Supplements - Selecting Supplements for your Pet

By Rania Gollakner, BS, DVM, MPH; Steve Marsden, DVM ND MSOM LAc DiplCH AHG, Shawn Messonnier, DVM and Cheryl Yuill, DVM, MSc, CVH

What are supplements?

A supplement is a concentrated ingredient that is added to the diet for nutritional or therapeutic benefits. Examples of supplements include vitamins, minerals, amino acids, herbs, botanicals, and enzymes. There is a great deal of confusion that surrounds the terminology of food additives, and sometimes terms are used interchangeably. For clarity, the following terminology will be used in this handout series.

Dietary supplements or dietary nutrients are substances that are added to a food, usually to make it nutritionally complete and balanced. Therapeutic supplements, also called nutraceuticals or animal health supplements, are foods or food nutrients that are taken orally to provide a health benefit, either for the prevention or the treatment of disease. To have this therapeutic effect, a nutraceutical is usually taken in a larger dose than the daily requirement of that same ingredient when used as a nutrient.

How do I find out what a supplement is used for?

You may learn about supplements is from a friend, a retail store employee, the Internet, an advertisement in the media, or from a health care provider. Sometimes, this information may be incomplete or biased.

"Information that comes from the Internet or other written sources may or may not be accurate or complete..."

Information that comes from the Internet or other written sources may or may not be accurate or complete, depending on who has prepared the information. Some of the published information about a nutraceutical may be biased, especially if the source of the information is the manufacturer or retailer of the product. The least biased information comes from publications that have some regulatory control (such as being regulated by a federal government agency). For example, with respect to herbal products, there is a database available at that lists general uses and the reference sources for these uses. Another good source for information about supplements and manufacturer quality is found at

With respect to vitamins, minerals, amino acids, fatty acids, and other nutrients, some information can be found in standard nutrition textbooks. However, these sources may provide outdated information and may only include the well-recognized and well-documented indications for specific nutrients. These sources may also discuss supplements as a nutritional requirement, rather than their role as a nutraceutical.

How do I know whether a supplement is effective?

Very few supplements and herbs have been subjected to rigorous scientific trials to determine their efficacy. Some supplements have been thoroughly researched in humans, but not animal species. Indeed, much of the information about the use of supplements comes from anecdotal or testimonial evidence (someone tells you about their personal experience or about another patient who showed some benefit when taking the product). Although this information may be of help, it may be incomplete and may not represent what effects the supplement could have on your pet.

"Very few supplements and herbs have been subjected to scientific trials to determine their efficacy."

It is common for supplements to be given to a patient along with other supplements, or in conjunction with other lifestyle changes.

" can be difficult to sort out exactly what effects can be truly attributed to the supplement..."

In these cases, it can be difficult to sort out exactly what effects can be truly attributed to the supplement and what may be attributable to other factors, especially if multiple changes were made simultaneously. For example, if a patient starts to take supplement Y, and at the same time changes their diet and starts an exercise program, then the observed changes may be due to any one of the factors, to a combination of all three, or even to a placebo effect.

To further complicate the issue of effectiveness, some supplements are only effective after they have been given for a period of time, and the patient may continue to show some of the positive effects for a few weeks after the supplement has been discontinued. An example of this is the use of glucosamine to ease the symptoms of arthritis. It may take approximately 4-8 weeks to show its effects, and can take the same period of time to 'wear off' after it has been discontinued.

How do I know if a supplement is safe for use in my pet?

Just because a product is natural, that does not mean that it is safe. All medicines and medicinal plants are potentially toxic if used inappropriately or given at high doses. Supplements can also have side effects, just like pharmaceuticals. The best source of information for the safety of supplements in domestic animals is your veterinarian.

"Just because a product is natural, doesn't mean that it is safe."

Because the use of supplements and nutraceuticals in veterinary medicine is a relatively recent practice, some veterinarians may be unfamiliar with the indications and precautions surrounding the use of various products. Fortunately, reliable information sources for veterinarians about the clinical application of supplements are becoming increasingly available. Some privately maintained websites, such as provide brief information and links to other relevant sites.

Another way to gather information about the use of a supplement in a certain species or for a certain disease is to consult the manufacturer of the product. If there is reliable information about the product's safety and efficacy in animals, the manufacturer should be able to provide you with this.

"If the manufacturer is unwilling to provide this information, it is safer for your pet if you err on the side of caution and not use the product."

If the manufacturer is unwilling to provide this information, it is safer for your pet if you err on the side of caution and not use the product.

What is quality assurance or quality control?

Quality control provides a measure of assurance over what a product contains, with respect to its medicinal ingredients and its purity. Not all distributors share the same concerns about ensuring that their products are high quality and free of contaminants, contain consistent levels of active ingredients and retain their potency after processing. Frequently, herbal supplements may not even contain the same species of plant as listed on the label. For example, a 1991 article in the Canadian Pharmacology Journal estimated that 50% of the Echinacea products sold in the US between 1908 and 1991 actually contained a plant referred to as Missouri snakeroot.

Are there any regulations about packaging of supplements?

With pharmaceutical products, the manufacturer is governed by strict legislation about contents and labelling. In North America, supplements, nutraceuticals and herbs are not considered to be pharmaceuticals (and in most cases are not considered to be foods either). The FDA requires that all ingredients in a pharmaceutical or food be listed, and that none of these products be recognized as a potential health threat. The FDA also requires that unsubstantiated claims cannot be made regarding the ability of a product to treat a disease. Unfortunately, because many natural health products and supplements are not considered pharmaceuticals, they are not regulated and therefore do not have to meet the same strict requirements.

Because of this lack of control, there is no guarantee of the package contents or product strength. This leaves it up to the consumer to become informed about the integrity and ethics of the manufacturer to provide any measure of assurance that the product is effective and unadulterated.

What should I look for on a label or package?

Every package should have the name and contact information of the manufacturer of the product. It should contain information about the product's contents, ideally with some sort of a minimum analysis of the active ingredients. It should also contain information about any inert or carrier substances that are present, such as milk sugar, whey, and vegetable or animal proteins.

For herbal products, the label should also include the Latin name of the plant, a harvest date or an expiration date, the part of the herb used, and the quantity of active constituents.

Who can give me advice about treating my pet with a supplement?

"A licensed veterinarian who is knowledgeable about the supplement of interest and about alternative medicine in general is your best source of professional nutritional advice."

A licensed veterinarian who is knowledgeable about the supplement of interest and about alternative medicine in general is your best source of professional nutritional advice. Veterinarians have been trained about the anatomy and physiology of animals, and are expected to be knowledgeable about the treatments they prescribe, including toxicity and predictable side effects.

What should I do if my pet shows an unexpected reaction to a supplement?

Unexpected reactions must always be reported to your veterinarian or the person who recommended the supplement, and to the manufacturer. There are often government agencies that collect and collate this information, and it is strongly recommended that these agencies also be informed of the concerns.

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