Your intestines host up to 1,000 unique species, and how often do you think of any of them? Probably not very often at all, but they’re really amazing little things. For starters, there are more of them than you: Bacterial cells outnumber human cells in most people by about tenfold.
But it doesn’t stop there. With an immune system adapted to fight off all kinds of bacteria and viruses, it’s amazing that so many are allowed to stay and thrive. What’s more, many are beneficial to your health — helping you thrive.
A Gut-Centered Immune System
You and the bacteria that live in your gut have a mutually beneficial relationship. “It’s really a partnership we all have,” says Dr. James Versalovic, a professor of pathology at Baylor College of Medicine. You give them a place to live, and in return they help regulate your immune system, digest your food, produce some key nutrients and protect you from toxins and pathogens.
One of the most important functions is the modulating of our immune system, Versalovic says. That is, turning it up or down when the time is right.
“The microbes that live within us effectively act as a dimmer switch for our immune systems,” he says. “Some enhance our immune responses, and others dim it down, or suppress inflammation.”
It Starts in the Womb
Gut flora is closely tied to immune health, and immune health starts in mom’s belly. For example, pregnant women who are exposed to stables, farms and house pet dander are less likely to give birth to children who eventually develop allergies. Conversely, children who are born and raised in a very sterile environment tend to develop weaker immune systems because they’re not challenged during development.
Gut microbiota, like the immune system, start mattering at a very young age. Animals that are bred and raised to be germ-free, or have no gut flora, develop abnormally.
“They look the same, but their anatomy is definitely different,” Versalovic says. “Their intestines are abnormal in shape and size, and their immune system is clearly underdeveloped. That tells us that our microbes contribute to the development and maturity of the immune system.”
The Obesity Connection
Obesity has become a major problem in recent decades, and because of that, more people than ever are trying to lose weight. “Calories in, calories out” is the mantra of many health and fitness experts, referring to the energy balance that determines weight gain, loss or maintenance. It’s a simple equation, but a growing body of evidence suggests the old trope may be a bit too simple.
“We know people who are obese have less diversity in their microbiomes,” Versalovic says. “They might not have fewer bacteria, but they usually have fewer species — lower diversity.”
That can be a problem because when it comes to gut health, more diversity, not necessarily more microbes, is better. Each species has a unique function in helping you metabolize nutrients — digesting specific compounds or nutrients, for example.
Researchers also know that certain diets, specifically those high in fat, affect ratios of gut bacteria. “We think a more diverse diet in terms of fruits and vegetables promotes a more functional, diverse microbiome,” Versalovic says.
However, recent research in mice was the first to establish that not only could fat affect microbiota, but the reverse is possible as well, according to a 2012 research review published in the journal Gut Microbes. In absence of gut microbiota, mice in controlled trials gained less fat and weighed less than mice with specific strains of bacteria in their bellies known to inhibit fat metabolism. This was despite the fact that the “germ-free” mice ate more and exercised the same amount as the others.
Other Disease Connections
Several gastrointestinal diseases are also associated with fluctuations in certain bacterial species, but it works differently than obesity. Crohn’s disease, inflammatory bowel disease, irritable bowel syndrome and colorectal cancer are all associated with intestinal inflammation, but they are all at least partially genetic conditions. That is, your genes decide whether you get them or not, or at least contribute to risk.
However, researchers such as Versalovic are looking at what role gut bacteria can play in helping those conditions, specifically colorectal cancer. “We’ve been actively exploring how gut microbes suppress intestinal inflammation,” Versalovic says. His team knows that colorectal cancer and inflammation are closely tied. “The hope is we can learn how to suppress colorectal cancer.”
Another possibility is that by working to suppress inflammation using gut microbes, his team can discover a new type of anti-inflammatory drug. Some bacteria also may promote bacteria, he says, but that research is still in its infancy.
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All About Flora: How Important Gut Health Really Is originally appeared on usnews.com
