A recent search of a popular Internet farm and livestock supply site returned more than 90 product hits for joint supplements.

Given that degenerative joint disease (DJD) causes an estimated 60% of lameness in horses, the popularity of oral joint supplements is not surprising. Confronted with this bewildering array of pastes, powders, pellets and liquids, horse owners often turn to equine professionals from veterinarians to trainers and farriers for guidance through the maze.

Pouring something into a horse’s feed feels more convenient and less stressful for many horse owners than pursuing surgery for a diseased joint or injection of the joint by the veterinarian.

Supplements are also perceived as “natural,” and some horse owners may feel that these products are safer for their horse than traditional pharmaceuticals such as phenylbutazone (bute).

But, how well do these products work? How can owners pick the right product for their horse from the legions of buckets and bottles on the shelves, catalogs and Internet? Is feeding a supplement more cost-effective in the long run than more aggressive therapies? What research has been done on these products? How do owners know what they are buying?

These questions may be at the back of a client’s mind when he or she asks a farrier for advice or opinion, and they may dog the farrier trying to give a horse owner relevant advice.

Joint Review

At its most basic level, a joint in the body is any meeting of two or more bone ends. Synovial joints, moveable joints enclosed by a capsule and bathed in a viscous fluid, are the most commonly referenced category. Examples of synovial joints in the horse include the fetlock, knee, hock and stifle, among others.

Within the joint, the ends of bone are covered with a thick layer of articular cartilage which both cushions and reduces friction between the bones. Surrounding and stabilizing the joint is a thick joint capsule lined by a synovial membrane.

This membrane produces the synovial fluid — think of this as the motor oil of the joint. Stress or trauma to the joint — ranging from a single injury incident to normal, repetitive wear-and-tear from movement and loading — produces inflammation within the joint.

The inflammatory process is a cascade of chemical and enzyme release. In the joint, these products (inflammatory mediators) degrade the cartilage and reduce the viscosity of the fluid. This cartilage and synovial fluid degradation, in turn, produces more friction and thus more inflammation, resulting in the cycle of trauma and inflammation known as DJD or, more commonly, arthritis.

The overall goal in managing DJD is to minimize this cycle by:

• Reducing inflammation.

• Protecting cartilage and synovial fluid quality.

• Decreasing stress on the joint.

• Removing damaged cartilage or bone.

• Repairing instability to the joint.

Therapies for joint disease may include: arthroscopic surgery to remove or repair damaged bone; cartilage or joint capsule surgery to repair damage to ligaments that may have resulted in instability of the joint; injection into the joint of anti-inflammatory or chondroprotective (cartilage protecting) medications; systemic administration of anti-inflammatory or chondroprotective drugs; therapeutic farriery to reduce uneven loading and/or ease breakover; or the use of oral joint supplements, known as “nutraceuticals.”

Nutraceuticals generally claim to address the first two aspects of joint therapy — reduction of inflammation and protection of cartilage and synovium.

Nutraceuticals — What’s In A Name?

Coined in 1989, nutraceutical is a combination of “nutrition” and “pharmaceutical” and has no regulatory definition. In fact, the regulatory status of nutraceuticals is one of the key points of controversy in analyzing the merits of these products.

“These are not pharmaceuticals. The industry is self-regulated; there’s no external oversight,” says Julie Dechant DVM, MS, DACVS, Associate Professor at the University of California-Davis School of Veterinary Medicine.

Barbara Eves, DVM, Senior Manager, Scientific Communications in the Veterinary Science Division at Nutramax Laboratories, Inc., makers of Cosequin Equine and other nutraceutical products, notes, “There’s an expectation with pharmaceuticals that you’re getting an equivalent when you buy a generic,” since pharmaceuticals are regulated by the U.S. Food and Drug Association. “Veterinary nutraceuticals, also referred to as nutritional supplements, on the other hand,” says Eves, “are regulated on a state-by-state basis.”

For consumers, including horse owners, this means that there is no consistent burden placed upon the animal-health manufacturer to ensure that their products meet specific standards of consistency or efficacy.

While some companies appear to make stringent efforts to self-regulate, there is considerable variation among products.

According to Eves, Nutramax Laboratories employs Quality Control and Quality Assurance departments that qualify raw material suppliers and analyze the raw ingredients before a product batch is manufactured. Then the finished product is evaluated at several points throughout manufacturing and at the end against pre-determined specifications to ensure label claims are met. Eves says that Nutramax Laboratories also tests for contamination and retains samples of each batch.

While a response to questions sent by email was not obtained in time for this article, on its website, Platinum Performance states that “We take great care in sourcing the highest quality and most bio-available form of ingredients, and we test each lot of raw ingredients for potency, purity and contaminants. We manufacture all Platinum Performance products in our own facility with a seasoned team of experts in nutrition, food science and quality assurance.” Grand Meadows, makers of Grand Flex, lists a similar quality assurance protocol to that of Nutramax on their website.

However, a 2002 study comparing the glucosamine and chondroitin sulfate content of 11 commercial products with the label claims for each product found widely variable results. Glucosamine content ranged from 63.6% to 112.2% of the label claim while chondroitin sulfate concentrations ranged from 22.5% to 155.7% of the amount claimed on the label.

“There is no way to predict, based on the product label, what is in the jar,” says Dechant.

Owners with performance horses also need to be concerned with the potential for drug-testing violations if using joint supplements. According to the United States Equestrian Federation 2011 Guidelines for Drugs and Medications:

“Trainers, owners, exhibitors and their veterinarians are cautioned against the use of medicinal preparations, tonics, pastes, powders and products of any kind, including those used topically, the ingredients and quantitative analysis of which are not specifically known, as they might contain a forbidden substance. This is especially true of those containing plant ingredients.”

Given the lack of regulation and enforcement between composition of dietary supplements and label claims, owners should be particularly vigilant when administering these products to performance horses.

Supplement Safety

Despite a lack of consistency in composition, and the lack of requirements to provide proof of efficacy, joint supplements are generally considered to be safe. In her time at the UC-Davis Veterinary Medical Teaching Hospital (VMTH), Dechant says that she has “not seen any adverse effects that were attributable to joint supplement products.”

While Dechant does say that there is a theoretical risk that some of the ingredients popular in joint supplements “could impact coagulation or glucose regulation,” those events just have not been seen. “In general,” says Dechant, “they are unlikely to cause harm.”

However, absorption, a potential factor contributing to the high safety of joint supplements, may also argue against their efficacy.

Do Joint Supplements Work?

The body is an efficient processing facility. Compounds that enter the body are broken down, converted, used as needed and eliminated regularly.

The degree to which a drug or other substance becomes available to the target tissue after administration is known as bioavailability. In other words, when a chemical enters the system, particularly through the mouth, and is digested, how much of the substance is absorbed into the bloodstream and how much reaches a target tissue such as a joint?

The question of absorption or bioavailability is a key point in the debate over the efficacy of joint supplements. Research studies fall into two broad categories:

• In vitro studies, which are conducted on laboratory specimens.

• In vivo studies, which are conducted on live subjects (animal or human).

The two most widely studied components of oral joint supplements are glucosamine hydrochloride and chondroitin sulfate. While several studies, including a 2005 study conducted by Dechant while at Colorado State University, have demonstrated a potential benefit to cartilage health, these studies — showing a decrease in the mediators that contribute to cartilage degradation in response to glucosamine and chondroitin sulfate administration — have been conducted in vitro.

In the CSU study, Dechant and co-authors found that high doses of glucosamine hydrochloride and chondroitin sulfate in combination (Cosequin Equine, Nutramax Laboratories) reduced the degradation of cartilage samples treated with an inflammatory mediator. However, Dechant says, “in the live animal, even with full absorption, we are unlikely to ever achieve those levels (found to be therapeutic in the study) in the joint.”

However, measurements of absorption of these molecules in the live animal have proven challenging. One study examining the bioavailability of glucosamine hydrochloride and low molecular weight chondroitin sulfate found a 2.5% to 6% absorption of glucosamine and a 22% to 32% absorption of chondroitin sulfate. Dechant also points out that with current measuring technology “it’s hard to know if the body is absorbing the intact molecule, which is what is needed, or just fragments.”

Eves acknowledges that questions regarding the absorption of nutraceutical products exist. However, she believes the increasing trend toward scientific research in the field is promising.

But study in the field of joint supplements still has a way to go. Authors of a 2009 review of the literature on the subject stated, “It is concluded that the quality of studies in the area is generally low, prohibiting meaningful interpretation of the reported results. New high-quality research on GBN (glucosamine-based nutraceuticals) is needed…”

While several in vivo studies have indicated some positive effects of oral joint supplementation upon factors such as lameness score and stride length, criticisms directed toward much of this body of research include:

• Small sample sizes.

• Short trial duration.

• Lack of blinding (whether the investigators know which horses have received a particular treatment).

• Lack of randomization (how horses are assigned to study groups).

• Lack of control group (a comparison group — usually treated with a placebo).

Eves points to several more recent in vitro studies showing a reduction in expression of multiple inflammatory mediators with administration of clinically relevant levels (levels attainable with oral administration) of glucosamine and chondroitin sulfate. She says “I’m comfortable the product is benefitting joint health.”

Dechant takes a more conservative view. With the current level of research “we can’t confidently conclude there is efficacy,“ she says. “Most properly performed clinical trials generally aren’t showing measurable effect.”

However, she says, in individual animals, “one may respond vs. another one that doesn’t. Studies take the average.”

Is More Better?

Many manufacturers add ingredients beyond glucosamine and chondroitin to their joint supplements. These compounds include: methylsulfonylmethane (MSM), myristoleic acid, hyaluronate, avocado/soybean unsaponifiables (ASU), omega-3 fatty acids, and plant products such as devil’s claw.

Among these products, omega-3 fatty acids were found to show beneficial effects in managing osteoarthritis in dogs, and both Eves and Dechant indicate that the in vitro research on ASU appears promising. Eves says that in a safety study, no adverse effects on clinical parameters or serum chemistry were seen with Cosequin ASU administration at 5 times the maintenance dose.

What To Take Home

In the absence of outside regulation of the nutraceutical industry, it falls upon the horse owner and other consumers to do as much research as possible on the products. Oral joint supplements may vary widely from each other and even from their own labeling.

In the paper analyzing the content of various joint supplement products, the authors cite a statement from the Arthritis Foundation suggesting, “when a supplement has been studied with good results, find out which brand was used in the study and use that.” For now, this may be the best advice with regard to product selection.

As Dechant says, “There is a wide variety of products with quite strong anecdotal evidence of success, but quite limited research-based evidence.”

Dechant also notes that while oral supplements may be beneficial in managing mild cases of joint disease alone, in more significant cases of arthritis, joint supplements should be considered an adjunct to more aggressive and direct therapies such as joint injections or surgery if indicated.

While oral joint supplements are unlikely to harm a horse, owners may find it both cost-effective and in the best interests of the animal to consult with their veterinarian about how best to incorporate these products into a full therapeutic management of joint disease