Top 10 supplements for dogs and cats: do they really work?

Much has been written about the dietary supplement industry, a multibillion-dollar industry in America with strong political ties.

Another widely debated topic is the lack of effective regulations, which now allow the markets of supplements to be disseminated without solid foundations or scientific studies.

The veterinary supplement market is little compared to the market for human use, but there is still talk of a trifle that is already worth billions of dollars and is growing rapidly. Unfortunately, the resources available for quality research in the field of veterinary health care are also insufficient and it is not uncommon for our pets to suffer or even be eliminated as a result of diseases that could be treated, but for which there is no money that could pay for the necessary treatment. And therefore, this billion dollars a year spent on nutritional supplements in the United States may not be so justifiable, especially if these products do not prevent or cure diseases effectively.

The variety of supplements available is staggering. Many blends claim to be owners of vitamins, minerals, herbs and other ingredients that can maintain their health, strengthen their immune system, delay aging or treat certain diseases. A complete review of this multitude of products is impossible. But only a few are continually rented, and these will be at the center of this analysis. Many of the ingredients they contain are also found in the most popular supplements for human beings. There will therefore be significant overlap with previous studies regarding plausibility and the scientific evidence supporting the use of these substances.


The most famous name in the world for veterinary supplements is by far glucosamine. It can be sold alone or in combination with chondroitin, methylsulfonylmethane, green mussel powder extracts and a million other ingredients. It can be sold as a substitute, through veterinarians, and as a feed additive in commercially available feeds. In addition, pet owners and veterinarians believe this is an effective treatment for bone arthritis.

The effectiveness of glucosamine against human arthritis has been the subject of much discussion. This theory is likely supported by reasonable probabilities, but decades of clinical trials have not yielded consistent benefits, and the balance between the evidence produced strongly suggests that it is not better than a placebo to treat human arthritis. Given the subjective nature of pain and the multitude of biologically inert interventions that may affect people’s perception of their own malaise, the placebo effect may be of marginal value to humans, but the same type of psychology does not apply to dogs and cats, although in some cases this concerns their owners.

There is very little clinical research on glucosamine as a treatment for arthritis in dogs and cats. Among recent clinical studies, there are only two studies on dogs. One found no benefit from using glucosamine and the other, whose schedule was lower, showed a benefit. Both have also benefited from far greater and predictable benefits of nonsteroidal anti-inflammatory drug (NSAID) therapy, which represents a significant failure in clinical research on glucosamine.

Since cats have low tolerance to NSAIDs, the use of glucosamines and other functional foods in the treatment of feline bone arthritis is of particular interest. Nevertheless, clinical trials that prove that this type of supplement is a treatment for cats are not currently available. The research closest to you is that of a diet containing glucosamine, chondroitin and a number of other supplements, which claim to be beneficial for the management of arthritis. In summary, however, there were no consistent differences between the tested regime and the control regime, also with respect to subjective comfort measures, and no objective difference in the extent of the two activities. In addition, the role of glucosamine would be impossible to determine in a study that also included the administration of many other ingredients.

After glucosamine, one of the most famous pet supplements is fish oil. In humans, the most common use of this supplement is to reduce the level of lipids in the blood and prevent cardiovascular disease. There are controversies about the number of these components that are really helpful for each specific condition, and it’s better to eat fish better than taking fish oil supplements, but in general, there is good evidence of some benefits in the prevention of cardiovascular disease.

Cats and dogs do not have problems with arteriosclerosis or cardiovascular diseases like humans, so they are not a valid reason to use fish oil. Instead, this supplement is most commonly used in the treatment of skin allergies. A 2010 article (pdf) summarizing the different approaches and their results in the treatment of canine cutaneous allergies clearly concluded that fish oil supplements improve the quality of the coat and reduce the dose of steroids needed to control itching. . However, these effects are marginal and not relevant enough to warrant replacement with other therapies. There is also no evidence to support the use of a specific dose or formulation of fish oil as better than another.

The other common use of fish oil in domestic animals is the treatment of arthritis. There is little evidence in humans to demonstrate that fish oil supplements are an additional treatment for patients with rheumatoid arthritis, but in general, this is not a well-documented intervention against rheumatoid arthritis. Degenerative bone arthritis. Numerous studies have been conducted on the use of fish oil as a treatment for canine bone arthritis and, as is common in dietary supplement research, they generally report negative results, but focus on then on some important results. , generally with subjective measures, to finally conclude that these studies demonstrate tangible benefits. The idea that fish oil as a supplement may have little benefit for feline and canine arthritis is not totally out of the question, but so far there is no evidence to encourage this theory.

Mark Crislip spoke eloquently about the theory and science of probiotics for humans, and in the end, with regard to pets, it seems like the same thing. We understand very little about the importance and complexity of the ecology of the gastrointestinal tract in the ecology, the number of bacteria present and their role. So while the idea of ​​influencing flora to restore or maintain our health makes sense, adding a little Lactobacillus to the mix and expecting more effects would seem like “sowing a little seed”. the grass in the Amazon rainforest and expect a golf course to grow there “, as Mark Crislip would say.

Clinical studies in humans have confirmed the existence of some benefits for certain conditions, especially antibiotics associated with diarrhea, but many claims regarding probiotic products, particularly regarding the maintenance of health or strengthening of the system immune, are not supported by the facts. . There is less research on the use of probiotics in dogs and cats, but some encouraging studies show a possible benefit of some products for acute idiopathic diarrhea in dogs (for example here and here, analyzed in detail.)

Quality control of a large number of veterinary probiotics also poses serious problems. A recent US study found that most of the products tested had inaccurate labels, of which many products were not really usable for all species and organisms claimed in the therapeutic indications. There are also many products sold with statements of results completely ridiculous and totally unsupported by research.

Thus, in general, the idea of ​​probiotics as a treatment for gastrointestinal diseases seems promising and some initial suggestions suggest their real utility in the treatment of certain conditions. Nevertheless, this optimism is tempered by the limited and preliminary knowledge we have on the ecology of the intestinal tract, as well as by poor quality controls and exaggerated and exaggerated scientific statements about probiotic products.


As Harriet Hall explained in the past, taking multivitamins is more of a form of self-induced psychotherapy than a preventive health practice. A 2006 article on tests available to date, as well as more recent studies, does not support claims that vitamin supplements would be beneficial to human health in the absence of vitamin deficiencies already confirmed. And there are circumstances in which vitamin supplements can be harmful (for example, increase the risk of cancer, interfere with cancer treatments, and even increase mortality).

As usual, there is no applied research on dogs and cats. Commercial pet foods are even more nutritionally balanced than the products available to humans, so it’s even more difficult to think that a multivitamin could be beneficial for dogs and cats. In fact, this type of supplement could easily lead to an excessive or even toxic level of fat-soluble vitamins or certain minerals. However, homemade raw food diets for animals are more likely to be nutritionally inadequate and, therefore, multivitamin supplements may be recommended.

Nevertheless, the moral of the story is that no good-quality epidemiological or experimental research suggests that dietary deficiencies are common or that apparently healthy whole-body multivitamins have any purpose. And instead, it is proven that supplements can also be harmful (eg, calcium in large dogs).

The lack of evidence may preclude a definitive declaration on this type of supplement and its useless and harmful nature; but this ensures that the statements of the sellers of these supplements are totally unjustified.


Lysine is an amino acid that may be useful in the prevention and treatment of Feline Herpes Virus (FHV-1) infections. This virus is extremely common and many cats are exposed to it and are already infected with puppies. Clinical symptoms include sneezing, nasal congestion and conjunctivitis, and range from mild and spontaneously resolving forms to more severe forms. Many cats manage to overcome the initial infection, but many remain chronically infected. With the suppression of immune functions caused by stress, medication or illness, the virus reappears and causes new symptoms. A small subset of cats may develop ongoing and chronic symptoms associated with this infection. Although vaccination reduces the severity of symptoms, it does not prevent infection.


S-adenosyl methionine (SAM-e) 
SAM-e is a chemical found throughout the body and fascinating for its variety of in vivo functions and its in vitro effects. In humans, it is sold to treat depression, arthritis and various other diseases. Clinical studies have been found in conflicting and generally not high quality tests (eg, a Cochrane article on arthritis and liver disease due to alcohol, and a summary of the Mayo Clinic on various pathologies) .

In animals, it is primarily presented as a liver protector in case of toxin damage, often in combination with milk thistle, although its use is often also recommended for arthritis and other diseases. Although the theoretical arguments for its use, particularly in the case of liver diseases, are plausible, there is no clinical research to prove that this compound is really beneficial to patients when administered as oral supplement. One study found no significant benefit in preventing liver changes associated with steroid use, and one recorded case confirmed some benefits in a dog suffering from acetaminophen poisoning. Another clinical case has suggested a potential value in the treatment of cognitive dysfunction in age-related dogs. And despite the extent of the use of this supplement and the degree of fluctuation of the affirmations, it is all that one can say for the moment.

Enzymatic enzyme
The considerations for digestive enzyme supplements are often fluctuating and dramatic, and may lead you to wonder how anyone can digest food without them. The subject we usually talk about is that these enzymes exist in raw foods but are destroyed during the production of commercial pet foods. Therefore, if you are foolish enough to give your pet a balanced and commercial diet, you should give it to your animals. even supplements, or something else! These unsupported exaggerations, which sometimes result from mythical claims about raw food diets for both humans and dogs, have been discussed. They are based on false beliefs about digestive physiology and nutrition, and are meaningless.

Humans and healthy dogs have all the enzymes they need to effectively digest food. The organs that produce these enzymes are not stressed or tired because, after all, it’s their natural function. The digestibility of commercial foods and their constituent ingredients has been extensively tested, and there is no evidence that an enzyme deficiency of these foods leads to nutritional deficiencies or specific health problems.

In addition to their use in healthy subjects, enzymes are also recommended for the treatment of cancer, anti-inflammatory effects and the treatment of many other diseases. Although studies published from time to time corroborate these recommendations, there is often no evidence in clinically relevant and consistent evidence in integrative medicine journals that digestive enzymes are an effective treatment for other diseases, in addition to their real usefulness in case of deficiency. pancreatic enzymes. And there is evidence that this approach can be ineffective or even harmful.

There is no surprise, no clinical research on digestive enzymes applied to dogs and cats. In addition to pancreatic insufficiency, in which enzyme integration is often effective, claims for the use of enzyme supplements rely solely on anecdotes, theories, or extrapolations from in vitro research.

Coenzyme Q10
Like most dietary supplements, coenzyme Q10, also known as ubiquinone, is recommended for a wide range of seemingly unrelated diseases. It is recommended in humans for cardiovascular disease, Alzheimer’s disease, migraine, diabetes and many other diseases, as well as for general tonicity and, of course, the inevitable “strengthening” of the immune system. In dogs and cats, it is primarily recommended for the treatment or prevention of heart disease and cognitive dysfunction related to age.