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Guest Blog by Lynne V. McFarland, PhD

Choosing the best probiotic is not an easy task. There are over 250 different types of probiotic products found on the market (grocery stores, pharmacies, on-line websites, etc.), but relatively little guidance on how to choose one probiotic over another. As more research is done, the guidelines of how best to use probiotics continue to be updated.

This post is to help you choose a good probiotic for what you need-either to prevent you from getting a C. difficile infection after exposure to antibiotics or to prevent a recurrence of C. difficile infection after you have recovered.

Why should I consider using probiotics to prevent C. difficile? Probiotics are living microbes that are especially beneficial when the normally protective microbiome has been disrupted. C. difficile infections occur after your normal gut microbes have been disrupted, typically after you have been given antibiotics to treat an infection.

How does bacteria in my gut protect me?  Normally, the “good” bacteria in your gut protects you from disease-causing organisms.  In addition to digesting your food, your normal microbiome (all the different types of microbes in your gut) also form a protective barrier that repels disease microbes.  However, this protective barrier can be disrupted. Taking antibiotics is the major culprit in killing off your good microbes. Once this happens, disease-causing microbes use this opportunity to infect your gut.  You are now susceptible to infection.

Why doesn’t everyone who gets antibiotics come down with C. difficile? The type of antibiotic and other factors (age, other medications, other current diseases) can make you more or less likely to be infected with C. difficile.  But you also have to be exposed to C. difficile. Once exposed to C. difficile spores (either already in low numbers in your gut or from external sources like other patients or room surfaces in healthcare facilities), these inactive spores germinate (like seeds sprouting) and C. difficile infects your gut.  Once C. difficile sets up housekeeping in your gut, it produces toxins that cause inflammation and diarrhea.

How can probiotics help?  Some types of probiotics can reduce the inflammation caused by C. difficile, some can kill the C. difficile bacteria directly, some can prevent C. difficile from attaching to your gut surface and some can destroy the toxins that cause the diarrheal symptoms.  Only certain types of probiotics can be helpful in preventing C. difficile infection.

Aren’t all probiotics alike?  No. Recent research has found that how well a probiotic works is different by the type of disease it is being used for (called ‘disease-specificity’) and that the choice of probiotic strain is important (called ‘strain-specificity’).  Some types of probiotics are useful against C. difficile, while many are not effective.

How do I know what strain or strains are in a probiotic product?  The label on the probiotic product should list all the microbes (bacteria or yeasts) contained in that product. Each microbe has a three-part name: the genus (for example, Lactobacillus), the species (for example, acidophilus) and the strain (for example CL1285).  As an example, a border collie is scientifically named as: Canis (the genus) lupus (the species) familiaris (the strain).  Just as not all dogs are like collies, not all Lactobacilli are alike.

If it says ‘probiotics’ on the label, can I use this for C. difficile?  Not all the products found on pharmacy shelves fulfil the definition of probiotic. The World Health Organization defined probiotics as living organisms that have an adequate dose and show a health effect. This means the probiotic is alive (can be a bacteria or yeast), must have a good number of organisms (dose) and shows an effect on health. Typically, effectiveness is shown by doing a clinical trial.  Not all types of probiotic products on the market fulfill even these three simple requirements.

Why aren’t the labels more helpful in choosing a probiotic? In the United States, most probiotics are sold as ‘dietary supplements’ available over-the-counter and can only have health claims on their labels, which give no specific guidance on how to use the probiotic for a specific disease or illness.  Because dietary supplements do not go through the rigorous FDA approval process as do prescription medications, your physician is not the usual role of recommending your medication.  The choice is left open to you as an individual.  Dietary supplements, by law, can not claim to ‘treat’ or ‘cure’ a disease.

How should I choose an appropriate probiotic?  One way is find a scientific review that provides you guidance on which probiotics are best.  I have listed a few good practical guides below.

Five tips for choosing a probiotic.

Another way is to look for these five tips of what a good probiotic product should have on the label (see box).  If the probiotic doesn’t meet all five criteria, you should just put it back on the shelf and choose another probiotic.

  1. FDA Disclaimer. All dietary supplements (including probiotics) are required to have an FDA disclaimer on the label.  “FDA Disclaimer:  The FDA has not evaluated this claim. This product is not intended to cure, mitigate, treat, diagnose or prevent a disease.”  Does your product have this disclaimer? If not, put it back.
  2. Which strains? Does the label list each strain of bacteria or yeast that is present in the product?  Some products just say “A Probiotic”, but do not list which strain or strains are present.  If no listing of each strain is given, don’t buy it.
  3. Dose. Is the daily dose or concentration given on the label?  This is usually listed as “number of cfu” (colony-forming units or number of organisms).  The number of bacteria or yeasts should be at least 5 billion per day. If the probiotic gives no dose information, don’t buy it.
  4. Who made the probiotic?  A reliable manufacturing company should have a history of producing a high-quality product and is certified by the appropriate authority.  If there is no information on who made the product, you should be suspicious. Although not required by law, most reputable probiotics list a website or source for more information.  This can be helpful for you to see if there are good clinical trials that might support their claims for a health benefit.
  5. Health claim. Dietary supplements are allowed to make ‘structure or function claims’ by law.  Allowable health claims include “boosts your immune system” or “strengthens your intestinal function”.  If the product claims that it ‘cures cancer’ or ‘treats diseases’, don’t buy it.

Because of the current FDA regulations for dietary supplements, you should not find any probiotics in the US claiming to treat or cure C. difficile infections. However, in the future some probiotics may be granted permission to say this if they are approved by the FDA as a medication or medical food. Other countries have different regulations that also may allow them to state different claims for their probiotic.

How do I know which probiotics can be used to prevent a C. difficile infection? Fortunately, there is over 35 years of research done in different countries with clinical studies and randomized controlled trials that have shown which probiotic strains are effective for different types of diseases. In 2020, the American Association of Gastroenterology recommends four probiotics to prevent C. difficile infections after antibiotic exposure, but five others types of probiotics were not found to prevent C. difficile infections. Only two of the probiotics had multiple trials to support this claim:  Saccharomyces boulardii CNCM I-745 [Florastor®, Laboratories Biocodex] and a three-strain mixture of L. acidophilus CL1285 + L. casei LBC-80R + L. rhamnosus CLR2 [Bio-K+, Bio-K PLUS International].

When should I start taking the probiotic to prevent C. difficile infection?  The probiotic should be started as soon as possible after the antibiotic is started (best within 24 hours) and continued while you take your antibiotic course and then for at least 2 weeks after the antibiotic is stopped to allow your normal gut microbiome to be restored. This combination (giving probiotic with antibiotic) has been tried in over 10 hospitals and has reduced their overall hospital rates of C. difficile significantly with no apparent side-effects.

If I’ve already had at least one episode of C. difficile, are probiotics useful to prevent further recurrences of diarrhea?  About 1 of 5 people with one episode of C. difficile infection will develop at least one more episode (recurrence).  Two clinical trials have shown when S. boulardii CMCM I-745 is given along with standard antibiotics to treat C. difficile infections, the recurrence rate is significantly reduced, especially if a high dose (2 grams/day) of vancomycin is given.  The probiotic should be started at the same time of the vancomycin and continued for at least four weeks to allow the normal microbiome to become restored.

Are probiotics safe to take?  Evidence from carefully monitored clinical trials has not found serious adverse reactions or side-effects for the probiotics described above. Generally, probiotics have been safe to take, reflecting the long history of clinical and safety trials.  However, probiotics are generally not recommended for severely ill patients with central catheters.

To summarize, remember that just because a product says it is a ‘probiotic’, does not necessarily mean it is one.  Also, not all probiotics are effective for the same type of health effect, so it is important to link the type of probiotic with the health effect that you need.

Lynne V. McFarland, earned her PhD in Infectious Disease Epidemiology at the University of Washington in Seattle in 1988 documenting how C. difficile was spread in the hospital. Since then, she has continued her research in C. difficile and branched out into the field of probiotics. She has published over 160 articles in scientific journals, is on the editorial board of several journals and has reviewed papers on probiotics and C. difficile for over 50 journals. She also has co-authored two books on probiotics including “The Power of Probiotics by Gary Elmer, Lynne McFarland and Marc McFarland”. She worked as a scientist for the Veteran’s Administration and as an affiliate associate professor at U. Washington, Seattle. She currently is active with the Public Health Reserves Corps fighting the COVID pandemic.

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