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  • Writer's pictureMarissa Mekelburg MS, RDN, CLT, HHP

What to Look For in a Probiotic? Your Ultimate Guide.

You’ve decided to start taking probiotics - But how do you choose?

The supplement aisle can be overwhelming and you’re wondering “What do I look for in a probiotic?”. If you’ve been reading my blog this year, you know we’ve been talking about probiotics a LOT! To find out more about what probiotics are, read my blog post Probiotics 101: What Are They and Do You Need Supplements?

I’m going to break down everything you need to know when looking for a probiotic, so you can be confident you are making the right choice.

If you are new here: Welcome! I’m Marissa, a digestive health registered dietitian specializing in IBS, food sensitivities, and autoimmune conditions. I help clients improve their GI symptoms with food and lifestyle programs using functional nutrition and a food-as-medicine approach.

Probiotics are classified as supplements which means they are not regulated by the Food and Drug Administration (FDA). This means that manufacturers can put anything into the supplement and claim that it will help a specific condition.

I’m going to teach you the detective skills you need to be sure you’re making a good choice. Grab your magnifying glass and we’ll start this investigation by looking for supplements that are third-party reviewed.

 A woman sitting on a couch reading a book.

Photo by Daily Nouri on Unsplash

Third-Party Reviewed

Even though your probiotic isn’t regulated by the FDA, there are several organizations that test supplements to ensure they have the ingredients they claim to have, and do not have harmful contaminants (1).

Organizations that offer this testing include:


  • NSF International

  • U.S. Pharmacopeia

Supplements that pass the testing will have a seal of quality assurance displayed on the label.

Once you’ve found a brand of probiotics that has been tested (and passed) for quality, you can start looking for the correct strain. Let’s dive in!


When it comes to probiotics, there isn’t just one kind that you need. Each type of bacteria contributes differently to help your body function well.

Think about your microbiome like an orchestra. You need to have the right number of flutes, violins, cellos, and french horns to make the music balanced and sound the best.

If you are taking probiotics to treat a specific condition, you need to know what kind of probiotics have been researched to improve that condition. Using our orchestra example, it won’t help to improve your IBS if you are taking a supplement of french horns if flutes are the type of bacteria shown to improve IBS.

Probiotic names have three parts: the genus, species, and strain designation. You need to have all 3 parts of the name to be sure you have a match. Just like mailing a letter - you need to have the right house number, street name, and zip code to have your letter get to the right destination.

Let’s look at an example:

Bifidobacterium bifidum MIMBb75 is a bacteria that has been shown to help with symptoms of IBS (2). In this case, Bifidobacterium is the genus, bifidum is the species and MIMBb75 is the strain.

Let’s circle back to our orchestra. If you take a supplement with flutes to improve your IBS, you are helping to increase the number of flutes you have… If you continue to take a supplement with only flutes, eventually your orchestra will have too many flutes and not enough violins, french horns, or cellos.

For this reason, I recommend rotating strains of probiotics every 2-3 months. This can be as easy as changing from a 7-strain probiotic to one that has 10 or 14 strains. You can also change from taking a lactobacillus and bifidobacterium strain to taking one that is more spore based.

Once you’ve found the correct strain of probiotics, you need to make sure you are taking the right amount. The next clue we’re going to investigate is how to find the right dose.


Probiotics are measured in colony-forming units or CFUs. This tells you the number of active bacterial cells you are getting in each dose.

Maintenance doses of probiotics can range from 1 billion to 5 billion CFU. If you are looking to address a specific condition, you may need as much as 20 billion to 50 billion CFU.

The label should list the number of CFU for each strain of probiotic in the supplement. Example for supplement XYZ (using the orchestra example again):

  • Flutes 50 billion CFU

  • Violins 10 billion CFU

  • Clarinets 10 billion CFU

If you want to improve a specific symptom, you will also want to research how many CFUs and what specific strain is needed to treat the condition. This is where a health professional familiar with the use of probiotics – that’s me! – can be helpful.

The last important part of our dosage investigation is how the CFU is listed. The number of active bacteria in supplements declines over time. Make sure the CFU is listed as “prior to the end of shelf life” instead of “at time of manufacture.” You want a guarantee that the amount listed is what you’re actually getting.

Now you know the strain and dose that you want. You’re ready to make your purchase! But there is another important clue to look at before you bring them home. How should you store them? Even more importantly - how are they stored in the store? Here’s a hint - You might need to be looking in the refrigerated section.

Keep reading for the full scoop!

An overhead view of several members of a symphony orchestra playing music.


The most common type of probiotics are lactobacillus and bifidobacterium combinations. Heat can kill these traditional probiotics and you will need to keep them in the fridge. This means they should also be refrigerated at the store where you purchase them.

Spore-based probiotics are different and only become active when they reach your GI tract. They do not need to be refrigerated during storage.

You can tell if a probiotic is spore-based because it will begin with “Bacillus” (for example Bacillus Indicus). Spore-based probiotics have been shown to help reduce serum triglycerides and help with inflammation (3).

If traditional probiotics are all instruments in an orchestra, spore-based probiotics are like members of a band. Both types help to create balanced music, but the instruments and the way they operate are a bit different.

The final piece of our investigation is the best before date - And does it matter? Let’s take a look!

Best Before

So you checked your cabinet (ahem, I mean the fridge) and found a bottle of probiotics from last year - Can you still take them?

The CFUs in probiotics decline over time. If you use the product past the “use by'' or “best before” date, you will not be getting the listed dosage.

It isn’t harmful to take the supplements past the best-before date, but you will not be getting the full benefit from taking them. This is especially important if you are trying to improve a specific condition with a targeted dose.

That wraps up our investigation. Congratulations! You are now an official probiotics label detective.

Keep reading for my pro tips on how to get the most out of your supplement.

Pro Tips

You’ve spent your hard-earned money on probiotic supplements, so let’s discuss what you can do to get the full benefit of taking them.

Help the Bacteria Survive

The truth is, not all the bacteria in the supplement are going to reach your intestine.

Once you swallow the capsule, the probiotics must make their way through the harsh conditions in your body to successfully reach their final destination. Think about stomach acid followed by digestive enzymes.

Traditional lactobacillus/bifidobacterium probiotics are vulnerable and it’s more difficult for them to make it through your digestive obstacle course. Delayed-release capsules increase the chances that the bacteria will make it to your gut to live happily ever after.

Spore-based varieties (remember our band?) are dormant until they reach your GI tract. This means they are able to tolerate the harsh conditions in your body and more of the bacteria will be successful on their journey to your large intestine.

Taking your probiotic with food will also help to reduce the acidic conditions in your stomach. Should you take your probiotic with your morning meal or in the evening? Take a look at my next pro tip to find out!

Take Them at The Right Time of Day

Starting probiotic supplements can cause some mild side effects in the beginning. The most common complaints are changes in your bowel habits including gas and bloating. This is OK and a sign that the supplement is working! Over time your body will adjust and the side effects will go away.

Taking your probiotic in the evening will make these symptoms less noticeable. On the flip side, some people report feeling less rested and having vivid dreams. In this case, you might need to change and take your supplement earlier in the day.

Let’s shift the conversation more towards food - and I’m not talking about food for you but rather food for your microbiome. Prebiotics are just as important as probiotics for you and your bacteria. Let’s take a look!

Prebiotics and Fiber

Prebiotics are a source of food for probiotics. Including prebiotics in your diet from food or supplements means that the good bacteria will have the best chance of surviving in your body.

Food sources of prebiotics include (4):

  • Whole oats

  • Wheat bran

  • Apples

  • Asparagus

  • Onions, garlic, and leeks

  • Flax Seeds

  • Barley

  • Bananas

  • Dandelion greens

Prebiotics in the form of inulin are also added to some probiotic supplements. This helps the bacteria grow once it reaches your digestive tract. Imagine showing up at your Mom’s house after a long journey and she has a nice home-cooked meal already on the table. Sounds inviting doesn’t it?

Sources of prebiotic fiber are often classified as high-FODMAP foods. If you need to follow a low FODMAP diet, you may not tolerate probiotics with added inulin.

Food as medicine is my first-line approach and you may be wondering if you can just get your probiotics from food and ditch the supplements altogether.

For many people focusing on adding probiotic foods can make a difference. In the next section, we’ll discuss the pros and cons of using food vs. supplements.

A single-serving glass dish with a yogurt parfait layered inside.

Photo by Niclas Illg on Unsplash

Food vs. Supplements?

This is a question I get asked a lot by my clients. Is there a benefit to taking supplements or can I get the same benefit from food?

As a food-first dietitian, I always recommend starting with food when possible. Probiotics are naturally found in fermented foods including (5):

  • Yogurt

  • Kimchi

  • Tempeh

  • Sauerkraut

  • Sourdough bread

  • Pickles

  • Miso

  • Some cheeses that have been aged but not heat processed like swiss, provolone, gouda, and cheddar (6)

In some cases though, using a supplement may be a better option. Supplements allow you to be more targeted with the strain of probiotics you are taking which can help when treating specific conditions. Other benefits of supplements include:

  • Increased diversity of bacterial strains

  • Accommodating food allergies and sensitivities like wheat, dairy, soy, or gluten

  • Can be used when food sources are not tolerated

Correcting an imbalance of bacteria in your body is not as simple as just adding a supplement. Many lifestyle habits common in North America make it difficult for good bacteria to survive inside your body.

It’s important to ask yourself - What contributed to developing the imbalance?

The population of bacteria living in your body can be affected by lifestyle habits including:

  • Stress levels

  • Sleep habits

  • Processed foods high in sugar and added fat

Combining daily food sources of probiotics with a variety of whole foods including vegetables, fruit, and whole grains will help to keep the probiotics growing and happy inside your body.

As a digestive health dietitian, I love seeing how improvements in GI health can positively impact all areas of life. But just like with any supplement, they are not safe for everyone. Keep reading to find out if probiotics are safe for you.

Can Everyone Take Probiotics?

There is never a one-size-fits-all recommendation when it comes to health and probiotics are no exception. Probiotics are not recommended in these situations:

  • Anyone who has a compromised immune system (i.e. critical illness, chemotherapy)

  • GI infections like SIBO

  • Pregnant women

  • Infants

If you are unsure if probiotics are the right choice for you, consult with a healthcare professional or your physician before starting any supplements.

Key Takeaways

Just like any supplement, probiotics are not regulated by the FDA. This means that you need to do your research and know what you’re looking for when you go to the store. The probiotics you choose should be reviewed for safety and efficacy. You should also be checking the label for the strains, dosage (measured in CFU), best-before date, and how the probiotics are stored.

You can also get probiotics from food sources like yogurt, sauerkraut, tempeh, miso, kimchi, and sourdough bread. Including both probiotics and prebiotics in your diet will help to keep your microbiome balanced.

If you want personalized diet and lifestyle recommendations that will help to improve your digestive health - I am here to help! Use this link to get started with me. Life is busy and I can help you do the investigative work to make sure you’re getting the right strain and dose of probiotics to help you feel better.


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