Probiotics Efficacy Disputes

What Attorneys Need to Know About CFU Counts, Stability, and Label Claims in Pet Foods and Supplements

I was on a call last month with one of my client's attorney. We were discussing around their new dog probiotic product's IP rights. Smart guy. Knew the consumer protection statutes inside out. But when I asked him if he knows what CFU means, there was a pause. And that pause is exactly why I'm writing this.

Pet probiotic and "microbiome support" supplements are one of the fastest-growing categories in animal health right now. And with that growth? A sharp rise in class-action litigation alleging false advertising, breach of warranty, and product liability. The claims center on inaccurate CFU (colony-forming unit) counts, strain misidentification, stability failures, and unsubstantiated label claims like "gut health" or "immune support."

If you're litigating one of these cases or evaluating whether to take one... you need to understand the science! I don't mean you need to know the data at at PhD level. But you should know enough to see the big picture.

The CFU Problem: What the Label Says vs. Bottle Contains

CFU stands for colony-forming unit. It's the standard measurement for live, viable microorganisms in a probiotic product. When a pet supplement label says "500 million CFU per serving," that's a specific, quantifiable claim. And it's testable. But this is also where it gets a bit ugly.

Independent lab testing routinely shows products contain a fraction of what's claimed on the label. I'm not talking about minor shortfalls. In the Zesty Paws class action, independent testing of their Aller-Immune Bites found 72,000 CFU of lactobacillus per serving instead of the promised 250 million. That's less than one-thousandth of a percent of the stated amount. Not a rounding error. A complete failure.

The Trader Joe's probiotic case told a similar story, testing across 12 samples and three lots showed CFU counts ranging from 118 million to 8.7 billion, against a label claim of 30 billion per capsule. Best case scenario, the product delivered less than 30% of what it promised. So... Why does this happen? I'd say mostly because of common three reasons:

Overstating at manufacture. Some manufacturers test CFU at the time of production, stamp that number on the label, and never account for the die-off that occurs during shipping, storage, and shelf life. By the time the product reaches the consumer, the live count has plummeted. And think about the time by end of shelf-life.

Poor formulation and packaging. Probiotics are living organisms. They need protection from heat, moisture, oxygen, etc. Without proper encapsulation technology, barrier packaging, and moisture control, viability drops... really fast! A soft chew in a product bag with no desiccant in a warehouse in July - don't have a chance.

No end-of-shelf-life testing. This is the big one. A responsible manufacturer guarantees CFU at the end of shelf life, not at manufacture. The difference between those two numbers can be enormous! This difference is also mostly the entire basis of a false advertising claim.

Strain Identity: The Secret is Hidden in the Detail That Changes Everything

I tell everyone the same thing: the strain is the whole story - discuss with your supplier / manufacturer about the strain instead of only species or the genus.

Lactobacillus acidophilus sounds impressive on a label. But there are hundreds of strains of L. acidophilus, and they don't all do the same thing. Some have clinical evidence behind them. Some have none. A label that says "Lactobacillus acidophilus" without a strain designation (like La-14 or NCFM) is making a claim it cannot support with strain-specific clinical data (and yes - mostly not in italics - and I am extremely sensitive on that!).

If you ask why does this matter in litigation - my answer is: because attorneys encounter labels listing genus and species names without strain IDs and that isn't a minor packaging oversight. It makes it impossible to verify whether the organism in the product is the one that was actually studied in whatever clinical trial the manufacturer is citing. Makes everything more and more difficult! But yes... strain misidentification can happen. Some products don't even contain the species listed on the label, let alone the correct strain. Third-party genomic testing (16S rRNA sequencing or whole genome sequencing) can verify exactly what's in a product and compare it to what's claimed.

Stability (science) and Shelf-Life (manufacturing) in pet food and supplements

If you ask me what is the biggest issue of any probiotic product around the globe... The answer is stability! Live organisms are sensitive to temperature, humidity, and time. A product can leave the manufacturing facility with a healthy CFU count and arrive at the retailer with substantially fewer live organisms. Then it sits on a shelf or in a consumer's cabinet for months (if not years). The gold standard in the industry is an accelerated stability study, where the product is exposed to elevated temperature and humidity conditions to simulate long-term storage. Real-time stability testing over 12–24 months provides even stronger data. Both should confirm that the labeled CFU count holds through the expiration date.

But here's what I see in discovery, over and over: no stability data at all. Or stability data conducted under ideal conditions (refrigerated, sealed, low humidity) that don't reflect how the product is actually stored by consumers. Or stability testing on a different formulation than the one being sold.

When a manufacturer cites clinical studies conducted on a product with a different formulation (same brand name, different manufacturing process or bacterial source...) that's where things get legally interesting. The VSL#3 dispute is the textbook example.

The VSL#3 Case - A Nice Blueprint for Probiotic Formulation Litigation

If you're working in this space, you need to know the VSL#3 storyhttps://exegipharma.com/verdict-against-vsl3-probiotic-sellers/ and take it as a template. Professor Claudio De Simone invented a high-potency, eight-strain probiotic formula backed by over 70 human clinical trials. That formula was sold under the VSL#3 brand through licensing agreements. When De Simone left the company and those agreements ended, VSL Pharmaceuticals continued selling a product under the VSL#3 name, but with a different formulation made from different bacterial sources!

The problem? They kept marketing it using the clinical data from De Simone's original formula. A Maryland jury found this was false advertising under the Lanham Act and awarded over $18 million. The appeals court upheld the verdict. In April 2025, a federal judge certified 10 classes of consumers in the related RICO case.

De Simone's original formulation is now sold as Visbiome. The VSL#3 brand continues with its different formula. But for litigation purposes, the case established something critical: you cannot change a probiotic formulation and continue claiming the same clinical evidence. The clinical data belongs to the specific formulation that was tested, not to the brand name.

This principle applies directly to pet probiotics. If a manufacturer reformulates a product (like changes the bacterial source, manufacturing site, or production process), the existing clinical evidence may no longer apply. Thus - the same marketing or label claims should not be there after this change!

Label Claims and Regulatory Reality

For animal products, the regulatory landscape involves FDA-CVM (Center for Veterinary Medicine) and AAFCO (Association of American Feed Control Officials). Neither agency has a formal approval pathway for probiotic claims on pet food or supplements (we are working hard on that - I promise). What exists is a patchwork of guidance, enforcement discretion, and state-level feed laws.

AAFCO's Official Publication lists certain direct-fed microbial organisms that can be used in animal feed. But being on the AAFCO list doesn't authorize health claims, right? It tells us that the organism is recognized as a feed ingredient. So when a pet probiotic label says "supports digestive health" or "promotes immune function" or "microbiome support".... where's the substantiation? Thus, FDA-CVM has historically taken the position that structure/function claims for animal products need adequate scientific support. However I have to declare that the enforcement has been inconsistent.

Plaintiff attorneys! This gap is exactly where you are stepping in! State consumer protection statutes, unfair business practices laws, and the Lanham Act don't require FDA approval as a prerequisite for a false advertising claim. If the claim is misleading to a reasonable consumer and the manufacturer can't back it up with credible scientific evidence, it's actionable.

The Poppi Pattern: Human Probiotic Litigation Signals What's Coming for Pet Products

The $8.9 million Poppi prebiotic soda settlement is a preview of where pet probiotic litigation is heading.

Poppi marketed its sodas as "gut healthy" based on prebiotic fiber content. But each can contained only two grams of agave inulin (literally an amount which is too low to deliver meaningful gut health benefits according to the existing scientific literature). The class action alleged that consumers would need to drink more than four cans daily to see any real benefit, and the sugar content would offset whatever advantage the prebiotics provided. The settlement doesn't resolve the underlying science... but! It does confirm that courts and consumers are increasingly willing to challenge health claims on products that don't deliver what they promise.

Let me help you to translate that to pet probiotics now! If your case has a soft chew claiming "digestive support" with a probiotic blend that tests at less than 1% of stated CFU at purchase, The Poppi Playbook applies.

What a Qualified Expert Brings to These Cases

I've commercialized over 20 probiotic and microbial products across five continents. I've built regulatory dossiers for FDA-CVM, AAFCO, EU, and APAC markets. I was the professional to register probiotic feed additives (over ten strains) for dogs and ruminants in Turkey back in 2013, from scratch. I know how these products are supposed to be made, tested, and labeled because I've done it myself. That means I can evaluate manufacturing records and identify where the production process failed to protect viability in any litigation. I can also assess stability data and determine whether it supports the labeled shelf life, naturally. I can review third-party CFU and strain verification reports and explain what the numbers actually mean while examining the clinical literature cited in marketing materials and determining whether it supports the specific product being sold or whether (like VSL#3) the science belongs to a different formulation entirely.

And most importantly I can translate all of that into language a judge, jury, or mediator can follow - because as I always say: the science doesn't help if it is not understood. My job for two decades is to translate science into different languages for public, education, industry and courtrooms!

If you're evaluating a potential case involving pet probiotic or microbiome supplement claims, early involvement of a qualified expert can make the difference in merit assessment, discovery strategy, and settlement negotiations. The right expert doesn't just review the data since they know what questions to ask, which manufacturing records to request, and where the science is likely to break.

I'm your person on that matter! If you have questions, I'd love to hear from you.

With warmth,

Dr. Nihan Marun, DVM, PhD Microbiology Founder & Scientific Director, Sigma BioVet Sciences, LLC

PS: If you're a pet owner reading this and wondering about the probiotic you're giving your dog or cat... Look at the label. Does it list specific strain designations? Does it guarantee CFU at end of shelf life? If not... you might want to ask why (simply send an email to manufacturer and put that pressure on them!)