), in the form of powder and lipid extracts, is a natural support that can aid the management of osteoarthritis (OA) in pets. Some GLM products have been shown to produce improvements in mobility after about four to six weeks of use.

This article outlines what GLM is, how it works and how it’s manufactured, all of which are important to understand for veterinarians looking to recommend this type of natural product to their patients.

GLM, also known as the New Zealand mussel, is a shellfish that has been a source of food for hundreds of years to the Maori, New Zealand’s indigenous Polynesian people. Endemic to the coastal waters of New Zealand, interest in the health benefits of GLM arose when researchers noticed that Maori living in coastal regions were purported to experience fewer joint and mobility issues compared with those living inland. The main difference between these groups was diet, and researchers soon focused on GLM as the most likely source of their better joint health.

GLM contains a unique combination of omega-3 fatty acids and other bioactive lipids, vitamins, minerals, antioxidants and glycosaminoglycans, including chondroitin sulfate.

 In double-blind, placebo-controlled studies of canine OA, this combination of nutrients has been demonstrated to reduce joint pain and swelling,

 reduce total arthritis score (a combined assessment of mobility, degree of joint pain, swelling, crepitus and reduction in range of movement)

 and increase activity (as measured by accelerometers).

Over the past 40 years, about 150 publications have reported on the health benefits of GLM. For further reading, a broader review of the literature relating to GLM research was published recently.

Extensive research has shown that omega-3 fatty acids have a natural anti-inflammatory action. In vitro studies propose that fatty acids from GLM affect the metabolism of arachidonic acid by both cyclo-oxygenase and lipoxygenase pathways,

 but other lipids (including pro-resolving lipid mediators, bioactive peptides and F acids) may also play a role via different pathways. Current research is exploring additional modes of action for the omega-3 fatty acids and the role of nonlipid bioactive compounds from GLM. There is now a strong body of evidence for both GLM in isolation

and in combination with glucosamine and chondroitin, demonstrating an effect in dogs with OA, including an objective improvement in mobility in dogs in placebo-controlled studies.

Supplements, foods and other products made with GLM are becoming increasingly popular, but not all GLM extracts are the same. In fact, extract quality can vary significantly. Four key elements affect the efficacy of a given product:

 The farming of GLM is one of the world’s most sustainable forms of aquaculture. However, the location of the bays and position of the lines within the bays can significantly impact the quality of the mussels harvested by affecting the levels of omega-3 fatty acids. To ensure that only the highest-quality mussels are sourced, manufacturers must select reputable farmers working in the best-performing areas of specific bays.

Exactly when mussels are harvested significantly affects their quality. This is why it’s imperative for manufacturers to research and understand the best time to harvest in each individual bay.

 GLM traditionally is freeze-dried for extraction, a lengthy process (24-48 hours) that involves high heat that may damage the quality of the product. The combination of lower-quality processing with poor-quality mussels results in a less effective product. Use of a very rapid vacuum-drying process that reduces the mussels to powder within seconds protects the essential omega-3 fatty acids and other important ingredients. This results in a comparatively higher-quality powder with significantly higher levels of important omega-3 fatty acids.

Stringent monitoring during the manufacturing process ensures a consistently high quality of GLM powder. Some manufacturers test every batch of GLM powder to check the levels of over 40 different fatty acids, measure bioactivity and evaluate oxidative stability.

In some studies, veterinarians and pet owners are seeing improvements in mobility within about four to six weeks in pets treated with a clinically proven GLM product.

 Some improvements may be seen ahead of that timeframe, including improved range of motion, ability to rise from rest and possible increases in the distance the dog can walk. This treatment timeframe allows for incorporation of the GLM omega-3 fatty acids into joint tissues, with concomitant reductions in discomfort and increased mobility. Owners may also observe that their dogs are able to climb stairs again or jump onto the couch, and enjoy chasing a ball or interacting with other dogs.

Veterinarians throughout the world are recommending products made from GLM. In fact, the clinically proven GLM-containing product 

 is the best-selling joint supplement in the U.K. veterinary market, having displaced the more traditional glucosamine/chondroitin supplements. Hundreds of thousands of dogs under veterinary care in the U.K. are now receiving GLM-containing supplements on a regular basis. Although GLM products have historically had limited appeal in the U.S., the introduction of products with higher levels of clinical proof is resulting in greater adoption of these products in the U.S. veterinary market.

Hielm-Björkman A, Tulamo RM, Salonen H, et al. Evaluating complementary therapies for canine osteoarthritis part i: green-lipped mussel (

Bierer TL, Bui LM. Improvement of arthritic signs in dogs fed green-lipped mussel (

Bui LM, Bierer TL. Influence of green lipped mussels (

) in alleviating signs of arthritis in dogs. 

Pead MJ, et al. A novel nutraceutical versus placebo in dogs with degenerative joint disease: a randomised double blind placebo controlled clinical trial. Data on file, Royal Veterinary College, London. 2018;1-19.

Eason CT, Adam SL, Puddick J, et al. Greenshell™ mussels: a review of veterinary trials and future research directions. 

Dr. Howie is CEO of Lintbells Ltd, the U.K.’s leading nutritional supplement manufacturer for dogs, cats and horses. He co-founded the company in 2006 after spotting a gap in the pet nutritional health market. Lintbells is one of the fastest-growing companies in the U.K. and has recently launched in the U.S. Beyond his overall responsibility for the business, Dr. Howie directs the company’s sizeable R&D program, which works with world-leading marine research institutes to advance the understanding and improvement of green-lipped mussel extracts and other marine-sourced bioactives.

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As pet owners and veterinarians seek natural aids as part of multimodal therapy for joint disease in companion animals, here’s a look at one potential supportive remedy that you may never have heard of. 