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

Summary

Life Kit (NPR): "Should I take a probiotic? And other gut questions, answered"

Air Date: June 22, 2026
Host: Marielle Segarra
Guests: Will Stone (NPR Health Correspondent), Dr. Alexander Koretz (GI Specialist, Univ. of Minnesota), Dr. Fergus Shanahan (National Institute of Ireland), Dr. Hannah Holscher (University of Illinois)

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Episode Overview

This episode of Life Kit unpacks some of the most common questions about the gut microbiome—should you take a probiotic? Are microbiome tests worth the money? What are the best diet and lifestyle practices for gut and overall health? Host Marielle Segarra explores these topics with health correspondent Will Stone and experts in gut health, delivering practical, science-backed guidance for listeners seeking to "optimize" their gut.

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Key Discussion Points & Insights

1. What Is the Gut Microbiome—and Why Does It Matter?

• Definition & Importance:
  The gut microbiome refers to the trillions of bacteria, fungi, and viruses living in our intestines. It's closely tied to digestion, immunity, mental health, and cognition.
  • Quote (Will Stone, 01:02): "Scientists know that our microbiome, it's not just involved in digestion. It's intimately linked with so much of our overall health."
• Still Evolving Science:
  There's no clear definition of what constitutes a "healthy" gut microbiome. Individual variation is high and depends on factors like geography and diet.
  • Quote (Will Stone, 02:01): "Scientists haven't quite figured out how to even define what is a healthy microbiome."

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2. Are Commercial Gut Microbiome Tests Useful?

• Expert Opinion:
  Most commercially available microbiome tests are not worth the money. They overstate scientific understanding and lack reliability—even the same sample can yield different results from different companies.
  • Quote (Dr. Alexander Koretz, 05:45): "It usually comes as an entire book, colorful, with many, many entries of different bacterial species ... and the reality is it's. Unfortunately, it's not very informative at all."
  • Quote (Will Stone, 06:17): "We've also seen research that's shown the same patient with the same sample can send it to different companies and they get very different results."

[Key Segment: Gut Microbiome Tests – 04:52–06:42]

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3. Should You Take Probiotic Supplements?

• Situational Effectiveness:
  Some probiotics can be helpful in specific scenarios:
  • For preventing antibiotic-associated diarrhea
  • For travelers' diarrhea
  • For certain at-risk infants
    Outside these situations, evidence does not support routine probiotic use for otherwise healthy people.
  • Quote (Will Stone, 06:57): "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."
• Watch Out for Marketing Claims:
  Not all probiotics are created equal; only those with specific, well-researched strains and proven effects should be considered.
  • Quote (Will Stone, 07:57): "Sometimes marketing on these probiotics [says] clinically tested—that didn't say they were effective, it just said they were tested."

[Key Segment: Probiotics – 06:42–08:36]

• Resource Mentioned:
  usprobioticguide.com for evidence on which strains are effective for what conditions.

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4. Best Practices for a Healthy Gut Microbiome

• Diet & Lifestyle Trump Supplements:
  The most effective changes are basic healthy habits.

  • Quote (Dr. Fergus Shanahan, 09:14): "Good sleep, plenty of exercise, fresh air, good food ... all the things you were ever told, they're all good for your microbiome as well."

• Diet Specifics:

  • Fiber is King:
    Most people do not get enough fiber (recommended: 20–40 grams/day). Fiber diversity (eating many types) is also important.
    • Quote (Will Stone, 09:53): "You want to aim for anywhere from about 20 grams a day to 40 ... 35 grams is generally a good target."
    • Quote (Hannah Holscher, 10:27): "If you picture the rainbow of types of foods that you can eat ... they have different fibers in them and different phytonutrients and different microbes can go in and use those fibers as energy sources."
  • Fermented Foods Help:
    Foods like sauerkraut, kimchi, and live-culture yogurt can support gut health, but check that yogurt has live cultures and minimal processing.
    • Quote (Will Stone, 10:57): "Fermented food in particular can be pretty beneficial for lowering inflammation and overall gut microbiome diversity and health."

  [Key Segment: Diet & Gut Health – 08:36–11:49]

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5. What To Avoid

• Overuse of Antibiotics:
  Use antibiotics only when necessary, as they can disrupt gut bacteria.
  • Quote (Will Stone, 11:56): "Antibiotics tend to be overused, overprescribed, so try to avoid those when not necessary."
• Ultra-Processed Foods & Alcohol:
  Heavily refined, low-fiber, and sugary foods harm the microbiome; alcohol is also detrimental.
  • Quote (Will Stone, 11:56): "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. ... Alcohol is not great for our gut."

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Notable Quotes & Memorable Moments

• "Scientists know that our microbiome, it's not just involved in digestion. It's intimately linked with so much of our overall health." — Will Stone (01:02)
• "There isn't any need for some health guru to come along and say, oh, I've got some major potion now that's going to improve your microbiome." — Dr. Fergus Shanahan (09:14)
• "If you picture the rainbow of types of foods that you can eat ... they have different fibers in them and different phytonutrients, and different microbes can go in and use those fibers as energy sources." — Dr. Hannah Holscher (10:27)

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Quick Recap (12:48)

• Don't waste money on commercial gut microbiome tests.
• Some probiotic strains help for certain issues (e.g., traveler's diarrhea) but not for general daily use.
• The best support for your microbiome:
  • Eat 20–40g of diverse fiber daily
  • Include fermented foods
  • Minimize processed foods, alcohol, and antibiotics (unless needed)
  • Get enough sleep and exercise

Helpful Resources

• US Probiotic Guide – Up-to-date info on probiotic evidence by strain.
• Life Kit Skincare Newsletter – For other health and lifestyle tips.

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Timestamps for Key Segments

• What is the gut microbiome? — 01:02–02:33
• Should you buy commercial microbiome tests? — 04:52–06:42
• Are probiotics worth it? — 06:42–08:36
• Diet and lifestyle for a healthy gut — 08:36–11:49
• What to avoid — 11:49–12:48
• Recap — 12:48–14:42

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Tone & language remained friendly, practical, and rooted in evidence, in keeping with Life Kit’s mission of accessible life advice.

Transcript

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[Mariel Segarra]

a little something for everyone. If you need advice for that big life change, try listening to Life Kit. If you want to know more about that new TV show, check out Pop Culture Happy Hour. And if you want to dive deeper into your favorite podcasts and enjoy perks like bonus episodes, archive access and more, check out npr. Find out more and support the shows you [e-mail].

[Will Stone]

Scientists know that our microbiome, it's not just involved in digestion. It's intimately linked with so much of our overall health. It influences our immune system, our mental health, our cognition, and much, much more. Some of these links are only beginning to be fully revealed.

[Mariel Segarra]

You're listening to Life kit. I'm Mariel Segarra, 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.

[Will Stone]

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.

[Mariel Segarra]

Now, given what scientists are discovering that the microbiome is important to our health, we 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.

[Will Stone]

Scientists haven't quite 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 you know are having symptoms, it's hard to be pin down what is healthy.

[Mariel Segarra]

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.

[Will Stone]

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

[Mariel Segarra]

on this episode of Life Kit 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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[Mariel Segarra]

it's easy to feel overwhelmed by skincare advice. Somewhere along the way, skincare got complicated and started to feel like a job. But what products and treatments will actually lead to healthier skin? Life Kit made a special newsletter series to answer that question. Sign [e-mail] skincare or or find the link in the description for this episode. Will There's a huge market for gut microbiome tests. Are any of these worth spending money on?

[Will Stone]

The short answer is generally no, at least when you look around the huge variety of products out there. And that's because they tend to overstate the science and be way ahead of the evidence. So just to run through, you know, a couple of these, you have these gut microbiomes tests that you can buy. 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 Koretz about them. He's a GI specialist and researcher at the University of Minnesota, and 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.

[Dr. Alexander Koretz]

It usually comes as an entire book, colorful, with many, many entries of different bacterial species, fungal species, different metabolites. And I think the message the patient gets, well, gee, my doctor never did this kind of testing. 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.

[Will Stone]

And the fundamental problem is one we already discussed, which is we don't have a definite consensus on what even is a healthy microbiome. But beyond that, we've also seen research that's shown the same patient with the same sample can send it to, 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.

[Mariel Segarra]

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.

[Will Stone]

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 eating, 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.

[Mariel Segarra]

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 traveler's diarrhea.

[Will Stone]

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 Holscher about this. She's at the University of Illinois, Urbana Champaign, and she pointed me to a website called usprobioticguide.com that outlines in a very simple way the levels of evidence for each strain that's been studied and for which cond.

[Mariel Segarra]

Okay, so what can people do, if anything, to try to optimize their gut microbiome?

[Will Stone]

Yeah, the first place to 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, we so to our gut bacteria. Take a listen to Dr. Fergus Shanahan. He's at the National Institute of Ireland in Cork and a longtime researcher in gut health.

[Dr. Fergus Shanahan]

Like good sleep, plenty 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's going to improve your microbiome.

[Will Stone]

Basically, he's like, 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.

[Mariel Segarra]

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

[Will Stone]

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 that most of us have. So you want to aim for anywhere from about 20 grams a day to 40, depending on your age and sex. 35 grams is a generally a good target. And it's not only the quantity of fiber. You want to make sure you're eating different types of fiber because this diversity in your diet ends up really supporting the microbes in your gut. I spoke to Hannah Holscher about this and here's the advice she gave.

[Hannah Holscher]

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 means these foods have different phytonutrients in them and they have different fibers. And just like an apple tastes very different from an orange and tastes 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.

[Will Stone]

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 trial with walnuts, and they found that it enriched a bacteria called roseburia, which is beneficial and linked to positive health. We do have some data showing that fermented food in particular can be pretty beneficial for lowering inflammation and overall gut microbiome diversity and health. So these are things like sauerkraut, 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. Those are a couple examples of, like, beneficial probiotics that you can get from your food.

[Mariel Segarra]

Okay. And then is there anything that people should avoid to help their gut microbiome?

[Will Stone]

Yeah. So probably no big surprise here, unless you really need it. Antibiotics tend to be overused, over prescribed, so 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.

[Mariel Segarra]

Wilstone, thank you so much.

[Will Stone]

Thanks for having me. It was fun.

[Mariel Segarra]

All 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 enough 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. And with our push notifications, we'll keep you up to date to the second download the NPR app today. This episode of Life Kit was produced by Margaret Serino. It was edited by Meghan Cain, Carmel Roth and Lauren Gonzalez. Our digital editor is Malika Garib and our visuals editor is CJ Ricolon. Our production team also includes Andy Taegel, Claire Marie Schneider and Sylvie Douglas. Engineering support comes from Peter Elena Fact checking by Andrea Lopez Crusado. I'm Marielle Segarra. Thanks for listening.

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