What is a probiotic?
Probiotics are widely available and increasingly popular as "alternative" or "natural" approaches to treatment and prevention of disease. When considering the use of probiotics, it's important to think about what a probiotic really is. A widely used (and my favourite) definition is:
Probiotics are live microorganisms that, when given in adequate doses, provide health effects beyond that of their inherent nutritional value.
It's a great definition and has some key points to consider:
- Live microorganisms must be present. That's not always the case with commercial products.
- An adequate dose must be present. Some commercial products have very low levels of viable microorganisms. We have limited information about the required doses, and these would vary between bacterial species and animals species, but the low levels present in some veterinary probiotics are a major limitation.
- There must be a health effect. This is the key. If it doesn't do something beneficial, then it's not a probiotic.
Which brings me to my "head shaking product of the day": probiotic floor cleaner. Yes, floor cleaner. And it has a nice warm-and-fuzzy name: Peace of Mind Floor Cleaner.
According to the manufacturer, it reduces the risk of infection (infection of what, by what and how, are completely unclear). It also allegedly "keeps protecting surfaces for up to 3 days by leaving a long-lasting layer of beneficial probiotics that create a safe, stable and odor free environment. Don't let your floors make you crazy."
I didn't realize that floors were the cause of such angst and that covering them with probiotics can improve your life (hopefully the sarcasm is apparent).
What does this have to do with probiotics for treatment or prevention of disease in animals? Not a lot. But it shows how easily people can throw around the word "probiotic" as a marketing tool. Floor cleaners can't be probiotics since they aren't ingested and don't have health effects. However, the same type of scrutiny needs to be applied to any probiotic that you are considering using.
- Demand evidence of a health effect (real evidence, not just testimonials).
- Demand information about the recommended dosing.
- Find out what specific bacteria are being used.
- Don't stop thinking once you read "probiotic." On the contrary, when you read "probiotic" you should start thinking and asking questions.
Probiotic safety
The November edition of Emerging Infectious Diseases contains a commentary about probiotic safety. The paper, entitled "Regulatory Oversight and Safety of Probiotic Use" (Venugopalan et al. 2010), focuses on a probiotic yeast, Saccharomyces boulardii, which is increasingly being used for treatment or prevention of Clostridium difficile infection in people. Because it is marketed as a dietary supplement, this yeast doesn't have the same requirements for demonstration of safety and effectiveness as a "drug" would. Systemic Saccharomyces infections have been reported, predominantly in people who are critically ill or who have other risk factors for an infection caused by a microorganism that is typically harmless.
The lack of regulatory oversight limits the identification and reporting of problems associated with probiotic administration, and means that safety testing is not required, even if the product will be used by high risk individuals. Often people consider probiotics completely innocuous, and they don't think about the potential for complications. While very low, the risk of infection caused by the probiotic organism itself needs to be considered, especially when dealing with high risk patients and situations for which there is little proof that probiotics might be effective.
Are probiotics safe for use in animals such as pets and horses? Probably. For the vast majority of animals, the majority of probiotics are likely safe. Given the very lax nature of licensing and poor reporting of complications, it's hard to be definitive, but the likelihood of a significant problem occurring from giving an animal a probiotic is pretty limited. The fact that most commercial products actually contain few live organisms, a fraction of what is claimed on the label, probably increases safety (while also decreasing the chance that they work).
My general line is that probiotics are unlikely to do any harm for your average healthy animal. I have no problem with people trying probiotics in those cases, with the understanding that we really have little evidence that they work, but that they might. I am hesitant to use them (or recommend them) in very young animals, very old animals and animals with compromised immune systems. These types of animals are at increased risk of infection by even rather innocuous organisms that would not likely cause disease in other animals. Since the evidence that probiotics might work is lacking, I'm more careful when dealing with such high-risk groups. What we really need is sound research to provide the required evidence of probiotic safety and effectiveness.
Image: Coloured scanning electron micrograph of Saccharomyces boulardii (source: www.vub.ac.be)
Internet advice: The good, the bad and the ugly
The internet can be a strange place at times. You can find great, reputable and unbiased information right next to complete garbage. Often, the garbage is pretty apparent, but sometimes it's dressed up well or mixed in with some good information. That's a problem with veterinary advice and information sites.
Among the creative myths identified in a couple of minutes of searching:
- Metronidazole is a proven treatment for parvovirus: No. Metronidazole is an antibiotic that doesn't have any effect on viruses. Antibiotics are sometimes used in the treatment of parvovirus, but they are drugs that are used to prevent or treat problems caused by bacteria from the gut entering the bloodstream as a result of the intestinal tract disease. Metronidazole won't do that.
- MRSA is a virus: You can't make much more of a basic mistake than confusing a virus and a bacterium. Anyone who says this when purportedly writing medical advice is completely clueless.
- If your dog gets an MRSA infection, your veterinarian will likely prescribe vancomycin: Only in extreme circumstances (if ever) should this ever happen. For more information on vancomycin and its use in treating animal and human infections, see our archives. (This gem is on a page that says it's information from infectious disease specialists).
-MRSA in dogs can easily become resistant to vancomycin so linezolid may be required: Fortunately, vancomycin resistance is extremely rare, having been found only a few times in people, in specific circumstances. It's never been found in a dog. Hopefully it will stay that way. (This site didn't even spell vancomycin correctly.)
- Cats can easily get a urinary tract infection if their litterboxes are not cleaned: No. There is no evidence of this and no reason to think it's an issue. Poor litterbox maintenance can lead to urinating outside of the litterbox or other problems like idiopathic cystitis, but not infection.
- In order to have a very healthy dog, it is often required to supplement your pet's diet to provide a high amount of probiotics: Nope. Certain probiotics might be useful in certain animals in certain situations, but we have no proof of this in dogs and cats, and they are certainly not needed for all animals.
There's no way to guarantee that a website is reputable or that the writers are knowledgeable, but here are some things I consider when scrutinizing information on the internet:
- Who set up the website? Is it clear who's in charge?
- Who wrote the information? Is it someone with actual credentials? For veterinary medical advice, is it a veterinarian? If it's a veterinarian, is it a specialist? If it's not a veterinarian, what expertise does the person have? Some people without veterinary degrees have expertise in some fields, but try to determine whether they truly have the qualifications to give advice on a particular topic. That's harder to do these days given the proliferation of mail-order "PhD" degrees, something that's not uncommonly encountered in unqualified people making poor veterinary recommendations.
- Why is the website there? Is it an educational site or is it there to make money? Commercial sites aren't necessarily bad but you have to consider any conflicts of interest or ulterior motives. If there is an article about something, and the last sentence tries to sell you a product to fix that problem, be careful.
- Does the information make sense and is it consistent with other websites? You can probably find a site somewhere to support any notion that you have, but does it really make sense?
- Is the site relevant to your geographical area? This is particularly important for infectious diseases since they can vary greatly between regions. A disease may be a big problem in one area, and a website might provide excellent advice... but only for that area. It may be completely irrelevant or inappropriate for other regions.
- Can they spell? The odd typo probably isn't a major issue (I do it myself). However, rampant and blatant abuse of the English language and an inability to spell important words properly should be red flag.
Searching the internet for pet health information is certainly not a bad thing to do. But, you have to critically assess what you read and remember that it's not always right. Use the internet as a resource but make sure that it's to supplement advice from your veterinarian, not to replace it.
Probiotics and obesity
A recent editorial in Nature Microbiology Reviews by Dr. Didier Raoult raised questions about the potential role of probiotics in obesity. It is based both on studies indicating weight gain in humans and farm animals in probiotic trials as well as some laboratory animal data. The conclusions based on clinical trials for treatment of disease are pretty weak, since while animals or people may have gained weight, that does not mean they gained fat (if you get better because of a probiotic, you gain weight, but that is probably a healthy response and not obesity). There is some interesting lab animal work that shows changes in fat deposition in response to some probiotics, but it's rather preliminary.
It's way too early to declare that consuming probiotics is a risk factor for obesity. Several letters to the Editor were submited by leading probiotic researchers in response to Dr. Raoult's editorial, contradicting some of the statements that were made. Personally, I don't see convincing evidence of a risk but Dr. Raoult's comments should serve as a reminder that probiotics can have broad and poorly understood effects on the intestinal bacterial population, and correspondingly broad and poorly understood effects on the body. That's why probiotics should be scrutinized like drugs, in terms of safety, effectiveness and quality control. If someone is using a probiotic for themselves or their pet for a defined reason and it seems to be working, I wouldn't recommend stopping because of these largely theoretical concerns about obesity. However, we should perhaps think about why we are using probiotics and the potential costs versus benefits. I doubt this is really going to be a major issue but it's a good one to think about.
Other Equine Infectious Disease Resources
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