microbiome lead

Meet Your Microbiome

It's the buzziest word in medicine. Why? Because the zillions of bacteria living in your body mastermind your health in amazing ways. Learn how to get them working for, not against, you.

Right now, there's a big party going on inside your body and on every last inch of your skin. The guests? Oh, just 100 trillion or so bacteria, each microscopically tiny — one-tenth the size of your human cells. They hang out everywhere, from your armpits and tongue to your lungs and gut. They eat the food you eat. They talk to each other. And just as at any gathering, the good ones add something to the vibe and clean up after themselves, while the annoying ones make a mess and get you into trouble.

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Until relatively recently, doctors and researchers had no idea that this bug bash is directly connected to your health. Then, about 10 years ago, a few provocative studies prompted microbiologists to consider the possibility that certain kinds of bacteria are not only useful, they're directly tied to well-being. Those first promising bites of research unleashed a feeding frenzy of studies on this inner world of bacteria we've come to know as the microbiome. So far, we've seen hints that gut bugs could possibly lower cholesterol, tame symptoms of irritable bowel syndrome (IBS), help with weight loss, and affect your mood, to name only a few findings.

Some scientists now think that microbes could influence your health just as powerfully as your genes do. "I have a feeling that in the next 30 years, we'll have so much more information about the microbiome — especially which bugs need to be present for us to stay healthy — that we'll be able to create highly specific treatments for patients and maybe even prevent disease," says Sarkis K. Mazmanian, PhD, a professor of microbiology at the California Institute of Technology.

While scientists had been captivated by microbes for a while, a 2013 study helped catapult these bugs into the media spotlight: Scientists took some microbes from human twins — one obese, one thin — and injected them into two normal-weight mice. They watched as the mouse with the heavy twin's bacteria put on weight and the one with the thin twin's microbes stayed slim. It provided the best indication so far that gut bugs could be tied to our obesity epidemic. Excitement also built around this less glamorous but still impressive finding: Microbes may be able to clear up the potentially deadly infection caused by Clostridium difficile, or C. diff, which antibiotics sometimes can't. Scientists treated it by getting the right bugs into affected people's guts via a fecal transplant. (Poop from a healthy donor is delivered to the recipient's colon during a colonoscopy, or via an enema or pill.) With such promising results, it's no wonder some people aren't waiting around to see which studies pan out in additional human trials. Believers are doing DIY fecal transplants in an effort to solve everything from Crohn's disease and ulcerative colitis to anxiety and depression.

All this microbiome exuberance has spawned a billion-dollar industry of probiotic products that are a lot easier for most of us to access (and stomach) than fecal transplants. Sales of probiotic supplements — which contain live bacteria similar to beneficial microbes in the gut — have doubled in the past five years. And foods and beverages with the stuff are projected to be a $10 billion industry by 2018. These include the probiotic juices, chocolates, peanut butters, cereals, yogurts, and you-name-its on store shelves.

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What makes the microbiome so fascinating and frustrating is all this promise, tempered by major unknowns. Microbiologists researching the topic say it's too soon to believe that our bacteria are the answer to everything that troubles us. Still, those same experts are making simple changes in their own lives — particularly when it comes to the food they eat — to give their bugs a push in the right direction. We prodded them for the science-backed steps they're taking, all ideas the rest of us can use to make the most of our microbes right now.

1. Say Hello to Your Little Friends

To manage your microbiome, it helps to know a bit about how this internal ecosystem works. All those tiny microbes started setting up shop the day you were born, attaching to you on your way out of the birth canal, explains Jens Walter, an associate professor of nutrition, microbes, and gastrointestinal health at the University of Alberta in Edmonton. Some docs think these bugs are so helpful that they advocate a bit of a wait before a baby is wiped off. (If you were born by C-section, you missed out on some of Mom's bugs. This could be why C-section babies tend to be more prone to asthma and allergies.) Your microbiome continued to populate until you were about 3. And after that, a slew of other scenarios affected how it developed.

The bugs that make up your particular collection are all different; microbes on your forearm aren't the same as the ones in your belly button or on your gums or in your gut. And while you and your partner, your coworker, your kids, and even the stranger next to you on the train may have some of the same bacteria, you may have some that they don't. Certain bugs are the kind you'd want to kick out of your body (no one likes a strep throat instigator), but there are also a bunch of good guys that help digest your food, regulate your appetite and weight, boost your immune system, and even influence your mood. The key, it seems, is to establish equilibrium between helpful and harmful ones. "Your microbiome is kind of like a rain forest,"says Vanessa Leone, PhD, a microbiome researcher at the University of Chicago. "Both 'good' and 'bad' bugs are like the plants and species that keep the ecosystem in balance, and while those good players help a rain forest thrive, even the bad guys are there for a reason and only cause trouble when there's a change — in your diet, for instance — that allows them to grow in such abundance that they become toxic." In a rain forest, diversity is the goal, and the same can be true for the microbiome. The more types of bugs you house, the healthier you're likely to be. There's a lot to be discovered about these microbes, but we do know that the gut holds the richest diversity of them in the body— maybe even a thousand species — and that there are some simple ways to manipulate them for the better.

Are the helpful or harmful bacteria dominating your GI tract? Depends on which you feed.
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2. What Your Gut Bacteria Do for You

The bacteria in your gut are like a United Nations of diplomats, each trying to make a mark on what happens in your internal world. To get the body's work done, you want more diplomats from a larger number of countries. At this point, experts think the little gut bugs may govern essential functions like these:

They regulate inflammation.

Some of your bugs extract nutrients from food, says Bob Hutkins, PhD, a microbiome researcher and professor of food science at the University of Nebraska. Eat right (more on this later), and these bugs help your body make vitamins and turn food into other essential nutrients like short-chain fatty acids, which are one of the most powerful anti-inflammatory agents the body makes, says Hutkins. But when you eat unhealthy fats and starches, your "bad" bacteria are more likely to predominate and secrete a substance called endotoxin. That stuff prompts your immune system to go on the defensive, sparking inflammation.

They help manage your appetite.

Scientists have seen that lean people's guts are brimming with a diversity of species, while the gut communities of those who are obese show less variety. Certain bugs may have extra sway over how hungry you get. New York University researchers found that a bacteria called Helicobacter pylori, once thought to be an all-bad player, helps keep ghrelin, the hormone that increases appetite, in check. H. pylori used to be plentiful in us, but antibiotics and our ultrahygienic lifestyles have helped prune it back.

They influence your immune system.

A whopping 70% of the SWAT- team cells that control your immunity reside in your gut — the antibodies, lymphocytes, cytokines, and other immune cells that watch for invaders and attack when necessary. Researchers think your gut bugs "talk" to your immune system and teach it to recognize which organisms are OK and which need to be crushed, though no lab has cracked the entire communication code yet. It's likely that the greater the variety of gut bacteria you have, the smarter and more finely tuned the immune system is, because it's gotten more lessons about what to attack and what should be left alone, says Gail Cresci, PhD, RD, a microbiome researcher at the Cleveland Clinic. "This might explain why one person can eat a piece of microbe-laden fish and get a bad bout of food poisoning while another has that same meal and feels fine," she says.

They affect your mood.

The gut creates a raft of chemicals that influence your emotional well-being, and your microbes have something to do with it. In fact, it's actually our gut bacteria that produce the vast majority of the body's serotonin, a chemical that improves mood and helps us handle stress. (Yes, this brain chemical actually originates in your digestive tract.) With mood, too, diversity rules: People without depression tend to have more types of bugs than people with it. Researchers are hoping to pin down strains that might boost mood, yet some folks aren't waiting around and are using probiotics (and referring to them as "psychobiotics") to try to treat conditions like anxiety and depression.

'Gut feeling' isn't just a phrase. Your bacteria there analyze emotions and 'talk' to your brain through a superfast nerve highway.
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3. How To Build a Better Microbiome

You don't have to do anything exotic or complicated to improve the ecosystem inside you. No point in obsessing about which strains of "good" bacteria you're getting, because scientists say there's not enough research yet to pinpoint the key players in big issues like obesity, heart disease, or brain health. For now, experts agree that a healthy diet is the number one way to create a robust microbiome. Once you start making changes, your bugs respond rapidly. "The composition of the bacteria in your gut can shift within hours," says Leone. What to do to bring things into balance:

Eat more fiber.

This is your microbiome's favorite food. While your bugs eat all the nutrients you eat, experts agree it's fiber that feeds the "good" bugs. The big problem with most simple starches and low-fiber foods is that few actually make it to your colon, where the vast majority of your bugs live, says Hutkins. "When you have simple carbohydrates and sugar, most of them are immediately absorbed through the small intestine and move on to various body parts to be used as energy or turned into fat," he says. Anything that's not used keeps traveling through your system. On the flip side, things that are rich in fiber don't get digested in the stomach or absorbed in the small intestine, which means they get to keep traveling until they reach the colon, where they become food for the healthy bacteria in the gut. With fiber, you might have to make an effort to get enough; most Americans consume only a third to half the amount of this nutrient that their bodies want in a day. Aim for 25 to 28 grams daily if you're a woman under age 50, and 22 grams if you're over that. (Men require more: 30 to 33 grams a day up to age 50, and 28 grams after that.) To be efficient, rely on some heavy hitters like beans (roughly 6 to 7 grams per half cup), blackberries (about 7 grams per cup), and oatmeal (4 grams per cup).

Throw two "new" fruits or veggies into your cart next time you shop.

Experts agree that another great way to set yourself up for optimal microbiome diversity is to eat a wide range of produce. That means not just sticking to your go-to broccoli, sweet potatoes, and other faves. Starting this week, toss jicama, leeks, jackfruit, garlic scapes, okra, or another type of produce you'd typically never buy (or haven't had in a long while) into your grocery cart, and keep on experimenting.

Control your "bad" bugs.

Just as feeding your "good" bugs with fiber-rich foods will help them thrive, eliminating junky foods could keep "bad" bacteria in check, says Cresci. "We know that when you cut sugar, unhealthy fats, and processed foods from your diet, you are more likely to keep your bacteria in balance." Also helpful for getting disruptive bacteria out of your gut: Cut down on animal meat. A glut of it can fuel endotoxin-making bugs. Even heart-healthy fish has this effect, says Rafael Kellman, MD, author of The Microbiome Diet, but fish has so many benefits, you still want to include it in your diet. Remember, since diversity is the goal, some meat is fine as long as you're eating plenty of plant-based foods in a day.

Take antibiotics only when necessary.

You've heard it before: Don't ask for these drugs when you've got a common cold. (You need them only when you have a bacterial infection, like strep throat or pneumonia.) While antibiotics are great at killing harmful bacteria, they also wipe out a lot of your "good" bugs in the process — and some of those may never come back, says Cresci. There's strong evidence in studies on mice that the change in the microbiome after just one course of antibiotics can cause weight gain, and scientists think this may be true in humans, too — especially children. Some docs suggest taking probiotics during a course of antibiotics in an effort to prevent antibiotic-associated diarrhea.

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Don't pop any old probiotic.

"Good" bacteria are flying off store shelves in the form of pills or foods that contain these organisms. (Those are the yogurt or kefir products with "live, active cultures," and the fermented ones like kimchi, sauerkraut, and kombucha.) Why? That's a head-scratcher for many researchers, who agree that manufacturers are making promises ("promotes gut health!") that are way ahead of the science.

"If your microbiome is a rain forest that's populated with all kinds of indigenous species, taking a probiotic supplement or eating a probiotic-fortified food is like trying to plant a random organism— say, a strawberry patch — in this already well-established ecosystem and expecting it to grow and flourish," says Walter. Occasionally, it may stick around and survive, but other times, what you take or eat just disappears without contributing anything at all to your microbial makeup.

If you want to eat probiotic foods, hoping to better your internal mix, "go ahead," says Cresci. But know that the foods may contain only one or a few strains of bacteria — and research hasn't proven if many of those strains are essential for health. There's also no way to know for sure which probiotics in processed foods — meaning the chocolates, trendy juices, trail mixes, energy bars, and more — truly survive the manufacturing process or the store shelf, or make it all the way to your colon so they can settle down in there.

Similarly, since your gut contains thousands of strains of bacteria, taking a supplement that has just one specific type may not help you out much. If you want to give supplements a try, look for one with a large number of strains. That gives you the greatest chance of getting something useful that might take root in your gut.

In the future, it's possible that individual microbiome testing will tell you specifically what you need to eat to lose extra weight or to be your healthiest. It could reveal particular microbes you're missing that might help you fend off cancer, heart disease, or diabetes. But right now, know that your bacteria love the same good-sense moves that the rest of you does.

Tonight, put some new produce on your plate and say cheers to your body's healthier, happier bug party.

4. Promising Probiotics

Despite what the zealous clerk at the health-food store tells you, there's not that much solid research on which probiotics affect which diseases. However, for a couple of problems, scientists have ID'd species with some hopeful results:


Controlled trials have shown that two strains of beneficial bacteria, Lactobacillus GG and Saccharomyces, can shorten a bout of diarrhea in certain cases. They may prevent the type that can come along with taking antibiotics or even the sort that can occur with the potentially dangerous colon bacteria called Clostridium difficile (C. diff).


In several studies, probiotic supplements containing the strains Bifidobacterium, Lactobacillus, or B. infantis helped calm some IBS symptoms, such as abdominal pain and bloating. There's no clarity yet on whether these are the only useful strains for IBS or how long you should take them. Studies have ranged from one to six months.

This article originally appeared in the January/February 2017 issue of Dr. Oz The Good Life.

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