C. diff) illustrates the potential power of the intestinal microbiota. This bug can colonize (live without causing symptoms or disease) the colon, but under conditions of prolonged pest control (antibiotic), the flowers (good bacteria) are destroyed, and the weeds (C. diff) overgrow, causing fever and bloody diarrhea from serious colonic inflammation. This infection can resist our best antibiotics.

In an exciting recent development, fecal matter transfer (FMT) aka poop transplant from a healthy donor (usually a family member or volunteer at a fecal bank in Boston where deposits are deposits) can eradicate resistant infections in 90 percent. This therapy is usually administered through a colonoscope while the child is asleep. This odiferous approach is likely to be used to treat other conditions as well.

Steve Werlin, MD, in our gastroenterology group has been our local FMT champion here at Children’s Wisconsin and has cleared institutional concerns and followed the latest national guidelines to ensure that family donors are safe. We performed the first one together, and are now up to seven, all successful, in eradicating C. diff.

Can you imagine wearing a bold sticker proclaiming “I donated poop today!”

What is the bottom line?

Joking aside, bugs in the bowel are a vital key to our overall health.

This area is so important that the National Institutes of Health has funded a national Human Microbiome Project. Nita Salzman, MD, Ph.D., in our group is a leader in the basic science research for that project. It appears that a more diverse population of bacteria of better microbiota could protect us from developing a slew of common chronic disorders.

We are just scratching the surface of a very complex area, but will eventually know how to treat or “untreat” (with fewer or more selective antibiotics) the intestinal microbiome.

Prepare your noses and get used to it. Poop transplants are here to stay.

As for my granddaughter who started this, if she doesn’t outgrow her toddler fixation in a few years, maybe she’ll become a gastroenterologist like Grandpa.