What Should I Look For in a Probiotic?

What Should I Look For in a Probiotic?

Probiotics fill the shelves of pharmacies, vitamin shops, health food stores, and online retailers and while there is a growing body of science and research supporting the potential health benefits of supplementing your diet with beneficial live microorganisms, that still leaves an essential question:

What should I look for in a probiotic?

Trying to sort through the multiple claims and wading through often unfamiliar jargon such as CFUs, enteric coatings, strains, and the rest (not to mention Latin naming conventions!) can be an exercise in frustration.

However, broken down, it can become fairly straightforward.  We’ll walk you through the top 12 things we look for so you’ll be better equipped to make a more informed decision regarding what you think might work for you.  Be sure to read through to the end, as some of things you need to consider just might surprise you.

Please note that these are not necessarily in any order, they are all important in their own way, and in ways that may differ depending on what you’re looking for or what your particular health and wellness goal might be.

1) Overall Quantity

When it comes to quantity, we’re not talking about pills in a bottle or scoops in a pouch, we’re talking about the number of microorganisms in a serving. And in the world of the microbiome (your community of microorganisms, also referred to as the microbiota), the counting typically begins at a billion and goes up from there!

That’s because the average person has just shy of 40 trillion microorganisms coinhabiting their body.  In light of that, one billion is almost literally, “a drop in the bucket.”

So how much should you look for?  That depends of course, and while there is no one clear answer, there are general conventions you can use as a yardstick.

First, a bit of terminology. The industry uses a unit of measurement called a “CFU,” or “Colony Forming Unit.” This is an important distinction as you are dealing with living organisms.  It’s relatively easy to count organisms, but a dead organism does you no good, and there are a lot of dead organisms in those pills and capsules (more on that later).  By getting a billion CFUs, you are getting a billion living organisms capable of reproducing. That’s what you want.

A typical multi-strain probiotic (more on that later as well) will contain between 5 and 15 billion CFUs.

Is 5 billion a good number? 15? Is either enough? I believe either is a good general starting point. (I started at 5, four days a week.) However, there are those, such as gastroenterologist and author, Dr. Robynn Chutkan, who maintains in her book “The Microbiome Solution” that you should choose a probiotic with at least 50 billion CFUs!

For someone just starting out, who had never taken a probiotic before, or had never or rarely eaten fermented foods (yogurt, kimchee, etc.) caution is warranted. I can take a 50 billion CFU formulation with no ill effects, but I’ve built up to that over time and I have a diet largely friendly to my microbiome, so I might tolerate it better now than I would have, say, ten years ago.

An additional caution: If you have never taken a probiotic before, don’t take your very first dose just before jumping in the car for a long commute to work. It is unlikely you will experience instantaneous digestive discomfort that could cause an “accident” (both kinds!) but it is not all that uncommon to have some level of initial adjustment when introducing a dose of living microorganisms to your digestive tract for the first time. (Maybe try it on a quiet Sunday at home!)

2) Individual Quantity

When it comes to multi-strain formulas, it goes beyond just the total number of CFUs. Ideally, you’d want to know the number of organisms per individual strain or species.

That’s the ideal, but we don’t live in an ideal world, and you are likely to run into the concept of the “proprietary” formulation (which I touch on again later), in which the maker of a 15-strain probiotic refuses to list the amounts of the individual organisms.  This can be troubling since you have no idea if the formulation includes say, 10 billion of one inexpensive, easily cultured strain, and 5 billion spread out among the other 14. Depending on the reputation of the manufacturer, I don’t consider this a deal-killer, but it is definitely a red mark and to the extent you can find a probiotic that provides more transparency, the better.

For single-strain probiotic supplements, 1.5 billion appears to be a pretty standard number, but it really can depend on the strain.  Some probiotics such as certain Culturelle products can contain as many 15 billion of one single strain!

I am personally not fond of over-supplementing on a single strain unless you are certain that is the strain you need or are doing so under the supervision and recommendation of your doctor. My fear is that you could end up crowding out other beneficial strains, just as beneficial strains can crowd out the ones that mean you harm.  (I’ll note that the research on this is not at all clear and that is more an intuition than anything else.)

Keep in mind, much of this remains entirely speculative. The science here is very new, and as exciting as it is, it is evolving. While we learn more and more every day, part of that learning process is discovering that we’ve been wrong about things in the past, which of course can raise yet more questions!

But there is more to this than just “quantity.” There is the notion of “when.”

3) Quantity at Expiration

To add one additional twist to this particular topic, you need to pay attention to whether or not the listed CFUs are the amount as of the date of manufacture or the date of expiration.

This makes an enormous difference. Take, for example, Hyperbiotics Pro-15.  The front of the bottle prominently claims 5 billion CFUs per tablet, however the fine print on the back of the bottle notes that the number is only valid as of the date of manufacture and that the product will have degraded to 1.5 billion CFUs by expiration, which, based on our purchase, can be less than a year into the future. You can be almost certain that by the time you purchase the bottle, it has fewer than 5 billion CFUs, and maybe a lot less.

By contrast, Genuine Health’s Advanced Gut Health Probiotic claim of 50 billion CFUs on the front of the bottle is actually what is expected to remain at expiration. As of the date of manufacture, it has 125 billion CFUs.

There are also companies that don’t include any information regarding CFUs beyond the date of manufacture, so you have no idea the extent to which the number of viable organisms degrades over time.

While I believe Genuine Health’s approach is the more consumer friendly one, it does not necessarily mean that you should never purchase the Hyperbiotics, or a probiotic that provides even less information, only that you need to pay attention and understand what it is you’re buying, particularly since there is no industry-set standard for presenting this information.

Rest assured, this is one of the things Microbiome Bulletin will highlight in our reviews, reaching out to individual companies for the information if they don’t volunteer it up front, and reporting back to you.

4) Identified Strains

Strains can make an important difference, but before we get to that, let’s make sure we understand the naming conventions typically used with probiotics.

Probiotic organisms are usually identified by, at a minimum, their genus and species, in that order. So, “Lactobacillus acidophilus” refers to a microorganism from the genus “Lactobacillus” and species “acidophilus,” while “Lactobacillus rhamnosus” is from the same genus but a different species, “rhamnosus.”  Note that the genus is often shortened to one letter for space purposes, so that “Lactobacillus rhamnosus” becomes “L. rhamnosus.”

Think of it in automobile terms.  A “Jeep Cherokee” is from the genus “Jeep,” and species “Cherokee,” while a Jeep Wrangler is from the same genus “Jeep,” but a different species, “Wrangler.”

That’s a bare minimum. Ideally, a probiotic manufacturer will add a third identification, the “strain.”

A strain is essentially a variant of version of a microorganism. (Think a Jeep Cherokee “Limited” vs. a Jeep Cherokee “Trailhawk.”)  While still of the same genus and species, strains can behave very differently and provide entirely different benefits, at least to the extent they have been studied.

For example, Lactobacillus rhamnosus GR1 (genus, species, strain) is believed to be effective in dealing with women’s intimate health issues helping with thrush and bacterial vaginosis, while Lactobacillus rhamnosus LGG (a strain often featured in Culturelle formulations) is believed to be effective in addressing traveler’s diarrhea and diarrhea brought on by antibiotic use.

As you can imagine, if you are attempting to address a specific problem, you want to make sure you are using a strain that has been specifically identified as addressing that problem.

A caution regarding strains (and you’re going to like this one):

They can also be made-up marketing slogans.

The proprietary probiotic found in Activa yogurt is called “Bifidus regularis, which, according Justin and Erica Sonnenburg’s book, “The Good Gut,” is “the trade name given to their strain of Bifidobacterium animalis.”  And the exact same strain has a different name in the UK, where it is called “Bifidus digestivum.”

This is not necessarily a bad thing, but it is a confusing thing, and, I would argue, an unnecessarily silly thing. We will try to alert you to these gimmicks when we come across them.

When it comes to multiple-probiotic formulations taken for general health, it might be less important, although still desirable, to know which strains are used.  It really depends on how deep a dive you want to take into the minutia of probiotics, although that is in part what we are here for.

That said, more information is generally desirable, and the more transparent manufacturers will provide that information.

Speaking of multiple-probiotic formulations…

5) Multiple Species or Strains

Circling back to a concept we first introduced when discussing quantities and CFUs, is the desirability of using formulations that feature multiple species or strains (terms that are unfortunately used interchangeably in marketing).

As I alluded to earlier, when it comes to general health, taking many different kinds of organisms is potentially desirable.

The reality is, our individual microbiomes are very different, as distinct as fingerprints in fact, and we will respond differently to various probiotic formulations.  I personally take a kind of “everything-but-the-kitchen-sink” approach, and so am comfortable taking a wide variety of probiotics.

The best you can do is to monitor yourself with care, and if a particular formulation causes you discomfort (and you’d want to give it some time) or strikes you as completely useless, it would make sense to abandon it and perhaps try something else.

And it doesn’t matter if your neighbor or friend or sister swears by something. If it doesn’t work for you, it doesn’t work for you.

A quick word about the notion of “multiple species” and “multiple strains.”

If you want a true broad-spectrum probiotic, you’ll want multiple genera as well. Therefore, you don’t want just Lactobacillus rhamnosus GR1 and Lactobacillus rhamnosus LGG (different strains, same species, same genus) and you don’t want just Lactobacillus rhamnosus and Lactobacillus acidophilus (different species, same genus). You want Lactobacillus acidophilus, Bifidobacterium adolescentis, and for that matter, Streptococcus thermophilus.  Not just different species and strains, but different genera as well.

Finally, as mentioned earlier, a single-strain or species probiotic is desirable if you are attempting to address a specific problem for which that probiotic has been found to be helpful, or if you are assembling your own mix, that is, rather than relying on a maker to provide a formulation, you cobble together a number of single, or limited, formulations to create your own multi-probiotic mix.

I do that as well, as you will see in our “MicrobioME” section.

6) Supporting Research

It is helpful, although not always determinative, if a maker provides references to research supporting their various claims.

We are still in the very early stages of understanding the human microbiome and the web of relationships between ourselves and the microorganisms with which we share our bodies.

There are going to be false starts, there are going to be skeptics, and those skeptics will be right sometimes.  And sometimes wrong. There is going to be excessive hype and also astounding new discoveries that live up to the hype.

Ultimately it depends on the quality of the research which isn’t always obvious.  I’ll do my best at Microbiome Bulletin to sort through the research when available, note its type (in vitro (test tube), in vivo animal (in a living organism, usually mice) and in vivo human), how recent it was published, and so on, but you are encouraged to look into it yourself.  I will always welcome comments and am a big believer in crowd-sourcing knowledge.

7) Third-party Testing

Some makers will make available the tests they perform, or have performed by others, ensuring such things as quantity of CFUs, delivery integrity (whether say, a capsule intended to survive the acidic environment of the stomach will actually do so and to what extent), the absence of impurities and so on.

This is nice to have and is an extra level of transparency and I will always ask a company if they will make it available.

8) Other Ingredients

You will want to closely examine the “other ingredients” that make up the formulations beyond the probiotics themselves. You will find this below the “Supplements Facts” label.  Ideally you want to look out for anything artificial or anything you personally find objectionable (say, animal byproducts if you are vegan/vegetarian).

We will be preparing lists of “other ingredients” that are potentially problematic in the near future.

9) Allergens

Speaking of other ingredients, if you have any food allergies be sure to check the label for those as well, typically listed below the “Supplement Facts” label.

10) Survivability in the Gut

As mentioned above, the stomach is highly acidic and extremely unfriendly to microorganisms of all kinds. This is a feature and not a bug, as they say. This is your first line of defense against pathogens (microorganisms that mean you harm) but it is lethal to probiotics as well.

There are a number of approaches probiotic manufacturers take to ensure as many viable CFUs make it to your intestines as possible where the environs are much more friendly.  Encapsulation designed to survive the stomach and dissolve in the intestines or some other forms of coating (“enteric” being common) is one approach.

Simply providing a massive dose of probiotics understanding that only a few will survive is another, as is using formulations of probiotics believed to be particularly hardy and that can survive in fairly large numbers such as Lactobacillus plantarum and Lactobacillus rhamnosus.

Many of the probiotics found in yogurt survive the transit through the stomach not because they are coated but because they are ingested with the yogurt itself, a dairy product, which helps suppress stomach acid temporarily.

The main point is that there should be some discussion regarding how the maker expects a material amount of the probiotic to make it to the intestines alive.

11) Packaging

Most probiotics are packaged loose in a bottle or resealable pouch. When you first open the packaging, and each time thereafter, you expose the entire contents to air, light, humidity and other contaminants which can accelerate their degradation.

To address this, some powders are packaged in individual sachets and some pills come in blister packs.  This protects each pill or dose from the environment until you are ready to take it.  This can add to the costs of the product, but also the time period the probiotics are viable.

While the latter is desirable, if you take care in the storage of your probiotics (I keep mine in the basement except for those that need to be refrigerated), you can reduce the affect environmental exposure has on your product.

12) Reputation of The Company

I will forgive a fair number of omissions of important information (strain identification, CFUs at expiration, research disclosure, and other transparency issues) if I am comfortable with the reputation of the company. This is highly subjective and will be based on an even greater degree of opinion than other things you will see from me and therefore I will welcome your input on that (as with everything else of course).


Those are the 12 things I look for, and the ones we will be addressing in our reviews.

However, let me leave you with some bonus material:  A few things that you should NOT put too much stock in:

“Doctor Recommended” 

Whether or not some random member of the medical community prepared the formula is far less relevant than the items I’ve already outlined, such as supporting research, strain identification, and CFU guarantees.  It’s not a red flag, and I take probiotics that are both doctor and dentist recommended, but understand that it is marketing and you should treat it as such.

Hyperbolic Claims or “Guaranteed” Results

Given the different makeups of our individual microbiomes, results can never be guaranteed, and claims regarding quick relief or miracle cures should be taken with a great big bag of rock salt.  These are, if not red flags, surely yellow ones.

“Proprietary” Formulas

I mentioned this at the beginning, but it deserves another look.  When a maker does not want to tell you which strains they use in a formulation and/or the individual quantities of each, they usually claim it is “proprietary” and therefore a closely guarded secret. Some even use it as a marketing device, so as to lead the consumer to believe they are getting something special apart from other makers.

In a sense they are, at least if you like surprises, because you are basically purchasing a mystery box of probiotics.


I’ll point out again, that depending on the reputation of the maker, and my personal experience with them, I will often give them a pass on this (Life Extension is one such company).  But I definitely do not consider proprietary formulas to be of intrinsic benefit.  I’d just as soon know what it is I’m ingesting.

Before I let you go, one last thing.

Please note I did not mention anything about refrigeration. This is an area of some contention, but when it comes to caring for your probiotics, simply follow the instructions on the label. Most formulations are shelf stable. Some require refrigeration only after opening.  Given uncertain shipping conditions, I prefer probiotics be shelf stable at least prior to opening. Afterwards, I don’t mind keeping some in the refrigerator. If they are shelf stable throughout, a cool dry place is usually recommended.  (I typically keep mine in my basement.)

Thanks very much for stopping by!  Your comments and opinions are always welcome.  These are only mine and are intended to provide you with some additional things to think about as you form your own.

Take care!