How to Choose Nutritional Supplements for Dogs and Cats
ACVIM 2008
Nancy Loes, DVM, MBA
Fort Worth, TX, USA


The benefits of nutritional supplements, for both people and pets, are increasingly more accepted and understood. It's another issue, however, to know how to choose amongst the myriad of options (within any given category of supplement) and find the supplement products that offer quality and value.

When assessing a particular nutritional supplement, it is important to be knowledgeable about label information, ingredients, manufacturing information, and whether research or safety and toxicity studies have been conducted. This guide is intended to help veterinary professionals critically evaluate available supplements in order to educate clients and help them select the best product for their pet.

Is the Label Easy to Understand?

Look closely at the label on a nutritional supplement product to see whether it contains the information necessary to use and store the product appropriately.

The instructions for giving the product should make sense, i.e., either so many tablets per a recommended number of times during the day per patient weight range or so many mg per kg. If the ingredients are in milligrams the recommended amount should also be in milligrams; if the product is a liquid, then the recommended amount should be stated in measures of volume.

The target species for the product should be on the label. If the product is best given on an empty stomach, or preferably with food, those specific instructions should be noted. Storage conditions necessary to preserve stability and activity of ingredients should be easy to find. This might include, for example, recommended environmental temperature ranges and, if applicable, whether exposure to light or humidity must be limited.

Lot numbers are important.1 In the event of an adverse incident, lot numbers facilitate tracking the original source of the ingredients. An expiration date on a label (as opposed to its absence) gives some credence that the ingredients have been evaluated for duration of activity and/or stability.

The administration amount and frequency, in addition to target species, proper storage conditions, a lot number, and an expiration date, should be clearly stated on the label.

Are the Active Ingredients Identified on the Label?

Some nutritional supplement labels do not list ingredients. It is important that the ingredients that are identified on a product's label are consistent with those listed in product brochures and marketing materials for that particular supplement. An inconsistency between the product brochure or marketing piece and the product label is problematic and raises concerns as to why an ingredient is mentioned in a brochure but is not listed on the label.

Products may sometimes contain the source material for an active ingredient as opposed to the purified extracted ingredient, or the labeling may not be clear as to which is present. Differences in absorption and ultimately efficacy may occur between an ingredient present in its purified extracted form and the ingredient present in its unrefined form combined with other ingredients in the source material. An example is the notation of "milk thistle" on a label but not the specification as to whether the milk thistle in the product reflects processing to the ingredient silymarin (and how much silymarin), or preferably, extraction and presence of the most active component of silymarin, i.e., silybin.

The active ingredients should be identified and quantified on the product's label.

Are the Ingredients That Are Listed on the Label Actually in the Supplement?

"Short changing" (i.e., what is on the label is not actually in the bottle) occurs frequently with nutritional supplements.2 Researchers from the University of Maryland School of Pharmacy analyzed over-the-counter products for people that "claimed" to contain chondroitin sulfate; 84% of the products did not meet label claim.3 Some of the products had zero active ingredient and some that cost $4.00 a day had less than 10% of the label claim (illustrating that paying a lot of money for a supplement does not guarantee label accuracy).3 The results on over-the-counter products for people are relevant for veterinary clients, as some clients may wish to purchase or may already be purchasing human products for their pets.

Short changing is also likely to occur with products for pets as evidenced in an April 2007 report noting 2 of 5 veterinary products tested in the glucosamine-chondroitin sulfate-MSM category that did not meet label claim. Equine products are not immune to the issue of label inaccuracy. A published evaluation of equine joint health supplements revealed that 9 out of 23 products did not contain labeled amounts of glucosamine with 4 of these products containing less than 30% of the amount claimed on the label.4

Even if the ingredients are present in the product, issues of quality and activity should be considered, in the same sense that not all cars are of the same quality and not all cars are equally reliable. For example, an analysis of various chondroitin sulfate raw materials revealed that they were not equally effective in inhibiting the expression of inflammatory mediators.6

The ingredients on the label should not only be guaranteed to be in the bottle but should be verifiable with a finished product analysis using a reproducible method.

How is the Product Manufactured?

The pharmaceutical industry must follow cGMPs (current Good Manufacturing Practices), a set of standards for ensuring purity and specific and detailed quality control measures for batch analysis. Currently, there is no such requirement for manufacturers of nutritional supplements for animals but some companies voluntarily self-impose standards of manufacturing that are guided by the pharmaceutical industry.5 These manufacturers track the product throughout the manufacturing process and use proven (= reproducible) methods for analysis of raw materials as well as the final product. An analysis of raw materials alone does not take into account how the product is manufactured and changes that occur during the transition from raw materials to finished product.

Consistency of ingredient content from lot to lot and bottle to bottle should be assured. Without quality controls and consistent standards of manufacturing, end products vary greatly in purity, content, and quality. Proper shipment and storage of finished products (including humidity and temperature controls) should occur to avoid degradation and exposure to contamination.

The reputation of the manufacturer is a factor when it comes to assessing veracity and quality, i.e., does the manufacturer stand behind its products (ready with replacement or refund if warranted), respond promptly when issues arise, support the veterinary community (with independent veterinary research, sponsorship of continuing education meetings, in-clinic seminars, involvement in non-profits, to name a few), and is there a high comfort level amongst veterinary professionals regarding the purity and safety of a particular manufacturer's products?

Quality control programs, from raw materials to finished product, should be in place.

Are There any Safety or Toxicity Studies?

Veterinary nutritional supplement manufacturers are not required to comply with the same standards and regulations that apply to drug manufacturers concerning safety.1,5 (See sidebar noting differences between pharmaceuticals and supplements).

A wide variety of nutritional supplements are considered "natural" but just because something is "natural" does not mean that it is always safe.1,2,7 Mushrooms are "natural" but it's well known that not all kinds of mushrooms are safe!1 The presence of harmful levels of contaminants (microorganisms such as bacteria or molds, environmental toxins such as insecticides and pesticides as well as heavy metals such as lead or mercury) in a nutritional supplement can present safety concerns.1,7 The purity of a product can be related to adverse reactions or unpleasant consequences.

A nutritional supplement must be evaluated (through safety studies) in terms of its potential for (and frequency of) adverse effects, its effect on laboratory analysis and clinical tests, and its potential to interact with other prescribed treatment regimens. Safety issues should be addressed in the target species, due to species variations in metabolism and tolerance.1

Insist that a product, or at a minimum its ingredients, be evaluated as to safety and the potential for adverse reactions in the target species.

Is There Any Scientific Evidence to Support Claims?

There is no pre-approval requirement for the safety and efficacy of a nutritional supplement for animals; however all claims should be truthful, not misleading, and substantiated by competent and reliable scientific evidence. Many outrageous claims are still made, though, such as "cures arthritis". It is common for multiple testimonials (often by famous people or individuals mirroring and/or appealing to the target audience) and anecdotal "evidence" to be used to promote products, rather than adherence to scientific data and research. It is important to note that no matter how many testimonials (or how persuasive the people are delivering the testimonials) the plural of testimonial is not data! Scientific research trumps opinion and if something sounds too good to be true, it probably is.2

Research should be objective, assuring data and conclusions that can be repeated and substantiated, data that veterinary professionals must proactively seek (in technical journals, medical websites, reference books and from manufacturers of veterinary supplements). Look for studies showing mechanisms of actions as well as seek out additional solid research which might include double-blind, placebo-controlled studies demonstrating efficacy (double-blind means that neither the investigator nor the recipient knows whether the active ingredient or the placebo has been administered to the recipient, thus the results are not biased with preconceived notions as to whether or not the ingredient under investigation will have effects).

Contact the manufacturer and request copies of research done on a nutritional supplement product that is under consideration for use in practice. If a manufacturer claims to have research, it should be made available.2 If a manufacturer sends research, the research should have been done on that particular manufacturer's product or ingredients and not on another company's product. Look for brand-specific research because there can be no "generic" comparison amongst products that have no benchmark specifications. Each product must stand alone on its own merits.

Nutritional supplements under consideration for use in veterinary patients should ideally have research in the target animal species. Veterinary professionals should support and patronize the companies that sponsor and underwrite independent veterinary research.

Information received should be evaluated for content, scientific basis and quality. Unsubstantiated claims will continue to be made and products without documented benefits will continue to be used unless veterinary professionals insist that nutritional supplements undergo scientific substantiation.

Consider the following recommendation from the Arthritis Foundation, which applies equally to both human and veterinary nutritional supplements: "When a supplement has been studied with good results, find out which brand was used in the study, and buy that."2

Is Technical Support Available From the Manufacturer?

The manufacturer or supplier of a veterinary nutritional supplement should employ technical staff, which may include veterinarians or veterinary technicians, to answer questions or address concerns. When recommending a product to clients, it is important to make sure that the manufacturer's contact information is listed on the label.

Be Open-minded, But Ask Lots of Questions and Proceed with Knowledge!

Enthusiasm for nutritional supplements should be balanced with tips from the FDA (, tips which are directed at consumers regarding supplements for humans but are useful guidelines for veterinary supplements. All supplement products should be evaluated for label content and accuracy, the existence of research and safety studies, and the reputation of the manufacturer.

The nutritional supplement products that meet or exceed high standards of quality, value and efficacy will be those that can be wholeheartedly recommended to clients and those that clients will, with your guidance, now be empowered to choose (and use) with confidence!


1.  Boothe DM. Balancing Fact and Fiction of Novel Ingredients: Definitions, Regulations, and Evaluation, Mandelker, L (ed) Veterinary Clinics of North America, Nutraceuticals and Other Biologic Therapies, Philadelphia, PA, W. B. Saunders Company, January 2004, pp 7-38.

2.  Horstman J. Nature's Remedies, Arnold, WJ (ed) The Arthritis Foundation's Guide to Alternative Therapies, Atlanta, GA, Arthritis Foundation, 1999, pp 175-185.

3.  Adebowale A, Cox D, Liang Z, Eddington N. Analysis of glucosamine and chondroitin sulfate content in marketed products and the Caco-2 permeability of chondroitin sulfate raw materials. JANA 2000;3(1):37-44.

4.  Oke S, Aghazadeh-Habashi A, et al. Evaluation of glucosamine levels in commercial equine oral supplements for joints. Equine vet. J. 2006;38(1):93-95.

5.  Skidmore-Roth L, Introduction, Mosby's Handbook of Herbs & Natural Supplements, St. Louis, MO, Mosby, Inc. 2001 ppix-xxii.

6.  Au RY, Phan PV, Au AY, et al. Effect of different chondroitin sulfate raw materials on pro-inflammatory gene expression in bovine chondrocytes, in Proceedings. 33rd Annual Conference Veterinary Orthopedic Society 2006, 75.

7.  Fetrow CW, Avila JR. Overview of Complimentary and Alternative Medicines, Hodgson, B (ed), Professional's Handbook of Complementary & Alternative Medicines, Springhouse, PA, Springhouse Corporation, 2001 pp 1-13.

Speaker Information
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Nancy Loes, DVM MBA
Veterinary Medical Education
Keller, TX

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