Walk into any pharmacy and you will find a wall of probiotic products, all promising the same vague benefit in different formats. Three quick checks cut through nearly all of it, and none of them require any science background. Probiotics also work alongside prebiotics, the fiber that feeds them, so it helps to know how the two differ.
What a probiotic is
A probiotic is a live microorganism, usually a type of bacteria, that gives you a real health benefit when you take enough of it. The key word is enough. For a probiotic to do anything, the bacteria must first survive the journey through your stomach acid into your gut and arrive in numbers large enough to make a real difference. Beyond that, real scientific evidence must exist behind that specific strain for your specific goal.
The strain name is everything
Every probiotic bacteria has three levels of identity, similar to a person having a family name, a given name, and a nickname. Take Lactobacillus rhamnosus GG as an example. Most labels only show the first two words, but the code at the end matters most. That code, GG in this case, is what researchers used in clinical trials, separating one studied strain from another within the same species. Research proving that GG relieves antibiotic-related diarrhea tells you nothing about a different Lactobacillus rhamnosus strain on the shelf next to it. Benefits are strain-specific and do not automatically transfer to similar-sounding products.[2]
A label that just says "Lactobacillus" or "probiotic blend" is giving you the family name only. Without the species and strain code, you have no way to know what research, if any, applies to it.
- Full strain name. Genus, species, and strain code. "Lactobacillus" alone is not enough.
- CFU guaranteed at expiry, not manufacture date. Live bacteria die in storage. A count guaranteed through the expiration date is the one that matters when you take it. For more on decoding the rest of the label, see how to read a probiotic label without getting lost.
- Evidence that matches your goal. A strain studied for diarrhea will not necessarily help bloating.
Which strain for which goal
- You are immunocompromised or seriously ill
- You are recovering from major surgery
- You are pregnant
What to do with this
Pull whatever probiotic is on your shelf and run it through the three-part check above. If it does not pass all three, now you know what to look for next time.
This content is for educational purposes only and is not a substitute for professional medical advice.
- NIH Office of Dietary Supplements, "Probiotics: Health Professional Fact Sheet." Read the fact sheet
- PubMed, "Towards a better understanding of Lactobacillus rhamnosus GG-host interactions." Read the study
