Sorting Through Supplements

Sorting Through Supplements

Photo: The Horse Staff

One equine product label claims the substance therein will help increase a horse’s longevity; another, his athleticism. Are these, in fact, miracle products, or are the assertions too good to be true? Called “nutraceuticals,” a wide variety of oral health products are available without prescription in feed stores and animal health outlets. The Dietary Supplement Health and Education Act of 1994 defines these feed additives as products taken by mouth that contain a supplemental “dietary ingredient.” But in the United States this delineation applies only to products intended for human consumption and does not pertain to products designed for animals, leaving the categorization of some of these products cloudy. 

In this article we will explore why the world of equine supplements is so incredibly complex, and we’ll describe how horse owners can make informed decisions when purchasing these products.


“Supplements can only claim to support ‘normal’ health, body structure, and function and should be from an FDA (Food and Drug Administration) approved list of additives,” explains Nicola Jarvis, BVetMed, Cert AVP, MRCVS, senior veterinary surgeon for Redwings Horse Sanctuary, in England. “Under the (FDA’s) Federal Food, Drug and Cosmetic Act, manufacturers of products claiming to ‘cure, treat, prevent, or mitigate disease or affect the structure/function of the body in a manner other than food’ must apply for consideration as a new animal drug and provide full proof of safety and efficacy.” 

Take, for instance, equine joint supplement labels—these commonly include claims that the product “supports joint health,” an acceptable wording for the classification. If the same substance label says the product is intended for “management of osteoarthritis,” however, then the FDA considers it a drug (because it is advertised to affect form and function), and manufacturers must follow strict regulation. 

Hence, the manufacturer claims on animal products labeled as nutraceuticals are not FDA-approved. Many veterinarians find this lack of regulation concerning because safety and effectiveness might be compromised in some products. 

“While it would appear that the FDA can regulate animal foods, additives, and supplements, the ultimate responsibility for safe and truthful production lies with the manufacturers and distributors,” Jarvis says.

Joe Bertone, DVM, MS, Dipl. ACVIM, professor of equine sciences at Western University of Health Sciences’ College of Veterinary Medicine, explains that the Association of American Feed Control Officials formulates the standards for manufacturing, distributing, and selling animal feeds. The FDA regulates these standards but doesn’t have the resources to enforce its authority.

There is, however, some measure of oversight by the National Animal Supplement Council (NASC), which audits and certifies manufacturing and packaging sites and tracks adverse events caused by nutraceutical ingredients. “The NASC process is voluntary and does not require pre-market research data in support of the product,” says Wendy Pearson, PhD, professor at the University of Guelph, in Ontario, and president of the Nutraceutical Alliance Inc., which aims to objectively assess veterinary nutraceuticals. “Instead, the certification process is connected to the manufacturing process, with safety data collected post-market.” (See page 50 for more on NASC regulation.)

She further reports that the FDA’s Center for Veterinary Medicine (CVM) has initiated a voluntary GRAS (generally recognized as safe) notification process that identifies and authenticates animal feed ingredients’ safety and functionality. Because this process is ingredient-based, however, it cannot predict interactions between ingredients in a complex product. 

Further, because animal nutraceutical products are not subject to the same good manufacturing practices (cGMP) as human nutraceutical products, manufacturers tend to be quite liberal on their label claims.

“There is limited enforcement action against ‘low-risk’ products for nonfood animals,” Pearson explains. “Most efficacy claims on products in the USA (and Canada) are based primarily on historical use, or sometimes upon research on ingredients in nonequine species. In most cases, claims of efficacy and safety are not supported by research specific to the product in the intended species. This is a serious problem in the industry, and it puts the consumer in a very vulnerable ‘buyer beware’ situation.” 

The Science of Clinical Trials

In recent years the veterinary community has placed increased emphasis on practicing evidence-based medicine, or procedures or techniques that are backed by repeatable results in clinical (live-animal, or in vivo) research. “To achieve reliable data, there must be adequate numbers of live cases conducted in well-controlled studies,” Bertone explains. Such studies can be very expensive, so many times researchers instead pursue in vitro (in the lab) studies, whereby substances are tested on equine tissue. “In vitro studies are the lowest form of substantiation for evidence-based medicine,” he says. “The studies must be ‘auditable,’ meaning they can be reconstructed (their results replicated) from the raw data. The results must show that the product is good for the intended claim. Very few studies outside of FDA studies for drugs can meet this standard.” 

Potentially clouding research results is a company’s conflict of interest in funding a clinical trial on a product they develop and market. “To assure that data is not biased, it is necessary for masked studies (which remove investigators’ subjectivity) to be performed in independent labs where the study can be reconstructed from the data,” Bertone says. “Bias that occurs may be completely innocent, but the fact that there is money to be made increases the likelihood of ‘entrepreneurial bias’” in anything other than independent, masked studies.

Many times, equine nutraceutical label claims that are based on use in humans are never substantiated with a clinical trial in people or in animals (and are, thus, anecdotal). Innate differences between species’ physiology complicate the issue further: The horse’s acidic GI tract can destroy most formulations before the horse can utilize them, Bertone says. So, in effect, many feed additive supplements simply increase costs to the horse owner without necessarily benefiting a horse beyond adding calories to his diet, he says. 

Jarvis explains that in addition to the hostile GI environment, many studies do not take into consideration how/where the active ingredient will be absorbed and utilized. Therefore, some supplement labels “may quote clinical improvements seen during in vitro laboratory testing where the active ingredient was directly applied in a concentrated dose to the target tissue, such as cartilage,” she notes. “It is hard to extrapolate these results to feeding it to a live horse, considering that the product may not be absorbed by the horse into the bloodstream or it may fail to reach the target tissue.” 

What’s on the Labels?

Beyond efficacy of active ingredients, researchers note, is the concern of whether products contain what is printed on the label. In one study (Oke et al. 2006), researchers measured levels of the joint nutraceutical glucosamine in 23 commercially available equine oral supplements. When comparing the actual glucosamine levels to the label claims, the team found that concentrations ranged from 221% to 0%. Nine products failed to meet corresponding label claims. 

“If vets and horse owners cannot receive a guarantee even as to what is in their tub of supplement, how can they be expected to gauge potential results?” Jarvis says. In another study (Pearson and Lindinger 2009) researchers reviewed 15 clinical trials involving glucosamine and concluded that the overall quality of evidence of efficacy for these products was low.

So, what is a horse owner to do when faced with lack of regulation, oversight, or policing of supplement label claims?

“The best advice to the consumer is to look at the manufacturer as a whole, rather than a product in isolation,” Pearson suggests. “An ethical manufacturer will be one that invests in third-party research and development as part of their business model. This commercial culture of research, together with third-party quality control audits can provide a high level of confidence to the consumer that the product likely does what the label says it does.” 

Quality control audits include cGMP examination, hazard analysis and inspection of critical control points (HACCP), or ISO22000, all of which confirm the manufacturer has taken food safety measures. A company manufacturing a product under the auspices of GMP, HACCP, and/or ISO22000 will include that information on their labels and marketing material.

“The best way to determine whether a product and/or company is ethical is to ask for both research supporting safety and/or efficacy and evidence of third-party quality control audits,” Pearson adds. “If an inquiry to the manufacturer does not result in a research report being offered to the customer, then you can be quite sure that the research doesn’t exist.

“The best advice,” she concludes, “is for horse owners to find themselves a trusted source of information that they can turn to with questions, much as they might do with queries about basic nutrition. There are people out there who are knowledgeable on nutraceutical products and willing to offer free advice. Your vet is a great place to start, as they often have access to primary literature and research that is out of reach of the average horse owner.”

Can it Hurt?

When it comes to nutraceuticals, we’ve all heard the saying “Well, (feeding the supplement) can’t hurt.” Yet, as long as many nutraceutical manufacturers aren’t required to provide full safety and efficacy evidence, this remains a gray area. “Trials (conducted in) both canine and bovine cartilage have shown that high doses of glucosamine can cause cartilage cell death in vitro,” Jarvis says. “While it would be quite difficult to achieve such high doses in ‘real life,’ this proves that further research to find the ideal dose is essential. Also, glucosamine is a glucose-derived substance and consequently could exacerbate problems in a horse with equine metabolic syndrome, pituitary dysfunction, or laminitis.”

Bertone notes, “Owners need to be careful not to blindly follow the latest vogue, or only believe what they hear at the latest horse show or read on a blog, advertisement, or label about nutraceutical claims that extend beyond nutritional benefits.”  

He recalls one farm at which he reviewed seven supplements the owner was feeding to the entire barn of 40 horses. He determined that all products were essentially the same thing and that the owner was likely wasting a lot of money. And while the cumulative effect of these supplements was not harmful in this particular case, big problems can develop “when an owner oversupplements by using multiple products containing the same additive, such as vitamin D or dietary fats—this could reach toxic levels,” he says. 

All three practitioners stress the importance of involving your veterinarian when deciding on products for your horse. Jarvis summarizes, “A vet is most likely to be aware of concurrent medications and potential adverse reactions for that horse.”

Bertone warns of another potential result of using equine health supplements: Owners often opt to spend too much money on multiple feed additives and too little on proper medical care. 

“The danger,” adds Jarvis, “Is that a caring owner will spend a small fortune on daily supplements and be less able to afford veterinary care that provides proven efficacious and safety-tested medicines and preventive health care.”

An aged horse with severe osteoarthritis, for instance, might be more likely to benefit from veterinarian-prescribed anti-inflammatory drugs, regular foot trimming, and a warm blanket than from an oral joint supplement. 

“Nutraceuticals are never a good substitute for good veterinary care,” Pearson advises.

Take-Home Message

Jarvis sums up the current state of supplements: “I would love to find ‘nutraceuticals’ that help our horses to live longer, healthier lives. But we need more high-quality evidence of efficacy, regulations for manufacture, standard dosing and proof that they really will ‘do no harm.’” 

Bertone points out that we can’t supplement ourselves or our horses to health. Just as we adopt healthy eating and exercise habits, turning to our physicians and/or nutritionists for advice, he urges us to supply our horses with quality hay, pay attention to their conditioning programs and fitness, and implement sound management practices (e.g., strategic deworming, vaccinations, and other preventive care) in consultation with veterinarians. From there, ask your veterinarian what additives, if any, might be necessary. 


About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

Stay on top of the most recent Horse Health news with FREE weekly newsletters from Learn More