Probiotics 101

What probiotics are, what they do (and don’t do), and what we’re still learning.

“People think that probiotics are all effective for the same health issues,” says University of Washington probiotics researcher Lynne McFarland. “That’s not the case.”

But you’ll never hear that from some probiotic manufacturers, who are happy to have you believe that their products are good for whatever ails you.

Bug basics

Probiotics are “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host,” notes the World Health Organization. The host? That would be you.

So the bacteria that are added to foods to ferment them—think sauerkraut, pickles, kombucha, and kimchi—are out because they have no proven health benefits. In are bacteria (or yeast) that, in scientific studies, help relieve diarrhea, irritable bowel syndrome, or other problems.

Tropicana describes the benefits of all probiotics, but says little about the Bifidobacterium lactis HN019 that it adds to its Probiotics juices… perhaps because it has nothing impressive to say.

Most bacteria have a first, middle, and last name. The microbe in Dannon’s Activia yogurt, for example, is Bifidobacterium (the genus) lactis (the species) DN-173 010 (the strain). All three parts are important. Lactobacillus reuteri NCIMB 30242, for example, may lower cholesterol (modestly), while Lactobacillus reuteri RC-14 can help with vaginosis.

“Consumers seeking help for a particular health problem should look only for the specific strains that have been successfully tested for that condition,” says Mary Ellen Sanders, executive science officer for the International Scientific Association for Probiotics and Prebiotics (which includes both academic and industry scientists).

But that’s not easy, since the Food and Drug Administration doesn’t require companies to disclose which strains they use.

For example, we recently asked Stonyfield which strain of Lacto­bacillus rhamnosus it adds to its yogurt. The information is “proprietary,” a company representative e-mailed us.

Good for what ails you?

“The time to think about probiotics is when your gut bacteria has been disrupted—like when you take antibiotics, travel, or have a chronic condition like irritable bowel syndrome,” says McFarland.

What about taking them just to reinforce your normal intestinal bacteria?

For a start, new bacteria are unlikely to take up residence in your gut. “Your normal bacterial flora does a great job of keeping foreigners out,” says Sanders.

That doesn’t necessarily mean there’s no benefit. Even though the probiotics haven’t colonized your gut, “they may still prevent disease-causing bacteria from gaining a foothold in the intestinal tract,” notes McFarland. “Some also produce their own antibiotics to kill other bacteria, or they may prime our immune cells for defense against invaders.”

Even so, “we don’t have good evidence that probiotics do any good on a day-to-day basis for healthy adults,” she adds.

Looking for a probiotic?

Here are four things to consider:

1. Find the strain for what you need. This post describes some probiotics that have the best evidence—and some that don’t do much.

2. Follow storage instructions. Some probiotics need to be refrigerated; others don’t. As long as you follow the package directions, one is no better than the other.

3. Check the expiration date. To increase your chances of getting the most live cells, look for probiotics that have months to go before their expiration date.

4. Try foods or supplements. Either is fine, though supplements generally have higher concentrations of probiotics and are more stable.

The information in this post first appeared in Nutrition Action Healthletter in July 2017.

Photo: Tropicana.

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34 Replies to “Probiotics 101”

    1. Bifidobacterium infantis 35624 (sold as Align) has the best evidence.
      Lactobacillus plantarum 299v (in Good Belly drinks and some supplements) also has some promising data. Those studies gave people 10-20 billion CFU of the bacteria, so if you want to try it, your best bet is looking for a product that has that much (Good Belly states that their products have 20 to 50 billion; just make sure to consider the added calories to your diet if that’s what you decide to try).

  1. I have been taking Align for years on the advice of a doctor. Not sure how much it helps but since I trust that doctor I will continue to take it.

    1. Align has the best data of any probiotic for IBS symptoms, though it may not work for everyone. Sounds like your doctor knows what he/she is talking about!

    1. There isn’t much research on probiotics and acne. There are some face washes that contain probiotics, but I haven’t seen ones that actually list the strain. Hopefully there will be more research on this in the future!

    2. Cut out any kind of dairy from your diet for three month and see if that makes a difference. I.e. No milk, no cheese, no yoghurt, no ice cream and so on!
      Also, look up Dr. McDougal’s starch based diet.


  2. Just started on Florastor yesterday. I have had Crohn’s for 16 years and recently had an attack of diverticulosis. It was recommended by my gastroenterologist and I’m hoping it works well.

  3. I felt I was more “regular” when I took an inexpensive probiotic I got at Costco. Maybe a placebo effect, but it seemed to make a real difference. Now I have a more expensive one that has to be refrigerated but I don’t see much benefit.

  4. The ones in the stores have numbers of how much probiotics are in the bottle. It varies by thousands. How do I know how much is a good amount? Is it possible that there are way more than you need and it is just more money?

    1. It won’t matter if it’s only varying by thousands since most probiotics have a dose of 1 billion CFU or more. The right dose will depend on the strain and the reason you’re taking it. One billion CFU is the general rule of thumb, but some evidence for certain probiotic strains show efficacy at much higher doses (like 20 to 50 billion).

  5. What about all of these companies out there now that are hard selling probiotics as a cure for candida – stating that it is the “cause” of most ills.
    I find it a bit hard to believe that a probiotic will cure joint pain, exhaustion, etc.
    And they want you to give it quite a long time to “set your system free”. Sounds like a sales pitch to me.

  6. What about soil microbes? I would love to hear more about research on bridging the gap between commercial and non-commercial agriculture and it’s affect on health and immunology.

  7. Why di something packaged Probiotics on drugstore shelves say may be refrigerated. And, are they okay not refrigerated until opened?

  8. Hi – do you have a suggestion for c-diff? My mother has this and her doctor has her taking Phillip’s Colon Health.

    1. There isn’t a lot of research on probiotics for UTIs. However, there is some research that shows that taking a combination of Lactobacillus reuteri RC-14 and Lactobacillus rhamnosus GR-1 may be as beneficial as taking prophylactic antibiotics for women who get recurrent UTIs. It’s unlikely that they’ll completely eradicate the UTIs, but they may reduce their frequency. You can find them in products like Femdophilus or RepHresh.

  9. I have been consuming 16 oz of kombucha a day for quite some time. Are there any complications that you are aware of with that level of consumption ?

    1. I haven’t seen anything that suggests that would be harmful. If it’s a sweetened kombucha, keep the amount of added sugar in mind, though.

  10. I’m unclear about the reason the live culture is kombucha would not contain beneficial probiotics, as indicted in your article. Why wouldn’t live culture in it snd in Braggs Apple Cider vinegar be good sources of probiotics?

    1. There are a few reasons that cultures in foods like kombucha, kimchi, or apple cider vinegar aren’t considered probiotics. First, and most importantly, the strains of bacteria in those cultures are numerous, can vary considerably, and aren’t well defined. Probiotics have to be a specific strain. Second, there has to be a known health benefit associated with the strain. There may be research in the future that points to a health benefit of specific fermented foods (research is pretty sparse now), but to be considered a probiotic, it can only apply to that specific strain. And third, they have to be administered in an “adequate” amount to confer health benefits. That comes back to the strain issue, but we also don’t know how much of the bacteria from the live, active cultures of some fermented foods survive passage through the stomach or how much is needed to confer the health benefit.

  11. There are claims that fermented foods add beneficial bacteria to the gut- yet the supplement companies constantly state that the acid in the stomach will “kill” the beneficial bacteria in fermented foods and that is why the supplements are in capsules that dissolve only when they reach the intestines i.e. they bypass stomach acid.
    Is it that fermented foods have just not been studied? Have companies done studies with supplements that dissolve in the acid of the stomach to see if they “work” – colonize the intestines as the acid resistant capsules do? would?

    1. Some bacteria can survive passage through the stomach whether they’re in pill form or in foods and some supplements do use “enterically coated” pills, which ensures passage through the gut. And you’re right about research: there isn’t a lot of funding pouring into studying fermented foods, so there may be some bacteria strains from fermented foods that do survive the stomach and can have beneficial effects in the rest of the GI tract. Hopefully new research answers those questions. But it’s important to point out that no probiotics – from supplements or from foods – colonize the gut. They may have beneficial effects as they pass through the gut, but they really aren’t taking up residency and becoming part of your gut microbiome.

    2. Make your own sauerkraut and see if you experience a difference. I do and I eat just a bit of sauerkraut almost daily.
      How to do It? Look it up on YouTube. It is very easy to do.


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