An article in the October 8, 2009, issue of the New England Journal of Medicine has reminded me of an issue that has bothered me for at least a couple of decades.  While horse owners seem more than happy to give their horses any number of supplements, the fact is that, no matter what the supplements promise, horse owners can’t really know if the supplements do any good.

Why? One reason is that there is not a requirement that any of the supplements actually do what they say they’re going to do.  Read that again; the claims made by supplements don’t have to be supported by any evidence.  If you buy a watch, you have a reasonable assurance that it’s going to keep time, because that’s what watches do.  But with supplements, just about any claim can be made, and there’s no requirement to prove it.  In addition, even if a product were to do what it was claimed to do, horse owners still wouldn’t necessarily be assured that it would be effective, because there’s no way to assure that the product that they’re giving has in it what the labels says it contains. 

This is a real problem in the human field.  The article, titled “American Roulette — Contaminated Dietary Supplements,” by Pieter A. Cohen, notes that the combination of no regulatory oversight of the dietary supplement industry, combined with a lack of resources by any agency that is supposed to oversee the manufacture of such products, has led to human supplement takers playing an involuntary game of therapeutic Russian Roulette. 

Manufacturers can put just about anything – or nothing – into their supplement products, and there’s really not much that consumers can do; there’s no practical way for an individual consumer to know what he or she is really getting in the product.  In addition, products are continuously being put into the human market with claims that can’t be supported, even if the product contains what it says is on the label (which it often doesn’t).  Finally, even though manufacturers of supplement products are required by law (since 2007) to report serious supplement-related adverse events to the United States Food and Drug Administration (FDA), the majority of them – estimated at 50,000 events per year – go unreported.

People certainly don’t seem to understand the extent of the problem.  They seem to want to take the claims made for supplements at face value, that is, they seem think that if a product says it can do something, it can, and it does, and that someone is making sure of it. 

Wrong. 

As a result, in 2002, a Harris poll found that consumers believed that dietary supplements were approved by a government agency prior to being sold.  That’s not true – supplements can be put onto the market without any approval at all, as long as they don’t make specific disease-preventing claims (for example, a supplement can claim to “support” joint health, as long as it doesn’t claim to help cure arthritis). 

The faulty beliefs about supplement regulation aren’t limited to consumers; a recent survey of internal medicine residents found that one-third believed (wrongly) that dietary supplements required FDA approval, and the majority didn’t know that it was mandatory to report adverse events to the FDA.

Perhaps even worse, some manufacturers of human supplement products have spiked supplement products with drugs, some of which are demonstrably dangerous, such as indomethacin, a pain reliever, or diethylstilbestrol, a hormone. 

Others have been shown to be contaminated with dangerous substances, such as heavy metals.  Because of all of the problems regarding dietary supplements in the human market, the author of the NEJM article concluded:  “Congress should give the FDA the requisite authority and resources to regulate dietary supplements so that the public can make well-informed decisions regarding the potential risks and benefits of consuming such supplements. Until that happens, millions of Americans will continue to be exposed to unacceptable risks in exchange for purported but unproven health benefits.”

So, what’s the situation in the equine supplement market?  Well, it’s certainly no better than the human field. 

Dozens and dozens of products are being promoted as being necessary or important for your horse’s health, and those products are accompanied by dozens and dozens of unsupported, but highly desirable, claims.  Just like the human market, there’s essentially no oversight over the manufacture of such products; there’s no information about what constitutes a proper dose; there’s little or no information about how doses are determined. 

The bottom line is that you simply don’t know what you’re getting when you purchase a supplement for your horse. 

Only a couple of studies have been done on supplements for horses, both on products that are said to contain glucosamine, chondroitin sulfate, or both.  Both studies found marked variability in the contents of such products – they also found substantial variation in the recommended dose.  Products that don’t have label contents can’t be expected to be effective, are an unnecessary expense, and, in extreme cases, may even delay the use of other, potentially beneficial, treatments

Fortunately, while horse owners may be lining supplement makers’ pockets with cash, there doesn’t seem to be much harm from feeding supplements to your horse.  There are probably a lot of reasons for that.  In fact, unless products contain substances that are overtly toxic (such as was the case with a vitamin product that was compounded for polo horses in Florida), it’s unlikely that an owner would see any direct harm. 

Furthermore, to a certain extent, the size of the horse protects it from toxicities (it usually takes pretty big doses of substances to hurt a horse). 

The bottom line is that the lack of supporting evidence, product variability, and differences in recommended doses make it essentially impossible for horse owners – or even veterinarians – to make any sort of rational selection of most supplements for their horses. 

It will take independent assessments of quality control, and possibly regulatory oversight, for the situation to get better.  In the meantime, horse owners pay their money, and take their chances.  And no one is looking over anyone’s shoulder to make sure that there’s a level playing field.

David W. Ramey, DVM, began veterinary practice in 1984 in the Los Angeles area of southern California, and he is still there today. His clinical practice specializes in the care and treatment of sport and pleasure horses. Dr. Ramey is a vocal advocate for the application of science to medicine, and, as such, for the welfare of the horse. He is an internationally known author and lecturer, and he’s written more than a dozen books on a variety of horse care topics. He’s also presented topics at the American Association of Equine Practitioners meeting seven times, most recently in 2008. To learn more about Dr. Ramey, visit http://www.doctorramey.com/.

The opinions expressed by www.chronofhorse.com columnists are entirely their own and not necessarily those of The Chronicle of the Horse. Always consult with your own veterinarian before undertaking any course of treatment for your animal or changing treatments or medications your veterinarian has already prescribed.