Probiotics: a Waste of Money?! When Do They Help and When Are You Just Paying for a Pretty Jar?

These days, probiotics are recommended for almost everything. Dog has diarrhea? Probiotic. Had antibiotics? Probiotic. Gas? Probiotic. Sensitive stomach? Probiotic. Stress? Probiotic again.

And on the pet-store shelf, jars stand side by side: one promises one billion, another ten billion, and a third contains such a bacterial army that the packaging makes it look as if the product with the biggest number simply wins.

But does it? Not necessarily.

A probiotic can be a very useful tool. It can also be a completely unnecessary expense.

The issue is not whether probiotics “work” or “do not work”. The issue is that the word probiotic does not describe one substance with one specific effect.

It is a little like saying “medicine”. Which medicine? For what? At what dose? For whom?

Exactly the same questions apply to probiotics.

Waste of money #1: the label does not tell you which strain is actually in the product

The effect of a probiotic can be strain-specific. That means the bacterial species name alone may not be enough. If a study used one specific strain of Lactobacillus or Bifidobacterium, the result cannot automatically be applied to every bacterium belonging to the same species.

For example, one controlled study in dogs used a specific combination of three canine-derived Lactobacillus strains and observed normalization of stool consistency in dogs with acute diarrhea.

That demonstrates the effect of that particular combination in that particular situation. It does not demonstrate that “Lactobacillus helps with diarrhea.”

So one of the first things I ask when I look at a label is: does the manufacturer list only the bacterial species, or the specific strain as well? The more precise the information, the better our chance of judging whether there is any meaningful evidence behind the product.

Waste of money #2: choosing the product with the biggest CFU number

10 billion. 50 billion. 100 billion.

From a marketing perspective, that looks impressive. From a biological perspective, not necessarily. CFU, or colony-forming units, tells us about the number of viable microorganisms. And that does matter. But a large number alone does not tell us:

• whether the strain is appropriate;
• whether it has been studied in dogs;
• whether it has been studied for this particular problem;
• at what dose an effect was found in the study;
• whether the dog actually receives that amount.

One hundred billion random microorganisms are not automatically better than a much smaller amount of one well-studied strain. A probiotic is not an auction where the highest number wins.

Waste of money #3: the promised bacterial count existed only at the time of manufacture

By definition, a probiotic must contain live microorganisms. So it is not enough to know how many CFU were in the capsule on the day it left the factory. What matters is how many viable microorganisms are still there when you give the product to your dog. ISAPP guidance on probiotics emphasizes that adequate viability should be maintained throughout the product’s shelf life.

So it is worth checking:

• whether the CFU count is guaranteed through the end of shelf life;
• how the product should be stored;
• whether a cold chain is required;
• how long the opened package remains usable.

The most impressive strain list and the biggest CFU number will not help if the microorganisms in the jar left the game a long time ago.

Waste of money #4: assuming “10 different bacteria” is automatically better than one

Not necessarily.

A multi-strain combination can be excellent. But only if the combination itself makes sense and, ideally, has been studied. A long ingredient list is not a quality marker in itself. Sometimes one specific, well-studied strain can be a much more rational choice than a blend of ten microorganisms when nobody really knows what that blend does at that dose and in that combination.

The same applies to practically all supplements: more ingredients do not automatically make a better product.

Waste of money #5: buying a “probiotic” without actually knowing what you want it to achieve

This may be the most common problem. “I want to support my dog’s gut.” But what does that actually mean?

Does the dog have:

• acute diarrhea;
• an ongoing course of antibiotics;
• chronic enteropathy;
• a stressful period;
• a diet change;
• gas;
• persistently soft stool;
• or is the dog completely healthy and the goal is simply to “give something beneficial”?

These are very different situations. And there is no reason to assume that one probiotic is suitable for all of them.

Veterinary reviews published in 2024 likewise emphasize that different biotics may be useful, but the appropriate product and its effect depend heavily on the individual patient, the goal, the strain and the dose.

So before buying a jar, I would ask: what am I actually trying to change with this product?

If there is no answer to that question, it is quite difficult to judge whether the product works at all.

Waste of money #6: using a probiotic as a substitute for a diagnosis

The dog has had diarrhea for a month. Let’s try a probiotic. Didn’t help.

Let’s try another probiotic. Didn’t help.

A third one? This is where it is worth putting on the brakes.

If a dog has:

• recurrent or chronic diarrhea;
• regular vomiting;
• blood in the stool;
• weight loss;
• severe abdominal pain;
• a change in appetite;
• other persistent gastrointestinal symptoms,

the cause needs to be investigated, because a symptom and its underlying cause are two different things.

Those symptoms can be caused by many different problems, from parasites and infections to pancreatic disease, chronic enteropathy or adverse food reactions.

A probiotic can be part of a treatment plan. But it is not a diagnostic test or a universal treatment. A pretty jar should not become the reason the underlying cause is never investigated.

Waste of money #7: expecting the probiotic to move into the gut forever

Older discussions about probiotics sometimes include the idea: “If the bacterium does not permanently live in the gut, the dog simply poops it out.”

That is too simplistic.

Many probiotic microorganisms may be temporary residents of the gut. They do not necessarily have to colonize it permanently in order to have an effect while passing through the gastrointestinal tract.

So the fact that a microorganism later leaves the body does not prove that the probiotic was useless.

Is a probiotic pointless without a prebiotic?

No. But that does not mean the prebiotic is unimportant.

A prebiotic is a substrate that certain microorganisms can use and whose use must confer a health benefit on the host. Put simply, it can be thought of as “food” for the microbes we want to support.

And this is where, in my opinion, one practical nuance matters.

When we give a dog probiotic microorganisms, it is not only important that they reach the gastrointestinal tract alive. The environment they enter also matters, including whether suitable substrates are available there.

A probiotic can have an effect even if it does not permanently colonize the dog’s gut. So a probiotic does not automatically become useless simply because a prebiotic has not been added to the same capsule. At the same time, it is not irrelevant whether a microorganism enters an environment where it can function actively and use suitable nutrients, or an environment that does little to support it.

That “food” does not necessarily have to come from the probiotic jar. A dog can also obtain suitable substrates from its regular diet, and a prebiotic may support both the dog’s resident microbes and, in some cases, the microorganisms given alongside it.

So for me the question is less: “Does the probiotic product absolutely have to contain a prebiotic?” and more: “Does the environment in the dog’s gut give this microbe a real chance to do the job we sent it there to do?”

A probiotic and a prebiotic can together form a synbiotic strategy, but the absence of a prebiotic from the same product does not automatically make the probiotic useless.

For a more detailed look at prebiotics, synbiotics, postbiotics and food-based microbiome support, see the FendaF article “Beneficial Bacteria and Probiotics for Dogs”.

Waste of money #8: assuming “made for dogs” is enough proof of quality

A picture of a dog on the jar is not a clinical trial. The quality of pet supplements varies.

I would like a product to provide as much of the following information as possible:

• the specific microorganism;
• the specific strain, where possible;
• the CFU count;
• information about when that CFU count applies;
• storage instructions;
• the recommended dose;
• ideally, studies in dogs;
• the problem or purpose for which the product is recommended.

The less real information a manufacturer provides, and the more the front of the package relies only on words such as: gut health, immunity, balance, wellness, natural, billions… the more cautious I become.

“But it contains 15 different strains!”

Maybe it is an excellent product. Maybe it is simply a very long label. Ask: have those strains been studied in that exact combination?

Because adding together studies on individual strains does not automatically prove that a mixture made from them behaves in exactly the same way.

What about natural probiotics?

“Natural probiotics” is a very common search term, and in everyday language people often mean kefir, fermented dairy products or other fermented foods.

Scientifically, however, not every fermented food is automatically a probiotic. To qualify as a probiotic, a specific live microorganism must be present in an adequate amount and its health benefit must have been demonstrated. A fermented food can still be a valuable part of food-based microbiome support even if it does not meet that stricter definition.

If the goal is long-term support of a healthy dog’s microbiome, food-based approaches can be very interesting. But if the goal is a specific clinical problem, a standardized and studied probiotic has an advantage: we know much more precisely which microorganism we are giving and at what dose.

We discuss food-based microbiome support in more detail in the FendaF article “Beneficial Bacteria and Probiotics for Dogs”.

Is a probiotic made for dogs always better than a human probiotic?

I would not give an absolute yes to that either. The canine and human microbiomes are not identical. But that does not mean that no microorganism used in a human probiotic could have an effect in a dog.

In practice, I prefer a product where:

• the strain is clearly identified;
• the dose is known;
• quality can be verified;
• and, where possible, it has been studied in dogs.

If the choice is between a well-studied dog-specific product and a completely random human product, the former simply gives us more directly relevant information.

Probiotics during or after a course of antibiotics?

There is no universal rule that says “always start after the final antibiotic dose”. The effect of an antibiotic on the microbiome begins during treatment.

At the same time, some antibiotics can also affect the bacteria contained in a probiotic. So the timing of probiotic use depends on the specific:

• antibiotic;
• probiotic microorganism;
• product;
• treatment goal.

The most sensible approach is to follow the instructions for the specific product and discuss it with a veterinarian when necessary. At the same time, a growing number of integrative veterinarians recommend probiotics already during antibiotic treatment.

The purpose of a probiotic is not to “neutralize the antibiotic”. An antibiotic may be entirely necessary. The goal is simply to support the gastrointestinal tract and microbiome as sensibly as possible, rather than setting the medicine and the probiotic against each other.

But what if the probiotic helps?

Then there is no reason to avoid it for ideological reasons. To me, this is an important point of balance in the whole discussion.

An integrative approach does not mean: “the jar is bad, real food is good.”

If a particular dog has a particular problem and we have a well-studied probiotic strain for that problem at an appropriate dose, a standardized product may be exactly the right tool. In some controlled studies in dogs, specific probiotics have been associated, for example, with improvement in acute diarrhea and stool consistency.

That is a perfectly valid reason to use the product.

But evidence for one product does not automatically make the entire probiotic shelf equivalent.

Does a healthy dog need a probiotic “just in case”?

Not necessarily. If the dog:

• is healthy;
• has normal digestion;
• has normal stool;
• does well on the diet;
• has appropriate variety and fiber in the diet,

I see no reason why the dog must automatically receive a daily probiotic supplement for the rest of its life. That does not mean you are not allowed to give a healthy dog a probiotic. It simply means: “healthy” does not automatically mean “necessary”.

Sometimes that money may be much better spent on good-quality food, suitable fresh additions or solving a health problem that actually needs attention.

When would I buy a probiotic?

When I can answer the following questions:

1. What am I giving it for?
2. Which microorganisms and strains does the product contain?
3. At what dose?
4. Has this strain or combination been studied for this purpose?
5. Is the amount of viable microorganisms guaranteed through the end of shelf life?
6. How should the product be stored?
7. How will I judge whether it is helping the dog?

If the manufacturer can answer almost none of the first six questions but the front of the package is glowing with a giant: 50 BILLION! …I would not reach for my wallet just yet.

When can a probiotic genuinely be a waste of money?

When:

• the strains are not properly identified;
• the CFU number is basically a marketing number;
• the promised bacterial count applies only at the time of manufacture;
• storage does not ensure microorganism viability;
• there is no meaningful evidence for the specific product;
• you use it for the wrong problem;
• you expect the probiotic to treat the underlying cause of disease;
• you endlessly switch products instead of investigating the cause of chronic symptoms;
• you give it simply because “probiotics are healthy”.

And when is it not a waste of money?

When you have: the right tool + the right goal + the right dog + reasonable evidence.

In summary

Probiotics are neither a miracle cure nor a scam. They are a group of tools. Some are very well studied. For some, we know very little. Some products may be excellent. Some are essentially very expensive jars of marketing.

So I would not ask: “Do probiotics work?” Instead: “Is this specific probiotic a sensible choice for this specific dog and this specific problem?”

And if the answer is yes, a probiotic can be a very good investment.

But if we do not even know which microorganism is in the jar, why we are giving it, or whether it is still alive at the end of its shelf life… then the only thing the microbiome may truly have made lighter is your wallet.

Sources used

• ISAPP. Consensus definitions of probiotics, prebiotics, synbiotics, postbiotics and fermented foods. ISAPP
• Gómez-Gallego C et al. A canine-specific probiotic product in treating acute or intermittent diarrhea in dogs: A double-blind placebo-controlled efficacy study. Veterinary Microbiology. 2016;197:122–128. PMID 27938673. PubMed
• Wilson SM, Swanson KS. The influence of ‘biotics’ on the gut microbiome of dogs and cats. Veterinary Record. 2024. PMID 39545542. PubMed
• Salavati Schmitz S. Evidence-based use of biotics in the management of gastrointestinal disorders in dogs and cats. Veterinary Record. 2024. PMID 39545596. PubMed
• Schmid SM, Tolbert MK. Harnessing the microbiome: probiotics, antibiotics and their role in canine and feline gastrointestinal disease. Veterinary Record. 2024. PMID 39545593. PubMed

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