Should I take a probiotic? And other gut questions, answered

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Some of these links are only beginning to be fully revealed. You're listening to life kit. I'm Mariel Sagata. And that was NPR health correspondent Will Stone. The gut microbiome is a way of describing the literally trillions of microbes that populate our intestines. A lot of these are bacteria, but we also have other organisms in there, fungi and viruses. So you want to picture this packed dense ecosystem that's alive within you.

“Now, given what scientists are discovering that the microbiome is important to our health, people want to hack it.”

They want to have the very best healthiest microbiome possible.

Will says the problem is the science hasn't come quite that far yet.

Scientists haven't figured out how to even define what is a healthy microbiome. There's a lot of variability when you look around the world, depending on where you live, your diet, all kinds of things. And so unless you are acutely ill and having symptoms, it's hard to pin down what is healthy. We do have some clues, though. It seems that the more diverse your gut bacteria are, the better. Also, if your microbiome bounces back well from disruption, like antibiotic use, that's a good sign.

And another area that scientists can look at are the different groups of bacteria that are present in your microbiome. And we know that some are associated with better health when you look around the world, you see this. On this episode of LifeKit, best practices for your gut microbiome.

I talked to Will about probiotic supplements, microbiome tests, and what you eat, which is still the most important factor here.

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Life kit made a special newsletter series to answer that question. Sign up at npr.org/skincare, or find the link in the description for this episode. Well, there's a huge market for gut microbiome tests. Are any of these were spending money on? The short answer is generally no, at least when you look around the huge variety products out there.

And that's because they tend to overstate the science and be way ahead of the evidence.

They're quite popular, and this isn't a test that your doctor orders because they think you have some illness. This is a test you would get commercially, a couple hundred dollars, to try to maybe optimize your microbiome or figure out what's wrong with it on your own. They'll give you hundreds of different measurements, and it looks pretty, pretty legit. I talked to Dr. Alexander Choritz about them. He's a GI specialist and researcher at the University of Minnesota.

He says he'll get patients who are worried about their gut health, maybe they'll have some symptoms, and they'll send him their results. He usually comes as an entire book, colorful, with many, many entries of different bacterial species,

“these fungal species, different metabolites, and I think the message, the patient gets, well,”

gee, my doctor never did this kind of testing, this, this, this amount of information.

This is, this looks very impressive. It must mean something, and the reality is, it's, unfortunately, it's not very informative at all. And the fundamental problem is when we already discuss, which is, well, we don't have a definite consensus on what even is a healthy microbiome. But beyond that, we've also seen research that shown the same patient with the same sample,

consent it to different companies, and they get very different results. So it's not just interpretation, it's also kind of the reliability and variability you can get when you go out onto the market. Okay, so don't bother with the tests, and what about supplements, like probiotics, for instance, if you walk into a health food store, there'll be shelves of many different probiotic capsules you can choose from. Yeah, and it can be pretty confusing, you know, to figure out, is any of this worth my money.

Now, probiotics can be helpful in specific circumstances. So, for example, there's good evidence they can be beneficial for reducing the risk of diarrhea associated with antibiotic use, also for preventing travelers diarrhea, or for preterm infants who are at risk of complications. These are a few examples where we have better data. But beyond that, the idea that most people who are otherwise healthy should be taking a probiotic daily to support their gut health,

it's really not backed by science yet. There may be a day where we actually have more targeted probiotics that can help people, but we are just not at that point yet. And for the cases that you mentioned, it's only certain strains that help with those things, right?

“Like, you need to pay attention to which strain you're using if you want to, for instance, prevent travelers diarrhea.”

That's right, certain strains have been tested in high quality trials and been shown to be effective. One point that was made to me was you'll see sometimes marketing on these probiotics saying clinically tested. That didn't say they were effective, it just said they were tested. So you have to be mindful about what's actually being promised here, and then what can be delivered by the evidence. I spoke to Hannah Holesher about this. She's at the University of Illinois or Banish campaign, and she pointed me to a website called usprobioticguy.com.

That outlines in a very simple way, the levels of evidence for each strain that's been studied and for which conditions. Okay, so what can people do if anything to try to optimize their gut microbiome?

Yeah, the first place is start and how you can make the most difference by far.

Isn't any special gut hack or magic solution? It's simple stuff that all of us already know we should be doing for our overall health. And that's because our gut microbiome evolved with us and when we are healthy and thriving, so to our gut bacteria. Take a listen to Dr. Furgas Shanahan, he's at the National Institute of Ireland in Cork and a longtime researcher in gut health. Good sleep, 20 of exercise, fresh air, good food, good food meaning real food, and not lots of low fiber, ultra processed foods.

Your mother probably told you all these things in different language, but all the things you were ever told. They're all good for your microbiome as well. There isn't any need for some health guru to come along and say, "Oh, I've got some major potion now that is going to improve your microbiome."

Basically, the gut researchers don't have some secret that they've been keeping from us that we all should know.

It's just not the case yet.

“Any specifics that you learned about diet, what we should be eating?”

Yeah, number one, without a doubt, fiber. And folks may have heard this, but most of us do not get enough fiber just in the general kind of Western diet. The most of us have. So you want to aim for anywhere from about 20 grams a day to 40 depending on your age in sex, 35 grams is a generally a good target.

I spoke to Hannah Holesher about this, and here's the advice she gave.

“If you picture the rainbow of types of foods that you can eat fruits, vegetables, whole grains, nuts and legumes, you're going to see all of these different colors of the rainbow.”

And that means these foods have different phytonutrients in them, and they have different fibers. And just like an apple taste very different from an orange and taste different from an avocado or broccoli, you know, they have different fibers in them. And different phytonutrients and different microbes can go in and use those fibers as energy sources. Hannah has spent a lot of time doing well controlled trials where they feed people different foods and then see how that can influence your gut microbiome.

One example they did a trial with walnuts, and they found that it enriched a bacteria called rose buria, which is beneficial and linked to positive health.

You have some data showing that fermented food in particular can be pretty beneficial for lowering inflammation and overall gut microbiome diversity in health. So these are things like sour crowd, kimchi, yogurt, but you want to look and see whether the yogurt has live cultures of bacteria in it, not highly processed kinds of yogurt with sugar and that don't actually have bacteria in it. These are a couple examples of like beneficial probiotics that you can get from your food.

“Okay, and then is there anything that people should avoid to help their gut microbiome?”

Yeah, so probably no big surprise here unless you really need it antibiotics tend to be overused over prescribed. Try to avoid those when not necessary beyond that Hannah and others brought up some of the usual culprits we hear when we talk about other issues with our health. Foods like highly refined sugary that are low in fiber sometimes called ultra processed foods. You want to try to keep those to a minimum. And you know, she's an advocate of moderation, you know, doesn't really think people need to be extreme here, but she says as much as you can. Unfortunately, alcohol is not great for our gut and, you know, best to avoid that if you're concerned about supporting your gut microbiome.

Well, Stone, thank you so much. Thanks for having me, it was fun. Right time for a recap, don't bother spending money on a gut microbiome test. They overstate the science and they're way ahead of the evidence. Some probiotic supplements have been shown to help with particular problems like traveler's diarrhea and diarrhea associated with antibiotic use. But the idea that most people who are otherwise healthy should be taking a probiotic daily to support their gut health is not backed by science yet.

We'll drop the names of a couple strains that are well studied in the show notes. And you can also check out a website called us probioticguide.com, which outlines the levels of evidence for each strain that's been studied and for which conditions.

“Now, the researchers who study the gut say the best thing you can do for your gut microbiome is eat in a fiber a day.”

That's about 20 to 40 grams a day, depending on your age and sex. Eat fermented foods like kimchi and yogurt, cut down on ultra processed foods and alcohol, and only take antibiotics when you really need them. Also get enough sleep and exercise. All right, that's our show. By the way, your phone is full of distractions. Make sure it's full of good tips and practical advice too. The NPR app gives you access to world-class reporting, like what we have on life kit, without a paywall.

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This episode of LifeKit was produced by Margaret Serino. It was edited by Megan Kane, Carmel Roth, and Lauren Gonzalez. Our digital editor is Malica Greed and our visuals editor is CJ Rekeland. Our production team includes Andy Tegel, Claremarie Schneider, and Sylvie Douglas, engineering support comes from Peter Elena. Fact-checking by Andrea Lopez Crustado. I'm Mary Elsa Garra. Thanks for listening. And then, probably a couple of years later, I started drawing them having sex.

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