Everything You Ever Wanted To Know About Choosing A Good Probiotic

Board-Certified Internist By Vincent M. Pedre, M.D.
Board-Certified Internist
Dr. Vincent M. Pedre is a board-certified internist in private practice in New York City since 2004. He serves as medical director of Pedre Integrative Health, president of Dr. Pedre Wellness, and is the author of Happy Gut.

Photo by Tatjana Zlatkovic

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Many patients arrive in my office with gut imbalances that manifest in all sorts of ways, including weight gain, chronic inflammatory diseases, fatigue, and skin conditions like eczema.

These gut imbalances result from numerous culprits. Chief among them are chronic stress, a high-sugar processed-foods diet, other dietary extremes, certain diseases, and specific gut insults, including unfavorable bacterial infections, parasites, and yeast.

Antibiotics are also a major contributor to gut imbalances. Many of us have been overprescribed antibiotics by well-meaning, conventional doctors from childhood onward. Antibiotic use as a solution for every infection is ingrained in our culture. Every time you take an antibiotic throughout your life, you disrupt your gut flora for up to 12 months.

When I say gut flora, I’m talking about the over 500 different species—trillions of microorganisms altogether—residing in your gut, whose delicate balance influences gut function, your metabolism, hormone balance, and overall health.

As the best-selling author of Happy Gut and a medical doctor who specializes in gut health and once suffered from IBS (irritable bowel syndrome), I have experienced for myself, as well as see on a daily basis, how a disrupted gut flora opens the door for unfriendly microbes to step in and take over, creating all sorts of pandemonium that causes patients to gain weight, feel sick and tired, and become more disease-prone.

Those problems aren’t as far-reaching as they might seem when you consider how much of your health begins in your gut. An out-of-whack gut can result in allergies, autoimmunity, weight gain, acne, skin rashes, yeast infections, hormonal imbalances, fatigue, depression and even accentuate the way you sense pain.

One way I help restore a patient’s gut to balance is with "probiotics." The term, derived from Latin, means "for life."

Among their numerous health benefits, research shows these friendly microorganisms help prevent bowel diseases, improve your immune system, reduce traveler’s diarrhea, help you maintain a healthy weight, heal various skin conditions, improve bloating and other uncomfortable GI symptoms, and even boost your mood, helping to reduce the effects of anxiety and depression.

Think of probiotics as your little helpers that restore order and help maintain harmony in your gut ecosystem. They outnumber and antagonize unwelcome pathogens, including unfavorable bacteria, yeast, and parasites.

Probiotic bacteria actually compete against unfriendly flora for bacterial binding sites on the inside lining of your intestines, further protecting you from these harmful pathogens. One way to repopulate your gut with probiotics to restore harmony and get all their many benefits is with the right foods, which can support the growth and proliferation of good bacteria that crowd out the bad ones.

These include cultured foods (such as yogurts or kefir); fermented foods like sauerkraut, miso, pickled vegetables, and kimchi; as well as cultured beverages, like kombucha, containing favorable live bacteria.

On my recent trip to Japan, one thing I noticed was the inclusion of pickled vegetables in almost every traditional Japanese meal. Unfortunately, many Americans don’t consume enough of these probiotic-rich foods and drinks. Even when they do, restoring equilibrium oftentimes requires therapeutic doses of these microorganisms, because most everyone has been on several rounds of antimicrobials. That’s where a probiotic supplement comes in.

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Bifido-what!? Understanding probiotic species.

You’ll find probiotic supplements containing freeze-dried bacteria in powders, tablets, and capsules. That’s the easy part: Turn the label around and you’ll see a list of unpronounceable ingredients. Many of my patients say choosing the right probiotic can feel baffling.

While there are endless species of beneficial bacteria, the ones you’ll most commonly find in probiotic supplements are Lactobacillus, Bifidobacterium, and Saccharomyces boulardii (which is actually a favorable, non-colonizing yeast, not bacteria).

Among these strains are specific species. Lactobacillus, for instance, includes the species L. acidophilus, L. rhamnosus, L. bulgaricus, L. reuteri, and L. casei. The most common Bifidobacterium species include B. animalis, B. infanti, B. lactis, and B. longum.

Let’s look at the benefits of these three groups—Lactobacillus, Bifidobacterium, and Saccharomyces—yemore closely:

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Lactobacillus predominantly live in your small bowel (the portion of your gut that follows the stomach). Probiotics containing Lactobacillus sp. help to repopulate the small intestine with friendly organisms that aid in supporting digestion and immune function. The most beneficial are L. acidophilus, L. plantarum, and L. paracasei. One study found Lactobacillus acidophilus could reduce gut inflammation. L. rhamnosus helps increase GABA expression (an inhibitory neurotransmitter that helps you feel relaxed) in the brain, resulting in lower anxiety and depression-related behavior. Another found that a combination of Lactobacillus and Bifidobacteria (which we'll talk about next) improved symptoms of bloating in patients with functional bowel disorders, and yet another found that when people took the Lactobacillus rhamnosus GG strain, it significantly reduced the risk for antibiotic-associated diarrhea.


The Bifidobacteria (Bifidus) predominantly live in your colon or large intestine. They produce the very important short-chain fatty acid butyrate, which supplies energy to your colon cells to keep them functioning optimally. But butyrate also gets absorbed by the body, regulating a variety of metabolic processes, including your sensitivity to the hormone insulin (which regulates blood sugar) and even memory formation in the brain. The most beneficial of these are B. lactis and B. longum. Research shows the benefits for Bifidobacteria include reducing inflammatory bowel disease and several cancers, especially colon cancer. Another study showed that a specific strain of Bifidobacterium lactis helped control body fat mass and reduced waist circumference and food intake.

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Saccharomyces is a friendly yeast that can be given concomitantly with antibiotics, in order to protect the gut lining from the effects of antibiotic-induced dysbiosis leading to leaky gut syndrome. S. boulardii can also outcompete other unfriendly yeast that may be cohabitating in the gut.

If that sounds confusing, don’t worry. With these three strategies, you don’t need to remember those names to choose the right probiotic.

How to tell if probiotics are high-quality.

I like a bargain as much as anyone, but buying a probiotic supplement is something you don’t want to skimp on. Warehouse stores are great to buy paper towels and grass-fed beef in bulk, but those mega-containers of probiotics are hardly the great deal they might seem.

Quality matters for any supplement, and that goes triple for probiotics. Many commercial brands lack the technology to identify specific strains and how much of that strain each dose contains. That could mean you get an ineffective or potentially harmful dose. It's a great sign if the company is using strains that have been used specifically in clinical trials at a dose similar to or the same as that used in the study. This is one of the only ways to guarantee a probiotic's clinical effectiveness.

And even then, with probiotics, it's all about survival. These delicate microorganisms must survive several obstacles: The manufacturing process, shelf life, and (once you take them) the acid in your stomach environment to reach your intestines, where they do their job.

Keep in mind that when supplements contain a specific number of organisms, this number may not be what is actually within each capsule at the time of purchase. Probiotics are living organisms and can die out easily. Especially if that supplement sits on your drugstore or warehouse shelf for months or longer, the number of organisms you get may be far less than what the bottle claims. Hardier strains have a longer shelf life. Capsule strength decays faster if the probiotic has been sitting around at elevated temperatures during transport to the store. Companies actually have to produce probiotics with a much higher CFU (colony-forming units; see below) count in each capsule in order to guarantee the label potency by the expiration date.

Unfortunately, many commercial brands don’t measure up. They are unstable in stomach acid. Quality control measures aren’t intact, including ensuring supplements have been handled correctly and maintain their freshness. Moisture slipping into probiotic supplements can reduce their efficacy. Companies that use bioshield capsules produce higher quality probiotic supplements that are able to endure the stomach acid, releasing their contents within the small intestine, where a more alkaline environment ensures the survival of the bacteria.

To avoid those and other problems, I strongly recommend buying a professional brand from a reputable health care professional or other vendor who stands by their products and undergoes third-party testing. Some of these professional brands have created advanced technology that preserves a probiotic supplement’s survival on the shelf and in your gut.

Photo: Alita Ong

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How to know which probiotics to buy.

If you do choose a commercial probiotic supplement, or if you’re curious about the brand your health care professional recommends or sells, here are some things to consider:

Billions is better.

Millions sounds like a lot, but not with probiotic supplements. You want one that contains billions of organisms. A probiotic dose will range from 5 to 100 billion colony-forming units (CFUs), the measure used to express its potency. Start low and increase as tolerated.

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Diversity is your best friend.

Your gut is diverse, so your probiotic should be too. Look for a supplement that contains multiple strains, sometimes listed as a proprietary blend. Inferior brands might only contain one probiotic strain such as Lactobacillus acidophilus. Aside from Lactobacillus and Bifidobacterium strains, probiotics may contain Strep. thermophilus and Saccharomyces boulardii, among others.

Go for dairy-free.

Ideally, look for a dairy-free probiotic supplement that contains at least 15 billion CFUs each of Lactobacillus and Bifidobacterium strains (a total of 30 billion CFUs) guaranteed by the manufacturer through the expiration date.

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Watch out for binders and fillers.

Read the other ingredients on the label. Some commercial probiotic supplements contain undesirable binders and fillers, including lactose or cornstarch that may cause a reaction, like gas and bloating, if you are sensitive to these ingredients.

Make sure your probiotics don't go bad.

Always look at the expiration date, after which the potency on the bottle can no longer be guaranteed. Some, but not all, probiotics require refrigeration. The label should tell you specifically whether or not to refrigerate.

How to find the right probiotic dose.

If you’re most interested in taking a probiotic supplement for overall gut health, I suggest starting with 30 to 50 billion CFUs. Take probiotics on an empty stomach once or twice a day for at least three months. After that time, reassess and decide if the benefits warrant continuing a maintenance dose of the probiotic supplement. However, if you have SIBO, beware of starting a probiotic too soon after your treatment. In this case, it’s best to work with a health practitioner on which probiotic is right for each stage of the treatment.

The sicker your gut is—in other words, the more imbalanced it is—the higher the probiotic dose that will be required to create a positive effect. If you have a leaky gut or inflammatory bowel disease (such as Crohn’s or ulcerative colitis), for instance, you may need to take up to a total of 200 to 400 billion CFUs daily.

To determine how specific strains can benefit your condition or to utilize higher doses, I strongly suggest working with a functional medicine doctor or other qualified health care professional.

Potential side effects of probiotics.

You'll be happy to know that generally, probiotics cause no significant side effects, other than the intended improvement in your gut health. However, probiotics can be tricky. Not every probiotic is right for each person. Sometimes it's about finding the right fit. For example, signs that a probiotic may not be right for you include:

  • Bloating after taking it
  • Constipation or diarrhea that resolve when you stop it
  • Anxiety or irritability that increase when you take the probiotic

If this happens, it's time to consider switching to a new probiotic. Other reasons a probiotic may not be the right fit: SIBO or Candida. If you have either of these conditions, the strain of the probiotic could potentially make your symptoms worse. Remember, if you think a probiotic is not helping, seek the advice of a functional medicine provider to help you navigate the choices out there.

Want to do more for your gut health? This is the best diet to follow.

Vincent M. Pedre, M.D.
Vincent M. Pedre, M.D.
Vincent M. Pedre, M.D., medical director of Pedre Integrative Health and president of Dr. Pedre...
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