how to read a probiotic label

Why do some labels say “mg” (milligrams) and others have also included “CFU” (colony forming units) - what are these and why these two measurements?
Milligrams are a measurement of weight, while colony forming units tells you the quantity of bacteria present. For example, if I tell you I will sell you 1 pound of marbles, you will know the weight, but not the number of marbles in the bag (as depending on the size, this number will vary). If I tell you I will sell you 100 marbles, you will know the precise number of marbles you are purchasing.

Currently, the Food and Drug Administration (FDA) requires almost all ingredients in dietary supplements to be listed by weight (mg). Milligrams tells you the weight of the bacteria contained in the product, but this measurement is not meaningful because the number of bacteria (CFU) can vary greatly and do not correlate with weight. On the other hand, colony forming units measures the total number of cells and tells you exactly how much bacteria is in the product. In practicality, this means that when comparing a product with a higher amount of milligrams per serving, it’s important to note that it could actually have a lower CFU count. To allow for more transparency with consumers, in 2018 the FDA allowed companies to add colony forming units to their labels as well.

Product quality and Clean Label Transparency:

Why do some products have the bacteria labeled with 2 names and others with 3?

When reading a bacterial name there are three components:





The genus is a very broad category that has hundreds of species within it. When labeling the species, it narrows it down to one species, but even within that species, there are numerous strains. When labeling to the strain level, it tells you exactly what bacteria is in the product. This is important, as each strain is genetically unique and the benefits of one strain may be very different than those of a similar sounding strain. When you see a product not labeled to the strain level, you cannot be sure what is actually in the product. An analogy would be if someone told you he would sell you a Toyota Rav-4 but not tell you the exact model, would you buy it? Of course not, as the models vary from each other, and you need to know exactly what you are buying (and be able to determine the value). Probiotics are the same, without the strain designation, you do not know exactly what you are getting in each bottle. 

Why do some products say “at time of manufacture” and others do not?
Unlike many other dietary supplements, probiotics are living bacteria. Being that they are alive, some strains do not survive the entirety of the product’s shelf life. Some manufacturers only guarantee counts when the product is first made (at time of manufacture), but as a consumer, you have no idea how many will still be alive when you reach the end of shelf life. Quality products will guarantee their counts throughout the entire shelf life of the product, ensuring the consumers will get an effective amount, even on the last day of shelf life. 

In summary. In order to identify high quality products that you can confidently say yes to, look for labels that show:

  1. CFU in addition to mg
  2. Genus, species and strain
  3. Guaranteed CFU throughout the entirety of shelf life



Article by Dr. David Keller, DPM, MBA • July 5, 2019

David is Nouri’s Leader of Research and the former VP of Scientific Operations at Ganeden. Dr. Keller has over 15 years of experience in the probiotic industry and has published 27 papers related to his research of probiotics. He led a joint task force between the IPA (International Probiotic Association) and CRN (Council for Responsible Nutrition) to create labeling guidelines for probiotic supplements.


Written by Caroline Beckman
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