The infant gut microbiome: New studies on its origins and how it’s knocked out of balance — ScienceDaily

Gut bacteria are suspected to be a source of nutrients and vitamins for a growing infant. Our intestinal tenants are able to interact with normal cellular processes to, for example, produce essential amino acids. Understanding the role individual gut microbes play in metabolism, immunity, and even behavior is an active area of investigation.

This new study, led by Bäckhed and Jovanna Dahlgren at the University of Gothenburg, Sweden, and Wang Jun at the Beijing Genomics Institute-Shenzhen, China, supports previous observations that most early bacterial colonizers of the gut are derived from the mother. The investigators noted that while C-section babies receive less of their mother’s microbes, they are still able to be passed on through the skin and mouth.

Once bacteria take hold in an infant’s gut, their populations shift depending on what a child eats. The researchers believe that the cessation of breast-feeding is such a significant moment in microbiome development because certain types of bacteria thrive on the nutrients breast milk provides. Once these nutrients are no longer available, other bacteria emerge that are more commonly seen in adults.

via The infant gut microbiome: New studies on its origins and how it’s knocked out of balance — ScienceDaily.

How probiotics and prebiotics team up in your gut – The Washington Post

How probiotics and prebiotics team up in your gut - The Washington Post

Everyone knows good hosts need to feed their houseguests. If the visitors are easy to get along with and especially helpful — they take out the trash, do the dishes, rake the yard and so on — it’s wise to feed them very well so they stay as long as possible.

That’s how it is with humans and probiotics (good bacteria). We are essentially hosting these living organisms in our guts. They go about their lives unnoticed, but they are doing important work keeping our digestive system healthy and, in turn, protecting the whole body.

Join Krieger for a live Q&A about healthful eating on Feb. 12 at 1 p.m.

Probiotics: Desirable houseguests

By now you have heard of the many chores probiotics do around our “house.” They help us absorb nutrients from the foods we eat, and they produce B vitamins we can use; they support our immune system and work to prevent harmful bacteria from making us sick. They are shining examples of good houseguests. With their reputation firmly established, chances are you have been actively inviting them in by eating such probiotic-rich foods as yogurt and kefir, or some types of sauerkraut, kimchi and tempeh. You may be also taking probiotic supplements.

Feeding your guests

But it’s not enough to just get beneficial bacteria into your body. To make sure these good guys stay and thrive, you’ve got to feed them. One of their preferred meals is a type of soluble fiber called fructooligosaccharides (FOS), found in a wide range of vegetables, fruits and grains.

via How probiotics and prebiotics team up in your gut – The Washington Post.

Gut Microbiota Influences Blood Brain Barrier Permeability | Neuroscience News Research Articles | Neuroscience Social Network

The more I read about the microbiome..Amazing stuff.

A new study in mice, conducted by researchers at Sweden’s Karolinska Institutet together with colleagues in Singapore and the United States, shows that our natural gut-residing microbes can influence the integrity of the blood-brain barrier, which protects the brain from harmful substances in the blood. According to the authors, the findings provide experimental evidence that our indigenous microbes contribute to the mechanism that closes the blood-brain barrier before birth. The results also support previous observations that gut microbiota can impact brain development and function.

The blood-brain barrier is a highly selective barrier that prevents unwanted molecules and cells from entering the brain from the bloodstream. In the current study, being published in the journal Science Translational Medicine, the international interdisciplinary research team demonstrates that the transport of molecules across the blood-brain barrier can be modulated by gut microbes – which therefore play an important role in the protection of the brain.

via Gut Microbiota Influences Blood Brain Barrier Permeability | Neuroscience News Research Articles | Neuroscience Social Network.

How Bacteria In The Gut Help Fight Off Viruses : Goats and Soda : NPR

So what is this magic antiviral bullet?

It’s those hairlike threads that dangle off some bacteria and help them swim. Yup, that’s right, the flagella.

When Gewirtz and his team injected pieces of the flagella under the mice’s skin, a part of the immune system kicked into action and stopped the rotavirus infection dead in its tracks.But these bacteria — and their flagella — are in our gut. Would they still be able to talk to the immune system? Hooper thinks so. Here’s why.

Just like our hair, flagella are constantly falling off the surfaces of bacteria as they swim around in the gut. “Cool immune cells, called dendritic cells, are constantly surveying what’s going on in the body,” Hooper says. They can bind to the pieces of flagella in the gut and then mobilize other immune cells to come and fight the viral infection.

via How Bacteria In The Gut Help Fight Off Viruses : Goats and Soda : NPR.

Malnutrition: Starving Children Lack Crucial Gut Bacteria – NYTimes.com

When children are starving, the bacteria that live in their intestines may determine whether they can be saved, scientists working in Bangladesh are reporting. And they say it may become imperative to find a way to give children bacteria as well as food.

The study, done by researchers from Washington University School of Medicine in St. Louis and the International Center for Diarrheal Disease Research in Dhaka, the Bangladeshi capital, was published by Nature last week.

Trillions of bacteria in the human gut help digest food and produce vitamins, and they amount to “a microbial organ within an organ,” said Dr. Jeffrey I. Gordon, an author of the paper. It takes up to about age 3 for a child to get all the species that seem to be needed, he said.

But stool samples showed that severely malnourished children often lack the needed species and do not acquire them even when they are fed nutrition-dense therapeutic foods like the peanut-based Plumpy’Nut or lentil-based porridges for weeks. As a result, they may remain stunted and mentally handicapped although they are getting enough calories to live.

Dr. Gordon said researchers were dosing sterile mice with different human gut microbes, hoping to discover which functions each performs. The goal may be to produce a sort of bacterial soup for children. Fecal transplants, sometimes used to cure severe gut infections in adults, are now unthinkable for Bangladeshi infants, he said, because they would probably also contain dangerous pathogens.

Study Sees Bigger Role for Placenta in Newborns’ Health:NYTimes

Not nutrition, but related..

A study led by Dr. Kjersti Aagaard found that the placenta has its own microbiome that may help shape the health of an infant.
SCOTT DALTON FOR THE NEW YORK TIMES
By DENISE GRADY

The placenta, once thought sterile, actually harbors a world of bacteria that may influence the course of pregnancy and help shape an infant’s health and the bacterial makeup of its gut, a new study has found.

The research is part of a broader scientific effort to explore the microbiome, the trillions of microbes — bacteria, viruses and fungi — that colonize the human body. Those organisms affect digestion, metabolism and an unknown array of biological processes, and may play a role in the development of obesity, diabetes and other illnesses.

During pregnancy, the authors of the new study suspect, the wrong mix of bacteria in the placenta may contribute to premature births. Although the research is preliminary, it may help explain why periodontal disease and urinary infections in pregnant women are linked to an increased risk of premature birth. The findings also suggest a need for more studies on the effects of antibiotics taken during pregnancy.

The new study suggests that babies may acquire an important part of their normal gut bacteria from the placenta. If further research confirms the findings, that may be reassuring news for women who have had cesareans. Some researchers have suggested that babies born by cesarean miss out on helpful bacteria that they would normally be exposed to in the birth canal.

“I think women can be reassured that they have not doomed their infant’s microbiome for the rest of its life,” said Dr. Kjersti Aagaard, the first author of the new study, published on Wednesday in Science Translational Medicine. She added that studies were needed to determine the influence of cesareans on the microbiome.

Previous studies have looked at bacteria that inhabit the mouth, skin, vagina and intestines. But only recently has attention turned to the placenta, an organ that forms inside the uterus and acts as a life support system for the fetus. It provides oxygen and nutrients, removes wastes and secretes hormones.

“People are intrigued by the role of the placenta,” said Dr. Aagaard, an associate professor of obstetrics and gynecology at the Baylor College of Medicine and Texas Children’s Hospital in Houston. “There’s no other time in life that we acquire a totally new organ. And then we get rid of it.”

She added, “We are just starting to catch a glimmer of this amazing organ that defines placental mammalian biology.”

Dr. Aagaard and her team became curious about the placenta when they noticed something puzzling in earlier research on the vaginal microbiome in pregnant women: The microbes that were most abundant in the mother’s vagina did not match the population in a newborn’s intestine. Scientists had assumed the bacterial profiles would be similar, particularly in babies born vaginally, who were thought to pick up the mother’s bacteria during birth. Dr. Aagaard and her colleagues began to question that assumption.

“It didn’t make a whole lot of sense to us,” she said. “It’s not like babies are hanging out in the vagina. They come shooting out pretty fast.” Also, she said, they emerge covered in a waxy substance called vernix, which most likely helps keep bacteria from latching on.

The researchers wondered if babies might acquire some of their intestinal bacteria before birth, maybe from the placenta.

So they collected placentas in the delivery room from 320 women, mostly black and Hispanic. Most had vaginal deliveries, and some had cesareans. Most of the births were at term, but some were premature.

The scientists searched the placental tissue for bacterial DNA, using a technique called shotgun metagenomic sequencing. They shaved off the outer layer of each placenta and tested samples from the inside, to avoid surface contamination.

“The placenta is not teeming with bacteria, but we can find them, and we can find them without looking too hard,” Dr. Aagaard said.

She said the placenta was less than 10 percent bacteria by mass, comparable to the eye or deeper regions of the skin, but very different from the intestine, which is 90 percent bacteria.

The study provides an “initial snapshot” of the placental microbiome, Dr. Aagaard said. About 300 different types of bacteria turned up, most of them harmless. The team compared the distribution of the types with what had been found previously in other parts of the body, including the mouth, skin, nose, vagina and gut. The closest match by far was between the placenta and the mouth, which, in turn, was much like that in babies’ intestines in the first week of life.

A scientist not involved in the study, Dr. David A. Relman, a microbiome expert at Stanford, said that Dr. Aagaard’s results agreed with those from his lab and others, which had found microbial DNA in amniotic fluid, apparently from the mother’s mouth, gut and vagina.

Dr. Aagaard said she thought that oral bacteria travel through the mother’s bloodstream to the placenta, take up residence there and find their way into the fetus. This is a theory. But research in animals supports it: Oral bacteria injected into a vein in mice home in on the placenta.

The idea also meshes with something that obstetricians have long noted: Women with periodontal disease have a higher risk of having premature or low-birth-weight babies. Treating the disease during pregnancy does not lower the risk. Preventing the disease or treating it before pregnancy seems more important, Dr. Aagaard said.

The study did not provide definitive evidence about periodontal disease because only one participant had it.

A disturbing finding was that when women had urinary infections early in pregnancy, even if the infections were cured, evidence of the bacteria still turned up in the placenta. Those infections increase the risk of premature birth.

The study also found that the microbiome of the placenta in women who had full-term pregnancies differed from that in women who had preterm births. But Dr. Aagaard said the researchers did not know if the difference contributed to the early birth, or was just characteristic of an earlier stage of pregnancy.

Dr. Martin J. Blaser, director of the human microbiome program at NYU Langone Medical Center, and the author of a recently published book, “Missing Microbes,” said that Dr. Aagaard’s study was important, but preliminary, and that it did not provide information that could be used in treating pregnant women.

“I’m intrigued by the findings about the mouth and also the relationship with preterm labor, which is a really important clinical question,” Dr. Blaser said. “Will this be a productive lead, or will it fizzle out? Time will tell us.”

He said that pregnant women were often given antibiotics, “for all kinds of reasons, many justified, but there’s a slippery slope.” Assuming that the placenta was sterile anyway, he said, doctors thought antibiotics would not affect the fetus. But if the placenta is not sterile, and is instead a portal for bacteria from the mother, he asked, “What are the antibiotics doing?”

My No-Soap, No-Shampoo, Bacteria-Rich Hygiene Experiment – NYTimes.com

For most of my life, if I’ve thought at all about the bacteria living on my skin, it has been while trying to scrub them away. But recently I spent four weeks rubbing them in. I was Subject 26 in testing a living bacterial skin tonic, developed by AOBiome, a biotech start-up in Cambridge, Mass. The tonic looks, feels and tastes like water, but each spray bottle of AO+ Refreshing Cosmetic Mist contains billions of cultivated Nitrosomonas eutropha, an ammonia-oxidizing bacteria (AOB) that is most commonly found in dirt and untreated water. AOBiome scientists hypothesize that it once lived happily on us too — before we started washing it away with soap and shampoo — acting as a built-in cleanser, deodorant, anti-inflammatory and immune booster by feeding on the ammonia in our sweat and converting it into nitrite and nitric oxide.

In the conference room of the cramped offices that the four-person AOBiome team rents at a start-up incubator, Spiros Jamas, the chief executive, handed me a chilled bottle of the solution from the refrigerator. “These are AOB,” he said. “They’re very innocuous.” Because the N. eutropha are alive, he said, they would need to be kept cold to remain stable. I would be required to mist my face, scalp and body with bacteria twice a day. I would be swabbed every week at a lab, and the samples would be analyzed to detect changes in my invisible microbial community.

Continue reading the main story

‘The M.I.T.-trained chemical engineer who invented AO+ has not showered for the past 12 years.’

In the last few years, the microbiome (sometimes referred to as “the second genome”) has become a focus for the health conscious and for scientists alike. Studies like the Human Microbiome Project, a national enterprise to sequence bacterial DNA taken from 242 healthy Americans, have tagged 19 of our phyla (groupings of bacteria), each with thousands of distinct species. As Michael Pollan wrote in this magazine last year: “As a civilization, we’ve just spent the better part of a century doing our unwitting best to wreck the human-associated microbiota. . . . Whether any cures emerge from the exploration of the second genome, the implications of what has already been learned — for our sense of self, for our definition of health and for our attitude toward bacteria in general — are difficult to overstate.”

via My No-Soap, No-Shampoo, Bacteria-Rich Hygiene Experiment – NYTimes.com.

Got Gas? It Could Mean You’ve Got Healthy Gut Microbes : The Salt : NPR

Got Gas? It Could Mean You’ve Got Healthy Gut Microbes

by MICHAELEEN DOUCLEFF

April 28, 2014 1:43 PM ET

Sulfur-rich foods, such as cabbage, bok choy and kale, can be popular with gut bacteria. And we all know how much the critters enjoy beans.

Not long ago, we heard about a catchy idea for a cookbook: “Fart-free food for everybody.”

In theory, these recipes would be helpful for some people — and those in their vicinity.

But being a bit gassy may actually be a small price to pay for a lot of benefits to our health.

We know that air often comes after eating nutrient-packed vegetables, such as cabbage, kale and broccoli. And researchers have found that fiber-rich foods, like beans and lentils, boost the levels of beneficial gut bacteria after only a few days, as we reported in December.

So all this got us wondering: Could passing gas, in some instances, be a sign that our gut microbes are busy keeping us healthy?

Absolutely, says Purna Kashyap, a gastroenterologist at the Mayo Clinic in Rochester, Minn.

“Eating foods that cause gas is the only way for the microbes in the gut to get nutrients,” he says. “If we didn’t feed them carbohydrates, it would be harder for them to live in our gut.”

And we need to keep these colon-dwelling critters content, Kashyap says. When they gobble up food — and create gas — they also make molecules that boost the immune system, protect the lining of the intestine and prevent infections.

“A healthy individual can have up to 18 flatulences per day and be perfectly normal,” he adds.

Gas gets into the digestive tract primarily through two routes: Swallowing air (which we all do when we eat and chew gum) and your microbiome. That’s the collection of organisms in the GI tract that scientists and doctors are currently all fired up about. (Check our colleague Rob Stein’s recent series on it.)

That microbiome includes hundreds of different bacteria. But there are also organisms from another kingdom shacking up with them: the archaea.

All these microbes are gas-making fools. They eat up unused food in your large intestine, like fiber and other carbohydrates we don’t digest, and churn out a bunch of gases as waste.

But that’s not all they make. They also produce a slew of molecules (called short chain fatty acids) that may promote the growth of other beneficial bacteria and archaea.

And the more fiber you feed these friendly inhabitants, the more types of species appear, studies have found. This bump in microbial diversity has been linked to a slimmer waistline.

“Undigested carbohydrates allow the whole ecosystem to thrive and flourish,” Kashyap says.

Most gas made by the microbiome is odorless. It’s simply carbon dioxide, hydrogen or methane. But sometimes a little sulfur slips in there.

“That’s when it gets smelly,” Kashyap says.

But here’s the hitch: Many of the smelly sulfur compounds in vegetables have healthful properties.

Take for instance, the broccoli, mustard and cabbage family. These Brassica vegetables are packed with a sulfur compound, called sulforaphane, that is strongly associated with a reduced risk of cancer.

Another possible benefit of a little smelly gas? It may reduce the total volume of air in the gut, Kashyap says.

Why? Because bacteria and archaea make the sulfur gas from other gases in the gut, like hydrogen.

“Bacteria that make sulfide gas are really important,” Kashyap says. “They can cause smelliness, but they can reduce the total amount of gas flow.”

Of course, having too much of anything can be bad. If gas and bloating start interfering with your quality of life, Kashayps recommends seeing a doctor.

But don’t immediately blame your diet, Kashyap says.

In many cases, people who complain about too much gas actually don’t generate more than others, he says. Instead, they perceive the passing more intensely. Or they pass it more often.

“Yes, a more fiber-rich diet will produce more gas,” Kashyap adds. “But completely eliminating fiber from the diet should not be the first option. You don’t want to starve your microbes.”

So go ahead. Enjoy those lentils. Chow down on the cabbage. Then if you stink a little, think of it as a thank you gesture from your microbiome.

via Got Gas? It Could Mean You’ve Got Healthy Gut Microbes : The Salt : NPR.

Modern Medicine May Not Be Doing Your Microbiome Any Favors: NPR

According to Dr. Martin Blaser, the overuse of antibiotics has contributed to killing off strains of bacteria that typically live in the gut.

According to Dr. Martin Blaser, the overuse of antibiotics has contributed to killing off strains of bacteria that typically live in the gut.

Joe Raedle/Getty Images

There are lots of theories about why food allergies, asthma, celiac disease and intestinal disorders like Crohn’s disease have been on the rise. Dr. Martin Blaser speculates that it may be connected to the overuse of antibiotics, which has resulted in killing off strains of bacteria that typically live in the gut.

Blaser is an expert on the human microbiome, which is the collection of bacteria, viruses, fungi and other microbes that live in and on the body. In fact, up to 90 percent of all the cells in the human body aren’t human at all — they’re micro-organisms.

Blaser is the director of NYU’s Human Microbiome Program and a former chairman of medicine there. His new book is called Missing Microbes: How the Overuse of Antibiotics Is Fueling Our Modern Plagues.

Missing Microbes
 
Missing Microbes

How the Overuse of Antibiotics Is Fueling Our Modern Plagues

by Martin Blaser

He tells Fresh Air‘s Terry Gross that with the overuse of antibiotics, as well as some other now-common practices like cesarean sections, we’ve entered a danger zone — a no man’s land between the world of our ancient microbiome and an uncharted modern world.


Interview Highlights

On why he thinks the number of diseases has risen

Since World War II, we’ve seen big rises in a number of diseases: asthma, allergies, food allergies, wheat allergy, juvenile diabetes, obesity. … These are all diseases that have gone up dramatically in the last 50 or 70 years. One of the questions is: Why are they going up? Are they going up for 10 different reasons, or perhaps there is one reason that is fueling all of them.

My theory is that the one reason is the changing microbiome; that we evolved a certain stable situation with our microbiome and with the modern advances of modern life, including modern medical practices, we have been disrupting the microbiome. And there’s evidence for that, especially early in life, and it’s changing how our children develop.

On the potential link between antibiotics and obesity

We have experiments in mice where, since we’re very interested in obesity, if we put mice on a high-fat diet, they gain weight; they get fat. If we put them on antibiotics early in life, they also get fat. If we put [them] on both together, they get very fat. … It’s clear that the effects of the antibiotics potentiate the effects of the high-fat diet. We’re not letting [the] high-fat diet off the hook, we’re saying that there’s another factor there. …

There’s a choreography; there’s a normal developmental cycle of the microbiome from birth over the first few years of life, especially the first three years, [that] appear[s] to be the most important. And that’s how nature has, how we have, evolved together so that we can maximize health and create a new generation, which is nature’s great purpose. And because of modern practices, we have disrupted that. And then the question is: Does that have consequence[s]? Our studies in mice show that it does have consequences. We’ve done epidemiologic studies in people that show that some of these modern practices are increasing the risk of obesity as well.

On how the birth process informs a baby’s microbiome

As far as we know, when the baby is inside the womb it is apparently sterile. … The big moment of truth is when the membranes rupture, the water breaks, and the baby starts coming out. And that’s where they first get exposed to the bacteria of the world, and the first bacteria they’re exposed to is their mother’s bacteria in the birth canal. So as labor proceeds, the babies are in contact with the microbes lining their mother’s vagina and, as they’re going out, they’re covered by these bacteria. They swallow the bacteria; it’s on their skin. …

That’s their initial exposure to the world of bacteria. That’s how mammals have been doing it for the last 150 million years, whether they’re dolphins or elephants or humans. … And we know a little about what those bacteria are. The most common bacteria are lactobacillus and there’s evidence that over the course of pregnancy the microbiome in the vagina changes, just as many other parts of the body are changing. The microbiome is changing in its composition in terms of maximizing lactobacilli, and these are bacteria that eat lactose, which is the main component of milk. So the baby’s mouth is filled with lactobacilli. The first thing that happens is they go up against their mom’s breast and they inoculate the nipple with lactobacilli and now milk and lactobacilli go into the new baby and that’s the foundation for their microbiome and that’s how they start their life. …

You could project that if they didn’t acquire these organisms or they didn’t acquire them normally or at the normal time, then the foundations might be a little shaky.

On a study comparing the microbiomes of babies born via C-section and those born vaginally

Shortly after birth, they compared the microbiomes in the babies that came out. The babies that were born vaginally, their microbiome, not surprisingly, looked like the mom’s vagina everywhere in the body — in their GI tract, on their skin, in their mouth. But the babies born by C-section, their microbiome looked like skin and it didn’t even necessarily look like the mom’s skin, maybe it was somebody else in the operating room. So it’s clear that the microbiome is different immediately depending on the kind of birth.

There have been more and more epidemiologic studies asking the question, really for the first time: Are there long-term health consequences of being born by C-section?

 

On how the microbiome can determine a person’s immunity and allergies

I’m concerned that the microbiome is part of our whole developmental process and if we disrupt it early, there are potentially consequences. …

What I can tell you is that our immune system is quite complex. There are many kinds of immune cells. There are cells that strongly recognize foreign substances, there are ones that try to damp [the immune system] and down-regulate it. There’s what we call innate immunity, which is the immunity we’re all born with, and then there’s adaptive immunity — the immunity that develops when we experience different kinds of exposures. So it’s very complex.

It’s developing early in life. That’s what sets, in essence, [the] immunological tone that will determine how allergic a person is, or how stoical a person is in an immunologic sense.

On probiotics

There are many different probiotics. If you go to the grocery store, the health food store, the drugstore, there are shelves and shelves full of probiotics [with] different names, different compositions. I think I can say three things: The first is that they’re almost completely unregulated; second is that they seem to be generally safe; and third is that they’re mostly untested. …

Right now, it’s the Wild West. I’m actually a big believer in probiotics; I think that’s going to be part of the future of medicine, that we’re going to understand the science of the microbiome well enough so that we can look at a sample from a child and say this child is lacking such-and-such an organism and now we’re going to take it off the shelf and we’re going to give it back to that child. … Just as today the kids are lining up for the vaccines, in the future, maybe the kids are going to be drinking certain organisms so that we can replace the ones that they’ve lost.

Can We Eat Our Way To A Healthier Microbiome? It’s Complicated : The Salt : NPR

While no one\’s sure which foods are good for our microbiomes, eating more veggies can\’t hurt.

iStockphoto.com

When our colleague Rob Stein got his microbiome analyzed recently in the name of science journalism, we were totally fascinated.

As Stein noted, it may be possible to cultivate a healthier community of bacteria on and inside us by modifying our diets.

Stein was advised to eat more garlic and leeks for his. But we wondered: Are there other foods that promote a healthy microbiome in most people?

The answer, we found out, is fairly complicated. Microbiome research is still in the very early stages.

\”We know quite a lot about associations between food and health, we know a bunch of associations between food and microbes, and we know a bunch about associations between microbes and health,\” says microbiome researcher Rob Knight.

What researchers don\’t yet know is how to put the whole picture together.

Are certain vegetables good because they have a positive effect on our microbiome? Or do they have a more direct effect on our metabolism? \”That\’s still very much an emerging area of research,\” Knight tells The Salt.

Still, some foods look promising. Dietary fiber serves as food for many of the bacteria that live in our guts, says microbiome researcher Jeff Leach of the Human Food Project. \”It doesn\’t hurt as a general rule to eat more fiber,\” Leach tells The Salt.

Too little fiber could starve the bacteria we want around. \”When we starve our bacteria they eat us,\” Leach says. \”They eat the mucus lining – the mucin in our large intestine.\”

Knight adds that when we do keep our bacteria well fed, they, in turn, give off nutrients that nourish the cells that line our guts. Fiber, Knight says, \”is thought to be good for your gut health over all.\”

There are a lot of different ways to get fiber. Leach recommends getting it from vegetables. Eat a variety of veggies, and eat the whole thing, he recommends. \”If you\’re going to eat asparagus, eat the whole plant, not just the tips,\” he says.

Fiber was also central to Leach\’s suggestion to Stein to eat more garlic and leek. Those vegetables contain high levels of a type of fiber called inulin, which feeds actinobacteria in our guts. In fact, inulin is considered a prebiotic, since it feeds the good bacteria, or probiotics, that live inside us.

Garlic actually has antimicrobial properties, which paradoxically, could also be good thing for our microbiomes. One study shows that garlic hurts some of the bad bacteria in our guts while leaving the good guys intact.

Whole grains are another good source of fiber — but evaluating its benefits is a bit trickier. Whole grain consumption seems to be associated with high levels of a type of bacteria prevotella, Leach says. \”Prevotella has been associated with inflammation in HIV patients [and] it\’s been associated with rheumatoid arthritis.\” We don\’t know why that is, Leach says. \”So the jury\’s still out on whole grains.\”

Another way to build a better microbiome may be to eat foods that naturally teem with probiotics. Michael Pollan mentions the puported benefits of organic veggies fresh from the soil in his piece on the microbiome for The New York Times Magazine.

But this can get tricky, Knight says. In the absence of pesticides, a lot of veggies turn on their natural defenses in order to fight off insects, and those defenses can be toxic to humans.

Fermented foods like kimchi, sauerkraut and yogurt might be surer sources of probiotics. Researchers are unclear about whether these have any lasting effect on the composition of our microbiome, but in some cases they do seem to help.

\”Epidemiologically there seems to be some evidence that eating fermented food is beneficial rather than harmful,\” Knight says. But researchers are still trying to figure out why.

Still, the big question is whether we can actually reshape our microbiomes by changing our diets. \”Short term dietary interventions,\” Leach says, \”don\’t have a dramatic impact.\” And slightly tweaking your diet probably isn\’t going to do much either.

\”The question is how dramatically are you changing your diet,\” Leach says. \”If you go from eating 10 to 15 grams of fiber a day to eating 40 or 50, you may see some changes.\”

via Can We Eat Our Way To A Healthier Microbiome? It’s Complicated : The Salt : NPR.