6 Things to Look for in a Probiotic

In the face of varying marketing messages, shopping for a probiotic can be overwhelming. Some companies champion products with high CFU (colony-forming units, which is the measurement of groups of living microorganisms observed under the microscope), while others showcase products with dozens of strains. With more product options than ever, it is important to know what to look for when selecting a probiotic.

So what is a probiotic?

Scientists define a probiotic as the following: “Live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.”1,2

Based on that definition, how do you find the probiotic you need? Here is a checklist of six things to look for:

  1. Personalization—What health benefits do you need?
  • Different probiotics can support your health in varied ways. Some probiotics specialize in aiding digestion, while others may support vaginal health.3 Consider the benefits you need, or your healthcare practitioner may identify them for you (e.g., which probiotic to take while on antibiotics).  Just remember—not all animals make great pets.
  1. Science—Clinically studied to demonstrate health benefits
  • Just as with anything you might take, you want to know more about probiotics’ proven safety and efficacy. Until a strain or strain blend has been studied, no one can say for sure how it will affect those who consume it. For safety’s sake, avoid buying probiotic-labeled products without scientific support for their usage.
  • Also consider the many clinical studies that demonstrate the benefits of single strains of probiotics, with specifically identified probiotics showing the ability to support the immune system or gastrointestinal health.4
  • Clinical studies differ in their design, methods, population characteristics, and results—which is why an expert review of the literature can help determine the recommended probiotic for your needs.
  1. Identity—Genus, species, and strain
  • Not all probiotics are created equal. Most “probiotics” sold by companies today are only designated in terms of genus and species (e.g., Lactobacillus acidophilus or Bifidobacterium lactis). However, there is something crucial not being disclosed: the strain. Probiotics are known by their genus, species, and strain (e.g., Lactobacillus acidophilus NCFM®). It would be overgeneralizing to say that all lactobacilli can deliver a benefit for people, but specific lactobacilli strains can be linked to real benefits. Keep in mind that bacteria can carry a name drawn out to genus, species, and strain, but without science to show their true benefit for a person, they can only be simply classified as bacteria. Be sure that your supplement contains probiotics that are strain-identified and clinically studied (such as Lactobacillus acidophilus NCFM® or Bifidobacterium lactis Bi-07).5
  1. Amounts matter—Billions are not always better
  • More is not always better when it comes to probiotics. The serving size recommended for a probiotic should be the clinically effective amount. For example, if a study showed benefits related to a probiotic provided at 10 billion CFU, that probiotic product should contain 10 billion CFU of that strain—no more and no less. An amount without scientific support but with claims of benefit should be considered questionable at best.
  • No two probiotic strains are identical, and no single amount has been defined as ideal, so any product claiming to work as a “one-size-fits-all” solution should provoke skepticism. It would be easy to look for a probiotic that contains “at least this many CFU,” but remember that not every probiotic needs to be administered in the same amount.
  1. Alive through expiration
  • Arguably the most important thing to look for when selecting a probiotic is a guarantee that the microbes in the product remain viable through a listed expiration date. Labeling for a given amount of probiotics only at time of manufacture should be a red flag. Probiotics may die over time and  lacking a potency guarantee through expiration can result in a far less CFU consumption than the label suggests. Look for products that have potency guaranteed through expiration so you can be sure that you are getting at least as many CFU as the label claims.
  • Probiotics are also very sensitive to heat, light, and moisture and must be protected against the elements. Desiccants (those little packets in the bottle) help reduce moisture, while bottles themselves provide barriers to moisture as well as light and heat. Multiple options such as amber glass bottles or desiccant-lined CSP bottles can be used for packaging probiotics. However, just because a specific packaging is touted to protect the probiotics inside does not mean that the product is stable under specific conditions. Stability studies must be conducted to ensure that the product will remain viable after exposure to extreme temperatures and varying humidity. Check the label for appropriate storage conditions and store accordingly.6
  1. Manufacturing quality/testing for contaminants and purity
  • Some probiotic products have also been found to contain specific contaminants (mold, yeast, and potentially harmful bacteria or even fungi) or food allergens (gluten, dairy, etc.), which may cause negative reactions or adverse health effects in susceptible individuals. Dig deeper into the type(s) of testing that the company selling your probiotic does to protect your health.
  • Experience the benefits of probiotics by choosing a quality formula that will deliver health benefits through, and up to, expiration. Look for a probiotic from a reputable company that carries Good Manufacturing Practice certification (GMP) as your assurance that it meets, or exceeds, third-party quality standards. Talk to your healthcare practitioner today about whether there is a probiotic that fits your needs and satisfies these criteria.


  1. Sanders ME. Probiotics. ISAPP. Available at: https://isappscience.org/probiotics. Accessed March 15, 2019.
  2. Hill C et al. Natur Revs Gastro Hepatol. 2014;11(8):506—514.
  3. Sanders M. Probiotics. International Scientific Association for Probiotics and Prebiotics. Available at: https://isappscience.org/probiotics. Accessed March 28, 2019.
  4. WGO Review Team. World Gastroenterology Organisation Global Guidelines. 2017. Available at: http://www.worldgastroenterology.org/UserFiles/file/guidelines/probiotics-and-prebiotics-english-2017.pdf. Accessed March 15, 2019.
  5. Probiotics: A Consumer Guide For Making Smart Choices. Available at: https://isappscience.org/probiotics. Accessed March 28, 2019.
  6. Best Practices Guidelines for Probiotics. Council For Responsible Nutrition. Available at: https://www.crnusa.org/self-regulation/voluntary-guidelines-best-practices/best-practices-guidelines-probiotics. Accessed March 28, 2019.

Submitted by the Metagenics Marketing Team

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