It's a typical hectic morning at Michele Comisky's house in Vienna, Va., when she gets a knock on her front door.
"Hi, how are you?" Comisky says as she greets Keisha Herbin Smith, a research assistant at Georgetown University. "Come on in."
Comisky, 39, leads Herbin Smith into her kitchen.
"Which one isn't feeling good?" asks Herbin Smith, glancing at Comisky's children. "That one," Comisky says, pointing to her 8-year-old son, Jackson.
Jackson has an ear infection. So he just started 10 days of antibiotics to kill the strain of bacteria giving him an earache. That's why Herbin Smith is here.
"What time did he take his antibiotic?" Herbin Smith asks.
She asks because the antibiotics won't just wipe out the bad bacteria. They could also disrupt the good bacteria in Jackson's body, which can lead to stomach problems, including severe diarrhea.
Herbin Smith had rushed to Comisky's house to deliver a special yogurt drink that scientists are testing in hopes of preventing those serious problems.
"We want him to take the first yogurt within 24 hours of taking his first antibiotic," she says.
The yogurt contains a probiotic — a living strain of bacteria that researchers think could help prevent diarrhea and other complications of the antibiotic.
Some previous research has hinted that probiotics could help, and some doctors already are recommending probiotics to parents of children taking antibiotics.
But researchers hope the new yogurt study will provide clearer evidence as to whether that's a good idea. It's the first large, carefully designed test of a probiotic to get reviewed by the Food and Drug Administration, says Dr. Daniel Merenstein, the director of research programs in the department of family medicine at Georgetown University, who is leading the study.
"The problem with a lot of probiotic research is that they haven't always been the best of studies," Merenstein says. "Many are done by industry. Many were done in other countries. We're looking to see if it actually prevents diarrhea in kids."
Merenstein's study is part of an explosion of interest in research on the microbiome — the billions of friendly bacteria, yeast and other microorganisms that live in the human body. There's mounting evidence these microbes play important roles in human health.
In addition to helping prevent diarrhea in children taking antibiotics, there is some evidence that probiotics could help prevent complications from antibiotics in adults as well and might help prevent gastrointestinal infections that sometimes occur when people travel to other countries. Other people have suggested probiotics might help treat vaginal infections in women, or possibly alleviate colic in infants or perhaps prevent eczema in some babies. Probiotics are also being looked at as a possibility to prevent a serious condition in newborn babies — necrotizing enterocolitis.
Some researchers even argue there's enough evidence to recommend that healthy adults take a probiotic regularly to help maintain their health.
"I think there's a generic benefit in ingesting high numbers of safe, live bacteria every day," says Colin Hill, a professor of microbiology at University College Cork in Ireland. "If I had my way, there would be a recommended daily allowance of bacteria."
But many scientists question whether there's enough evidence to support that suggestion or the many claims some companies are making about the alleged benefits of probiotics. Some products are being promoted to help prevent obesity, heart disease and even alleviate mental health conditions such as anxiety and depression.
"The marketing of every claim under the sun with every product under the sun is definitely questionable," says Linda Duffy, a program director at the National Center for Complementary and Integrative Health. "There's not much in the way of a magic bullet anywhere."
The net benefit of probiotic use with certain conditions "is looking very, very promising," she says. But there are still a lot of unanswered questions.
While probiotics are probably safe for most otherwise healthy people, Duffy and others note that the products could pose some risk for people with weakened immune systems, such as those infected with the AIDS virus or for people undergoing cancer chemotherapy.
Another caution is that probiotics are not regulated as closely as prescription and over-the-counter medications. So there's no guarantee that what's on the label is actually in the bottle — or that whatever organisms were originally in the bottle are still alive. There are also concerns about potentially dangerous contaminants in products that could pose a risk even to healthy people.
"Are there contaminants out there? Are there adulterated products? Are there marketed products without the appropriate claims? Absolutely," Duffy says. "Like anything, you have to be a wise consumer."
For his part, Merenstein hopes his study will provide strong new evidence that probiotics provide benefits for children taking antibiotics.
In the study, 300 children will drink specially made strawberry yogurt. Half will drink yogurt that contains a probiotic called bifidobacteria. The researchers will then compare the incidence of diarrhea and other gastrointestinal problems in the two groups of kids.
In addition, the researchers are gathering fecal samples from the children to try to determine exactly how probiotics might work.
"One of our goals is to show that taking a probiotic will get your microbiome back to what it was before you started the antibiotic — and/or protect you from the changes," Merenstein says.
So, back at Comisky's house, Jackson takes his first gulp of Merenstein's special yogurt.
"All right, here you go — you can drink it right out of here," Comisky says as she takes a bottle out of the refrigerator, opens the cap and hands it to her son.
"Is it good?" she asks.
"Yeah," says Jackson, as he gulps down the yogurt and declares: "Done!"
It will take years for Merenstein's team to gather and analyze the results of the study. So it will be a while before they can say for sure whether this particular probiotic treatment works.
RACHEL MARTIN, HOST:
Go online, walk through any health store or supermarket, and you'll find all kinds of products being sold as probiotics. They're being promoted for all kinds of things - preventing upset stomachs, boosting the immune system, fighting anxiety and depression even. Americans spend billions of dollars every year on probiotics. But what is the science behind all these claims? We asked NPR health correspondent Rob Stein to take a look.
ROB STEIN, BYLINE: It's a typical hectic morning at Michele Comisky's house in Vienna, Va., when she gets a knock on her door.
MICHELE COMISKY: Hi. How are you?
KEISHA HERBIN SMITH: I'm Keisha. It's nice to meet you.
COMISKY: Nice to meet you, Keisha.
HERBIN SMITH: Hi.
STEIN: Comisky leads Keisha Herbin Smith into her kitchen.
COMISKY: This is the one not feeling good.
STEIN: Comisky's 8-year-old son Jackson - he has a bad ear infection. So he's starting 10 days of antibiotics to kill the bacteria that's giving him the earache. That's why Herbin Smith is here.
HERBIN SMITH: And what time did he take his antibiotic?
COMISKY: He just took it about 10 minutes ago.
STEIN: These antibiotics won't just wipe out the bad bacteria. They could mess up the good bacteria in Jackson's body, too. This is why antibiotics can cause stomach problems, including sometimes nasty diarrhea. Herbin Smith's a research assistant. She rushed here to test a special yogurt drink scientists hope will prevent that.
HERBIN SMITH: We want him to take the first yogurt within 24 hours of taking his first antibiotic.
STEIN: The yogurt contains a probiotic. That's a living strain of bacteria that researchers think could help prevent diarrhea and other complications of the antibiotic. Daniel Merenstein of Georgetown University says this yogurt study will hopefully prove it. He says it's the first big, carefully designed test of a probiotic to get reviewed by the Food and Drug Administration.
DANIEL MERENSTEIN: The problem is with a lot of probiotic research is that they haven't always been the best of studies. Many are done by industry. Many were done in other countries.
STEIN: In this study, 300 kids will drink the specially made strawberry yogurt. Half the kids will drink yogurt that contains a probiotic called bifidobacteria.
MERENSTEIN: So we're looking to see if it actually prevents diarrhea in kids.
STEIN: During a visit to his office, Merenstein offers me a taste.
MERENSTEIN: You're going to be our guinea pig?
STEIN: Sure. Not bad - it's pretty good, actually.
The study is part of an explosion of research into the microbiome. That's the billions of friendly bacteria, yeast and other microorganisms that live in the human body. There's mounting evidence that these microbes play important roles in keeping us healthy. So Merenstein and his colleagues are also studying the kids' microbiomes to try to figure out exactly how probiotics might work.
MERENSTEIN: One of our goals is to show that taking the probiotic will get your microbiome back to what it was before you started the antibiotic and/or protect you from the changes because there's no question that taking antibiotics, which the kids need - they have an infection - is good for their infection. But it does wipe out other good bacteria.
COMISKY: Jackson, you want your yogurt?
STEIN: Back at Michele Comisky's house, Jackson takes his first gulp of Merenstein's special strawberry yogurt.
COMISKY: All right.
COMISKY: Was it good?
COMISKY: Oh, good. OK.
STEIN: It'll take years for Merenstein's team to gather and analyze the results of the study. So it'll be a while before they can say for sure whether this probiotic works or not.
MARTIN: That's NPR's health correspondent Rob Stein, who joins us in our studios right now to talk a little bit more about this. Hi, Rob.
STEIN: Hey, Rachel.
MARTIN: So it's going to be a while before we know if probiotics and yogurts like this really work. In the meantime, what should parents with kids on antibiotics do?
STEIN: Well, the short answer to that is it may be worth a try. There have been some other studies that suggest that it does work. And some doctors are already recommending it to parents. So if your child is otherwise healthy, it might be worth a shot.
MARTIN: OK, so what else do we know about probiotics? I mean, what do we know that they're really good at addressing?
STEIN: You know, honestly, at the moment, there really isn't anything that we're 100 percent sure that probiotics will work for. That's the truth, unfortunately. But there is, you know, some evidence that it could work for some other things, like, you know, for example, what we call traveler's diarrhea - you know, you go to Mexico or someplace like that. If you take a probiotic every day while you're traveling, it might help prevent that. It could help adults who are taking antibiotics have - not have stomach problems. There's some evidence that it could help women who have vaginal infections, maybe soothing colicky babies. And there's some evidence that, you know, people with the condition known as irritable bowel syndrome - it could help alleviate some of their pain. So there's some evidence that kind of thing.
MARTIN: Could being the operative word in all this. I mean, at the same time though, it seems like probiotics are everywhere. They are marketed for all kinds of different things, right? - boosting the immune system, preventing heart disease. They can combat obesity, so they say. How do we as consumers know what's true and what's not?
STEIN: Yeah, I've been talking to a lot of scientists about that over the last couple of weeks. And, you know, the short answer to that is it depends who you talk to. There are some researchers that are pretty gung-ho and say that probiotics can do all sorts of things and even think you should take one every day to sort of maintain your health. But many of the scientists I talked to said, look, the bottom line on this is the marketing of these things, of these probiotics, has gotten way ahead of the science. And we really don't know anything for sure. We need do a lot more research. And, you know, it's important to note that the Food and Drug Administration has not approved a single probiotic for anything at this point.
MARTIN: So I've heard you say in the course of this conversation that some people think you should take probiotics every day just as a preventive measure or that it could help with a variety of things. But is there a downside to taking probiotics?
STEIN: Well, you know, probiotics are not regulated like regular medicines. So, first of all, there's no guarantee that whatever is on the label is actually in the bottle and whatever was in the bottle is still alive. These are living organisms, don't forget. So it could be they don't last forever. And, you know, they are living organisms. So there are concerns about some people, like people with weak immune systems, people with HIV or taking chemo, they could be dangerous. And if they get contaminated with something, they could be - cause serious problems, even for healthy people. And the other issue is, you know, the cost. These things aren't cheap, you know? And you could just be wasting your money. And you'd be better off buying fruits and vegetables, which we know will improve your health.
MARTIN: Yeah, bottom line - don't assume that they will work for your particular ailment.
STEIN: That's right. That's right.
MARTIN: Do some thinking. Do some research.
STEIN: The bottom line is buyer beware with this stuff.
MARTIN: NPR health correspondent, Rob Stein.
(SOUNDBITE OF TEEN DAZE'S "BY LOVE") Transcript provided by NPR, Copyright NPR.