The issue of joint supplements

by Kathryn Cowley BVSc MRCVS, Canine Arthritis Management

It is inevitable in your line of work that you will be asked questions about joint supplements. Nutraceuticals are a multi-million pound business and there are thousands of dogs in the UK being given them to try and prevent or treat arthritis. Owners will often see them as a safe and natural cure all and unfortunately the marketing for many of these products reinforces this misconception.

There have been many studies carried out looking into the efficacy of joint supplements but results are often inconclusive and comparison between studies reveals contradictory findings. One of the big problems we have is that most of the studies currently available are not always of great quality – most don’t involve a large enough population of dogs and are not carried out over a long period of time.

It is also important to bear in mind that regulation of the nutraceutical market is managed by the food standards agency, who are mostly concerned with food safety, composition and labelling rather than proven efficacy, meaning manufacturers do not have to prove any clinical benefits of their product. Knowing where to start with recommendations for supplements, with so many available, can be difficult. We should aim to educate clients and direct them to the products that are most likely to bring about benefits for their pet so their efforts and finances are not being wasted.

While there is little scientific evidence that supplements as a whole have clinically meaningful effects in dogs, the individual components of the supplements have quite good evidence behind them when tested in vitro (ie experimentally in a lab) and there is certainly a host of anecdotal support for their use.

One of the most popular supplements currently in use is fish oils, and for potentially good reasons. The three supplement components with the most evidence of beneficial effect are omega 3 oils, Avocado-Soybean Unsaponifiables (ASU) and Undenatured Type II collagen (UC-II). Of these, omega 3 is the one with the most basis for its use and this is found in high levels in cold water marine fish oils.

Both omega 3 and omega 6 essential fatty acids cannot be made by the body and must be acquired through the diet. It has been shown that the omega 3 fatty acids Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA), sourced primarily from cold water marine fish, are well absorbed through dietary supplementation. It is important to note that some supplements will offer omega 3 in the form of plant based alpha-linolenic acid (ALA), which is often from flaxseed, canola, walnut or soybean oil. ALA is not as bioavailable as marine sources of omega 3. ALA is the precursor to both DHA and EPA, but the process of converting one to the other is highly inefficient in dogs. Therefore, provision of DHA and EPA directly is much preferred.

Omega-3 fatty acids produce anti-inflammatory, antiarrhythmic, and antithrombotic properties whereas omega-6 fatty acids are proinflammatory and prothrombotic. These two dietary components compete for the same enzymatic pathway to reach these endpoints. By increasing the level of omega 3 in the diet through supplementation, less harmful inflammatory mediators will be produced as a preference. Through increasing serum levels of EPA and DHA there is evidence of reduced incidence of many chronic diseases including not only arthritis but also cardiovascular disease, inflammatory bowel disease (IBD) and cell proliferation in cancer.

Cod liver oil capsules are cheap and widely available, and so are a tempting source of omega 3 for owners to use. Getting an appropriate dose though is difficult, especially when we consider that they also contain vitamin A, which is toxic if given in too high a level. A dog specific supplement containing whole-fish marine sourced omega 3 oil is very much preferred.

ASU (Avocado-Soybean Unsaponifiables) is another component of supplements with evidence behind its use. This is a plant extract comprised of one-third avocado oil and two-thirds soybean oil. ASU has been used effectively in the treatment of osteoarthritis in humans for a number of years, showing a reduction in both joint stiffness and pain. New studies are emerging that show benefits for our canine arthritis patients too, including early on in the disease process. It works via both anticatabolic and anabolic effects on joint cartilage by affecting a number of key mediators of structural joint changes in osteoarthritis. ASU also increases chondroprotective factors within synovial fluid.

Undenatured Type II collagen (UC-II) is collagen extracted from chicken sternum cartilage. It has been found to have an immunomodulatory effect by suppressing the T-cell mediated inflammation within joints. This helps to slow down joint cartilage damage. UC-II has been shown to help dogs with moderately severe arthritis. Some canine supplements, such as Kruuse Vitalchews Joint and Mobility Support contain both marine sourced omega 3 and UC-II.

Another common component, but one with perhaps less evidence for its use, is Glucosamine. It has been shown to positively affect chondrocyte function in vitro. Similar findings have also been seen with chondroitin. There is also evidence that glucosamine can reduce inflammation, which would be great news in an arthritic joint, but we don’t know if these products actually reach the joint in a usable form and in high enough levels to have a clinical effect.

As already discussed, there are a host of supplement options available to choose from. Each company gives its own claims. Definitely beware of any claims to cure or totally prevent arthritis. In the book Multimodal Management of Canine Arthritis (Fox, 2016) the author outlines the ACCLAIM criteria for choosing a nutraceutical as follows:

A – a company name that you recognise, an established firm that provides veterinary educational materials.

C – clinical experience, i.e. companies that invest in clinical trials, and who publish data for respected journals.

C – content, all ingredients should be clearly indicated on the label

L – label claims, i.e. if they sound too good to be true, they probably are. Reference to clinical trials is better than simple testimonials. Any label suggesting they treat arthritis, cure arthritis or prevent arthritis are likely to be suspect.

A – administration, the dose recommendation should be accurate and easy to calculate

I – a lot identification number to indicate some form of surveillance is possible to test product quality

M – manufacturer information and ideally a link to website.

As with all parts of arthritis management, nutraceuticals are by no means the whole picture. We need to focus on a multimodal approach and educate clients to this end. The core aspects of weight control, exercise management, environmental adaptation and analgesics cannot be overlooked. Close monitoring is vital, with changes made to the management programme as needed.


Omega-3 Fatty Acids, M. B. Covington, American Family Physician Volume 70, Number 1, July 1, 2004.

Osteoarthritis Cartilage, Knott et al, 2011 September; 19(9): 1150–1157 Investigation and management of canine osteoarthritis, R. Pettitt et al, In Practice, Vol 37, Nov 2015

Fox, S.M., 2006. Multimodal Management for Canine Osteoarthritis In: Multimodal Management of Canine Osteoarthritis. 2nd Ed. New York: CRC Press.

Deparle, L.A., Gupta, R.C., et al., 2005. Efficacy and safety of glycosylated undenatured type‐II collagen (UC‐II) in therapy of arthritic dogs. Journal of Veterinary Pharmacology and Therapeutics 28(4), pp. 385-390.

Gupta, R.C., Canerdy, T.D., et al., 2011. Comparative therapeutic efficacy and safety of type‐II collagen (uc‐II), glucosamine and chondroitin in arthritic dogs: pain evaluation by ground force plate. Journal of Animal Physiology and Animal Nutrition 96(5), pp. 770-777.

Au, R.Y., Al-Talib, T.K., et al., 2007. Avocado soybean unsaponifiables (ASU) suppress TNF-α, IL-1β, COX-2, iNOS gene expression, and prostaglandin E2and nitric oxide production in articular chondrocytes and monocyte/ macrophages. Osteoarthritis and Cartilage 15(11), pp. 1249-1255.

Boileau, C., Martel-Pelletier, J., et al., 2009. Protective effects of total fraction of avocado/soybean unsaponifiables on the structural changes in experimental dog osteoarthritis: inhibition of nitric oxide synthase and matrix metalloproteinase-13. Arthritis Research and Therapy 11(R41).